What idle specs should I use for my new engine (Crane #529551 cam, TFS heads)?

Set the initial timing to 12. Then close down the idle screw to get 900-950 rpm. That is probably where it will wind up at idle wise? You need a vacuum gauge and you need to work those three eliments together. Idle set screw, initial advance, highest idle vacuum.

If it winds up at 16 degrees initial timing, so what? Don't fight that. The same with total timing. Don't expect that to be 32. That is for big blocks. Probably 34-36 is where it will run best. It isn't necessarily the total advance, it is the rate at which you get it. All in at 2,000 is way to fast. Whatever your cruise rpm is, is what you would like to have close to all in advance, so all in probably around 3,000 rpm.

Are you using an vacuum advance distributor?

You might be able to get it to idle down to 850rpm at idle. That would be better for the automatic transmission, if you can get it, otherwise the brakes won't hold the car well at idle. I'm not sure that you can though?

It's running on now after you shut it off because the throttle plate is open too much at idle. You need to close that down.

Tx Panteradoug,

I will try. Well it has new ALUMINIUM Heads with top chamber, so you think 16 deg at idle is what to go for?

The procedure I can do, incl. vacuum measures - have a device.

YES it is a stock vacuum advance distributor..

Tx for help

Matg

Aluminum heads mean nothing. The only change is that they make less horse power for the same static compression ratio.

All things given equal, they require the same specs as their iron counterparts.

Mine has aluminum heads and the engine likes 16 degrees initial. It doesn't respond to 34, 35, or 36 degrees.  Drag racers reduce total timing to raise top end speed through the lights.

I would immediately go to at least 14 degrees. Then you need to close the throttle to lower the rpm and to reduce or eliminate run on.

One of the things Ford needed to do in the mid-70s to reduce run on was to install a throttle solenoid. It enabled essentially a two position throttle. Don't be surprised if the thought occurs to you.

If you have to go that way, there is the Boss 302 solenoid and bracket for the Holley carb. When you switch the ignition off, the solenoid collapses and closes the throttle 100%.

If you wind up with low idle vacuum, i.e., under 14 inches, you may need to use one anyway because of your particular combination of cam, carb, intake, etc.

ok I see,
will get it to 14 deg advance at idle and play a bit with it, and check the vacuum. Let me  see how it behaves. So far engie has seen only 3200RPM as all brand new..

============ your text ======

It doesn't respond to 34, 35, or 36 degrees.

does mean what?  This is the full advance at may be 3500???

Tx again!

panteradoug posted:

… All things given equal, aluminum heads require the same specs as their iron counterparts ...

Agreed … but are all things equal in this situation?

True, SVO aluminum heads of the 1980s were cast with the same combustion chambers as the factory iron heads of the 1970s. All things are equal between those head castings in terms of combustion chamber dynamics.

But even old school Cleveland heads (iron or SVO aluminum) require more total ignition advance when used with pop-up pistons, compared to the total ignition advance they require with flat tops or dished pistons. The pop-up domes change the combustion chamber dynamics, and the speed of the pressure rise (flame travel) within the combustion chamber.

I am under the impression that TFS heads have revised "Yates/Weslake" style combustion chambers. What are also called "high swirl" combustion chambers. If so, might they not alter the combustion chamber dynamics, and thus require a change in total ignition advance compared to iron or SVO aluminum heads?

I have no experience with TFS heads, so that rhetorical question is all I have to offer on the subject of total ignition advance; however I would like to make a few observations regarding static ignition advance too:

If an engine "diesels" when you try to turn it off, that is a sign of insufficient static ignition advance. If a starter can't turn-over an engine when it is hot, that is a sign of excessive static ignition advance. Ideal static advance obviously falls between those two extremes.

One reason I recommend 16 to 18 degrees static advance with iron heads is because it improves low rpm torque, but it is not so excessive as to overwhelm the starter's ability to crank the engine when it is hot. Manifold vacuum usually doesn't increase much, if at all, above 18 degrees static.

But static ignition is only one of several concerns for setting the idle. A Holley carburetor is designed with an ideal setting for the butterfly opening at idle. The ideal setting exposes (opens) the "transfer slots" below the butterflies a specific amount.  Setting the primary and secondary butterflies at that specific opening is a second concern. The idle mixture screws are then adjusted to achieve the highest idle rpm … which will also correspond to the highest manifold vacuum.

I have more than once set the butterfly openings while rebuilding a Holley, then adjusted the idle mixture screws for 1-1/2 turns off their seats, bolted the carb to the manifold, started the engine, and had the engine idle perfectly at 700 rpm with no other adjustments.

However, if the idle rpm is too high when everything is optimized, which variable will you alter to lower the idle rpm? Folks argue that one. I would suggest decreasing static ignition advance, and increasing centrifugal advance.

Food for thought. I hope it helps.

Tx all

Well I try to get a decent STARTING POINT for STATIC  adv. for idle as the fist step.

=============from Geroge ===========

I am under the impression that TFS heads have revised "Yates/Weslake" style combustion chambers. What are also called "high swirl" combustion chambers. If so, might they not alter the combustion chamber dynamics, and thus require a change in total ignition advance compared to iron or SVO aluminum heads?

===========

these modern heads have a highly modified Trick Flow calls it "hight swirl", I was assuming LES advance to start with vs classical iron heads. The pistons are FLAT. I had the engine runnig,  set  per flash lamp to app 8 deg adv. and then moved the distributor back and forth at idle to chase for best rpm. May be it is too low now with app 5 deg.?  I will add the vaccuum gauge now. But hope for Modern Alu Heads info - if they differ from steel with doom pistons - but will try also the classic 16 deg..again.

SO please any knowledge/experience with Alu heads would be fine, otherwise I need to play with it for long, and as def the Carb needs adjustments other stuff might not be correct usign a non valid starting point - I understand from panteradoug it is a iterative provess to get it maxed..

The Holley I left untouched so far except the idle screw setting the end play of the gas thread, I need to learn much more for them. 

We're/I'm just trying to help you to get the idle right, dealing with the symptoms you described. Run on is caused by a throttle plate open too much at idle. (or a vacuum leak)

I saw no difference between 34, 35, 36 degrees total advance. I was not on an engine dyno. This isn't NASA here.

IF you are trying to optimize the engine to the ultimate degree like a race engine is then you need to put it on an engine dyno and play with everything there for optimization.

The Yates heads are designed as only one of the components of a system necessary to optimize a race 351. If that's what you want then you need to run the entire system including 106 or even more leaded race gas. Also it depends on which rules you are running under.

Remember originally the engines had to run under carb size restrictions of I think something like 450cfm. There is where tricky ports and high swirl become more important along with exhaust gas exit angle and velocity.

The cam profiles are also tailored to maximize those features as well but lets just say that typically the valve lifts used tend to be well over .700" lifts and designed for 8,000 something rpm's.

I'm not even sure that kind of an engine is compatible with the concept of a C6, C4 or FMX automatic transmission at all. At that point you need to seriously consider the specs on a Pence cam.  A manual trans car can get away with a lot more bad maners stemming from border line cam profiles then an automatic trans car can.

On a street engine with compromises necessary to make the engine streetable, seemingly any of the aluminum heads are worth 25 or 30 more horsepower over a worked iron 4v head. That's mainly due to a much better exhaust port configuration, not a better intake port AND their value wouldn't even begin to show until something like 5,000 rpm and up. Their biggest value is less weight and shinny appearance.

Sure you can, and some have put legitimate former race "Clevelands" on the street with 700 or 800 hp but they didn't stay like that for long and IF they are still in running condition needed to be seriously detuned from those configurations.

They can be run on the street but it doesn't make them good street engines.

If you can't get the thing to idle right with your set up and playing with the timing and carb idle setting then the cam is too radical. Let George write a cam profile for you.

As far as worrying about low idle vacuum, don't waste your time with it. Been there done that. Just install a vacuum pump. You really want 17 or 18 inches of vacuum for the brakes and I can't think of any off the shelf aftermarket cams that can deliver that. Perhaps a Pence profile can?

Loss of engine vacuum too at idle in addition to the cam timing can be from a bad vacuum diaphram in the power brake booster.

Just to recap what cam I use, so really NOT a race mashine..so should do decent idle (may be it is only the cumbersome trottle cable set up ..will take it off as well).

still  need advise on MODERN ALU HEADS with "high swirl".  Stat. Compression is 10.5

Any thoughts by modern Alu Head owners...Edelbrock, TFS, CHI etc...

TX

Matg

I certainly hope we shall hear feedback from members who have engines with TFS heads (that have been tuned on an engine dyno) and can share with you their ignition timing. Please.

If not I would personally start with 12° BTDC static advance, plus 12° centrifugal advance, for 24° total ignition advance.

Caution: Are you re-using the original crankshaft damper … or did you replace it with a new one? If you're re-using the original damper the timing marks are not viable. The positioning of the ring on the hub has almost certainly moved. I see them displaced on cars that are only 20 years old.

Regarding your Crane camshaft 

Crane Cams HR224 (part number 529551)
Hydraulic roller tappet camshaft

286°/294° duration at 0.004 (advertised)
224°/232° duration at 0.050
0.586/0.609 gross valve lift at 1.73:1 rocker ratio
LSA = 112°
Overlap = 66° (based upon advertised duration)
Intake lobe centerline ℄ = 111° ATDC
The lobes are asymmetric thus the intake lobe “max-lift” occurs at 107° ATDC

This is the "off the shelf" hydraulic roller camshaft I would recommend for a street engine using small port (2V-style) heads and the OEM 3.50" stoke crankshaft. Roller rocker arms are mandatory with this much lift, but they are also mandatory with the TFS heads. I would hope the valve springs provided by TFS have 150 lbs seated force, approximately 420 lbs/inch spring rate, and accommodate at least 0.610" maximum lift.

Although Crane advertises  the cam as having 286°/294° duration, that is measured at 0.004 tappet lift. That unfortunately does not represent valve motion. Tappets hydraulically lock at 0.005 lift, this is why 0.006 lift was chosen as the standard for advertised duration; 0.006 tappet lift best approximates true seated valve events. Here are my estimated specs based upon an "assumed" hydraulic intensity of 56°:

280°/288° estimated duration at 0.006
LSA = 112°
Overlap = 60° (based upon estimated duration)
Intake lobe centerline ℄ = 111° ATDC
______________________________________
Seated valve events (based upon estimated duration)
EVO = 77° BBDC
IVO = 29° BTDC
EVC = 31° ATDC
IVC = 71° ABDC

Since the intake valve is closing at 71° ABDC, not 74° as advertised, I suspect you have more dynamic compression than calculated. I would also caution you that 8.0:1 dynamic compression is a good limit in consideration for the limitations of the cylinder walls. I normally target 7.8:1 dynamic compression as this allows a margin for cylinder to cylinder variations in dimensions, ignition timing, and in fuel/air ratio, and for variability in gasoline performance.

Danke Geroge

will try the 12 deg.  idle static, but hope for some dyno data from a team member.

1) new ATI damper
2) 4.02 bore (only)
3) Ross pistons
4) rest of engine is stock,  ok double groove mains, oil channel mods etc.
5) using the TFS 195 heads (so the small heads 190 cc in port and 112 cc
    out port, 62 cc chamber) ... to overhaul the iron heads was too expensive
    in Germany

5) newly calculated compression with now 71 deg. IVC with assumed gasket thickness of 0.0625 (Fell pro standard) provides app 10.2 static and app 7.8 dyn.

=> could not identify any detonatons on Germyn 95 gas up to 3500.. 4000 rpm (max for new engine for now, with my current 6 deg advance)...worst case we have super+  with 98)..

Willkommen

A start is a start. I hope others with better information will reply.

Gruß

(Pence = Benz, my family arrived in the new world 1749, wir sind brüder)

I have Scott Cook heads and intake, he recommended starting with 28 degrees total timing. My last engine dyno run made more power at 24 degrees total and I run 15 degrees at idle but my camshaft and comp ratio is a lot higher than yours. My engine idled at 900 rpm, also run with 8 degrees vac advance unported.
I also get 8 - 10 inches of vacuum at idle but I have never had an issue with brakes. I have had my brake servo reconditioned and run EBC RedStuff pads on the stock large later style brakes and they work great.
You will never know what is really best for your engine configuration unless you have it correctly tuned on a dyno.

Your engine running on after shutting off at 1,000 rpm is not good. Have you checked the spark plugs that you are not getting uneven fuel distribution?Running correct spark plugs, extended tip, correct heat range?

BDUD Tx, this gives me an indication for the timing. Currently it is def too low, hence probably also the reason for "runnig after".

Spark plugs are new, well need to see if correct temp. rating - good point. As I have only less than 300 miles on the engine I will run it a bit longer to get a clearer view on the burn pattern/color.

The only way to know what the advance curve and total advance should be is to put the engine on an engine dyno.

As far as I know and have seen, 24 degrees total is for a big displacement engine like a Chevy 454 on current pump gas.

Ignition advance builds cylinder pressure. The camshaft that you are using is old school and is designed with "standard advance curves" as part of the choices selected in cam timing events.

No one is going to know everything about every possible combination out there.

What I know is limited to Ford Motorsport, TFS and Edelbrock aluminum heads and small blocks up to 357 cid.

Those are all going to use a "standard" ignition pattern.

If Scott Cook is running 24 degrees total advance on a 350 cubic inch engine then that is an animal that I have never seen nor even heard of. Not that I should be a determining factor in any decision.

I am told though, that even if one comes from Mars, which the talk is that I am, the laws of physics still apply?

There simply is no scientific way to determine any of this on your engine without spending the dollars to put it on an engine dyno and prove what numbers will work and what won't?

I can understand trying to be economical and resisting investing in your own scientific research. I've done that myself on more then one occasion so certainly I'm not angel? However personally I have found that even when I have mooched info, there always has seemed to be just one little bit of proprietary information significant to a completely successful solution that has been withheld that can or does but the kibosh on it. Likely intentionally?

That's what I know, granted limited, but I have to cut this short because I am being called by someone on Zenos to come home ASAP as there is radioactivity happening on Jupiter that is effecting the spring crops on the planet. It's my Brother-in-law so I'm not really in a big hurry. He's a helpless individual who resists doing anything for himself but that's a personal thing that I have with him anyway?

Incidentally. It's a nice place to visit. No need for medical marijuana there. There is a natural hallucinogen already in the atmosphere. It's very enlightening. Gives illusions of grandeur amongst other things.

Here is a thread about Chevy LS engines and even between different generations, what timing works best.  https://ls1tech.com/forums/adv...on-timing-101-a.html

Heck even the 2019 Ford engine now runs 12:1 compression with pump gas.

MATG, you really should ensure you do not get run-on. It could cause serious problems. 

Panteradoug tx for comment

well dyno I can try at a later stage when I am confident the engine is working nicley as a dyno over here is def 1000$. I will test, as this is what I read from your update.

Well a person from Mars  needs to go through sever learning curve as lots of paramters are different on mother earth and I want to excellerate the learning curve as much as possible, not going into any little hole - no more BLEEDING edge work - time is too precious

TX anyways

BDUD wooow what an article..TX for digging it out, req. some digestion

...my 67 C2 turbo fire corvette runs nicely..so will do the same for my top class CAT.

Danke

matg posted:

Panteradoug tx for comment

well dyno I can try at a later stage when I am confident the engine is working nicley as a dyno over here is def 1000$. I will test, as this is what I read from your update.

Well a person from Mars  needs to go through sever learning curve as lots of paramters are different on mother earth and I want to excellerate the learning curve as much as possible, not going into any little hole - no more BLEEDING edge work - time is too precious

TX anyways

 

Agreed. Mostly it's little things that I need to learn about Earth. Like human table manners. I need to be careful about the INS. This administration is cracking down.

short update, I am playing now with 10 deg static advance and 28 max

i got also hold of the TFS guys and they recommended 10...12 static and 28 to 32 max..

keep you posted..