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Old 03-17-2010, 07:30 AM
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Hopefully my last pushrod question

I have been measuring my pushrod length for days now and I think I've zeroed in on the right length and now it time to order.

Using the Comp Hi Tech adjustable pushrod checker I zeroed in on a 7.050 length that gave me the best centered contact pattern. 7.100 gave a similar width mark, but was slightly on the outboard side.

Comp says their checker shows gage length and that their catalog list pushrods by gage length. This lead me to Comps Hi Tech 249-7937.

Looking at Summit's site I noticed that the 249-7937 was listed at a 6.950 length in the description, but the "actual length" was listed at 7.050 like the Comp catalog. I also see a Trick Flow pushrod 21407050 that also list it's "actual length" at 7.050 and list for $45 less.

So I don't understand where the 6.950 length in the Comp pushrods description comes from. And I would like to order the Trick FLow set and save $45 if I could be assured they are actually the same length that I need. They seem identical when compared on the Summit site.

http://www.summitracing.com/parts/CCA-7937-16/

http://www.summitracing.com/parts/TFS-21407050/

Also I find different opinions as to whether any hydraulic pre-load length needs to be added to the measured length of the pushrod before ordering. I was careful to insure that the lifters were not compressing when making my measurements.

Thanks guys,

Bruce, shade-treeing in the hills of TN

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Old 03-17-2010, 08:12 AM
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Go w/ the "gage length" measurement from your checker. That is what it is designed for- to give you their recommended p-rod, do not confuse the "actual length w/the gage length.

"Actual length" is what you'd use, if you used an adjustable checking p-rod (like I do). The length is measured from tip to tip w/calipers, w/consideration for the oil holes.

You're on the verge of over-thinking this. Use the tool, and- if it's used correctly- it points to the exact p-rod to use. No adding preload, nothing.

From Comp:

"This technique assumes that you have purchased one of our Hi-Tech pushrod length checkers. These are marked with a standard length stamped in them. This number represents the gauge length of the part (.140" gauge diameter) with the two halves screwed completely together. Extending the pushrod one rotation lengthens the gauge length .050". For example, a pushrod stamped 7.800 screwed apart one rotation would be 7.800" + .050" = 7.850" gauge length. Therefore you would order the part number from the catalog that matches this gauge length, since gauge length is how they are listed." (Bold, italics mine)

More on "actual" vs. "gage" length HERE.

Last edited by cobalt327; 03-17-2010 at 11:36 AM. Reason: Add link to Comp.
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Old 03-17-2010, 11:18 AM
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I'll forget about the pre load adder.

But most of my confusion comes from the Comp information you referenced. Using the method you quoted is how I decided on the comp pushrod I mentioned (7937). They say their P-rods are listed by gage length, which according to their own diagram is the shortest of the measurements. So the shorter 6.950 length mentioned in the Summit description was throwing me off.

I talked with Comp's tech line, who verified my choice. And then with Summit's tech line, who said they weren't sure where the 6.950 description came from, and also assured me if the length didn't check out I could return them. So I decided to order the Trick Flow set since they're much cheaper. I'll run them through the paces when I get them. $45 isn't chicken feed.
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