How to Measure PUSHROD length? (GT40X heads & Cobra rockers) - Vintage Mustang Forums

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post #1 of 4 (permalink) Old 02-29-2004, 11:29 AM Thread Starter
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I am almost done bolt my new 347 stroker engine together and I ran into a snag. I'm using a 90 roller block, comp extreme energy roller cam, GT40X ford racing heads, 1.72 cobra rockers from ford racing. The rocker setup is the pedistal (non-adjustable). The stock 5.0 pushrods are to short. How do I determine the right length? Do I measure between the valve tip & the roller and equat it back using the rocker ratio and then add for lifter preload? How many thousands of an inch should the lifters be preloaded? Help Please

Thanks Craig ::

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post #2 of 4 (permalink) Old 02-29-2004, 11:57 AM
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Ok... I believe (if i recall correctly) that you need to put a non hydrolic lifter in when measuring, insuring that you get the right length. after you have one in, you'll need to get a pushrod checking tool. Crane sells them. It's basically like a pushrod with ends that screw out. Once you have it in there and expanded to the longest it can be, you shoulkd be able to turn the pushrod with your hand with slight tention. Hope this helps! Look on Crane's site for more info!

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post #3 of 4 (permalink) Old 02-29-2004, 12:45 PM
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Here is how I did it. It turned out fine.
You will need an adjustable push rod checker. I used Trick-Flows version. You will need the heads on with gaskets and torqued to spec. Work with #1 at TDC. Assemble the rockers for #1 with no shims. Use the adjustable push rod on the intake of #1. Torque the rockers down with the push rod loose. Expand the pushrod until it just touches the lifter and just begins to collaspe it. This takes a little educated feel but it's easy once you try it. Lock the push rod down so it doesn't move. Dissasemble the rockers and measure the push rod length. This length will be your starting point. Ford like the lifter preload about .020-.060. Shoot for .060. Add this to the length of your push rod. Repeat this procedure for the exhaust and at least four other cylinders. Hopefully you will come up close on all the lengths. Now, check with the vendors and see how close they are to what you need. Remember that longer is better as you can use shims to decrease preload but not the other way around. Good luck!

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post #4 of 4 (permalink) Old 02-29-2004, 01:44 PM
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