[TransAm 474]

Good evening everyone, don't kill me here, but this is questions about the 383 Small Block Chevy that we just built and installed in our 1983 K10 4x4 Chevrolet, but as many of you know, my family and I own and build a lot of Pontiacs as well.

Everything on this 383 build is brand new, Carb to Pan, as well as the new 700R4 trans and Converter, so it has some bugs to get worked out, like most new builds often do. We just got the engine broken in, and ran great through the whole break-in process without a problem, so now today we have been trying our best to get the timing set and carb adjusted to run and idle it's best, but have ran into an issue I want to see if you Carb and Timing guru's can help us solve. We first set the timing with the Vacuum Advance unplugged, set it to 12° Initial. We then adjusted the Mixture Screws on the S.M.I.(Sean Murphy) 800 Q-Jet(#17084231) until we got the highest Idle Speed we could achieve, which ended up being right at 6 turns out from seated. We then adjusted the Curb Idle Screw to achieve an 800 RPM Idle. Here is where the problem begins .... when you plug the vacuum advance back up the the "ported" vacuum port, to the left(drivers side) of the Fuel Inlet, it throws a bunch of timing back in the engine, because, for some reason, that port seems to have vacuum on it, even at 800 RPM Idle? That of course, causes a bigger problem, because each time you place it into gear, the idle drops low enough that it loses the vacuum off the port, and drops the added timing from the vacuum can, causing it to drop so much RPM it stalls. We bought what was suppose to be a 2300 Stall 12" non-lockup converter for the 700R4 when we built it as well, but it seems to drag the engine down an awful lot when you put it into gear, like it doesn't have much slippage, which causes the problem to be even worse it seems. You can get it to run without stalling when you put it in gear, IF you leave the vacuum advance unhooked and readjust Idle RPM to 900 or so, but the engine still drops down to 600-620 RPM when it goes into gear. Can someone tell me what the cure for this problem is please? Why does that port have enough vacuum on it to pull the advance can, even down at 800 RPM? Other than this, it seems to be doing pretty well, so far atleast. Here is a little more about the combination


383 Cubic Inch

350 block
"Zero" Decked
4.030" Bore
3.750" stroke Eagle cast crank
5.700" Eagle SIR floating rods
Speed Pro Hypereutectic -12cc pistons
Total Seal Plasma Ductile rings
New Promaxx "Project X" 185cc aluminum cylinder heads
2.02/1.60 stainless valves, 115lb seat pressure/315lb Open
Felpro 1010 Head Gasket .039" thick
Quench Distance- .039"
Lunati VooDoo 10120704 Camshaft
281/289 Advertised Duration
233/241 Dur@.050"
.538"/.560" Lift(with 1.6 Rockers)
110° Lobe Separation
Camshaft Installed at 104° Intake Centerline
Compression- 10.16-1
Performer RPM Intake(Non-AirGap)
S.M.I #17084231 800cfm Q-jet calibrated for this engine
Factory GM HEI recurved by Cliff Ruggles
1 5/8" headers, dual 2 1/2" exhaust
700R4 Transmission with Transgo 2&3 kit, converted to non-lockup
Torco 12" 2300 Stall converter, non-lockup
4.10 Gears
1983 Chevrolet K10 4x4 truck

Any help would be greatly appreciated