Lifter Preload on a 258

[atblis]

NOTE: The following what I posted on Pirate4x4.com and got a bunch of TJjockytard responses. I should have known better and just asked here first.

Do the lifters have to be empty of oil when measuring preload (not pumped up)?

Some details on why I ask.

258 block and crank. Stock Cam. New lifters. 258 push rods. 4.0 head and rockers.


This is on a fresh rebuild. I haven't been able to get the motor to run. It'll fire, but something isn't right. It seems to have compression when turning over by hand, but sounds odd when cranking. A compression tester yielded basically no compression. I don't entirely trust the tester, but it should read something.

I double checked the timing chain. There are two circles on the crank, but one is clearly a stamped mark, and the other appears to be a casting dimple. I went with the stamped circle. The cam sprocket doesn't have a circle, but has a little arrow looking thing. Using the line between the shafts, both marks on that on the inside, and then turning and counting pins, yields 15. Looks correct.

Next thing is lifter preload.

This is my procedure. Turn engine till there's no tension on the rockers. Scribe line on pushrod. Loosen rocker arm bolts till pushrod stops rising. Scribe another mark. Measure distance between lines.

The thing this, when I tighten the rocker arms down, they appear to compress the valves some. The Preload measures at .038" This is with the lifters full of oil.

Any ideas?

 

[Yay!Gurrr]

my haynes book says that when setting the crank sproket that the key way should be almost pointing up.. This leaves the mark just to the left of it (CCW).. Everything else sounds right as far as setting the chain..

To set valves book says zero lash, which would be correct with a hydraulic lifter...

On a small block, I always just turn the engine over a little at a time until each valve is fully released and loose. Then take out any slack in the arm, attempting to spin the push rod or wiggle the arm to check for tension, when it hits, go 1/4 turn more. Repeat for each valve..

 

[atblis]

Yeah

my haynes book says that when setting the crank sproket that the key way should be almost pointing up.. This leaves the mark just to the left of it (CCW).. Everything else sounds right as far as setting the chain..

Yep, that's about where it was/is. I don't think I had the timing off.

I think my pushrods are too long. It doesn't seem to ever have no tension. I ordered some rods that are 9.59ish. I think the current ones are 9.62ish. I used the rods out of the 4.2, as they were shorter than the 4.0 rods.

 

[Yay!Gurrr]

my book showed 2 types of rocker configurations. 1) Common rail/shaft where there is no adjustment. Simply bolt it all together.

The #2 was an stud mounted adjustable arm, with a pivot ball inside the rocker. You should be able to back the nut off creating enough room ?

.030 difference is a 1/2 turn of the nut ?

Can you snap a pic it would help a lot.

(FWIW: I've never done valve work on a 4.2, I'm just applying basic engine fixing procedures.. )

 

[atblis]

Hmm

Here are some pics off of the net. I don't think they are adjustable.

Problem is I have no idea if the head gasket is a different thickness than stock, and or if the head has been milled. My latest attempt at measuring lifter preload has yielded .10" which is way to much. I found a write up which said you have to let the lifters bleed down. It definitely compresses the valves when I torque down the rockers. I ordered what is supposedly a set of shorter rods.

 

[Caver Dave]

That's standard AMC bridged rocker junk (have the same on my 304)... the stems are ground to "adjust" everything out

PM Uglyjeepoffroad... he did the same 4.0 head swap and IIRC, he ran into the pushrods being too long also...

 

[atblis]

Update

Got some shorter ones from advance. I think they're 0.047" shorter. My preload is measuring out at .080", so that should put me in the ball park.

Kinda wanted the cam to die so I could order a Crower anyways.