just curious

[herbiehind]

what's the consensus on decking(how much) and need for new pushrod length.? i know i'll be checking but like to be prepared . i'm thinking taking the full .038 off and likely need pushrods . that about right?

[gonridnu]

Pushrod length can be effected by cam grind so how much you deck your block is not necessarily how much you shorten your pushrods by. Deck ur block to where it works with your combo and desired compression then measure for pushrods length There is no other reliable way.

[herbiehind]

Pushrod length can be effected by cam grind so how much you deck your block is not necessarily how much you shorten your pushrods by. Deck ur block to where it works with your combo and desired compression then measure for pushrods length There is no other reliable way.

copy that . just was curious as to whether there has been a rule of thumb gained over the years. like "you're probably close to x pushrod now" or " definately gonna need pr's" follow? thanks

[SilverXJ]

If you were using a stock cam and stock rockers you could probably just go off how much material has been removed from the head or block. Also, using non-stock rockers can change the push rod length as well.

[Retlaw01XJ]

A valve job might sink the valves a little (and raise the tips), but the shop should grind the ends of the valves for a consistent height.... but some shops don't.

I cut my block 0.020" and had the head shaved flat (don't know how much).
I took the quick and cheap route and used shims under the rocker studs to get the proper lifter preload.
I needed a 0.075" washer to get 0.030" of lifter preload.
I found 5/16" washers were either approx 0.082" or 0.063" thick. Had to sand down the thicker ones to get the right preload. Or you can buy shims from Summit that are 0.060" and 0.030".

Shimming the rocker studs may throw off the rocker ratio a bit, but I'm using a mild Crower 44243 cam so the rockers won't be at their extreme limits anyway.

[SilverXJ]

A valve job might sink the valves a little (and raise the tips), but the shop should grind the ends of the valves for a consistent height.... but some shops don't.

Yes, that too.. forgot about that.

Shimming the rocker studs may throw off the rocker ratio a bit, but I'm using a mild Crower 44243 cam so the rockers won't be at their extreme limits anyway.

Shims also change the rocker to valve stem geometry. Shims aren't the way to adjust for pushrod length or cutting of the deck or head. They are best left to adjust for valve job differences. However, if all boils down to how perfect you want everything.

[herbiehind]

k . cool no biggy . i'll be doing pr's no doubt.

[Retlaw01XJ]

Shims also change the rocker to valve stem geometry.

Ahhh, yes.... that's what I meant to say.... rocker geometry, not rocker ratio. The ratio change is likely near insignificant with a mild cam.
Stud shims would be good for guys that install longer valves....it would keep the geometry near stock.
Here are a couple of articles on rocker geometry:
http://www.circletrack.com/techarticles ... ewall.html
http://www.aera.org/ep/downloads/ep10/E ... _20-30.pdf

I wonder if the stock Jeep geometry is even optimized?

[SilverXJ]

I doubt it. Probably just close enough.