Team Camaro Tech banner

Pushrods

1K views 12 replies 5 participants last post by  SoCal805 
#1 ·
I have a 454 engine bored over 30. Are the pushrods different lengths for intake and exhaust? What would be the length for these? I’m not getting good compression.
 
#2 ·
Yes they are different sizes. Don't know the exact measurements, but you should be able to see the difference.
 
#6 ·
I had Straub send me correct length push rods. There's a process for measuring for the correct ones. I came up with the following for the engine in my signature below which is a 454ci +.030" full roller motor:

Intake: 7.684"
Exhaust: 8.622"
 
#7 ·
OP

rebuilt motor with the block likely being decked along with the heads plus thickness of head gasket that was used, rocker ratio and cam lobe profile will affect PR length so you need to measure using a PR length check tool. You want a PR check tool that has a range of 7.5-9.5"


Process is not hard but there is knowledge required on how to do it. You can start by setting the PR check tool to the length of stock PR. Mark valve tip with a Sharpie and lash that valve and rotate motor over 2 revolutions. Remove rocker and look at where the witness mark is on valve tip. You want it to be center and narrow. If the mark is more towards the exhaust side you need a shorter PR. If towards intake side of motor you need a longer one. "Generally" you wind up with shorter than stock lengths.


Lets say for example you get a length of 7.123". Many PR companies make lengths in .050 increments so you would get 7.150". No need to order custom ones of 7.123 as you are not building a $100k Nascar motor.


On rebuilt motors there is no "one size fits all" so you need to measure. If your current PR are to long the valves will not close and that would absolutely affect compression...and the motor would run like a$$ also.
 
#8 · (Edited)
Only thing I will add is that the plastic Push Rod check tools are junk. Not even close to accurate. Custom push rods from Straub aren't any more money than a good set of off the shelf ones. Incidentally, Scott Foxwell is likely to answer the phone at Straub when you call. He's a hell of a nice guy and extremely knowledgeable and patient.

 
  • Like
Reactions: SoCal805
#9 ·
^^^, good video Hawk

agree the plastic tool, Proform IIRC, is not as good. I use a adjustable PR, Comp. Also use calipers to measure them

Also depending on the spring retainer and using RR, especially aluminum ones with bulkier bodies than steel ones, you need to confirm the RR geometry does not allow the body of the RR to hit the retainer with valve fully opened and closed. If so you need to use a larger keeper (degrees) and matching retainers so slightly more valve stem sticks up above retainer. But that affects installed height of spring so always measure, using a valve spring height measuring tool, and add/subtract shims as needed to maintain "installed height" per spring specs.

Bottom line is correct valve train geometry makes or breaks a engine performance and longevity so set it up right
 
#10 ·
That video really pulled valve train geometry out of the black arts realm for me. I have about 4,000 miles on my motor that I built from scratch, so I'd say the methods Scott taught me are working out pretty well. Here are pictures from when I was building my engine that show about an 1/8" gap on the exhaust and a 1/2" gap on the intake between the correct geometry and what the "better" Manley plastic checker would have had me at.


One more thing for the OP: Have you tried pulling your rockers or at least getting a lot of slack in them and then checking your compression to see if it really has anything to do with your pushrods?



20180415_150225 by Dave H, on Flickr


20180411_210012 by Dave H, on Flickr

20180411_205919 by Dave H, on Flickr
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top