Ok 1st time posting on this site. Have viewed others threads so many times to answer my questions and now i have one to ask.
I have a 1995 z28 with 114,000 mi. i recently blew a head gasket so i deco
ided to take on the task of replacing them myself. After removing the heads the machine shop showed me they had cracks. therefore i went ahead and ordered some edelbrock lt1 performer heads. I figured i have it down to the block i mine as well change as much as possible. So i ended up putting bbk shorty headers,downpipe and high flow cat ,new cap ,plugs and wires, coil, etc. Put it all back together car started right up on 1st turn. not bad for my 1st engine rebuild. After testing it around the block a few times decided to bring it on the highway. Backfires here and there while on throttle and when i get to about 45-50 when it shifts as soon as it hits low rpm it feels like its bucking, when i let off gas it stops. only does it at that speed any faster it goes away and same at low speeds. Not sure what is going on. figured i would need a tune anyways for more flow with the headers but this vibration is killing me feels like my motor is jumping around.. if anyone can shed some light on my problem all help is welcome.

 

Ok i do need to add a few things. i have a small exhaust leak at the down pipe and at cat where i clamped them, gonna have it welded later. Thats why i think it backfires and idles funny sometimes. I inspected new wires no burns from new headers. someone said it could backfire due to melted wires. other than that just the vibration issue.

 

best advise is get all the bugs out, then start diagnosing, then get it scanned see wat it tells you

 

What method did you use to set the lifter preload? Sounds to me as though you may have your preload set too tight........

 

as in lifter preloud your refering to the rocker arms? spun rods in my fingers while tightening until they stopped moving then did a half turn. i was having idle problems as well but seems to have fixed itself. I new this was gonna be a big job but went step by step on every part.. contimplating on taking valve covers off and redoing the rockers.

 

Plug wired mixed up?

 

plug wires are good all new and checked twice

 

would not having the dipstick bolted to the head be causing the car to lug? when i was putting it back in there was no way to secure it to the block again. it is in the pan but not secured down

 

Probably a good idea to idea to redo these. Try moving the pushrod up and down while tightening the rocker arm nut. When all the vertical motion os gone, go another half turn.

The twist the pushrod until it stops method is tough to do correctly....

 

Triple check that your wires are routed correct. Also make sure they are plugged in ALL the way.

 

I agree completely! The spin method can be very confusing, much better to lift the push rod to verify zero lash and then set your preload accordingly. Be sure that you are setting your preload with your cam on it's base circle for that particular valve, not verifying this will also cause problems.

Good Luck!!