Measured pushrod length question

[amceaglesx4]

My problems are pushrod length related but I have gaps to be filled before I know what I need hopefully someone can help here. I have had between block and head 12 thou removed , 43 thou head gasket versus whatever stock is , and a valve job which alters pushrod length. What I dont know is how many thou a 3 angle valve job roughly takes off and compressed stock head gasket thickness versus a 43 thou.

What size pushrods am I looking for here. Long story again with a local guy !!! But he said my pushrods are too long. Any help appreciated. This whole adventure has sucked !

[jeepman]

The best thing is to actually measure the length you need...
Ebay has adjustable push rods that you use to find your proper length this is just a quick Ebay search on Adjustable pushrods so they are not meant to be specific to your application and just a reference...

http://www.ebay.ca/sch/i.html?_from=R40 ... s&_sacat=0

[Russ Pottenger]

To expand on what jeepman pointed out.
There's just too many variables involved with figuring out pushrod length by the decking of the block, surfacing head, gasket thickness, valve job, .... You get the idea.
Using an adjustable pushrod is the easiest method to mock up and check for length

Because Jeeps have a pedestal style rocker arm we won't get into valvetrain geometry discussions.
Lifter preload should be around .030 to .060 or roughly 1/4 to 3/4 of a turn.
Pushrods are typically sold in .050 increments.

[amceaglesx4]

Well i got a comp cam adjustable today. It doesnt say measurements on it like i thought it would like a tapemeasure. I can figure length out so whatever. So how is this done ? Set first rocker to number one on the cap and thats first valve open and then pull rocker and lifter out , put in adjustable pushrod, turn till the pushrod has no slack then thats the size I need ? Obviously torque rocker first the adjust pushrod. What in not getting is the preload measurement.

[amceaglesx4]

Well i got a comp cam adjustable today. It doesnt say measurements on it like i thought it would like a tapemeasure. I can figure length out so whatever. So how is this done ? Set first rocker to number one on the cap and thats first valve open and then pull rocker and pushrod out , put in adjustable pushrod, turn till the pushrod has no slack then thats the size I need ? Obviously torque rocker first the adjust pushrod. What in not getting is the preload measurement.

[amceaglesx4]

Since the lifters are full of oil already and when the pushrod becomes snug is that zero lash then I add whatever preload number to my length and thats the size pushrod I need ?

[SilverXJ]

Yes. In short, rotate the cam until both valves are closed on TDC of the compression stroke of the cylinder you are checking. You can then remove the pushrods you have in. Wait a minute for the lifters to fully pump up. Then insert the measuring push rod. Torque down the rockers and start to expand the measuring pushrod. When you get to 0 lash (no preload, no lash) that is your pushrod length + preload. Finding zero lash can be a bit tricky as you can start to compress the lifter with out even knowing it. Just until it is slightly snug and you can't spin the rod even gently. Repeat it a few times until you have repeatable measurements. Then do a few other valves as well as intake and exhaust.

[amceaglesx4]

The only thing I dont understand is wait for the lifters to pump up ? Once you remove the pushrods do the lifters release oil ? Im not quite following you

[SilverXJ]

The pushrod compresses the lifter when installed. There is a small spring inside of the lifter. Sometimes it take a few seconds for the lifter to fully decompress because it is filled with oil. Kind of like how a pressurized shock decompresses slowly.

[amceaglesx4]

I understand what you are saying. I took an old one apart and get how they work. My only question now is when both intake and exhaust valves are closed, that means there is no pushrod tension correct ? Since time is my enemy maybe you can save me some time here please ? If I set the rotor to number one which cylinder has both valves closed. Number one as in piston it at the top by the head. Thanks

[SilverXJ]

Its called preload for a reason. And don't go by the rotor position to figure out which cylinder is doing what.

[amceaglesx4]

So how do know for sure when both valves are closed ?

[amceaglesx4]

If two pushrods in a row spin relatively easy ? That would mean theyre not compressed right.

[Russ Pottenger]

So how do know for sure when both valves are closed ?

Chris,
When a lifter is on the heel of the lobe the valve is closed.
When a lifter is on the nose of the cam lobe the valve is open

[amceaglesx4]

I understand that but I cant visually see the camshaft. I understand the functions of everything. Even the rocker knotch on top of the valve . I guess if I measure bottom of valve spring to top of rocker and find length of valve travel then I can find a cylinder with both closed. Idk... Everytime i have a engine builder or so called mechanic shop i get ripped off or they make it worse. For example the local shop i took the eagle to they charged me one gour labor to pull the vc to look at rockers. Really !!! Takes me twenty minutes to pull it. Then they didnt want to measure pushrods and fix the problem and reccomended i do it at my leasure. The wife drove it home yesturday and last night i pulled the vc. WTF... First two pushrods werent even under the rickers. One of them was REALLY flippin bent. I mean bent !!!!!!!!!!!