Pushrod measuring confusion
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Joined: Nov 2007
Posts: 458
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From: Birmingham UK
Pushrod measuring confusion this I thought was an easy task...
ive bolted the heads on and used my Comp Cams pushrod checker, I’ve come out at 7.275 zero lash so going for Cam motion 7.350 5/8 pushrods, i then checked the checker with my large vernier and found at 6.800 it actually measures 6.822 tip to tip.
I phoned the manufacturer of the checker, the guy said been as I have the large vernier use that as the ultimate figure, I wasn’t convinced, I rang the cam manufacturer and he said depends who your pushrods are made by depends on on where they are measured from, but as it’s a hydraulic set up don’t sweat it, but the difference is a full different order part to me so I did “sweat”, i rang cam Motion and they said go with what the checker says as this is where the joints make contact, so yeah bit of a mess around for a simple job!
ive bolted the heads on and used my Comp Cams pushrod checker, I’ve come out at 7.275 zero lash so going for Cam motion 7.350 5/8 pushrods, i then checked the checker with my large vernier and found at 6.800 it actually measures 6.822 tip to tip.
I phoned the manufacturer of the checker, the guy said been as I have the large vernier use that as the ultimate figure, I wasn’t convinced, I rang the cam manufacturer and he said depends who your pushrods are made by depends on on where they are measured from, but as it’s a hydraulic set up don’t sweat it, but the difference is a full different order part to me so I did “sweat”, i rang cam Motion and they said go with what the checker says as this is where the joints make contact, so yeah bit of a mess around for a simple job!
The confusion comes when different manufacturers use different reference points.
Some measure from the theoretical center of the sphere between each end, and others measure from the "flat" where the oil hole intersects the sphere.
Ever wonder why a pushrod checker has a flat on each end, this is why.
I have always used the "flat-to-flat" measurement of the pushrod checker.
I have also made my own "checker" by taking an old pushrod and cut a section of the tube out of the center and drilled/tapped threads and installed a 2" allen head set screw and two jam nuts. Then I can measure the "actual" length from "flat-to-flat" or "oil hole-to-oil hole" whatever you want to call it.
Cole
Some measure from the theoretical center of the sphere between each end, and others measure from the "flat" where the oil hole intersects the sphere.
Ever wonder why a pushrod checker has a flat on each end, this is why.
I have always used the "flat-to-flat" measurement of the pushrod checker.
I have also made my own "checker" by taking an old pushrod and cut a section of the tube out of the center and drilled/tapped threads and installed a 2" allen head set screw and two jam nuts. Then I can measure the "actual" length from "flat-to-flat" or "oil hole-to-oil hole" whatever you want to call it.
Cole
Just measure tip to tip on the flat spots and contact Trend and order the correct measurement for EACH Cylinder. Don't forget to add the preload.
If you tell them what you're doing, they'll help you do the math. Give them all of the info on the parts you're using. I find that most every engine I build takes several different sizes to get "Dead on" between every rocker.
Just my opinion and two cents... Good luck.
If you tell them what you're doing, they'll help you do the math. Give them all of the info on the parts you're using. I find that most every engine I build takes several different sizes to get "Dead on" between every rocker.
Just my opinion and two cents... Good luck.
Been there and done that! I have that same checker and my dial caliper reads 6.810 when measure the overall length. I also have the pushrods from my LS1 and the dial caliper reads 7.396 on those.
