C14UNK

Can someone help with some base refence points for the timing on my 400 in my 69 442.
It has had big cam, HEI ignition, carb and headers on it.
I’ve read and tried the technique of 36 degrees advance at 3500rpm and working back but it dieseled when switched off.
At 8 degrees idle it appears to ping under load and Is heavy on fuel.
Any advice on advance and rpms to start would be appreciated.
im in the uk too so running on 95 RON fuel.

oldcutlass

Your octane rating is equivalent to our 91. Which HEI are you using? Has the mech adv been modified? Is it pinging with or without vacuum advance hooked up? Is it pinging at light cruise or wide open throttle? What is your idle rpm?

C14UNK

There’s no vac advance on the carb on it. When I checked the timing I’m getting about 21 degrees mechanical advance from the dizzy. I’m checking it at around 1000 rpm but with comp cams 274h cam in it, it may need to go to around 1100 I believe.

oldcutlass

Whats causing the dieseling is too high of an rpm at idle. Your octane level is probably not high enough for your engine. Try hooking your vacuum advance (its probably set for 16*) to manifold vacuum and drop your idle to around 8-900 rpms. That will put your initial timing to 8+16=24* and help your idle with the cam. Is there any gas with a higher octane there?

C14UNK

We can get 98 RON super unleaded. There’s no vac advance to connect up on this set up so just initial timing plus mechanical advance. Do you think I should try 850 rpm idle and up to 16 degree initial advance?

oldcutlass

Not until you get some good fuel in it. Which distributor are you using, make and model?

C14UNK

I’m not entirely sure, it was on the car when I brought it.
It looks like it giving about 21 degrees advance when weights fully engaged. I did the 36 degrees at 3500 rpm and worked it back to idle. Do you think I should have 36 degrees at lower rpm?

oldcutlass

I read that in your previous posts. I'm asking which distributor, make and model to see what you are looking at. I like the advance to be in at around 2800 rpm.

C14UNK

ill have to do some investigation and let you know, I’ve not had the car long and trying to get it running a bit better.
it diesels after switching it off and is also heavy on fuel.
Let me take a look tomorrow and get back to you
thanks for taking the time to talk.

cutlassefi

Thats too early for this combination in my experience. And I believe there’s about a 6 point difference in their RON vs our R+M/2.

oldcutlass

98 ron is equal to our 93/4 R+M/2.