I'm having a senior moment that I hope you guys can help me with.
I'm dialing my distributor on a '68 with a 325 hp 402 bbc and so far what I have is 12* base and 38* total in at 1800. I know this is too soon (going to 2 med. weight springs) but when should this start to happen for best results.
I'm aware each setup is different but looking for a baseline to start with, say initial 12*@ idle; 20*@1500; 30*@ 2000; 38*@ 2500.
This is a fairly stock engine except for the cam in at 224*@515 lift.
MSD suggests that you set your base timing as high as possible without stressing out the starter. Your centrifugal timing curve should start advancing just above idle and be "all in" by 2500-2800. Set total timing for 34-36 deg with vac advance disconnected and plugged. NEVER exceed 36 deg. My big block timing is set at 15 deg base with total at 36 deg and all in by 2600 rpm. I run 93 octane pump gas. Here is a good link to setting timing with links to other useful articles.
Thanks guys, I knew it was too much too soon, but just couldn't remember advance start and ramp rate .
Updated changes with two med. springs result in 16* base; advance starting in
at 900-1000 rpm with a slower ramp rate. Advance ramp stops aprox. 2800 rpm. with
total timing set in at 35*, with added 10* of vacuum adv. on top.
I believe stock early 4 pin HEI's are produced with 20* mechanical, so I'm glad I didn't have to mod. the slots.
I'm also running 93 octane pump