measuring for proper push rod length • The Dodge Challenger Message Board

by **MLMFLCN** » 14 May 2007 23:59

Hello,

I have a set of 1.6 Harland Sharp roller rockers and a Comp cam 274/286 hydraulic for by 440. I purchased an "adjustable" push rod with a ball end and cup end to check the measurement, but was not certain how to get a precise measurement.

I imagine that the rocker shafts need to be torqued down on the heads, and my thought was to measure the push rod length off the heal of the cam (i.e. - fully closed) to garner the shortest measurement. Is that all correct? Should I be starting with #1 at TDC as a reference point, and if so, which valve should I use to measure? Finally, do you need to take multiple measurement points and take an average? :roll:

Thanks for all your help with this build.

by **dave-r** » 15 May 2007 9:53

Just check what you think will be the two shortest rods and cut the rest the same.

You can tell by looking at the valve stem heights. The higher the valve stem the shorter the pushrod. Hopefully they are all more or less the same.

Adjust the rockers so that there is only one or two threads showing on the underside of the rocker.

The less adjuster is sticking out the stronger it is. But check clearence because too short and the rocker will bind against the pushrod cup. Good rockers have plenty of clearence.

by **dave-r** » 15 May 2007 9:55

Check out this thread.

http://challenger.mpoli.fi/forum/viewto ... 1377#21377

And I forgot to say. You need to check pushrod length on the lowest part of the can lobe.
DON'T GUESS THIS POINT!

Use the Mopar chart to adjust the valve you want.

by **MLMFLCN** » 28 May 2007 21:35

Thanks Dave...

Since this is a hydraulic cam/lifter set up, the pushrod length would need to include the required preload on the lifter, right? It seems that if you determine the pushrod length with one thread showing and no preload, that once you add in the preload, no more than 1.5 to 2 threads will be showing. Does that sound reasonable? From what you supplied 1.5 to 2 is in the okay range.

Sorry to be so anal, but I just want to get the most from this motor. :s004:

Thanks again for the speedy accurate replies.

by **dave-r** » 29 May 2007 9:36

Yeah. You want a bit of thread showing WITH the correct pre-load.

The adjusters should be 3/8ths? and fine thread?

So that would be 24 threads per inch.

That would be 41.66 thou preload per turn.

If you have lifters with the stock type wire clip holding the lifter together go for 3/4 to 1 full turn.

If you have race type lifters with a real cir-clip in the top of the lifter just do a half turn for 20 thou.