Push rod length confusion
 

I bought the comp cams part number 7702 push rod length checker. On web sight it states it measure from 6.800"-7.800". When I measure it with caliper fully collapsed it comes in at 6.825" so whats the deal? Thats an extra .025". When doing my math should I just use 6.800"?

Why wouldn't you just measure the length checker with the calipers after finding zero lash?

Thats what started this mess. Lets say I never measure asuming it was 6.800" my measurements would be .025 off. depending where your at could help or hurt.

I guess I don't understand. Do you trust the length checker or the calipers? I would trust what the calipers are telling me 1000 times out of 10.

I guess your right but sucks that for someone that dosent have calipers to check they could get screwed.

Pushrod length is not measured end-to-end. Comp uses the gauge length as illustrated below. What you measured is the actual length if it has a hole drilled through the center, or theoretical length if it doesn't. Lengthen the pushrod until the rocker just barely gets to zero lash when tight. Then remove the rocker and pushrod, count the turns, multiply by 0.050, add 6.800", add desired preload, then get the correct pushrods from Comp.

http://www.cpgnation.com/filehost/fi...d%20Length.jpg

OH. Okay I understandy now.

Ferocity nailed it! Counting turns on that tool is always going to be more accurate than measuring tip to tip on any combo! Everyone should have this $20 tool in the box!

Thanks guys for clearing that up. I've never heard that before.

So if I measure comps 7.400" pushrods with calipers, it won't read 7.4?

Tolerance stack...