To make a long story short. #8 cylinder is dead.It is getting fire,ch.plug,ck firing order,ck vacuum leaks,ck valves,ck timing,ch carb.It runs fine,but when put in gear[auto tran] and a/c on it may die or run rough.Took out on road it runs great. I am at a lost to what the problem is. please help.:mad:

I forgot this is a new engine,with less then 4hours running time. 6 gallons run throuht it.broke in with royal purple breakin oil .

Sounds like the added drag from ac may be bringing the idle rpm too low. There should be a solenoid available that will raise the engine rpm to compensate for the extra drag from ac. Hope this helps

did you do a compression test?

how does it run with out a/c on?

you may need to get to a shop that can scope/infared
exhaust to see if its running to lean!
you can turn up idle speed to see what happens
when a/c is on if it runs ok with a/c off

good luck j

Thanks Jay. I also forgot to mentioned compression on #8 is 180,also took reading on another cylinder. It reads 180 also.The #8 spark plug is white.All the others are black shutty.

Please post some more information on you're combo, dist, intake, carb, timing @ initial start up. On my way out right now, I'm sure many others will chime in to give some advice. Good luck! Did you notice a miss at idle or while driving the car?

Ken
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The engine is gmpp turnkey fast burn 385.Cylinder heads part#12464298 alum. fast burn head 62cc.Dist 93440806 gm HEI,The carb.is holley 750 cfm.80508-6.I also tryed another holley 750cfm 80508-1,wth same results.timing at start up set dist.to#1 and started when started move to smooth out idle.Then set at 12o btdc.

The engine is gmpp turnkey fast burn 385.Cylinder heads part#12464298 alum. fast burn head 62cc.Dist 93440806 gm HEI,The carb.is holley 750 cfm.80508-6.I also tryed another holley 750cfm 80508-1,wth same results.timing at start up set dist.to#1 and started when started move to smooth out idle.Then set at 12o btdc.
try advancing timing to 16btdc.this speed motor up a little.set timing with advance pluged off.12 is kinda low

Clayton I advance timing 16btdc,helped but #8 was still dead. I pulled all vacuum lines off back of manfold and pluged vacuum port.#8 cylinder started firing.but if i hook all lines up (brake booster,a/c vacuum,auto trans.) #8 is dead again.I am only getting 10 in.of vacuum at idle with trans. in gear.but when set timing to 16 it will idle in gear and a/c on but has a bad miss.I disconected the brake booster line,the a/c line and the trans vacuum line .#8 dead again.Far as i know this is a stock cam.It is the same cam as a zz4 350.

I know you mentioned good fire but......I know this a shot in the dark......Have you looked at night with engine running ,look for any sparks around #8 .Wondering about good fire to #8.Plug wires?

At this point i will anything .I try it tonight,thanks alan

Good Luck, I've heard of guys finding bad plug connections at night.

No spark around #8.or no plug wire glowing

#8 cylinder is firing(getting gas).Intake manifold vacuum leak was the problem.tighten the bolts.Search vacuum leaks found cylinder#4 not getting fuel. don't lift engine and transmission with carb. flange with a vortecs manifold.Thanks team camaro