Have been having a hell a hard time getting this sbc to idle slow enough to not lunge and hot start. Was told it was a zz4; but hardly has enough *** to be true. Although does have vette-like alum late 80s heads. I've been setting total time at 3000ish, and have been from 32*-36*. At 32 it seems lazy through the mid rpm. At 36... It idles much better, but bogs when plates open. Hot starts for both settings result in what feels like a fat condition or not enough vacuum to get going. Forces a longer cranking. Then a shot of gas to build up rpm.
I think your best bet would be to find tdc and start over om the timing' there are a lot of things it could be tom
Does the distributor have a working vacuum advance, connected to a source of full manifold vacuum? It can make a big improvement on a street driven engine. What kind of idle and cruising manifold vacuum does it pull? Auto or manual trans? What carb and intake?
Disconnect the vacuum advance if it has one. Then set tour initial timing around 12 degrees and shoot for total around 35. If it pings back off the total don't ping add a little more. You have to change the advance springs and weights or take it to local speed shop and have it curved. What do you mean by lunging? It could have more cam than converter in it.
Also you could put a wide band o2 on it and see what your afr is doing instead of stabbing In the dark w jetting.
You need to know how much timing your dist. has to really be able to set total timing correctly. Vacuum advance can add a little extra timing at idle to help but, doesn't affect overall performance that much because it drops out @ WOT/0 vacuum It may help with part throttle cruise MPG. Also , what carburetor do you have. The bog could be a failing accel. pump or, incorrect adjustment of the throttle plates.
First before you ever even start think about total timing get it tuned to run and idle. Do the basics and get them right then worry about fine tuning. Forget the high tech timing light, they are finicky and you have no way to even know if it is calibrated correctly and is accurate. Find RDC get your pointer set so that it properly reads TDC and buy a timing tape for your balancer. install it and then if you want to know total advance once you get it tuned so that it will run play with that. Now that you have got it to run and idle start playing with jest in the carb and whatever else your carb has to make it run and tip over properly. You cannot do all the fancy schmancy stuff until you first do the basics. Get it to run and idle then worry about the rest.
X 2 and you probably have a converter that is too tight. When your total timing is 36 deg. , what is the initial? If you use a vacuum gage to move the distributor at idle and find the highest reading/ smoothest idle, then you know how much centrifugal advance you can have to keep the 35 or 36 total. If you know the idle vacuum, you'll know if you have the correct power valve. ( if you have a holley).
wife's '50 Chevy PU has a ZZ4 crate motor, which included installed distributor. it runs best with vacuum disconnected. post some pics of your motor, carb, distributor, exhaust manifolds, etc. what kind of trans? have someone help you start the motor with throttle cable disconnected. get it to a true idle, then reset cable adjustment. next reset idle mixture screws.
Thanks for the replys... The inlaws are in town; so I haven't had much time. Vac source is full and disco-ed while making adj. Idle signal is fairly steady at 17" Lunging when put into 'drive', significant idle drop when in 'drive' 1406 carb, standard zz4 intake, turbo 350 MSD dizzy (adjustable) I have an afr... but I need to adapt it tothe new car. Accelerate pump...it could be, but Im leaning towards the timing; because it's a lengthy dropoff during acceleration. Throttle plates seem adjusted well. (Idle 'screw' adjustments, still result in vac signal changes). Thanks again... More to come when I can get some time
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