help me double check my lifter preload?

[xuv-this]

hey i'm about done with my stroker, and i'm not completely sure about the preload. from what i understand both rocker arms in the same bridge need the same thickness shim. but for some reason my intake lifters average about .022 more preload then the exhaust-? the most preload on the intake side is .047(or just a hair over 1 full turn to torque spec.), and the least the on exh. side is .028(about 1/2 turn to torque spec.) this is with stock length pushrods and .035 comp cam shims. the head and block are slightly decked to about .030 or so (combined) is this ok or am i just paranoid?

 

[Talyn]

The exhaust side is a bit low but still with in spec. What you are probably seeing is that the cam you are using may have different diameter lobes on the heel. You are checking these with the piston at TDC, right?

 

[wolfpackjeeper]

I just put all the rockers right back where they came from with the same bolts. Torqued them down and let her rip. But I also did not use a new cam, and we set the spring height back exactly to spec when we rebuilt the head. I did use new lifters and pushrods though.

 

[xuv-this]

i rotated the crank to check every valve on the heel(not the lobe). everything from the pushrods down is new. the cam is a 505 performance grind. any ideas?

 

[Talyn]

I don't see how the rockers could be bent all the same. Even if you had two different length push rods I don't see how you could get the installed with the longer ones on the exhaust sides.

So that leaves two options. 1) The valve stems are a different height, or 2) the base circle of the cam lobes are different between the intake and exhaust side.

I would check the two valve stems on a cylinder with a straight edge to see if they are the same height. Maybe one valve was installed deeper than the other. If the straight is straight across both stems then the valves are not what are different heights. That would rule out the valve stems.

You may want to verify this with others, but I think 1 full turn is greater than .047"
IIRC 3/4 turn is .047".. one full turn would be .060", which is the limit. 1/2 a turn is .030"

 

[xuv-this]

i just got off the phone with zach from 505(really nice guy). he said it was the valves were set at different heights. i asked if i could set different height shims under each side of the bridge to compensate, and he said that it would be ok. but i didn't need to unless it was turbo'd. i'm gonna double check that height, but if it's other wise just within spec other than that intake/ex. height difference, should i leave it or swap out one side of the shims? i just want to know that everything on this motor is right...

 

[Talyn]

You are using stock rockers, correct? I don't think it would matter that much as the bridge isn't that strong and will bend. When you get into after market rockers you will have problems with different sized shims under it. Just make sure you don't go over.060".. like that 1+ turn you said you did. As I said 1/2 a turn is .030 which is fine.

Besides what someone said did you actually check the valve stems yourself?

 

[xuv-this]

i used a stainless ruler and a feeler gauge and sure enough, the ex. valves were at a slightly different height. i double checked the preload, and they're all within spec. i think too i was just getting different readings where i got a little "generous" with the cam lube. i turned it over a couple of times w/ everything torqued before i rechecked, and it settled down. but there's still about .020 difference in the int. and exh. i could add .020 shims to the exh. or switch out the .035's on the int. for the .020's, or do you think i should just leave it? {oh yeah, the rockers are stock.}

 

[wolfpackjeeper]

just leave it, if you get some valve clatter you can always pull the cover again