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Author Topic: Push rod length  (Read 1168 times)
mopar346
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« on: November 22, 2010, 10:36:20 PM »

Does anyone know if there is a stock length push rod for this application or will I have to have them built to length?

late model 350 4 bolt roller block (87-96 not a vortec) Comp hydraulic roller with factory roller lifters and 492 early heads with crane roller rockers (1.5s).

Thanks, Kevin
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CNorton
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« Reply #1 on: November 23, 2010, 08:48:12 AM »

Your engine assembler should determine the appropriate length for the pushrods in the course of fulfilling his responsibility.  There is a procedure that is normally followed for accurately calculating length and it comes into play, especially when using roller rockers.  Many factors affect the length, including the amount of material removed from the block/head components in the process of truing the decks, the thickness of the head gasket, the depth of the pushrod cup in the specific lifters used, and the base circle dimension of the camshaft.  In my experience, factory pushrods for roller cam motors are typically shorter than those for flat tappet motors.  One thing that you should verify is that the pushrods are hardened for use with guideplates.  If you combine guideplates and unhardened pushrods, there is the likelihood that the pushrods will shed metal into the motor in the area that they come into contact. The fact that they are made from chrome moly material doesn't guarantee that they are hardened sufficiently.   If the valve spring pressure and RPM are held at reasonable levels, there should be no real need to increase the wall thickness or the O.D. of the pushrod.  For reference, you might wish to do a search for Manton Pushrods and read through the introduction to their catalog.  I'm not suggesting that you will need to buy really expensive pushrods for this application but getting the correct length and hardness will help avoid future problems.

c
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mopar346
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« Reply #2 on: November 23, 2010, 05:55:15 PM »

Thanks for the info, I will look them up. Roller lifters are tall and therefore the push rods are shorter. The hydraulic lifter has some variance that will usually forgive deck surfacing, the heads have not been cut to my knowledge but that will be verified tomorrow. I am assembling the top end and didn't know if the this was a common enough combo that someone knew the answer or if I need to measure then and have built to length. After the measurement, I will trust the contact pad on the roller rocker to make sure it is functioning correctly all the way through the cylinder cycle. I will read the intro as recommended, the more knowledge you gain the better you are.

Thanks again, Kevin
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mopar346
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« Reply #3 on: December 04, 2010, 06:38:09 PM »

Installed the heads today and check the contact with a set of factory roller push rods, colored the valve stems with a marked and the rollers ride perfectly in the center of the stem. Just thought I would pass it along. The factory length works perfectly on my combo, just have to get hardened ones.
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