FE timing

[mr0077]

Like another thread on a 351W, I'm wondering what you FE guys are running and recommend for ignition timing curves. I have an MSD dist, mechanical advance-only. My dyno guy said it made best power at 38 degrees, so I kept fiddling around with it working on drivability, working backwards from 38 deg. Right now have it with 20 deg initial, 18 deg mech adv for a total of 38, all in by 2800. Feels good coming off idle, but sometimes cruising at about 2000 rpm I feel an occasional surge, like it has too much advance. Huh? With no vacuum advance, I'm surprised at that, but...and when I drop the initial timing back (16 or 18) it tends to bog a little more coming off the line. The motor has Edelbrock heads and intake, 780 Holley, 282/.571 solid cam, 10.5:1...
Anybody out there running different curves, and how do you like 'em, for best drivability and for best power? TIA

[chopper]

I'm using 10 degrees at idle (900 rpm) and 38 degrees total at 3200 rpm. This is with an MSD mechanical advance billet distributor.

[Trans-Am Jim]

I'm real close to Choppers settings. Mallory unilite (converted to magnetic breakerless), mech. advance.

She seems to be happy all-around - (i.e. - good drivability and power) - with 9 initial @1,000, 36 total, in @ 3,200.

I would definitely up the initial going for power, and quite possibly drop a couple of degrees for drivability (to limit run-on and promote a cleaner idle)

[Toivo]

could you expound on your comments regarding cleaning up the idle with lower advance?

I'm currently running 18 initial up to 34 degrees all in. We had it up to 36 where it crackled nicely but backed it down for street use.

Anyone tried 24-28 initial up to 38 all-in?...what a rush, if you can get it to catch.

Anyone wanting to explain timing and its consequences, I'd like to listen.

[Jeff Frigo]

The surge has nothing to do with the timing, its your carb. Could be many different things, Im not a carb. expert. Seems to me that 38 degrees total is too much. My strocked 427 (454) made the most power at 33 degrees total. This may be due to the porting that was done on the heads and intake. The more efficient an engine is, the less advance you need. I am also using Edelbrock heads and intake, 10.8 to compression, but a sligtly bigger cam.



Jeff

[Trans-Am Jim]

With dual quads and my cam (Lunati performance grind):

At 11 degrees initial, idle fuel screws adjusted according to Holley, and throttles completely closed, the car idled @ 1300

Leaning out the idle fuel to reduce rpms just resulted in a surging idle. Backing down the initial advance to 9 and setting the idle screws where they're supposed to be, allows me to crack the throttle a scosh, getting a real nice idle mixture, and an idle rpm of 950.

The car will idle all day at that with no stumble on acceleration. No load-up or stench because of a too-rich idle.

Jeff is right on about the breathing of highly reworked or aftermarket heads heads. I have the iron MRs that flow like crap.

[SCOBRAC]

Thanks guys.. I just got my MSD and was hoping I was not going to spend a day messing with it.. I think the consensus is 33-36 total.. by 3200 rpm.. Possibly 10-12 initial Lets see.. I think I will try the blue springs and blue stop bushing.. Just like those kids clothes where you match the tags..

[Joe Rutledge]

Jimbo was correct on the timing issue. FE's with original heads tended to like lots of total timing (around 38 degrees total). There usually was a significant power difference (less power) between lets say 34 degrees total and 38 degrees total. So you when setting your initial timing needs you have to keep in mind your total timing needs when having the distributor curved. Obviously, if you are going to cut it very close (37/38 total), you had better be damn sure the timing damper is properly marked/indexed. With stock type dampers, it was not that unusual that they were not.

This discussion assumes you have the proper octane for the compression you are running. Running higher compression than street gas allows and compensating for it by retarding the timing often results in less power than proper compression (for the street) with proper advance.

As Jimbo said, I think it is fair to assume that the modern aluminum heads from Dove, Edelbrock, and Shelby may change the total timing requirements somewhat based both on improved chamber design/plug location, and the material as well (However, they still are all "Wedge" head designs, with the chambers being very close to MR heads (except for the DOVE CJ based stuff). Hopefully, the head manufacturer can lend some insight on this subject.

Modern cam profiles may change some of this also?

[Cobrabill]

Aluminum headed 427 made the most HP on the Dyno when timing was at 44 degrees.

[bigmike]

T-A Jim;
Talk to me about that part "limiting Run-on"
BigMike

[Toivo]

Originally posted by Cobrabill
Aluminum headed 427 made the most HP on the Dyno when timing was at 44 degrees.

What kind of domes were under these heads?

When you need 40+ degrees of timing it usually means a sloppy flame-front, usually caused by monster domes in the way.

So, are you running domed pistons? Why else might you need 44 degrees of timing?

Thanks

[Trans-Am Jim]

Big Mike:

When backing into the garage, I usually just let the car idle for 20-30 seconds then turn off the ignition. With the 11 degree advance, I got some dieseling. Knocking it back to 9 sort of solved it. 'Course that only works if ya got your carb idle circuit set correctly.

I think sometimes ya have to make tradeoffs between power and driveability. On the street, top end HP is meaningless to me. Others feel differently and have to have the motor on the sharp edge all the time.

[CobraEd]

Run on has nothing to do with timing directly, only indirectly (see below). It is a function of dieseling (not to be confused with pre-ignition which is timing related). Deiseling is due to hot spots in the combustion chamber which ignite the fuel/air mixture like a spark plug and keep the engine running aftet the ignition is turned off. The source of this excessive combustion chamber heat in order is:

*Too hot a spark plug
*Lean mixture
*Retarded timing

So, richen up your idle circuit, switch to a colder heat range plug, and put your static timing to at least 10 degrees advance.

Ed

[SCOBRAC]

Well I finished my MSD install. Done.. (for now) I ended up as follows.. If I go more than 10 degrees initial I can't keep the idle below 1050 rpm.. but I find if I go more than 36 degrees total it falls off on the top end.. So I am at 10 degrees initial with 35 overall at 2200 rpm.. I started at 3200, (blue springs) then 2800 (blue/silver springs) and finally I used the lightest springs, (silver) without pinging through the rpm range.

Regards

[Cobrabill]

Toivo-no domes.Flat-top Arias'.Edelbrock heads with no chamber work.

Run-on:Make sure your accelerator pump arms aren't too tight.Reset mine to .10 and my run-on vanished.

[Toivo]

One of the advantages of DIS...complete control of timing across the RPM spectrum at the click of a mouse (or at least that idiot red finger-control in the middle of the keyboard). No springs, all-in by a certain point or even the need for a smooth curve.

Sorry, just happy. Nevermind me.

[Whaler]

Originally posted by SCOBRAC
Well I finished my MSD install. Done.. (for now) I ended up as follows.. If I go more than 10 degrees initial I can't keep the idle below 1050 rpm.. but I find if I go more than 36 degrees total it falls off on the top end.. So I am at 10 degrees initial with 35 overall at 2200 rpm.. I started at 3200, (blue springs) then 2800 (blue/silver springs) and finally I used the lightest springs, (silver) without pinging through the rpm range.

Regards

Mike which advance stop bushing did you use with this setup..MSD starts you off with the blue one in place..


I am trying to setup my distributor for when I start my engine for break in. Any advice on how to quickly get it set up

I was told 10-14 static/initial and no more than 30-34 deg. all advance in by 2500-3000 RPM ( George A. gave me that advice)

How do you go about setting the initial when flashing it up for breakin? On breakin this engine has to vary between 1500 and 2500 rpm for 20 to 30 minutes
.....Do I just ballpark it with a timing light for 10 deg. or so and worry about the MSD curve after cam break-in?

I would guess my priority is the cam breakin.

Any advice would be much appreciated. Out of the box the MSD dist has the biggest springs in it (silver heavy)and the blue bushing. With these springs its the slowest curve.

Last question..for later, what RPM should this idle at?
I am using the edelbrock RPM package( cam,heads,intake)

Tim

[Whaler]

An interesting read

http://members.aol.com/dvandrews/timing.htm

Tim

[Whaler]

As you can see I have asked this question once before and didn't get an answer so here it goes again.

Originally posted by SCOBRAC


Well I finished my MSD install. Done.. (for now) I ended up as follows.. If I go more than 10 degrees initial I can't keep the idle below 1050 rpm.. but I find if I go more than 36 degrees total it falls off on the top end.. So I am at 10 degrees initial with 35 overall at 2200 rpm.. I started at 3200, (blue springs) then 2800 (blue/silver springs) and finally I used the lightest springs, (silver) without pinging through the rpm range.

Regards

Hi guys farting around today with my MSD and may be flashing it up for break in tomorrow if all goes well.
Wondering what advance stop bushing you ended up using in the end.

You initially thought you could use the blue stop with the two blue springs and look where you ended up?

I have to find my MSD book that came with the billet dist. I am ideally going to plunk in what will stay in . Looking for about 10 initial and maybe 34 total all in by 3000. If I recall thats what George Gessford told me over the phone once.

Thanks
Tim

[rritchey]

I agree with cobrabill, it is unusual for an aluminum-headed FE to want so much timing. I built a stroker 427 (454) just 3 weeks ago and ran it in on a dyno, it made best power at only 26 degrees. It was a mild engine, a smaller street hydraulic cam, Arias flat tops, Edelbrock heads and intake. I have also built higher performance 427's (600 HP range) that made peak power at not much more than 30 degrees. The new Edelbrock heads seem to reduce the total timing on every motor I have used them on, because if I had put factory heads on these motors they would have wanted closer to 40 degrees. I'm not sure what it is about them, but the aluminum heads don't need the timing advance. If you are running aluminum heads and have your timing set in the 40's you probably have something unusual going on and are not getting your full potential. Just some thoughts.....