I need some head help

[l28ets13]

I got an 83 block with a 79 head on a l28e. The block and the head were in ok running condition at one point. The problem im having is that it is running like there is a fire late or early or maybe a miss. Now ive checked the timing, all sensors and plugs. I have spark and fuel so ive tracked it back to valve trouples. Ive also attempted to set the valves to factory specs and it seems to run worse. I also cant rev past 5 grand. Thanks to anyone who can help
Modified by l28ets13 at 10:36 AM 3/15/2010

[evildky]

I'd test the afm, might have a dead spot, next step would be a compression test to verify the condition of the engine

[l28ets13]

man ive got compression. Ive checked the afm ill check again though. The thing that gets me is its the same sensors and plugs off the 83 head i just swapped them over, and the 83 head ran good it was just warped and had super low compression. So i threw my 79 head on which i seen run

[evildky]

so you've had the head off....you sure you got the cam timing correct? not 180 out? on these engines the distributor is driven form the crank, assuming you didn't mess with the distributor position you might have flipped the cam, if you pulled the old head with the cam at tdc intake, and put the new one on tdc exhaust stroke

[l28ets13]

i did have a dead spot in my afm. and it runs ok, i have also just found a huge exaust leak i couldnt hear bc i was running open header. that im about to swap

[evildky]

exhaust leak around the exhaust port from cyliner #1? if so you might have to have the head and or the manifold surfaced by a machine shop

[l28ets13]

im pretty sure i put a crack on it somewere on it. i have two other manifolds so ill see what i can make work. This is also the reason i cant rev past 5 grand correct, lack of power. Thanks for the help

[evildky]

an exhaust leak should not limit your abulity to rev past 5k but a dead spot on the afm will

also it's not uncommon for these fuel pumps to fail under load, but in a free rev it wouldn't present

[l28ets13]

your right my fuel pump went out last year so replaced it, junk yard dont carry good electronics like an afm, were would be your best bet to get a good one

[evildky]

sumit sells a high flow MSD external pump for around $100, a bargain in my book

[l28ets13]

Thanks