ok heres the deal, the LG4 in my 87 is about to be replaced in a couple month so its not real important to me I just need to get it moving like ASAP because its been takin up space in my moms garage since november. This is the problem; the engine runs fine 97% of the time, that other 3% it develops a knock in the top end (#8 or #6 cyl) but only after its been running and not all the time. there are days where i can drive for hours and it runs like a charm and other days where i just start it up and it will knock, but the thing is the knocking goes away after about 5-10 seconds. i think the longest ive ever heard it know was about 15-sec and it doesnt lose power or oil pressure while its knocking. the sound sounds exactly like if u were taking ur knuckles to a fiberglass door. ive noticed a bit of smoke comin from the area but i believe its just the valve cover leaking onto the rear of the pass side exhaust manifold but the knocking comes from that area. Any ideas?? BTW im only using 87 octane but ive always used 87 because its only a stock LG4 305 with a 650 holly carb and street dominator intake, and if that was a problem wouldnt it be more consistant?

 

also i pulled the plugs and everything is normal (i.e. no oil in the chamber, air fuel mixture is fine)

 

I had that symptom on a vehicle once. A guy had done some work and it immediately developed a knock afterward. It would come and go, sometimes not noticeable for days at a time. I suggested he pull the heads. When he did, he removed the spare nut from the top of a piston and soon started shopping for a new engine.

 

so what was the cause of the problem?? Im starting to think that if it was a major problem it would really be more consistant. Like I said before, Im building up a L05 out of a 94 2500 pick up and it should be ready to drop in in a month or so. but i just wanna get my car on the road for the time being and i want to kno that im not gonna have a problem for that time.