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3 cams, all very similar, the lower-end of their cruise rpm ratings are about equal (2400 - 2600).

I like the one on the right. The one on the left "sounds" like the better choice if you read Crane's description (1400 - 5400 rpm range, daily driver, fuel efficiency) but the one on the right actually has 1 degree less overlap. Low overlap, centered at TDC, for good low rpm power. Early opening exhaust valve (opening at 80) allows the engine to rev at high rpm. The torque curve is being stretched at both ends. The overlap is not "too low" the engine should have a bit of a lopey idle.

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Hi George. I'm resurrecting this thread. I'm thinking of having
one of these Cobra Jet cams ground for solid rollers in a 357 C.
so far the info from above is:
Comp intake lobe 1498 ground on 112 ICL
Comp exhaust lobe 1476 ground on 116 ECL
Use 1.8 rocker on intake, 1.73 rocker on exhaust.
276/288 advertised duration.

Using those lobes, what would the duration @ 0.050" lift be?
What would the LSA be?
What would the valve events be at 0.050" lift?
What kind of idle would it have, smooth or lopey?

Yes, many questions and no doubt more to follow :-}

Danford1
Since this thread is being resurrected, I am wondering how to determine the redline of this (or similar) cams.

I have a Bullet Hydraulic Roller with similar specs to the one described on Page 1 of this thread. My valve lift is a little higher (.610/.610).

How do I know the true redline without risk of engine damage?

All valve train components from Bullet Cams except my Smith Brothers Heavy wall pushrods, and 1 piece SS valves. Lifter bores bushed.

Rocky
Last edited by rocky
Safe rpm limit will be determined by the valve spring pressure vs. the total mass of the valve train.


I think that stock you are looking at a single spring and dampener at something like 285 #'s open. Maybe 35#'s on the seat? Right there with those valves the safe rpm limit is probably just a little over where the cam runs out of enthusiasm? About 6,000 rpm.


The rpm potential of the camshaft, by the timing events mostly. A little by the valve lift? But the valve lift is more to match the flow of the valves.

The iron 4v heads with a good valve job on the intakes flow around 300cfm at .600" lift. Less lift, less flow. So you match the lift to the flow of the ports.


The fact that it has roller lifters has almost nothing to do with the cams performance. That would effect total gas mileage more than anything else from less internal friction (maybe 1 mpg better?) and lower your need for ZDDP in the oil. Thats all that they do here.


It strikes me that the timing events on this proposed cam are very similar to the stock CJ cam, just with roller lifters.

The characteristics then should be very similar to a stock CJ cam, i.e., all done by about 6000rpm.

It doesn't have enough duration or overlap to continue past that. Centerlines are wrong for high perfomance. Those need to be 110.

If you want to go faster, more rpm with power, then you need more duration, tighter centerlines, and more overlap.

On a 2 valve engine, that's the only way you can do it.

That means you need to put up with a more radical idle, more valve train noise, more exhaust noise.

If not, then you have to go to a 4v, dual cam engine and have the primary cam idle like a pussy cat, and the secondary cam goes ape?
That's interesting.

It seems like a free breathing motor like a 351c would continue to spin and suck air through until effects like valve toss and inability to control the valve train impose a physical limit (which can result in damage) to the engine, and that is what I was asking about...

But now I am seeing reports that cams / engines are "all done" at 5x00 RPM.

As a fluid dynamics-type question, what are the primary effects that would limit an engine before physical valvetrain damage? Just inability to flow enough air?

It would seem that 300 CFM still is healthy, and power ought not "drop off a cliff".

But what do I know?

Thanks

Rocky
so in reply to the fluid thermodynamics of maximun rpm

bare with my comments as I am dusting out a remote corner of though from decades back.
the engine's "redline" is a function of piston speed and ability of the components to keep it attached
the engine's power "limits" are
1)a function of valve train speed and the springs ability to keep it on the cam
2)power produced is a function of flame propagation of the fuel/air and piston speed.
there is probably more key points to engine design, but I just was able to pass that class with extra credit work
thus a short stroke to reduce piston speed, exotic valve train, and highly explosive fuels would let you easily reach the rpm that will throw pistons off the rods
quote:
Originally posted by JFB #05177:
so in reply to the fluid thermodynamics of maximun rpm

bare with my comments as I am dusting out a remote corner of though from decades back.
the engine's "redline" is a function of piston speed and ability of the components to keep it attached
the engine's power "limits" are
1)a function of valve train speed and the springs ability to keep it on the cam
2)power produced is a function of flame propagation of the fuel/air and piston speed.
there is probably more key points to engine design, but I just was able to pass that class with extra credit work
thus a short stroke to reduce piston speed, exotic valve train, and highly explosive fuels would let you easily reach the rpm that will throw pistons off the rods


I agree, correct.

The engine is an air pump. It must be able to pump a sufficient atomized fuel mixture to enable it to reach a particular rpm.

While the intake ports of an iron 4v head have the capability of flow a mixture at the rate of 300 cfm, 5.7 liters will be around 8,000 rpm (I don't have that chart in front of me, might be more, might be less).


The camshaft is the device that controls the opening of the valves in a way that compliments that but that flow of mixture to a preset number. It is not an infinitely variable timing device.


The most scientific and accurate answer to Rocky's question has to come from an engine dynamometer. Other than that all you can do is "modelling" and you do that roughly by comparing timing/lift specs on a new cam design to a know existing one.

The timing on the roller cam proposed is very similar to the stock 4v cj cam. Similar, not exact.

What are the characteristics of that cam? 6,000 rpm.

That's all I said...and I think that maybe that is why George is calling it a "Roller CJ Cam"?
quote:

Originally posted by Danford1:

Hi George. I'm resurrecting this thread. I'm thinking of having
one of these Cobra Jet cams ground for solid rollers in a 357 C ...



In the process of penning a cam for another person I needed a
different intake lobe, which after I penned the cam I decided
I liked it better, its more universal, so the spec has changed
a bit. The benefits are two fold, increasing the intake duration
means that engines with non-4V heads, i.e. smaller ports, shall
still peak at about 6000 rpm; and both lobes now have the same
lift, so having different rocker ratios for intake & exhaust is
no longer necessary.

No 351C with 4V heads has a "smooth" idle, because of the big valves.
But this low overlap cam will have an idle about like the 351 Cobra
Jet, maybe just a bit "rougher". The engine shall have a slight lope,
a nice 1960s burble. I don't do rough idling cams, there's a million
of them already I don't need to add to the list. I uniquely pen street
cams that people can't find in the aftermarket. That's where my usefulness
lies. Lowering the engine's idle speed increases the lope, raising the
idle speed decreases the lope.

Here's the revised spec:

Ford 351 Cleveland solid roller tappet street cam
Grinder: Comp Cams
Lobes:
High Energy Street Roller
Intake #1474
Exhaust #1476
112° ATDC intake lobe mathematic centerline
117° BTDC exhaust lobe mathematic centerline



280°/288° advertised duration (284° average)
236°/244° duration at 0.050"


Indicators
44°/44° intensity (advertised duration – duration at 0.050)
35° major intensity claimed by Comp Cams
Overlap at 0.050” = 11°
Lobe separation angle = 114.5°


0.3666"/0.3666" lobe lift
0.020”/0.020” lash
0.634”/0.634” theoretical valve lift (1.73:1 ratio)
0.614”/0.614” net valve lift [(lobe lift x 1.730) – lash]
0.603”/0.603” factual valve lift [(lobe lift x 1.70) – lash]


EVO = 81° BBDC
IVO = 28° BTDC
Overlap = 55°
EVC = 27° ATDC
IVC = 72° ABDC

Suggestions:
• Install tappet bore bushings having 0.062” orifices. A do-it-yourself installation kit is available from Wydendorf Machine.
• Utilize Isky solid roller tappets #3972-RHEZ (they roll on solid bushings instead of needle bearings and they feature forced lubrication instead of splash lubrication).
• Valve springs, Manley Nextek #221432. Dual valve springs plus damper. 1.53” diameter, 1.90” installed height, 150 lbs. seated force, 435 pounds per inch spring rate (412 pounds over the nose), 0.630” max. lift, 0.730” coil bind.
• Utilize a steel distributor drive gear for steel roller cam cores (never a bronze gear). They are available from Crane Cams and Ford Racing.
• Best possible rocker arms are T&D Machine #7200 individual shaft mount rocker arms, 1.70:1 ratio, having rocker arms manufactured from steel. Yella Terra YT6321 would be a less expensive substitute.
quote:

Originally posted by Rocky:

... I am wondering how to determine the redline of this cams ...



An engine will rev as high as the induction, the exhaust, the ignition, the valve train allows it .... or until something breaks. Smiler An engine's rpm isn't necessarily the limiting factor ... it may be how fast the engine accelerates, and therefore how fast the valve train accelerates. The old time sports car guys remember that dual over-head cam valve train was universally fitted to in-line 6 sports car engines of the 1950s because they had very light crankshafts (no counter weights) and they revved as fast as hell. A V8 is not as demanding of an application as an in-line 6.

The factory M code engine had a low lift cam, a small carburetor, and a single point distributor. It didn't rev too high or too fast, in spite of the 4V heads. Uncorking the engine with a 780 carb, headers, a CJ cam & dual point ignition made a big difference, the engine revved faster and higher. But it still had limitations ... i.e. the push rods and the valve springs. The Cobra Jet engine only had 277 pounds valve spring force over the nose, and the factory push rods were only good to about 6000 rpm in spite of the low valve spring force.

I have a friend named Bob, the 351 Cobra Jet in his 1972 Mach 1 Mustang had 351 Boss valve springs, stiffer push rods, & dual point ignition. It revved to 7000 rpm easily ... even with the 4300D carburetor and factory Cobra Jet cam. There's an instance when an engine equipped with the Cobra Jet cam proved it could rev. Should I have told Bob it wasn't supposed to do that?

Any hydraulic tappet valve train will eventually be limited by tappet collapse. If the engine revs to 7000 rpm its doing good, don't expect more. Tappet collapse is the reason why, when making a hydraulic cam motor rev higher, its better to lighten the valves than to use more spring force.

quote:

Originally posted by Rocky:

... But now I am seeing reports that cams / engines are "all done" at 5x00 RPM ...



Most "hot rod" engines built following modern guidelines open the exhaust valves too late, due to using cams with 108 or 110 LSA. See my reply to Jack DeRyke (i.e. Bosswrench) on page 4 of this thread. Street engines (muffler equipped) gotta open the exhaust valve early to prevent the torque curve from falling-off like a brick at upper rpm. Aftermarket cams are designed to make the buyers happy. They have narrow LSA, narrow power bands, and lopey idle. They make an engine sound "cool" at a stop light, they burn rubber real well, and they flatten-out between 5000 to 6000 rpm. As far as the cam grinders are concerned, that's what the public wants. And they're right. Most North American kids, the young guns who buy all the parts sold in magazines, relate to drag racing. My oldest son is one of them. Every performance parts catalog lists dozens of street/strip cams. When is the last time you saw a "sports car" cam?

Notice in this instance 110° LSA does not equate to higher rpm and more power. Just a narrow power band.

Such lore and mysticism has sprung up around the lobe separation number. Grinders don't grind cams with more than 110° LSA because nobody will buy them. The number was never meant to be that important. In order to grind a low overlap cam with 110° LSA it is necessary to use very short duration lobes, like about 265° to 270° duration. Combine short duration lobes with the small cross-section ports of the average cylinder heads and the result is an engine with a very low rpm power band. A tractor motor. And since the exhaust valve is opening very late, well the torque curve doesn't just flatten out at high rpm, it drops-off like a brick. Combine that cam with an engine having decent static compression, like 10:1, and it will ping on premium gasoline because the intake valve closes so early that DYNAMIC compression is too high. How many of those complaints have you heard over and over? But tell a guy his engine will perform better with a cam having 114° LSA and he'll think you don't know what you're talking about. He'll think you're crazy, and old, and behind the times. I know people think this about me.

The other issue causing engine revs to flatten out early is the newest high-ramp-rate lobes, i.e. the Comp Cams X-treme Energy lobes and the Lunati VooDoo lobes. They tax the valve train and cause valve float & lifter collapse to set in earlier, or they cause other sorts of valve train issues such as spring surge.

The 351 Cobra Jet having a cam with 270° intake duration, and the 351 Boss having a cam with 290° intake duration, both make peak horsepower around 5800 to 6000 rpm. There's another instance, like the CJ engine in Bob's Mach 1, where intake duration had no bearing on rpm and horsepower. This is because the 4V heads are tuned for 6000 rpm. The power band is not dependent upon camshaft intake duration like it is in other engines. If you have an engine, equipped with 4V heads, that flattens out before 6000 rpm, it has a problem. Floating valves, collapsed tappets, valves sticking in their guides, carburetor secondaries that don't open, malfunctioning ignition, exhaust valves opening too late, somebody's pounded a potato up the tail pipe ... but the problem is not a short duration cam.

One very common problem is a retro-fit hydraulic roller cam using the Ford factory 5.0 hydraulic roller tappets. Those tappets are not designed to endure the side thrust forces of the Cleveland valve train, they distort, and they collapse at relatively low rpm.

quote:

Originally posted by PanteraDoug:

... It strikes me that the timing events on this proposed cam are very similar to the stock CJ cam, just with roller lifters.

The characteristics then should be very similar to a stock CJ cam, i.e., all done by about 6000rpm ...

...and I think that maybe that is why George is calling it a "Roller CJ Cam"?



Factory Cleveland street cams

1971 M Code (4V, 118.5° LSA)
EVO = 81° BBDC
IVO = 18° BTDC
Overlap = 37°
EVC = 19° ATDC
IVC = 70° ABDC


1971 Q Code (Cobra Jet, 117° LSA)
EVO = 82° BBDC
IVO = 18° BTDC
Overlap = 46°
EVC = 28° ATDC
IVC = 72° ABDC


1971 R code (351 Boss, solid tappet, 116° LSA)
EVO = 86° BBDC
IVO = 34° BTDC
Overlap = 58°
EVC = 24° ATDC
IVC = 76° ABDC

1970 D1ZZ-BX cam (505 cam, 114° LSA)
EVO = 84° BBDC
IVO = 36° BTDC
Overlap = 62°
EVC = 26° ATDC
IVC = 74° ABDC

SVO A341 cam (112° LSA)
EVO = 77° BBDC
IVO = 28° BTDC
Overlap = 61°
EVC = 33° ATDC
IVC = 72° ABDC

Look at all these street cams, notice they all but one open the exhaust valve (EVO) by at least 81° BBDC. The A341 cam opens the exhaust valve 4 degrees later than the others because it was ground "straight-up". The cam was known to flatten out early, it works better if it is advanced by 3 or 4 degrees. All the cams close the intake valve (IVC) at about 70° ABDC.

This valve event timing is not peculiar to the Cobra Jet cam. Or even to the 351C! I can show you cams in the current Crane Cams catalog, ground for the 302/5.0 engine which have the same timing events. In fact, I can show you a similar cam ground for the 289, in an early 1960s Ford performance parts catalog. The M code engine, which revved lower, and the R code engine which revved higher, share these timing events. Truth be known, these are just well performing, wide power band, valve timing events.

My cams are not "all done" by 6000 rpm, not in the least. Ask Chuck, his engine has one installed. It wants to rev, doesn't it Chuck? The original 351 Cobra Jet engine was limited by valve springs & push rods. The Autolite 4300D carbs didn't always work perfectly either. But with a good carb, good springs, good push rods it revved!

Low rpm performance and drivability of 351C engines diminishes quickly as overlap exceeds 62° due to their large valves; this is especially true of engines equipped with factory 4V heads. Street performance, low rpm pep, drivability and manifold vacuum all improve as overlap decreases. The exhaust valve opening (EVO) should occur at 80° BBDC or earlier to extend the engine’s upper rpm performance and to allow the engine to perform better in conjunction with muffled exhaust systems. The intake valve closing (IVC) should occur at about 70° ABDC to avoid reversion and preserve dynamic compression. Staying within those 3 parameters requires camshafts having lobe centerline separation (i.e. LSA) no less than 112°. Camshafts having a 10° difference between intake duration and exhaust duration can be timed to center the overlap event on top dead center while meeting the criteria of the two valve events (EVO & IVC). Centering the overlap event on top dead center aids low rpm performance and drivability because piston motion is almost nil from 30° BTDC to 30° ATDC (known as the “dwell” period); piston motion provides the energy making intake and exhaust gases flow where we don’t want them to.

Valve event timing, duration, nor anything else had any bearing regarding why I chose to call the cam a Cobra Jet cam. My motivations were far more sinister. You see, I like the name Cobra Jet, it sounded better than "M code" cam, which in reality my cam more closely duplicates the valve event timing of the M code cam.

Make good decisions.
Last edited by George P
Counterpoint.



All excellent points and do not interpret what I say as arguing against them.

In the Pantera there are a couple of significant points which can make those particular camshafts qualities more or less significant.

One is how you feel the nature of the engine should be, i.e., should it more have the expected sound qualities of an Italian exotic with a sound tone like that of classic music being listened to on a bottle of wine with a loaf of bread and Italian cheese while you relax on a blanket in the shade of big oak tree on a warm summer day?

If you have enough of that wine, you won't care how hard the engine pulls and if the engine pulls like you are "sober" and listening to AC/DC playing "Listen to the Money" with their amps set on 11?

To some this is significant to others it just makes you too tense and you need to have some "herb" and chill? Whatever?

I say if you talk the talk, you better be able to walk the walk? Wink



There are a couple of very significant factors in selecting a cam for what really is a big ugly "Detroit" race engine monster (potentially) in a "Mona Lisa" chassis.

First, do you want to retain the silly factory Ansa exhausts and the steel tube "log" exhaust manifolds? Second, do you want to take advantage of the full flow potential of the 4v intake ports?

It is undeniable that going to a 110 centerline cam is much better suited to a MUCH better flowing exhaust system than stock.

With the restrictions and lack of scavaging in the stock system, it's doubtful that you could use the potential that it has to offer? Why put up with the "discomfort" of the rumpity-rumpity of a cam like that? I reluctantly agree with that.

Second, do you want to take advantage of whatever the flow potential of those 4v heads offer...whatever that may be?

That is kind of a tough decision really.

The iron 4v head flows right around 300 cfm on the intake at .600 lift (remember that lift number now).

Back in the day when this engine was concieved, that was an earth shattering number. Particularly in a street engine.

For example, the Ford 289 High Performance head, maybe you heard of these and know what it went on to accomplish, in it's best race configuration flowed 180 cfm as cast, 220 as race ported, and 258 in the race prepared GT40 configuration, with the GT40 special head casting.

The 427 medium riser, race prepped? Try 278-285 (depending on who preped it) in race form.

Here you have an as cast out of the box 4v Cleveland, outflowing both and those are Thoroughbred race engines.



Back to my point. If you look at an extrapolated intake port flow chart, you will see that at a valve lift of .520, this head will flow about 260 cfm.

First off, that lift is not permitting you to get maximum flow. Period. Question. Do you need to get 300 cfm flow? Apparently not, but don't go strutting around with your Ferrari or worse your Chevy friends quoting the flow rate of those big radical Ford 4v ports...'cause simply put..."you ain't got it" with that camshaft!

I am not arguing for or against. I am just saying that the data shows if your criteria is to maximize the intake flow and therefore maximize the horsepower potential, you are not doing it with this camshaft. That's all I said before, and all I am saying now.



To say that one person is satisfied whether it is Billy Bob, Giuseppe, or Carlos and that is your proof is like telling me that one 25 year old religious leader guru of a sect in India is in fact the true God because he has 7 million people that follow his ministry is well...hum...poppycock? At least it is to me. That's how my logic runs?


You can't put a Guru on an engine dyno and test it, but you sure can on an engine.
Show me the beef. I can't argue with that? Has anyone actually dynoed one of these camshafts yet?



I didn't take a mail order course in camshaft design and have a degree mailed back to me and declare myself an expert in camshaft design. I have never ever in fact even made one of these cams AND ACTUALLY TESTED IT, so I don't know if it will work as intended.

I am admittedly limited to comparing, i.e., modelling the proposal after ones that are know entities. That's how it's been done for, well, a long time. Some things work, some don't.

To continue to say that the cam manufactures are only selling something that doesn't work and that they are giving the customer just something that is expected using Chevy technology? I wouldn't make that foolish of a statement. That won't even get into court to defend. Your attorney will recommend to settle out of court.

Even so, Chevy is no stranger to canted valve head technology. It is not exclusive to Ford. They do use it in their big blocks rather than the 350 SB. Wink



I also readily admit that my approach for the vast majority of Pantera owners is much too radical for them.

The camshafts I pick are sure to turn your nice bottle of Merlot wine to vinegar with that first turn of the key. Rattle your brain so that surely you will need that bottle of migraine headache relief?

Even worse, the power I want will surely crinkle the sheet metal in your roof, put a crick in your neck and I am much more at home on the stage with AC/DC turning the amplifiers up over 11...IF THAT IS POSSIBLE? No Verdi for me.

Did I disqualify myself enough here yet? That's all you get on one cup of coffee on a quiet Sunday morning...quiet until I go start the car and wake up the neighborhood? Big Grin



That's how we rock and roll here? Consider yourself lucky I don't live next door? It might even make you sell your Pantera and buy something civil like a Tesla? Your mileage may vary? Big Grin
Last edited by panteradoug
I resurrected this thread because I was looking for a really good cam for my Clevo. But. It isn't in a Pantera. Mine is in a street/strip 68 Mustang. Now after reading all of this I like a couple things I read.
I like where George said "Low rpm performance and drivability of 351C engines diminishes quickly as overlap exceeds 62° due to their large valves; this is especially true of engines equipped with factory 4V heads. Street performance, low rpm pep, drivability and manifold vacuum all improve as overlap decreases. The exhaust valve opening (EVO) should occur at 80° BBDC or earlier to extend the engine’s upper rpm performance and to allow the engine to perform better in conjunction with muffled exhaust systems. The intake valve closing (IVC) should occur at about 70° ABDC to avoid reversion and preserve dynamic compression. Staying within those 3 parameters requires camshafts having lobe centerline separation (i.e. LSA) no less than 112°. Camshafts having a 10° difference between intake duration and exhaust duration can be timed to center the overlap event on top dead center while meeting the criteria of the two valve events (EVO & IVC). Centering the overlap event on top dead center aids low rpm performance and drivability because piston motion is almost nil from 30° BTDC to 30° ATDC (known as the “dwell” period); piston motion provides the energy making intake and exhaust gases flow where we don’t want them to. "


I also like what PanteraDoug was saying about a rumpidy rump cam making good hp for drag racing , or something to that effect.

What I would like to know if there a cam design that will satisfy both opinions.
One with the 80 degree exhaust opening 70 intake closing, 110 or 112 LSA and enough
Duration and overlap like 60-61 degrees to have a rumpidy idle yet still have some low end performance And top end pull?

I know George doesn't like lopey idles and I know a drag race cam does have a very lopey idle. Is there a middle ground cam that George can say is borderline Ok for his criteria and borderline Ok for PanteraDoug's criteria?

I guess I want it all. Is that possible? A good middle ground cam?

My car is probably more toward strip than street but still sees fair bit of street. Let's say 60% strip and 40% street to put some numbers on things.

If it matters it is a wide ratio AOD, 3000 stall lock up converter with 4.11 gears.
The lock up keeps the rpm down for street driving and freeway cruising. The stall helps it out of the hole. It weighs about 3250 without me in it.

Danford1
Last edited by danford1
Look at this one. It could use more lift but the timing that you asked for is there and it would work with the automatic transmission.

This is the hydraulic version. Personally I like the solid lifters.

A .580 or so lift would be a compromise between the .600 you need for full intake flow and loosing some torque right off of idle.

This one is .530 lift. It is a hot street grind. Probably idles right around 950 rpm or so?

http://www.compcams.com/Compan...s.aspx?csid=843&sb=2

The answer is that you may need to try several cams to get close to what you are looking for.

One of the points George made about this kind of cam way back at the beginning of these camshaft discussions is that they are tough to live with in an everyday use car, stuck in traffic and all of that.

I do agree 100% to that. A true high performance car IS NOT what I want to drive everyday, everywhere. Never was. Never will be.

For a solid lifter cam, I would use this one. Same overlap, more lift at .570.

http://www.compcams.com/Compan...s.aspx?csid=860&sb=2

With a solid lifter cam you get the full advertised lift. With hydraulic, because of the hydraulic lifters, you only get a percentage of the advertised lift.


The main thought in George's "Roller CJ" cam was inclusive of the stock "Pantera" exhaust system and the nature of the car, I think, and it is a VERY GOOD CONSIDERATION. No question.

I think it would more aptly be titled "Pantera Roller CJ cam". That would entirely be complimentary to it?


I did run this engine in a Mustang. It was in my '68 GT350 for about 10 years. It liked 2" x 36" long primaries, 3-1/2" collectors. That right there should tell you something about the nature of what the engine wanted to be. Even 428's like 1-3/4" primaries. Wink

It definitely likes gears. The more the better. It liked 4.33's the best.
bottom line Dan is No you can't have it all,

that's what the OHC 4-cam w/phasers is all about, basically they can change camshaft LSA on the fly. the new motors can see 'cam swap' improvements with only a plug-in tuner

here's a couple reads on vintage stuff if you have a minute, not sure if either of these were ever offered for 351C, too early?
http://speedtalk.com/forum/viewtopic.php?f=1&t=1545
http://www.jalopyjournal.com/f...-the-cam-a-go.84631/
Dodge Viper variable LSA camshaft
http://www.thehemi.com/news.php?id=20080211-1

Rhodes type leakdown lifters are another early/poor man's variable cam timing, but the opposite way of what you're looking for in that they smooth the idle & rage the top end

==========================

Come On Dan! give the Cobra-Pence cam a shot!

I was gonna say Group Buy but I want a flat tappet
quote:
Originally posted by Rocky:
quote:
My cams are not "all done" by 6000 rpm, not in the least. Ask Chuck (Rocky), his engine has one installed. It wants to rev, doesn't it Chuck?


No - my motor is not "all done" by 6000 rpm - it wants to keep going!

That's why I am asking the question - how far can I (safely) let it go?

Rocky


It's your engine, a motor is an electrical rotary device, let it ride! Then you will find out.

Let us know what you find out, ok? I'm very interested where it blows up. I need to fill that data into my spreadsheet. Wink
I don't believe anyone will give you a guarantee like that Rocky

I've always heard 'don't race it if you can't replace it'

George, is this still your preferred lobe choice for the mechanical flat tappet Cobra-Pence cam?


Grinder: Bullet Cams
Intake: Lobe #F285/355
Exhaust: Lobe #F295/358
-----------------------------
285°/295° advertised duration
290° average duration
Exhaust valve opening = 85° BBDC
Intake valve opening = 30° BTDC
60° overlap
Exhaust valve closing = 30° ATDC
Intake valve closing = 75° ABDC
------------------------------
250°/260° duration @ 0.050
0.585"/0.590" net valve lift (0.029" lash)
115° lobe separation angle (camshaft degrees)
Intake lobe mathematic centerline = 112.5° ATDC
Exhaust lobe mathematic centerline = 117.5° BTDC
quote:
Let us know what you find out, ok? I'm very interested where it blows up. I need to fill that data into my spreadsheet.


I'm sneaking up on it.

I'll let you know if something bad happens, although any RPM tabulation I post is probably going to be exaggerated (to emphasize my cam selection and engine building abilities), so you can plan to knock 1000 RPM off whatever number I post up....

I hope you are waiting for a while for this info for your spreadsheet....
quote:

Originally posted by Danford1:

... I guess I want it all. Is that possible? A good middle ground cam ...



I knew you preferred a "tough" sounding idle, which is why I reiterated what my cams do. You can't have it all, but close. As we dial in more overlap to give you the idle you want, the low rpm performance diminishes. There's no avoiding that. But I may find some lobes that allow me to put a cam together that walks that line somewhere where in the middle. I have a couple of ideas. Answer these questions for me, I'll look at the lobes I have to choose from, I'll get back in a couple of days:

(1) Is your engine equipped with iron 4V heads? If not, which heads?
(2) At what rpm would you prefer the peak horsepower occurring?

quote:

Originally posted by PanteraDoug:

... do not interpret what I say as arguing against them ...



No problems Doug. I have dealt with specifying custom ground cams for people since the 1980s. I can be very clear what the cams I pen do, and let people decide if those cams perform how they want. It doesn't hurt my feelings if they don't. There are other people on the internet who will provide info that meets their needs. I understand there are differing preferences. I also admit there is some peak horsepower to be lost, I disagree that it is significant for the varying applications. This is based on experience. Street performance engines, sports car engines, road race engines require low rpm performance ... and a wide power band ... to accelerate out of corners, or pull gears to higher rpm when passing. Drag race engines do not have to do any of that. Drag racing cars can leave the line at 4000 rpm or higher, they normally wear drag slicks or street legal versions. They work best with a narrow, steep torque curve. Street cars don't leave the line at 4000 rpm unless the owner wants to attract the cops, or burn-out the clutch prematurely. Street cars are equipped with high performance street tires which are less sticky than drag slicks. Burning rubber is fun and dramatic, but when the car is burning rubber it isn't moving forward as fast as it could be, and so in terms of a street car or sports car a "peaky" torque curve isn't necessarily conducive for achieving the fastest acceleration, controllable traction is better. In my experience. A 351C with 4V heads accelerates hard enough as it is.

quote:

Originally posted by Rocky:

... how far can I (safely) let it go ...



With the car parked in the driveway, in neural, slowly rev it higher and higher, at increasing 100 rpm intervals. If the engine makes it to 7000 rpm without issue, I would call it good enough and not explore further. I have done exactly that in the past.

quote:

Originally posted by 4V & Proud:

... is this still your preferred lobe choice for the mechanical flat tappet Cobra-Pence cam ...



Well, I'm not sure. There are two specs. That's an old 7000 rpm street spec. There's also a 7000 rpm street/track spec.

I would slightly change the lobe centerlines of the spec you posted to:

112° ATDC intake lobe mathematic centerline
117° BTDC exhaust lobe mathematic centerline

Guys who wanted street-ability plus competitive road racing performance are currently using this street/track spec, and they love it:

Ford 351 Cleveland solid flat tappet street & road race cam
Grinder: Bullet Cams
Lobes:
Intake #FF280/371 (Asymmetric)
Exhaust #F292/373 (Asymmetric)
110° ATDC intake lobe mathematic centerline
115° BTDC exhaust lobe mathematic centerline


280°/292° advertised duration (286° average)
251°/263° duration at 0.050"


Indicators
29°/29° major intensity (advertised duration – duration at 0.050)
Overlap at 0.050” = 32°
Lobe separation angle = 112.5°


0.371"/0.373" lobe lift
0.022”/0.019” lash
0.642”/0.645” theoretical valve lift (1.73:1 ratio)
0.620”/0.630” net valve lift [(lobe lift x 1.730) – lash]
0.609”/0.615” factual valve lift [(lobe lift x 1.70) – lash]


EVO = 81° BBDC
IVO = 30° BTDC
Overlap = 61°
EVC = 31° ATDC
IVC = 70° ABDC

Note to Doug, take a look at this cam. Modern lobes are sometimes wonderful. This is a race cam and shall wear like a race cam, but outside of wear it does it all. This cam gives the 351C a power band like a carbureted V12 Ferrari. The engine is a little soft on the bottom, but it builds steam as rpms rise, and it revs to the moon. Peak BHP is around 7000 rpm. The engine still has the mid-range rush in acceleration that makes the 351C so dominant. But the spec is not too different than others I have posted, just the cam lobes. The charging Rhino has never charged any harder.
Last edited by George P
Thanks George.
I have 4V iron heads. Two sets. I have closed chambers and open chambers. Both have home "porting" where I smoothed things out and cone shaped the valve bosses. I use a Holley Strip Dominator intake, 750 DP carb, Hooker 1 7/8" primary long tubes with 3 1/2" collectors 3" exhaust for the street open headers at the strip.

Rpm peak? I guess that would be up to you. I can shift accordingly. My car goes through the traps at about 6300 - 6400 rpm around 115 mph. Currently I shift at about 7000 rpm.

I have a couple converts also. A 3000 stall lock up Edge and a 3500 non lock Lentech.

I hope this info helps. If not, let me know what you want to know.

I'm looking for a solid roller cam as I have the expensive Crower HIPPO
Lifters already. Also if you have spring specs let me know I have more than my spare
Of springs to pick from.

Thank you
Danford1
Last edited by George P
Here's the first cam spec. I'm using the same lobes as mentioned previously, I couldn't find any better. There's a very limited amount of solid roller street lobes to choose from. Look the spec over, as you'll see I've just moved things around a bit. There's more overlap, and the overlap event is not quite centered on top dead center, the intake valve is opening sooner, exposing the intake system to more piston motion, making the engine lope at idle as you prefer. Or at least that's the plan.

Application: Ford 351 Cleveland solid roller tappet street cam
Grinder: Comp Cams
Lobes:
High Energy Street Roller
Intake #1474
Exhaust #1476
107° ATDC intake lobe mathematic centerline
114° BTDC exhaust lobe mathematic centerline


280°/288° advertised duration (284° average)
236°/244° duration at 0.050"


0.3666"/0.3666" lobe lift
0.020”/0.020” lash
0.634”/0.634” theoretical valve lift (1.73:1 ratio)
0.614”/0.614” net valve lift [(lobe lift x 1.730) – lash]
0.603”/0.603” factual valve lift [(lobe lift x 1.70) – lash]


Indicators
44°/44° intensity (advertised duration – duration at 0.050)
35° major intensity claimed by Comp Cams
Overlap at 0.050” = 19°
Lobe separation angle = 110.5°


EVO = 78° BBDC
IVO = 33° BTDC
Overlap = 63°
EVC = 30° ATDC
IVC = 67° ABDC
Here's my other idea. This single pattern cam raises peak horsepower by about 500 rpm, into the range of 6500 rpm. There's more overlap than the first one, the intake valve opens even earlier than the first one, it will lope harder than the first one. The torque curve has been moved 500 rpm higher, the low rpm performance is declining as is intake manifold vacuum.

Application: Ford 351 Cleveland solid roller tappet street cam
Grinder: Comp Cams
Lobes:
High Energy Street Roller
Intake #1476
Exhaust #1476 (same)
106° ATDC intake lobe mathematic centerline
116° BTDC exhaust lobe mathematic centerline


288°/288° advertised duration
244°/244° duration at 0.050"


0.3666"/0.3666" lobe lift
0.020”/0.020” lash
0.634”/0.634” theoretical valve lift (1.73:1 ratio)
0.614”/0.614” net valve lift [(lobe lift x 1.730) – lash]
0.603”/0.603” factual valve lift [(lobe lift x 1.70) – lash]


Indicators
44°/44° intensity (advertised duration – duration at 0.050)
35° major intensity claimed by Comp Cams
Overlap at 0.050” = 22°
Lobe separation angle = 111°


EVO = 80° BBDC
IVO = 38° BTDC
Overlap = 66°
EVC = 28° ATDC
IVC = 70° ABDC
George. The second cam (single pattern) is very very close to the Comp Magnum 288R cam. Part number 32-771-9. I had that cam for a couple years. It run great. I shifted it at 7200 rpm
And ran a best of 11.54. The distributor gear portion of the cam got chewed up so I couldn't use it anymore. I replaced it with a custom cam that would be the equivalent to a magnum 280R, but Comp never made one. It has 236/236 duration and I think .609 lift but don't remember exactly. I believe a 112 LSA. At the time I also took off the CC heads and put on my OC heads and smaller 2400 stall converter. The car ran a best of 12.59. I'm not home right now so I can't look at the cam card. I like the cam as it lets me chug along in 4th gear with a locked converter about 1600 rpm without bucking and kicking. It has an burble at idle that I wish was a bit lopier.

Your first cam sounds like it might be between the Comp 288r and my current cam.

I'll have to wait a week or so until I get home to check.

I think I like the first cam. It would go into the car with 4v CC heads and a 3000 stall lock up converter. 11.9x would be perfect.

Danford1
Last edited by danford1
Lobe #1474 has 280° advertised duration.
Ground with 112° LSA and 106° ATDC ICL, the exhaust centerline = 118° BTDC
The valve events look like this:

EVO = 78° BBDC
IVO = 34° BTDC
Overlap = 56°
EVC = 22° ATDC
IVC = 66° ABDC

I've seen your comments on Blizz's forum about valve events and cam design for the 302, you're getting it. I love it when that happens. Figuring out the valve event data is a matter of being able to figure out the lobe centers, and knowing the advertised duration. I could probably crank-out some math equations, interested?
quote:

Originally posted by Danford1:

... couldn't I just re-degree it so my events are closer to 80 and 70 ...



Yes but the events are going to be about 3 degrees short on each end. Doesn't hurt to try it and see what happens. A good exhaust system really helps make up for the exhaust valve opening later than ideal. The early closing of the intake valve simply boosts dynamic compression.

My time is limited at the moment due to the Concorso Italiano occurring next week. I'll work on the equations as time permits and reply here when I'm done; if not before the Concorso then afterwards.
The events we are truly interested in are the "seated" valve events. The point where the valves just lift-off the seats or just touch-down on the seats. In lieu of that information we use advertised duration, because its the best information we have, i.e. its closer to seated valve events than duration at 0.050. Duration at 0.050 has its uses too, but not when we are trying to define the characteristics of an engine's power band based on seated valve events.

You'll need 4 pieces of information, usually available
  • Advertised Intake Duration
  • Advertised Exhaust Duration
  • LSA
  • Intake Centerline

_________________________________________________________________________
Valve Events:

EVO = (Advertised Exhaust Duration ÷ 2) – (180 – Exhaust Center Line)

IVO = (Advertised Intake Duration ÷ 2) – Intake Center Line

Overlap = IVO + EVC
Overlap = Average Advertised Duration – (LSA x 2)

EVC = (Advertised Exhaust Duration ÷ 2) – Exhaust Center Line

IVC = (Advertised Intake Duration ÷ 2) – (180 – Intake Center Line)
___________________________________________________________________________
Other Terms:

Average Advertised Duration = (Advertised Intake Duration + Advertised Exhaust Duration) ÷ 2

LSA = (Intake Center Line + Exhaust Center Line) ÷ 2

Exhaust Center Line = (LSA x 2) – Intake Center Line

Intake Center Line = (LSA x 2) – Exhaust Center Line
____________________________________________________________________________

One other term I find useful to calculate from time to time is overall valve event duration which is the total duration in degrees of crankshaft rotation between the moment the exhaust valve begins to open and the moment the intake valve fully closes. Overall valve event duration must encompass at least 510° of crankshaft rotation to make it possible to open the exhaust valve at 80° BBDC and close the intake valve at 70° ABDC. There are two methods to calculate that figure:

Overall valve event duration = EVO + 360° + IVC
or
Overall valve event duration = (Advertised Intake Duration + Advertised Exhaust Duration) – Overlap
Last edited by George P
Thank you for the formulas. I printed them out.
I used them to figure the events listed on the 288R cam card. Everything worked out as listed.

If a cam has the events at advertised duration, can we figure out what the events are @ 0.050" lift?

That brings me to another question, why don't cam cards list both valve timing events, adv and @ 0.050 ?

Danford1

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