Total timing advance

[MFPvette80]

I've just adjusted the timing on my 1980 (350 SB) to around 10 degrees BTDC at idle with vac adv. off and plugged. This is higher than the factory setting of 6 degrees, but with the RV cam it seems to run better with no pinging. I remember reading somewhere that the "total" advance for a SBC should be about 36 degrees BTDC. With the vac adv. on and running at 3000 RPM I'm seeing around 50 Degrees BTDC. Should I set the timing at total (high speed) or at idle? Do I have a bigger problem in my HEI distributor?

 

[wishuwerehere82]

Mike,

That's about right. Mechanical advance is 36 max plus the Vacuum advance will come out to about 50-53 degrees.
I see you got the new balancer on. Hot enough for you today?

 

[JohnZ]

"Total timing" is only initial plus centrifugal, measured with the vacuum advance disconnected and plugged - that's when you should see around 36 degrees advance at high rpm when it stops advancing. The vacuum advance adds to that at idle and at steady cruise speed; if you had a timing light rigged up so you could see the balancer at cruise, you'd see 50-52 degrees advance.

 

[magoo]

Pete and John Z. are right on as usual. I think they will agree that based on what you said if the car keeps improving with more advance, you might even try 12 degrees initial as long as it doesn't ping. I'm running a 9.5 to 1 comp. ratio 350 with a comp cams 268 extreme energy cam in my 62. It likes 16 initial without pinging.
Well there is 2 more cents.

thanks,

Mike