Stock '74L engine intake swap

I have been running the Carter AFB 625cfm with electric choke for 20 years and I like it. I am running it on top of the aluminum Edlebrock Performer manifold. I do recall buying the jet kit to tune it.

EGR plate under the carb?

did you pull it off, inspect it for clog / burnthrough & replace the gasket under it?

BTW, that gasket under the EGR is not just a common carb gasket, it needs to be exhaust rated

also verify that the vacuum & mechanical advance mechanisms in the distributor are functioning properly, and that all vacuum lines are sound

It was a good move to disable the EGR. A poorly operating EGR valve can cause all sorts of engine performance issues.

A word of caution however, you can purchase a bunch of parts chasing what you think is a carburetor problem, when in fact its an ignition problem, a vacuum leak, a gasket leak, etc.

If you plan to service the ignition beyond a spark plug change do that first, and test drive the car prior to buying a carb or manifold. Besides the usual distributor cap, rotor, and ignition wires also check the centrifugal advance mechanism, perhaps spritz the pivots with a bit of WD40 to soften up any hardened grease. If the pivots look worn, that may be the cause of your stumble. Also remember, the long ignition wire between the coil & the distributor cap is always the first one to wear out because it fires 4 times per engine revolution, whereas the others fire only once every other revolution.

I would also suggest eliminating all the vacuum hoses and connect the vacuum advance directly to either ported vacuum or manifold vacuum. Which vacuum source you use is dependent upon how the ignition has been set-up, check out the picture below. If the motor is equipped with a Ford distributor leave the vacuum retard connection open to atmosphere, don't connect it to anything.

Whether or not the carburetor is the issue, I do recommend you eventually replace the carb & manifold, if not now, sometime down the road. Replacing the manifold will allow you to toss all of the EGR equipment! The iron Ford manifold & the Edelbrock performer can both be purchased used on eBay for about the same price. The Ford manifold has 4 holes sized for a carb of about 600 to 650 cfm. To use a larger carb requires machining the holes larger or using a 4 hole spacer between the carb & manifold.

The Autolite/Motorcraft 4300A and 4300D carburetors were factory calibrated lean for emissions, especially the 4300D version. Recalibrating the carbs for something close to 14.7:1 air-fuel ratio will improve the motors drivability, and increase horsepower by 10 to 25 bhp. But finding someone who can tune those carburetors in this day and age is difficult to do. It is easy to warp the 4300A/4300D air horn (top casting) and once it is warped the fuel bowl will leak fuel dangerously. The 4300D is also known to cause the engine to stumble during high G-force cornering. For day in and day out driving and even moderate street-type performance it is just fine, but it is not suitable for the high G-forces encountered during high speed cornering on performance tires or on race tires. Properly chosen aftermarket carburetors offer better fuel bowl designs and castings that don’t warp, they have features making them easier to tune, and they offer features such as annular booster venturis that enhance performance. These are some of the reasons people choose to replace the Autolite/Motorcraft 4300A and 4300D carburetors rather than refurbish and re-use them.

In regards to the selection of a replacement carburetor, you'll receive a myriad of recommendations. As a basic spec I would recommend a carb with "street" calibration, an electric choke and annular booster venturis. If you read down sticky #3 of this forum you'll find a bunch of carb recommendations that meet that spec.

Sticky #3

The Edelbrock carb you mentioned does not have the annular booster venturis, but it does have some nice features; for instance its easy to tune in the car, and there are no gaskets below the fuel level. Some guys like that carb. I'm not going to be adamant about your carb choice, because the bottom line is any well calibrated carburetor shall perform well.

The 4300A was rated at about 630 cfm, a carb that size is fine for daily transportation purposes, but it will choke the 351C, especially the 4V version. The motor will flatten out at higher rpm and lose its eagerness to rev. It will also lower the rpm at which peak horsepower occurs. Ford used a carburetor of that size on the M code version of the 351C 4V specifically for the purpose of limiting the horsepower. The 4300D Motorcraft carb you'll be replacing is about 750 cfm. I would suggest the 750 cfm Summit Racing carb will provide the most bang for the buck, and serve as an equivalent to the 4300D carb. Like the Edelbrock carb, the Summit Racing carb has no gaskets below the fuel level, and it can be tuned in the car. The Summit Racing carb also has annular booster venturis which make a larger carburetor perform like a smaller carburetor at low engine speeds, similar to the manner in which the small primary bores of a spread bore carburetor like the 4300D improve low rpm performance.

I've always used 750/780 cfm Holley 4150 style carbs on my Cleveland powered vehicles. Guys will argue & stress over the size of the carburetor, but the most important aspect of any carburetor is not its size but how well it has been calibrated to suit the parameters of your Pantera's motor. A 351C 4V likes a bigger carb than a SBC or SBF, but if you decide to use a smaller carb its not the end of the world.

Good luck with the Pantera, keep us informed how the search for the cause of the stumble is coming along.

Back in early 2013, I had an annoying “sneeze” – a backfire through the carburetor. This always occurred in the same conditions – engine at low RPMs, transmission in 3rd gear, under acceleration.

My mentor, advisor and good buddy was convinced that this “sneeze” was an electrical, rather than a carburetion problem, based on the work we had done on the carburetor and distributor (as described in the aforementioned article).

I dug into the archives of the past, and I found this tidbit of information, recorded in an exchange between George Holley and Henry Ford. This was recorded during discussions in Detroit, Michigan, as George Holley was working with Henry Ford to integrate the “new-fangled” Holley Model NH carburetor in Ford’s then-new Model T horseless carriage.

(HF) “George – This carburetor is not adjusted correctly!”

(GH) “Henry – I am telling you for the last time: 90% of Carburetor Problems are Electrical!” (Ref 1)

In light of the confirmation of this revelation (which by now is common knowledge among the Pantera / Ford High Performance community), you might want to look at the issue at the electrical level as George suggested.

Maybe, maybe not!

Reference 1: Conversation between Henry Ford and George Holley, Ford Motor Company, Detroit Michigan, recorded by Thomas Edison, on an “Edison Cylinder Gramophone” on 12 February, 1908.

I had an intermittent problem last summer,
with all kinds of strange issues when driving - stalling, jerky ride, backfires etc...
It seemed carb related but I got a tip to check the ignition.

I had the Duraspark II ignition then, printed a schematic from this forum, measured ballast resistor, primary and secondary resistance in the coil etc. Evertything checked out fine.

A mechanic had a look, he found the fuel pump was semi-faulty and under dimensioned. Enter new fuel pump in better location.

Car ran better, but sometimes those bad behaviours came back.

Then one day she wouldn´t start at all. Did all kinds of testing to no avail... Then, for some reason I decided to check the ballast resistor again, just for the hell of it, I guess, and voila - meter showed overload, meaning no contact. First I thought it was burnt, disconnected it, but then it was ok (about 1.3 ohm)

Stupid poor contact problem... which in turn, most likely, eventually fried the Duraspark module. Scott at SACC was kind enough to send me his old Duraspark system, and yes, installed that and everything then worked fine again. (But now I have installed the EIS form PE)

So, gentlemen, check your ballast resistors

/Martin

Wow! Thanks all.. Let's see, I did revolve the egr plate, cleaned and bead blasted before I installed with new gasket. Point(s) very well taken about electrical/distributor issues. I have not yet removed the firewall/bulkhead so my distributor inspection was limited to trying to stand on my head in the engine compartment when I had the carb off. I was able to verify that the mechanical advance was moving freely and that there were no points but by then the blood was rushing to my head and I had to get out...vac advance was verified with a hand vac pump and it is connected directly to the carb.I have not verified timing either. The reason I continue to suspect the carb is that it seems that the condition is improved when the choke is still slightly on which is why I richened the idle screws up but now they are about 3 1/2 turns out which seems excessive. Hooked up a vac gauge and engine draws a decent steady vacuum.
I know this rather long winded but my original plan for the car was to strip the top end down,install some closed chamber alum heads to bump the c.r. And install a bit of a cam with a performer and street demon. But then I started reading posts about the connecting rod bolt/nut issue and concluded that it may not be prudent to work the original 40 year old bottom end too much. Sooo now my plan is to make this stocker a nice driver for now and then when time and money permits, build a complete new motor. I know this sounds blasphemous to the originality types but I would keep the original number matching motor with it's 35 feet of vacuum hose so the originality would not be lost.
Upon further review, I am now thinking that I am leaning toward a Performer ipo the '70 cast iron intake. First, I could use it later as long as the new motor had 4v heads..I would want the new engine combo to fit under the stock cover. Second,the alum intake would be easier to install because it wouldn't be as heavy. One last stock engine question: I had read that these smog era Clevelands have the cam timing retarded with a different timing chain crank gear. Is that true? And if so does the performance improvemment justify the effort to change it?
Thanks again,Steve

depending upon the cam that's in the engine, some engines got the smog crankshaft sprocket AND altered valve event timing

generally a few degrees can help 'across the board' but to reverse the possible 8* of retard can run afoul of certain valve timing events that were not retarded, causuing them to occur too early & possibly hurting performance that way

the early crankshaft sprocket is PN C8SE-6306-A and uses a 13/32" wide 5 plate chain

D3AE-6306-A, D5AE-6306-A and D7TE-6306-A are all retarded crankshaft sprockets, probably all 1/2" wide 4 plate chains

it's not clear whether the 351C-4V ever used any of these retarded sprockets or one that's not listed here?

also, you can't take for granted that an aftermarket timing set has its' Zero key slot in the ideological Zero position, they don't. the only way to know what change you've effected by installing a new timing set is to check it using cam degreeing methods

3 different manufacture timing sets will have 3 different Zeros, and the +/- key slots should be verified to cause the changes that they claim they will, again using degreeing methods

quote:

Originally posted by SteveD:

... I had read that these smog era Clevelands have the cam timing retarded with a different timing chain crank gear. Is that true? And if so does the performance improvemment justify the effort to change it? ...

Good question Steve.

Yes the camshaft of the 1972 - 1974 Cobra Jet motors was retarded 4°. As far as I know the cams were ground 4°retarded, they had different part numbers than the 1970 - 1971 Cobra Jet cam. D1ZZ-6250-A verses D2ZZ-6250-B.

I know what you're thinking ... there was no Cobra Jet in 1970. True, but the cam became available over the counter from the Ford parts department sometime in 1970.

Its a good idea to replace the camshaft timing set, because the original timing set had plastic teeth on the cam gear, and those plastic teeth are 40 years old! i.e. they're brittle. Its no fun when the timing chain slips on its sprocket. Ever seen a set of 16 bent push rods? So pick up a timing set with steel gears, having a 9 keyway crankshaft sprocket. Swap the timing set while the intake manifold is off, this will allow you to check the timing with a degree wheel & dial indicator. This way you can make sure you've set the timing to 1970 - 1971 spec, regardless if it was ground retarded or retarded via the timing gears.

The 1970 - 1971 Cobra Jet camshaft spec:

Specs based on advertised duration
270°/290° intake/exhaust duration
Exhaust valve opening = 82° BBDC
Intake valve opening = 18° BTDC
46° overlap
Exhaust valve closing = 28° ATDC
Intake valve closing = 72° ABDC
-------------------------------------------
Specs based on duration @ 0.050
205°/220° intake/exhaust duration
Exhaust valve opening = 47° BBDC
Exhaust valve closing = 7° BTDC
-21° overlap
Intake valve opening = 14° ATDC
Intake valve closing = 40° ABDC
-------------------------------------------
Lobe separation angle = 117°
Int lobe mathematic centerline = 117° ATDC
Ex lobe mathematic centerline = 117° BTDC

Advancing the cam 4° will not make a drastic improvement. Every improvement you make to de-smog the motor shall be incremental. Advancing the cam to 1970 - 1971 spec raises the dynamic compression ratio, it improves low rpm power, it extends high rpm performance and it better avoids low rpm reversion. The dynamic compression shall raise from 5.86 (or less due to chain stretch) to 6.08. The carburetor with richer jetting will net you another nice improvement in both power and drivability.

Another step in un-smogging the motor and pepping it up significantly would be a set of 1970 quench chamber heads, D0AE casting numbers. Tease Tease The pistons in your Pantera's motor have 4cc dishes in them, and the combustion chambers of the 1970 heads are 3cc smaller than the combustion chambers of the 1971 heads. Therefore the 1970 heads brings your Pantera's motor pretty close to having 1971 spec compression. Replacing heads makes for a good time to replace the OEM valves which fail from time to time. And the worn-out OEM valve springs. Perhaps for another day.

Replacing the 4300D carb with a 750 cfm carb having better jetting, eliminating the EGR system, advancing the cam, raising the compression and installing a good exhaust system will raise the horsepower to about 320 bhp to 330 bhp. But the increase in the motor's "pep" will feel more like a gain of 100 horsepower! Blocking the intake manifold's exhaust heat passage is worth another 20+ horsepower too.

If you're going to replace the timing set ... and if its in the budget ... here's some ideas for other parts that are in that same area.

(1) The OEM crankshaft damper is unbonded, and at its age the rubber has hardened. The ring no longer has an adequately tight grip on the hub. I haven't seen an OEM 351C damper in quite a while in which the ring hasn't started to walk off the hub or spin on the hub. This is not a good thing. The ring is made of cast iron, and under the right conditions, banging around while the engine is running, it can turn into a little hand grenade. The OEM damper was never heavy enough any way. So a new aftermarket damper that is heavier, and in which the ring is bonded to the hub, is a wise investment.

(2) If the engine is equipped with the OEM fuel pump, the rubber diaphragm in that pump is going to fail and start leaking gasoline dangerously close to the exhaust system one of these days.

(3) SACC restorations has a wonderful small diameter coolant pump pulley that speeds up the pump and improves cooling system performance.

(4) Speaking about the coolant pump, is your Pantera's motor equipped with the original pump? The rubber pump shaft seal is 40 years old. If there's any play or wobble in the pump's shaft it should be replaced.


I know stuff like this snowballs, and it can become over whelming. I'm mainly bouncing ideas at you. I'm not adamant about anything, other than that you get the Pantera running well and reliably, and that you enjoy the heck out of driving it. You live in an area of the state that is blessed with a bunch of fun back-roads for driving.

Thank You George! This is just the type of advice I need. If I change the waterpump, is there one brand that works better than the others. My car has been modified with the alum radiator and twin sucker fans and silicone hoses. Also, as I make these changes, should I be concerned about the stock connecting rod bolts/nuts? Car has about 35k miles on it. And lastly, to grow the snowball further, if the intake is off,timing cover removed,valve covers off,etc, would there be any benefit in a cam change to say the '70-'71 spec? Still thinking about a nice running stocker at this point...and last,last, came across a fellow who has a set of closed chamber 4v iron heads for sale. Are they worth pursuing or do they push the C.R. too high?
Thanks again,Steve

quote:

Blocking the intake manifold's exhaust heat passage is worth another 20+ horsepower too.

George - I am putting together my newbuild 351c, and intrigued by this statement.

Would this apply to a Edelbrock Performer manifold, running a well-tuned Holley 735 CFM 4150 (Vacuum Secondary)? How is it accomplished? I have one of those turkey pan gasket sets about to go on.

Regards -

Rocky

George,

And I am curious of the balancer change out. is it okay to change the balance without having the rotating assembly balanced? Mine is stock and looks okay visuallly. But I'd be willing to replace it if I do not have to disassemble the motor to have it balanced. Can you recommend a replacement balancer?

Steve

quote:

Originally posted by SteveD:

... If I change the waterpump, is there one brand that works better than the others ... should I be concerned about the stock connecting rod bolts/nuts ... would there be any benefit in a cam change to say the '70-'71 spec ... closed chamber 4v iron heads for sale. Are they worth pursuing or do they push the C.R. too high ...

I'd recommend the Flow Kooler pump. It raises the coolant flow at low rpm. Lots of guys have given testimony to improved cooling during stop and go driving using that pump. The stock rod nuts are a liability, as are the stock valves. But unless the oil pan is coming off there's nothing you can do about them. Your Pantera's motor has the good cam in it, the Cobra Jet cam. It just needs to be advanced 4 to 8 degrees. Your Pantera's motor has dished pistons. Combined with quench chamber heads the static compression shall become 9.1:1 to 9.4:1, depending upon which heads you acquire. I recommend the 1970 heads, casting D0AE, with 3cc smaller combustion chambers. That is not too much compression. It will easily run on 91/92 octane pump gas, and it may run on 89 octane pump gas.

I like the idea of a nice running "stocker" by the way. That was my original concept back in the 1970s, the formula I mentioned in my previous post is basically just that.

quote:

Originally posted by Rocky:

Would this apply to a Edelbrock Performer manifold, running a well-tuned Holley 735 CFM 4150 (Vacuum Secondary)? How is it accomplished? I have one of those turkey pan gasket sets about to go on.

Yes it applies to the Edelbrock Performer manifold too. Living where you do, the engine doesn't need an exhaust heated manifold. Two ways to accomplish it. (1) Have the exhaust heat ports welded up to block them, or (2) slip some flat pieces of tin between the manifold and non-turkey pan type manifold gaskets to block the exhaust heat passages. I wouldn't trust the strips of tin to seal well with the turkey pan style gasket. If the exhaust heat is blocked, you don't necessarily need the turkey pan gasket anyway.

The air inhaled by a Pantera's motor is already pre-heated fairly well by the engine compartment, which runs hotter than the engine compartment of a typical front engine car. Heating the intake manifold with exhaust heat seems redundant to me in a Pantera.

quote:

Originally posted by T.Solo:

... is it okay to change the balancer without having the rotating assembly balanced? Mine is stock and looks okay visually. ... Can you recommend a replacement balancer ...

Yes its OK to replace the damper without having the reciprocating assembly re-balanced. I recommend the Romac #0203 damper. Its a quality manufactured piece, heavy, and fully bonded. Its a good equivalent to the original Boss 351 damper. Even though the OEM damper "looks" OK, believe me it isn't. Its a liability, a problem waiting to bite you in the arse. It most likely has "spun" on the hub, so that the balance weight isn't where it should be, and the reciprocating assembly is most likely operating "unbalanced" anyway. This means the timing marks are off as well.

The rubber in the OEM 351C damper is 40 years old, its been heat cycled a bunch of times over the last 40 years. And remember, that's a 1970s era rubber formulation. So the rubber is very hard, and it does not grip the ring or hub as tightly as it should. The rubber is not bonded to the ring or hub in any way, it relies purely on "stiction" to keep the damper assembly together. The Boss 351 is the only 351C that was equipped with a bonded damper. In my experience, damper rings seem to start moving on unbonded dampers after about 20 years. For instance, I saw 351C dampers with rings that had moved as far back as the 1990s. My sons are fans of Fox body Mustangs (late 1980s), and we began seeing damper ring problems with them about 10 years ago.

Another great post George; thanks. So here's a brief summary of my plan. My target is a self imposed redline for the motor of 5000 rpm. I am going to use a stock doae ford iron intake with a 625 cfm afb. Will change the timing gear set, water pump, harmonic balancer and plug off the exhaust crossover per your suggestions. Also considering Hall's GTS headers and mufflers. Given this combo, what is your best guess as to the performance difference between my '74 heads and the doae heads? I was looking at the Mr gasket 5836 intake set. It appears that the exhaust crossover is blocked; would it still be best to cover the passage with metal as well?
Thanks again,Steve

If the gasket blocks the manifold exhaust heat passage, that should be enough, I see no need to install a piece of tin.

With installation of a new carb with richer jetting, advancing the cam, blocking the exhaust heat from the intake manifold, and installation of the GTS exhaust system, the engine is going to feel stronger to you, not a drastic difference, but one that you can feel and enjoy. I must emphasize that the carb tuning shall need to be dialed in to get maximum benefit from the carb change.

If on top of that you change the heads the low rpm combustion chamber turbulence improves a bit due to the quench chamber design of the heads, and the compression increases from 8:1 (what it is now) to 9.4:1. That would add quite a bit of snap to the engine's response, the impression of feeling stronger would double.

The only changes I could recommend beyond those things would be dialing in the ignition timing, raising the compression a bit more via milling the heads and/or flat top pistons, better mufflers for the GTS exhaust system, a 750 cfm carb and the Blue Thunder intake manifold. Then you'll become a high rpm junky and want stiffer valve springs and stiffer push rods. Maybe the "505" camshaft ... there goes that snow ball again. Now you're talking about a real honest to goodness 1960s muscle car engine, 370 horsepower. That's the engine Ford could have built if the social/political/economic conditions had been different.

Ford's 1960 "Super Interceptor" V8 produced 360 horsepower from 352 cubic inches with a small 540 cfm single four barrel carburetor, 10.6:1 compression, large port heads, cast iron shorty headers and a solid lifter cam. You might find it interesting this motor was an "R-Code" motor, the same engine code given to the 1971 Boss 351. It could accelerate a 4160 pound Ford Starliner from zero to sixty in 7 seconds! That was impressively fast in 1960.

Thanks again George. You have me sold. I'm going to take my time and shop for some heads.(know of any available in our part of the world?) I'm also feeling much better about my bottom end. I had read some posts that led me to believe that the only way to fix the con rod issue was to replace the bolts and nuts but then I found your post about dropping the pan just replacing the nuts with the arp 300-8371. Looks like a worthwhile addition to the snowball. But then, I must ask,what about the oil pump?..Last question for now. As I shop for the DOAE heads, are there any problem areas I should look out for? Maybe I'll be lucky enough to find a set with new valves but probably not. Any issues with cracking between the intake and exhaust seats like the sb chev? What should I expect to pay for good heads that need to be rebuilt? What springs should I use for the stock cam,(and have upgrade potential for a future snowball)?
Good news is that my car is drive able now and the longer I drive it in it's current state, the more I'll appreciate the changes.
Thanks again!

If you plan to drive your Pantera "vigorously" ... then when you replace the con-rod nuts, please install one of the good oil pans at the same time. It is the most important part of the lubrication system.

Without tappet bore bushings I would advise the high volume oil pump, or the standard oil pump with a 1/8" to 3/16" shim (washer) between the pump spring and the cotter pin that retains the spring. The shim raises the pressure in which the pressure control valve is fully closed from 50 psi to about 60 psi. But be cautious. If your Pantera's motor has worn bearings and/or stuck piston rings, increasing oil volume will lead to an increase in oil consumption.

No problems to look for when shopping for heads. The 351C ain't no SBC!

Beware of the guys who want to gouge you on the shipping charges. You can ship a pair of heads anywhere in the country for $80 or less. 351C parts are drying up in some areas of the US, people living in those areas may think their 351C parts are worth more than people living in areas where the parts are still available. I've paid $400 to $500 for the last few sets of heads I've purchased, which included the price of shipping. Of course, if they're rebuilt with good valves and bronze valve guides, they're a bargain at $1000. But you have to stop and consider, why are they being sold after putting that much effort into them? Good valves are just about any valve other than the OEM Ford valves. The only aftermarket valves I've heard about failing have been Ferrea valves. By mentioning that I'm stepping on quite a few toes, because a lot of people use them. I like Manley valves, because the valves have been reliable for 4 decades AND because the folks at Manley are pleasant to do business with. If you would like to eventually be able to rev the motor above 6000 rpm, then you may want to pay attention to the weight of the valves and valve spring retainers. In other words, use light weight intake valves and titanium spring retainers on the intake valves. With a hydraulic valve train, the upper rpm limit may be due to valve float, or it may be due to hydraulic tappet bleed-down. You can't use unlimited spring force to raise the rpm limit, its best to use a combination of lightweight valve train and increased spring force.

Crane’s #99839 valve spring are the springs I recommend for flat tappet applications.
The specs are:
*121 lbs. seated pressure
*354 lbs. /inch spring rate
*0.660" maximum lift
*1.80" installed height (0.020” less than the stock spring)

More details are available in sticky #3 of this forum. Please, if you replace the springs, install stiffer push rods at the same time. And spec the push rods to restrict oil flow to the valve train too.

Thanks George, I now have a plan.
Steve