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  #16 (permalink)  
Old 09-24-2013, 05:05 PM
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Quote:
Originally Posted by ritzbitz625 View Post
I checked my push rod length with a checker and im caught between using 7.900 or 8.000 pushrods what do u think?
I think that if you're using one of those gray plastic checkers, you should call up your favorite cam grinder and order up an adjustable pushrod and begin from scratch.

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  #17 (permalink)  
Old 09-25-2013, 02:47 AM
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Originally Posted by ritzbitz625 View Post
Okay understand im finding that its centered but wide why?
The pattern is made by the combination of the parts involved along w/the exact placement of the rocker stud and valve guide in the casting, but the main thing that drives the pattern is the length of the pushrod itself. Next to that is probably the design of the rocker arm, but most of the time we work w/whatever rocker that is on hand and change the p-rod length to get the narrowest pattern.

If you are handy you can make a checking p-rod from an old p-rod. Click on the image below for details:



Other homemade pushrod length checking tools at HomemadeTools.net

When talking about the pattern of the rocker roller across the valve tip, "wide" and "narrow" are relative. By using an adjustable pushrod, you can see what length gives the best pattern overall.

Last edited by cobalt327; 09-25-2013 at 02:56 AM.
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  #18 (permalink)  
Old 09-25-2013, 01:34 PM
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Problem with making a checking pushrod yourself is that different manufacturers measure pushrods differently. Please read this.....
COMP CamsŪ - Pushrods
Now, pick up the phone and order a checking pushrod from your favorite cam grinder. When you have found the length that works, send it back to the cam grinder so they can make you a set of pushrods to the exact length specified.
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  #19 (permalink)  
Old 09-25-2013, 03:27 PM
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The different methods used to measure a pushrod are also covered in the link I provided earlier, "Valve train geometry".

Measuring a checking p-rod is not too much for someone to grasp once the maker's method of measurement is known. And most manufacturers are capable of working w/the length that's provided to them as long as they know it was taken w/a p-rod having oil holes. The only real problem I see is not everyone owns a large enough caliper or micrometer to do the measuring precisely. In that case, I would recommend taking the locked-down checking p-rod to your local machine shop, who would be able to measure it. Then that figure would be given to the p-rod manufacturer or used to select an off the shelf p-rod.

For that matter, the homemade checking p-rod can be sent to the manufacturer just as easily as one supplied by the maker. Granted, $20 for a store-bought checking p-rod ain't likely going to break the bank, and making one may be beyond the ability or too time consuming, etc. If that's the case, by all means- go buy a checker and more power to you. Personally, I would simply order an off the shelf p-rod from one of the several trustworthy p-rod makers based on the measurement taken from the homemade checking p-rod, working w/the way they measure their p-rods. I mean, this ain't rocket science.

Comp has a couple p-rod lines that may work well for you, their Magnum or Hi-Tech. They're available in 0.050" incremental lengths from standard, are thick-walled and are hardened for use w/guide plates. IMO these off the shelf Comp p-rods (or any of the several other vendors like Comp) will be considerable cheaper than custom p-rods, w/o sacrificing durability in your build.

Should you want to go top shelf, here are some high-end pushrod makers:

Last edited by cobalt327; 09-25-2013 at 03:36 PM. Reason: Add link.
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Old 09-26-2013, 05:30 PM
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My mark is in the center of the valve tip but it is wide not narrow...do i need to go smaller or bigger? I have it at an 8 inch pushrod right now. The push rods i had in there before were 7.8.
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Old 09-26-2013, 08:42 PM
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Quote:
Originally Posted by ritzbitz625 View Post
My mark is in the center of the valve tip but it is wide not narrow...do i need to go smaller or bigger? I have it at an 8 inch pushrod right now. The push rods i had in there before were 7.8.
What are you using to check the length with? If it's a Comp plastic checker, I have had no good experience using it. Others may be able to comment.
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Old 09-27-2013, 09:20 PM
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Get an adjustable pushrod as mentioned. One full turn is .050. 1/2 turn is .025

Try at different lengths to get the best pattern. Marking the top of the valve stem with a dry erase marker leaves a good witness mark.

Replace the valve spring with a light checking spring so you can get full lift during the cycle without depressing the lifter plunger.

Post some pictures of your different patterns and them someone will be able to help make a decision.
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Old 10-01-2013, 09:15 PM
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What push rod guides should i use with my dart pro 1 heads 230cc , + 1.000 valve, 8 inch pushrods.
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Old 10-02-2013, 01:38 PM
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Quote:
Originally Posted by ritzbitz625 View Post
What push rod guides should i use with my dart pro 1 heads 230cc , + 1.000 valve, 8 inch pushrods.
Dart 27001410 Dart Pushrod Guideplates
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Old 10-04-2013, 11:46 PM
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also a thicker wall rod will help lessen deflection and could be worth 10- 15 hp comp cams (hi tec) makes a 5/16 chromolly with a .105 wall thickness for around $180
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Old 10-05-2013, 12:29 AM
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comps hi tec non standard wall pushrods are 17 percent stiffer than .080 wall pushrods part # for a (7.800 is 8411-16 ) ( 7.850 rod its 8412-16 ) (7.900 its 8413-16) (7.950 its 8414-16) (8.000 is 8415-16)
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