Bacon505

iTrader: (1)

OK, I need some help. I put together a 5.3 '63 falcon wagon. It's running a msd 6012 box, edelbrock intake and a holley 570 street avenger.

It's never really run right, and figuring late was better than never I did a compression test on it today and I have 3 (yes, 3) cylinders with 0 compression. 1, 5 and 7 are dead until you loosen up the rocker arm and close the valves, then compression comes back. Into all 3 cylinders. At once.

So, in my mind, the valves seal, the rings seal, the problem must be in the valve train. Right? Lifters junk? It is a gen 4 and when we tore it down to check it out we replaced all of the DOD lifters with used, stock lifters.

Is there a chance it's just the cam? Is there any way I'm getting out of this without pulling the heads? Is it possible I have a minimum of 3 bad stock lifters?

Any thoughts are hugely appreciated....

Bacon505

iTrader: (1)

Even bad thoughts...

Lifters stuck and holding the valve open all the time?

poltergeist 02

iTrader: (65)

Did you check your preload/pushrod length?

Realcanuk

This.

Bacon505

iTrader: (1)

Nope, but I replaced the stockers with trick-flow, fancy pants pushrods when we tore the motor down to look in it. That's all we did as far as upgrading parts.

I'm just gonna take it as an opportunity to put a proper cam in it and do the lifters at the same time, and valve springs. Just replace valve train stuff with new, good parts.

poltergeist 02

iTrader: (65)

I would bet your pushrods are too long for the application. What length pr's did you use?

87silverbullet

iTrader: (11)

^^^^x2 on this. I put 7.400 pushrods in my ls2 vette and when I took the stockers out you could see they were a good bit shorter. Ended up putting the stockers back in.

Bacon505

iTrader: (1)

I've got the 7.4, I used a set on my other turbo 5.3....damn, it would figure that the one part I bought trying to be proactive and safe would bite me in the ***....

If they're too long, why would I only be having this issue with 3 cylinders? Unless only a few were too long...seems strange...I've got good compression 130-150 psi on all the other cylinders. ****. Think we should switch back to stock pr's?

I don't even have a set anymore, I was told they're the weak link on these engines so I replace 'em whenever I pull one down to check it out.

Thanks for the help so far, keep those suggestions coming!

Realcanuk

It can happen where you need different length pushrods or to shim some rockers on some cylinders. This can be due to different length valve stems, worn rocker stands, etc etc.
Its rare but to be safe I check every valve when I do my pushrod length check.