ok this is going to be a long thread so be prepared. 91 305 carb(switched fromt tbi. i have an edel performer intake, edel 1406 carb, brand new HEI dizzy(vaccuum and mechanical advance) with new cap and rotor. New autolite plats and wires, new stock fuel pump with a BG AFPR. Car ran great after the swap for 4 months but now Im having electrical problems( I think). I kept frying my ignition module and coils. Felt like the car was running off 2 cylinders at idle and would bog down when u gave it gas. Now ive got it where it will rev up after sputtering for like 3 seconds.(had a grounding issue on the coil) Seemed to have fixed the electrical problem but I noticed that cylinders 4 and 6 arent getting spark to the wires but I have spark at the cap. replaced the wires and still no spark. The spark seems kinda weak too like a dark red color instead of the blue. Anyways ran a compression test and wasnt happy with the results so I have a mild crane cam with lifters, new rods, double roller timing chain and cover, forgot the casting but 1985 tpi heads with a valve job and z28 springs for the cam. I guess my question is since i did the compression check its leaning more towards the heads, the head gasket, or the cam wiped some lobes. Does it sound like rebuilding the complete top end would fix this problem or should I look elsewhere? I cant find any shorts under the hood or dashand am running out of ideas. I just dont think rebuilding the top end would fix my weak spark issue but im no expert so I'm asking first. And I am getting 12 volts to the coil while running. Or is there a better way to test this because I have no clue. Sorry for the long thread but I'm lost on this one. Thanks for reading

Dustin

 

How do your cap and rotor look?

How many PSI did you get when did the compression test?
Did you run the compression test hot or cold?
How many cylinders did you check?

Rebuilding the top end seems drastic. I think more troubleshooting will pay off.

 

my cap and rotor are brand new, and i had to run the compression check cold because the car wasnt wanting to run. highest reading i got was 165 and the lowest was 110. All others hovered in the 140-145 range. Only reason I wanted to rebuild the top end is because I have all the parts already from a future plan and I am out of ideas. Ive been trouble shooting for 2 months now any more suggestions?

 

anyone out there have any suggestions? Im going to do this build tommorow unless I can find another problem first. We have reset timing TDC 5 times,made sure the firing order is correct, and tried 3 different types of plugs. 4 ignition modules, 3 coils, 2 cap and rotors, and 2 distributors. All there seems well. Im just out of ideas!