this is a conitinuation of this post:
https://www.thirdgen.org/techbb2/sho...ight=zupmanZ28

I replaced the rocker studs, and grinded the guideplates back a bit. The tap is still there with a vengence. So now im thinking maybe its the summit brand rockers i have, or i have a bad lifter. Can rocker make a tap, or am i buying a new cam and lifter set?

I drove it, and the car has no power, i've ridden in lg4 cars that pull harder than it is right now. I don't know what to do. I pulled the valve covers and let it run and all the valves are opening and closing, so it's not a wiped lobe or anything.

It did backfire everytime i hit the throttle hard, but i think thats more carb related than anything.

i'm about at my wits end with this thing, couple more tries at this, then the stock 350 in the garage is going back in the thing and i'm never touching a motor again...

Eric

 

I wiped lobe will still move the valve- just not much.

We're back to simple basics right now. Do a compression test on all 8. A wiped INTAKE lobe will cause HIGH compression on that cylinder. A wiped exhaust lobe won't affect cranking compression at all.

Any idea on where the tap is coming from? I've used a mechanics stethescope touched to the rocker stud of each valve of a runnign engine to determine which one EXACLY is tapping- not just a rough"it's around here somewhere" kinda estimate.

Have you tried setting the valve lash with the motor running? Back the rocker arms off till they tap, then back down till they stop plus 1/2 turn. Messy for sure without rocker arm clips, but definitely the best way to adjust them accurately (on a hydraulic cam- not a mechanical one).

 

by the way, autozone carries those clips for about $6 or so for a complete set of 16 iirc.

 

The tap is coming from both sides, in more than one place, or so it seems. I have tried setting the lash with the motor running, but i haven't been succesful. There is always a tap, so it's impossible to tell when that particular valve is making noise. Besides that i can tighten or loosen multiple turns with no change in sound.

all the rockers appear to be travelling the same distance ( thought obviously it's impossible to tell just by eyeballing it).

How can i check the lifters? Those are my next suspect. I'm also considering going back to 1.5rr's to eliminate the possibility of too much lift...

Eric

 

I put my stock set of stamped 1.5 rockers on it today, and i can still hear a faint tap. So that rules out too much lift, bad rockers, and pushrods hitting the guideplates.

A logical next step woudl be replacing the lifters now correct? Can i even replace the lifters without putting in a new cam? Will this hurt my cam in any way?

Eric

 

Well it just so happened I worked on an eng. that backfired out of the carb on hard accl. but ran fine otherwise, and it turned out to be a broken valve spring. Really tough to find Had to use a bright lite and get right down there and trace every coil on each spring. I replaced that spring (intake) and all was well.

Auggie

 

this car doesn't run fine at any time, it sucks constantly.

Actually the 1.5 rockers seem to fixed the tap problem, but not the dog slow problem, but i'm making a new post about that...

Eric