I'm stumpped!!! Car was running fine before I changed the cap, rotor and plugs. Oh yeah, this is a 77 Vette. After changing that, it started popping through the exhaust. I thought the Q jet had seen it's days. I replaced the intake, and carb. Still popping. Changed the plugs, and wires. pulled each wire till I found #8 had no change after pulling wire while car was running. Did comp check, 140#. Did leak down, 1%. Changed cap again, same thing. adjusted valves, same thing.Shot timing again, and sounds retarded at 10*. Maybe timing chain went at the exact same time I'm changing the plugs?????? This has 94000 miles, HEI. I also shot the temps on the headers and #8 was 400* cooler, so it's not firing at the right time. Any thoughts? My head is sore already.

Thanks guys !!!

You may be 180 degrees out. Pull the 1st plug and crank the engine while your finger is in the plug hole. When it blows real hard...stop cranking and see where the rotor is and check the timming mark. You may need to turn the pully to bring it to TDC. Firing order is 18436572

Kev

check the plug wire or swap with a another cylinder and see if the problem moves to that cylinder. Also check the plug, did you drop this plug before putting it in? It could be bad if it dropped buy you or at the store, do the same thing and move the plug to different cylinder and see if the problem moves.

Being a 77 Vett 140# sounds about right for a smog era engine but you might want to check the others to see where your at. YOu could have a weak valve spring on the exhaust side or a sticky valve. I would be looking at what I changed out first, also look you cap over closely for cracks, maybe put on the old one to see if it works better.

Joe

Make sure that #8 plug gap is set right. Maybe it got hit against the head before you screwed it in and the ground electrode closed. It has to be something simple because you said the car was running fine before you changed the cap, rotor, and plugs. Make sure the wires aren't arcing to ground. Maybe when you pulled them off to change the plugs, #8 could have been damaged.

I checked for the 180 out and TDC with the finger feeling compression, and a screw driver after verifying the piston there. Swapped wires and plugs, and it's still #8. I was thinking sticky valve or broken spring too. spring was alright, and I was thinking leakdown and comp test ruled out the valve. I threw away the old cap, and even got a new one, same thing. I'm wondering if it's the dizzy. I even pulled the dizzy, moved the firing order over one tower, and it still popped. Only thing is, I didn't verifiy #8, I just assumed it was #8 because it was still popping on that side,and the next tower would be #4... still being on the even side!!!! I already switched it back to normal. I could pull the ing, system out of the other cars, but would have to wire the MSD box too. I think if I could find another HEI would be easier. Dang, and to think I just used to throw away those HEI's!!!
Thanks for the replys guys !!!

You do have the firing order correct right? 1-8-4-3-6-5-7-2 follow each wire just to make sure. take look at the reluctor in the dist under the rotor, it the star shaped part. see where it's at for firing #8 and make sure it's not cracked, chipped or broken.

I pulled the dizzy again and checked the reluctor, besides the common rust color, looked alright.

I found the problem. The new manifold I bought had a vacuum port which I hooked up the vacuum for the lights. Well there was a leaky line causing a lean condition, and the fitting was on the #8 runner. Oh those beers tasted great after finding that.

Thanks for all the help and replys!!!!

Congrats finding the problem. :beers: