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77 CJ5 258 Valve Lash

4K views 8 replies 6 participants last post by  82Laredo-7 
#1 ·
I sent my 258 head in for recon and they sent it back with a bag of little black washers and told me that since that motor did not have hydraulic lifters I would have to adjust the "valve lash" using these washer of various thicknesses to the fulcrum (cylinder head pedestal)
WHAT THE HELL!!
So I have been adding one here taking one out there and I just cant get the motor to run good (close)
Is there a correct way to go about this adjustment process?
 
#2 ·
HI, ? so You have solid lifters? and it so were they stock or is this a performance build? A picture of what you have in the way of lifters, rockers and your head along with how the rockers bolt up would be a great help..
Usually if you have solid lifters you have to have poly-locks so you can set lash with a feeler gauge , I forget how much lash/gap but the exhaust is different than the intake and there is a Cold and a Hot setting.
if you do have Hydro then the adjustment is 1/2 turn after you can't turn the push rod with your fingers (When at Center max valve closed).

good luck
tim
 
#3 ·
tofweldonspring said:
I sent my 258 head in for recon and they sent it back with a bag of little black washers and told me that since that motor did not have hydraulic lifters I would have to adjust the "valve lash" using these washer of various thicknesses to the fulcrum (cylinder head pedestal) WHAT THE HELL!! So I have been adding one here taking one out there and I just cant get the motor to run good (close) Is there a correct way to go about this adjustment process?
Something, or someone, is screwy here. All AMC 258s came with hydraulic lifters, that I'm aware of.

Solid lifters usually require adjustable rockers, and it's usually a high performance, high RPM setup.

Having to use shims to adjust hydraulic lifter preload indicates a shoddy valve job.

Matt
 
#6 ·
tofweldonspring said:
I guess ill dig into the motor and visually inspect the lifters The machine shop told me that who ever rebuilt the motor shaved the bottom of the rockers to achieve lash
Before you go crazy, remove a rocker on a valve that is closed. Then push down on the pushrod by hand. If you feel a little spongy give, then it's a hydraulic lifter. If it feels solid, then...you know.

Matt
 
#8 ·
Back when I first got my '66 Chev Malibu it had been re-engined with a SNC 350. This thing came off the line like a raped ape. I learned from the dealership that I had to adjust the screw down SBC rockers to 30/1000 for intake and exhaust. This motor was a smoker but it ran so dang strong. Come to find out that it had a holed piston but the camshaft was an older Chev racing cam 30/30 (as my mentor called it) whom used to dirt track race up in Washington state in the early 60's.
It turned out that other than re-camming it, there were no other mods save for headers. When the motor finally went south, I got one from a maching shop with the stiffest hydraulic cam available, but it never performed like that 30/30. The real PITA was this was before I learned about fastener tech and was unaware of poly locks. Double nutting was all I could do and every klinking week I was under the hood, closing the opening gaps.
 
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