Mech Advance Only Distributor Timing

[Argess]

I am having a heck of a time getting my 428 to run right. Since I first built the engine in 1996, it has been more or less fine with the non-vacuum Mallory YL distributor set up as follows:

Initial 10 Deg BTDC
Max 38 Deg BTDC

However, those numbers turn out to be all wrong for two reasons:

1/ My harmonic balancer outer ring had slipped, and

2/ some of the dist advance was already used up at an 850 rpm idle (5 degrees).

Regardless, I didn't realize those things, so late last summer I thought I'd try playing with the timing. First I set the intial back to 6 Deg and the engine sounded very smooth and free rev'ing all the way up through the rpms. Next I made a big mistake and tried 15 Deg. Engine was fighting hard at higher rpms and "oh-no", I broke a piston. ...........so now.... I've just finished my re-build which includes a new damper which I have triple checked to make sure it reads TDC correctly.

OK....now I fire it up with intial set to 10 Deg. Engine gets hot very fast with a lot of heat from the headers and a bad bog when I give it gas. Bump the timing up to 16 (14-16 intial is recommended for my cam) and it's better, but still a bad bog when I give it gas (although a little better). So I look at what my old timing figures would be if I corrected for the slipped damper and already slightly advanced dist mechanism.

So I set it up for 28 intial and 38 max (baseed on those old figures of 6 deg intial and a 22 deg slipped damper). This gives me 23 @ zero rpm. Much better, bog is basically gone, maybe a tiny hiccup. Engine runs cool.

Still not the same as before I broke the piston. A person should always write things down. I thought my damper was out by 22 Deg, but I just rechecked and it's out by 29 Deg.

So to correct for that, I should be at 30 intial and 38 max.

This seems way to high and I'm nervous about doing it.

Here's a tidbit. I adjusted my engine for max vacumm and rpm at idle. Timing was at 38 Deg BTDC. I am certain once the throttle opens at 38, I will get detonation until the rpms build, so that's out.

I am of the theorey that if an engine needs a ton of advance with no-load, and very little advance under full load, then a vacuum advance would be a terrific help. And since I don't have one yet, my car benifits from timing somewhere in-between. I just havn't figured out where yet.

Keep in mind, I only use 1/3 to 1/2 throttle zipping up through the gears, so there will be a partial vacumm to keep the ignition advanced. It's not like a heavy car or truck with an automatic transmission where you can successfully floor it..

So for now, I am trying to get this mechanical dist dialed in until I can sort out which vacuum dist I should buy (that will fit for one thing).

ooh...this is a long post....not in keeping with the KISS principle. Sorry about that.....

OK, so what I would like to know is where everybody who has a mech advance only distributor, has their initial and max timing set. Please let me know.

ps: Next I'll be asking how you can tell if it pings or not when the sidepipes are deafening you...I think may stepping on it in 3rd gear at 1000 rpms will keep the exhaust noice down and let me hear any pinging from the engine.......