427 FE SO Total Ign. Timing
 

I'm wondering what most of you 427 FE guys are running for ignition timing?

I think my distributor is a MSD Duel Point that was converted over to a Petronix. It doesn't have a vacuum advance, just mechanical advance with adjustable stops.

When I got the car the (base) timing was *severely* advanced. I set it to spec (8*) and checked the total timing. With base at 8d, total is mid 20's. I set the total up to ~32d and base is looking like it's between 10 and 20 (15-ish).

I ran a quick search of this forum and find most are running between 36 and 38 total. I can adjust the stops so I get more advance allowing me to set my base back to spec, or there about.

I'm limited to "mountain" formula 91 octane Premium gas. As most know, hearing detonation or pre-ignition with loud pipes is pretty much impossible so I can't tell you for sure if it's pinging or not.

Right now, I'm just picking brains.


Thanks In Advance,

Phill Pollard - Co. Springs, CO
ERA #446

Timing
 

I run 18 int and 38 total in @2600 on my 428 w/mech dist...Iron heads
Jon

Here's my curve -- remember I have aluminum heads. The light silver and blue combo is tried and true. My all in timing is 35 degrees, so I use the silver bushing and that translates to around 10 at idle. The benefit of that is very easy cranking. Make sure your colored bushing and initial timing add up to what you want, then you can monkey with your springs. This, of course, assumes you have the MSD bushing and springs.

http://www.clubcobra.com/photopost/data/500/curve.jpg

Phill,

The reason you found it *severely* advanced, is because there is no vacuum advance. The factory spec may have been 8* but the vacuum would pull in another 18-20*.

If you set the initial down to 8* the only time that it will not be severely retarded is when it is at WOT. So people set the initial timing high, for a half ass compromise.

If all the engine is used for is racing, eliminating the vacuum advance is smart. One less variable to tune and fail. You never run at light throttle. You don't care about fuel mileage or emissions.

If you drive it on the road, with one exception, it is stupid to eliminate the vacuum advance. Without a computer, as in EFI, about the only way to get the right timing under most operating conditions is vacuum advance coupled with mechanical. The one exception is if the cam shaft is so radical that you just don't have enough vacuum to make it worth your while. In which case, you have an engine that really shouldn't be on the road.

Put a vacuum advance distributor in it and let someone who knows what they are doing tune or advise you. At least that is one opinion.

Others will argue and tell you what they are doing. You can get by with the compromise approach without vacuum advance. You will be wasting fuel at light loads and running hotter than needed. Ovoid WOT at low rpm, as you will have too much timing and could damage your engine.

PS
You need to know what your vacuum is at idle and buy the correct range vacuum canister. The vacuum must be pulled in solid at idle or the idle will hunt all over the place, because the timing and vacuum will be jerking each other off in a tail spin. Again this needs to be done correctly.

I have the 10 degree bushing from FBO Ignition, Distributor tuning and Carburetion Professionals, FBO Ignition systems, Ford Ignition, Mopar Ignition, Ford Distributors, Mopar Distributors, Ford distributor curving, Mopar distributor curving, HEI Ignition, MSD ignition tuning,, and I run at 27 initial 37 total. I haven't seen (or heard) any signs of detonation on the plugs or pistons.

The more I think about it, the more I think I'd like to have a vacuum-like curve, and more programmability. I'm thinking of adding an MSD 6AL-2 Programmable and a MAP sensor so I can get those benefits, or maybe a CBPerformance box.

A lot depends on your engine and cam profile. I have an aggressive cam and aluminum racing heads with a Holley double pumper. We tried 36 degrees of total advance at 3,000 rpms, but the engine just roars with 38 degrees of total advance. If you are running on 91 octane I would not suggest going to 38 degrees. I am running 93 octane and that is the minimum for that much advance.

I do not run vacuum advance on my distributor. I have the MSD 6 AL with adjustable rev limiter. With the aggressive cam that I have it probably would not make enough vacuum. I do not have any problems at low rpms. You need to go back to the build sheet and see what you have. A trained ear will know where the advance should be when you are setting your timing. Make sure you find a good mechanic who understands carbureted engines without computers, they should be able to dial it in correctly.

Not sure mine will be representative of what you need as I have mild compression and iron heads. Keith Craft recommended 40 deg total timing but I'm running 38 total with 16 of it initial timing. I'm running an original dual point 427 distributor.

Without vacuum advance you need to be able to run fairly high initial timing to get any sort of reasonable idle for the street and to prevent it from running hot. If you are at about 15deg +/- initial and 32 with full centrifugal advance, you have a distributor that is pretty aggressive. To get up to 38 degrees you need 20 to 21 degrees initial. As long as you have a strong starter that will turn it over that could be OK.

I'm running an MSD system and timing is 18/35. Starts easily, no detectable detonation. I do get run-on so got in the habit of giving it a bit of clutch when turning it off.

I have used both boxes, and the CB Black box is the winner in EVERY area.
Great value for money.
I will not run a mechanical/vacuum only distributor on it's own from now on.

Kevin - my old Corvette used to run on when trying to shut it down. The problem I had was the cam was big enough and idle vacuum so low that my primary throttle plate was resting above the idle slots to achieve a 850 - 900 rpm idle - which was also making it unresponsive to idle mixture adjustments. I finally did the old Hot Rodders trick of drilling a hole in each idle plate butterfly to allow a bit more air to pass and that allowed me to close the primary plate to where it rested at mid-point on the idle fuel slot at a reasonable idle speed. I was able to get normal idle mixture adjustment response after this also.

Instead of drilling the holes I probably could have opened the secondary throttle plates slightly with the adjustment screw on the underside - to allow a bit more air to pass at idle and also allow closing the primary plate to where it was in the proper position with the idle fuel slots.

This adjustment and keeping the idle speed below 900 rpm pretty much took care of my run on.

Thanks Dan, I'll look into that.

I run 18/36 on a 482 BBF. With the good gas I have gone to 38. Dyno was done at 36 and 38. 36 was actually better. With my cam, I have very little vacuum to work with.