the timing was set according to the specs from the cc carb and its dist. anyone know if its different for a dist. with vac advance and non cc carb? also does anyone know how much to back out the screw on the vac advance? its for an lg4 btw.

 

if youre using a non cc carb and a vac advance dizzy, then you set the inital at about 12*.

 

i know very little about motors but trying to learn..i was told to set timing at like 1500 rpms and not at idle (1500 was a guestimate) and also i dont really know how to set the timing above 8 cause my timing marks only reads up to 8..so i dont really know what setting it to 12* or even when they say set it to somewhere in the 20's and 30's at 2-3000 rpms means

 

you can set it by ear. pop the hood and rev the engine to about 3k and listen for pinging. if you hear none advance the dizzy a lil and do it again. keep going until you hear pinging then back it down a tad and tighten the dizzy down.

it wont be as acurate as a timing gun, but itll work good enough.

 

basically you have an inital timing. thats how far the dizzy is advanced with no other things being taken into account. then you have a set of weights and springs under the cap that advance it some more as rpm increases and they max out around 3k. (you can get a weight and spring set to fine tune the advance curve) then theres the vacuum advance can that supplies a little extra vacuum at idle. once you mash the go pedal the vacuum drops off and that advance is no longer there and it relies on the inital plus the mechanical from the weights. usually SBC like around 32* total at 3k (inital of about 10-12* and a mechanical of around 20*).

fuel injected cars dont have the vacuum advance or the weights and springs since the computer can control the timing curve.

 

You should be be good if you stick with 8 degrees initial (which is the timing with the engine idling and the vacuum hose removed from the distributor vacuum advance canister). If you want to read total advance you need to get a timing tape from Jegs or somewhere and install it on your harmonic balancer, then bring the rpm (again with the vacuum hose off) until the timing stops advancing, should be around 34 degrees at 3000 rpm. You can also check total advance with the vacuum connected by bringing the rpm up to 3000 rpm or whatever rpm your mechanical advance stopped advancing and holding the rpm steady, I do not want to see anything above 48 degrees, personally. If you have too much total at a steady cruise you will probably notice slight surging or pinging when first accelerating.

 

ok thanks for the help guys.

 

8* inital for a non CC SBC will get it running, but not very well. itll be happier with more advance that than.

 

an old post, but have an answer for the question about the screw in the vacuum advance canister as far as how much and or reason to adjust it? it does something...also we havent messed with the idle mixture screws on carb (two at the base in front, require a 'special' tool) because tool we needed to adjust it was too big to fit in the hole where screws were located. so starting from scratch with timing if we set initial to 12* anyone got a guestimate on how many turns back from all the way tight on the idle screws? another issue we have (and we need to go over all vaccuum lines again still) is when you hit the throttle full bore (revving with throttle cable not driving) the car makes a hissing sound at its peak and engine wants to die..like a major vacuum leak. but revs and idles fine on anything below that. i dont have the all the lines from exhaust manifold closed up yet (air pump seized and we pulled out all the vac hoses from it) the only things hooked up are brake vac line, vac advance and one other thing that i cant think of cause its 240am.

 

stock type hei doesnt have an adjustable vac canister. they are available in some aftermarket units and as an aftermarket replacement peice. you turn it to adjust the amount of advancement you get at idle and cruising (there is no vacuum advance at WOT). its just a fine tuning thing.