push rod length???

[strokin96xj]

ok so i got a stroker 4.0 liter motor givin to me and all i dont' have to assemble the motor are the push rods. so my question is do i use the pushrods out of 4.0 liter or the 4.2 liter? the block has been bored out .30 over, .30 over pistons 4.2 liter crank, crane cam, all bearings and rings, all redone cylinder head just no pushrods. please let me know if there is any other information you fellas need to be able to tell me what pushrods to get. also is there a way to tell if i have 4.0 connecting rods or 4.2 connecting rods just by looking at them? O one more question this is going into a 96 cherokee so what do i have to do to make it work with the OBDII system to make it run with the computer? any answers would be greatly appriciated thanks.

[ajmorell]

You would use the 4.0 pushrods since you are using the 4.0 block and head. You should be able to tell the difference between the 4.0 and 4.2 connecting rods by holding the two up next to each other. The 4.0 rods are longer than the 4.2 rods.

[dwg86]

I would spend $20.00 and buy a pushrod length checker. That way you know what size pushrods you need. Comp cams 7704-1 is good for 8.800 to 9.800 length. One turn of the pushrod is +.050. Start at 8.800 and count how many turns you need to get the length you need. Summit sells them for $16.95 plus shipping.

Are you using stock rockers? If so, install the rockers, adjust the checking pushrod untill it just touches the rocker, and then add .040-.060. That should give you the correct lifter preload. You can add shims to the rocker stands if you need to increase length or buy custom length pushrods(if you need shorter or longer than stock). Trend pushrods sells one piece, 5/16 diameter, .080 wall, chrome moly pushrods for $5.60 each. They stock them from 6.00 to 10.00 inches in .025 increments. They were shipped to my door in 3 days after my order.

[strokin96xj]

ok thanks guys i'll take a look at the push rod checker and yes i'm running stock rocker arms for the torque specs on that motor when i'm assembling should i just buy like a chiltons manual? for a cherokee? and use the 4.0 liter specs?

[gradon]

Chilton's is ok(better than haynes), but the FSM is the book to have. I bought a used one w/o front cover, with brand new supplement(cause alot changed mid-year 96), and barely used diagnostic manual for $30 shipped off ebay(score). IIRC the rocker studs are torqued to 21#.

[strokin96xj]

ok thanks i'll check on ebay here in a bit and just to make sure i got this right i need to get stock 4.0 liter rods cuz i have the 4.0 liter block and head correct with stock rockers correct?

[gradon]

You'll use stock 4.0 rods(6.123") if you buy the KB944 or 45s or a custom piston, or if you're just rebuilding the 4.0. Otherwise you should be looking for 4.2 rods(5.875").

[tirod]

Use the 4.0 torques. After all the only 4.2 parts are the crank and connecting rods.

Measuring the push rods assures that the correct length is used to make the center of the rocker arm movement at the center of the valve stem. Wrong length push rods run them off the end of the valve one side or the other. Not good.

You may find the action stays on the valve stem, but isn't centered as much as you like. Some builders will order or go through a bunch of stock push rods and select ones that will be closer. Nice if they are laying around. Budget builders usually can't go the expense and live with the results if close enough. Hydraulic lifters create a range of variable length anyway - heat, rpm, valve spring pressure, etc will change how much the lifter pumps up. Street motors aren't precise in that regard.

[SilverXJ]

Actually, being that the stock valve train is non adjustable, push rod length only dictates lifter preload, not the location of the rocker on the valve. In order to change where the rocker contacts the valve stem you have to get an adjustable rocker that has an adjusting nut on the pivot stud, or use shims under the rocker pivot or shave the pedestals.

Personally if you are shaving the head or decking the block I would get an adjustable checking push rod... measure for 0 lash then add what ever you want your preload at.

[way2evil]

My first length check was 9.45" do you guys think it could be right?
Spec: Block Mill 0.02", Rockers 1.6 ratio and 232 comp cams.

may i have a list of vendors that sell push rods

[SilverXJ]

I personally prefer Smith Brother's Pushrods. There is also Manton Pushrods and Trend.

[herbiehind]

Chilton's is ok(better than haynes), but the FSM is the book to have. I bought a used one w/o front cover, with brand new supplement(cause alot changed mid-year 96), and barely used diagnostic manual for $30 shipped off ebay(score). IIRC the rocker studs are torqued to 21#.

check out great lakes 4x4 they have pdf's for free . complete manuals i've downloaded plenty of them and they're quite safe .

[Muad'Dib]

My first length check was 9.45" do you guys think it could be right?
Spec: Block Mill 0.02", Rockers 1.6 ratio and 232 comp cams.

may i have a list of vendors that sell push rods

Smith Brothers FTW!

http://www.jeepstrokers.com/forum/viewt ... 425#p24425

[goincommando]

hey i had the same problem my engine builder had to use ls1 valves instead of the jeep. so there for my spring height was changed, then led to the problem that my push rods where to short for the rocker arms to hit, so i had a set of 4.0 and 258 lifters laying around and the lifter heights were different so, idk what lifters your running but my plans were to run a carb. so everything the hyd. 258 stuff. so the 4.0 lifters were taller so i used them problem solved check into that maybe you wont need new push rods......

[SilverXJ]

hey i had the same problem my engine builder had to use ls1 valves instead of the jeep. so there for my spring height was changed, then led to the problem that my push rods where to short for the rocker arms to hit,

That didn't fix your problem of improper rocker arm geometry, which you have if the pushrods needed to be changed due only to the valves.