BBC timing question.

[bulletholez]

Hey guys. every day i’m slowly improving the car, but i’m having little luck with the timing. car has an 8.0:1 truck 454, 800cfm edelbrock thunder AVS mechanical secondary carb with a summit vacuum advance HEI unit. running almost stock everything minus cam and valve springs, cam is a .502/.501 and 218/228 at .050, 114 LSA. motor seems to love 18-20 degrees at idle, which causes insanely hard hot starts, and at full advance puts it to 40-42 degrees which seems like quite a bit. i’m new to the whole carb/dist thing as i’ve been an efi guy forever but wanted to learn. running the dist off of ported vacuum right now, would switching to manifold vacuum, re-timing base to 12-14 and limiting vacuum advance to 4-6 degrees or so get me going in the right direction? sorry if this doesn’t make sense i’m new to this stuff haha. thanks!

 

[New Vintage USA]

Had a similar issue on my 302DZ. Went with lighter advance springs on the dizzy and helped out tremendously. That thing loved lots of timing, and spinning way up high.

 

[pontiacgp]

when you set your base timing do you have the vacuum advance unplugged and the port capped?. As far as using ported I'm not sure on the Edelbrock carb but you always have a small amount on the ported vacuum but that can be increase to almost manifold vacuum depending on how far the throttle blades are open at idle. The other thing is if you are running headers the starter/solenoid may be too heat soaked and causing what seems to be a hard start.

 

[bulletholez]

when you set your base timing do you have the vacuum advance unplugged and the port capped?. As far as using ported I'm not sure on the Edelbrock carb but you always have a small amount on the ported vacuum but that can be increase to almost manifold vacuum depending on how far the throttle blades are open at idle. The other thing is if you are running headers the starter/solenoid may be too heat soaked and causing what seems to be a hard start.

base timing is set with vacuum advance unplugged and capped. running headers but there is a good amount of of space between them and the starter, high torque mini.

new vintage good call i’ll have to order up the advance spring kit see if that’s causing my issues. having some flooring it off idle just straight bogging and dying also, got the carb used going to rebuild that first before i get crazy completely blaming timing.

 

[pontiacgp]

You can try the lighter springs but they won't affect anything when starting the car and with the lightest springs they won't give you any advance until your over 1500 revs, at 2000 rpm you'll have about 10° mechanical advance.

 

[fleming442]

You can also wire a toggle switch into the distributor feed, so you can delay the spark until it's turning over. Being an Olds guy, I have a hard time believing 18 degrees is causing a hard start, especially with 8:1 compression. My 468 is 11:1, locked at 35, and only gives a little bit of drag on the first revolution.....