Mr White

Hello folks!
I'm trying to check what length my pushrods need to be and can't for my life get the numbers to ad up.
So I checked my measurements with my old 7.400" long pushrods and ofc they are to long by about 0.0138". Or maybe I should say, they are that much longer than if I set the tool to 7.400"

​​​​​​I am measuring with one of those machining dial gauge.
And don't worry. I know how to use the dial gauge, I used to be a cnc machine operator.
​​
So.. Is there a reason to why the length checking tool is measuring to short?

Some numbers never hurt anyone.
With the 7.400" pushrod I get 0.0472" of preload.
With the tool set to 7.400" I get 0.0334" of preload.

I'm using comp cams short travel lifters and aim for 0.025" of preload. Does that sound alright?

G Atsma

Comp Cams quality gone astray...... AGAIN....

Stampede4ever

How are you measuring preload? What is your method of checking push rod length?

QwkTrip

iTrader: (23)

The checker pushrod has a different end shape than the real pushrods, so you're going to get different lengths. You don't actually order the length that you measure with the checker tool. There are other factors that need to be added in.

LLLosingit

iTrader: (4)

I bought one a while back and found it measured .034 per turn instead of .50, Seems I got a counterfeit checker, Looked identical to the second one I bought that was legit.
What pissed me off more than anything was that I bought a china brand one under another name found measured .034 per turn and when I contacted the company that I bought it from they said they got a batch that was wrong so they updated their website... No offer to send me a good one. At that point I figured I would buy the Comp brand and that was the one that was also junk, That seller made it right and sent me a legit comp pushrod checker.

Mr White

I checked the lash with my dial indicator on the rocker arm at the push rod.
As for method. Sinse it's hard to adjust the tool in place, I adjust it to a length, let's say 7.300" (on the tool) and assemble it with rocker and check for lash. Disassemble, adjust the tool until no lash.
Record the data. Recalculate data based on that the tool is short. Ad 0.015" -0.025" to get suitable push rod length.

I was actually thinking of remeasuring and recording preload on all lifters and using that as well to determine a good push rod length.



I bought mine on Summit and I hope they only sell genuine stuff, but I'll check it.



So it's a useless tool for someone like me.
Maybe I'm just better off using my old push rods and my dial indicator and just count the turns on my fasteners?

QwkTrip

iTrader: (23)

I think the tool is fine, you're just maybe using it the wrong way. You don't measure preload with a length checker tool. You measure zero lash and then you mathematically figure in the preload and what other factors need to be considered.

You can then validate preload after you receive your new pushrods.

It's pretty much irrelevant whether or not the checker tool is advertised length. Ignore the "turns to length" method. Measure the length with a caliper instead. I use a bit of teflon tape on the threads so the tool doesn't move on me when handling.

Mr White

I see what you're saying. But I think I am using the tool the right way, but it might be better to use it the way you described, wich would be the wrong way to use a tool with a readable scale on it.
I can however agree on that sinse what the tool says is all wrong, I don't think there would be any better use for it.

QwkTrip

iTrader: (23)

I think the tool is aimed at people with stock lifters with a huge preload tolerance. It is not adequate for the job you're doing though (short travel lifters with tight preload tolerance). That's why you'll need to use the caliper. I have 4 of those Comp Cams check rods and none of them are right. Hell, they're not even the same!

Measure length at zero lash and add the preload you want. But that still won't be the length you order. You'll need to call up your pushrod manufacturer (Manton is a good one) and share your measurements and the brand and part number of length checker tool you used. They'll compensate to account for shape of the ends of the pushrods vs. the checker tool, and things like growth of the block after engine warm up. Then they'll group your results according to the length increments they are able to manufacture. You'll likely end up with 4 or more different pushrod lengths when they're done, and you'll need to keep track of which one goes in which hole.

BOOT77

Ok this use to be more common knowledge but if someone mentioned it then I missed it when skimming replies

There are three ways manufacturers use to measure pushrods(some change for their different lines of pushrods[comp cams]) you can google it for the descriptions on the 3

Comp cams has two types(not actual tools they have many) of pushrod checking tools that I know of. Each checker is for their line of pushrods and may work for some other brands. That is maybe why your tool isn't exactly 7.400 because their 7.400 pushrod isn't 7.400 total length.

Just be glad your not flat tapped SBC they sized them so you gotta buy two, for example I need checkers 6.8-7.8 & 7.8-8.8