Technical SBC timing question

Hey gang! Im working on a friends car that has a 350 with HEI dist. I dont know what cam is in it. Vac advance is hooked to ported. I set total advance to 33 degrees, thats where it seemes to like it best. Everything seems to run great, throttle response is nice and snappy, starts at a bump of the key, etc.. my concern is that base timing is now at 4 degrees retarded. Is this normal for a later small block with HEI? Should I switch to manifold vac to get more advance at idle, or is such a low initial timing ok as long as everything else is happy?

 

switching to manifold vac will give you more advance, which you need at idle. Try it and it will be better. To really dial it in, you have to play with the advance weight/spring and the vacuum canister but you should be able to get it running pretty well just by switching to manifold vac.

 

It will be a lot happier using manifold vacuum..... set your initial at about 8-10 degrees without the vacuum hooked up.

 

Don't set the initial that high if it truly is set at 33 degrees total right now (with the vacuum line disconnected and plugged) and 4 degrees retarded. If you do, you will be at around 45 degrees full advance.

First, disconnect the vacuum line and plug it. Then, set the distributor for full advance of no more than 36 degrees. I like 33 better. Then, check your idle advance at 7-750 rpm. See what if it is still showing a low value. If it is, then reconnect the line up to the manifold vacuum port. It should idle much better.

If you are not prepared to recurve the distributor and get into more of its inner workings, that's the best you can do with what you have.

 

make sure, as stated above, that the timing is chekced with the vac adance disconnected and plugged.

With a dial back light or marked damper you can set the total timing to 33-36 by reving the motor unil it stops advancing.

Most HEI dizzys have about 20-24 degreess mechancial in them stock. So 10 -12 initial would be a good way to start.
of course this is all based on the fact that you are starting at true TDC