Comp Cam Push Rod Length Checker Sucks...

91BlckGT · Sep 17, 2016

Comp cams custom push rod length checker doesn't fit AFR valve guides due to knurling on the side. And the only way to accurately validate the length of my push rods are by leaving those guides in place. Argh.

Waste of money that was.

So now I'm looking at the marks where the roller hits using the stock push rods (6.248") and they seem spot on, so I think stock length are good.

I almost bought Comp Cams High Energy push rods, but just realized those do not appear to be "Hardened", so I think I need to pick up the Chrome moly Magnum rods (which makes sense since i have the magnum rockers now). I'm pretty sure the 7621-16 is the model I want, right?

http://www.compperformancegroupstor...&Product_Code=7621-16&Category_Code=516Length

liljoe07 · Sep 17, 2016

Can almost bet that will be too short. Can't go by looks alone. Turn the pushrod checker upside down. Put the knurling close to the lifter. Or just grind the knurling smooth.

91BlckGT · Sep 17, 2016

liljoe07 said:
Can almost bet that will be too short. Can't go by looks alone. Turn the pushrod checker upside down. Put the knurling close to the lifter. Or just grind the knurling smooth.

I was thinking about doing that, but the AFR heads are designed for stock lengths (I have 165cc), and I tested 4 different pistons. Each, with the stock length, put them near dead center. And stock are 6.248" vs 6.250". I'll remeasure everything when I get them.

I also decided after further reading to get seemless Chromoly versions, the Hi-Tech model 7917-6.

jrichker · Sep 18, 2016

@91BlckGT

Use a drill bit to gauge the size of the pushrod hole in the guide; a slightly smaller bit is better that a larger bit.. Then take that same drill bit and drill a hole in a piece of bar stock or a common nut. That will be your go/no go size gauge for the pushrod.

Chuck the pushrod in a drill or preferably a drill press and get it running as fast as it will go. Then take a file and file the knurl down. Use the go/no go gauge you made to check your results. Bingo! Perfect fit!

91BlckGT · Sep 21, 2016

Just a follow up. I picked up 6.250" pushrods. They seem a bit too long. I thought that was within 0.002" of the stock size. Here's the wear pattern:

I got off my lazy butt and measured them. They are the same length, I think the welded ball joints at the were confusing my eyes.

liljoe07 · Sep 22, 2016

The mark being toward the intake side shows they are too short. Mark also looks too wide. Try longer lengths till the witness mark gets narrower.

91BlckGT · Sep 22, 2016

Ed Curtis agreed. Here's 3 more tests. I "fixed" the comp cam tool using a sandpaper and tape.

Here's the baseline. The new 6.250" rods are left, the cam tool on the right set to 6 5/16"

And here's the second test, with the length tool set a little over .1" longer, at 6 and 6/16"

liljoe07 · Sep 22, 2016

The best looking pattern to me is in the second picture. Valve to the far left.

91BlckGT · Sep 22, 2016

liljoe07 said:
The best looking pattern to me is in the second picture. Valve to the far left.

You mean the one with the stock pushrod length, where i didn't set it at TDC or set valve lash properly, thus having it right at the far outside of the valve? Yeah, I'm not going to go with that one.

liljoe07 · Sep 23, 2016

Regardless, it's the best looking pattern. But, you don't seem to want to listen to me. So good luck.

91BlckGT · Sep 24, 2016

liljoe07 said:
Regardless, it's the best looking pattern. But, you don't seem to want to listen to me. So good luck.

Are you talking about this picture?

The far left valve stem (there are three) is what I was talking about. The far right one is the proper wear pattern (disregarding where I smudged the ink in pulling the roller off). I'm "listening" to you, and was confused when you said the second picture was best. I actually do appreciate people taking the time to respond to this post, but I know the best pattern is going to be the one where the mark is dead center in the valve to maximize lift. Just want to make sure we're looking and talking about the same wear pattern.

liljoe07 · Sep 24, 2016

Dead center sweep is not always what you are after. Proper geometry will be the narrowest sweep. And more often than not, that pattern will be off center. And yes, the far left was also what I was talking about.

91BlckGT · Sep 25, 2016

Ah.

That said, I did confer with Ed Curtis and he indicated he preferred the right-most one after these series of photos were taken, so I ended up buying 6.350" Hi-Tech rods and returned the 6.250" once I confirmed the measurement of the measuring tool. So your initial hunch about the stock length being too short was spot-on. AFR's instructions said that it would be one of those two lengths anyway, so I feel comfortable with the new measurement. Now to just master valve-lash settings...

Comp Cam Push Rod Length Checker Sucks...

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