inspecting a push rod

69 Mach I · #1 (**permalink**) 07-11-2005, 03:06 AM

I am looking at the receipts for my build and I have a notation for Comp Cams 8600 pushrods. I assume this to mean I have 8.6 inch push rods in there. I check the Comp Cams catalogue and notice that the standard length for a 69 351W is 8.150 and that you can go short or long by .050. It occurs to me that I might have pushrods in there that are too long, which could be catastrophic. How much work/time is involved to pull a pushrod out and measure it?

trularin · #2 (**permalink**) 07-11-2005, 06:09 AM

Open valve cover.
select a rocker that appears to be all the way down.
Unlock the set-screw.
Unscrew the rocker nut ( note the tension on the nut )
turn rocker arm sideways.
pull push rod.

Reverse to install.

make sure you set either lash or hydraulic stop, depending on the lifter used.

Hope this helps

69 Mach I · #3 (**permalink**) 07-11-2005, 06:41 AM

Quote:

Originally posted by trularin

Open valve cover.
select a rocker that appears to be all the way down.
Unlock the set-screw.
Unscrew the rocker nut ( note the tension on the nut )
turn rocker arm sideways.
pull push rod.

Reverse to install.

make sure you set either lash or hydraulic stop, depending on the lifter used.

Hope this helps

Cool. Thanks a bunch.

vettestr · #4 (**permalink**) 07-11-2005, 08:29 AM

Hey 69,
The best path to pushrod verification is to watch the travel of your rocker. Regaurdless of the length (it may have been changed or installed to correct the geometry). When you deck block = heads = line bore = or hone cam bores for any reason it alters the BIG picture or relationship and stack up of all these paramiters that are magnified by the rocker ratio in the end.
There are many web sites that can explain much better than my writting abilities. What you need to check or verify is the fact the rocker face is contacting the valve stem face properly. You have a stud in the head that your rocker pivots on = the pushrod is moved up and down by your cam (various lifts etc..) You can also install different ratio rockers that make checking the proper reference to each other a must.
@ valve closed cam just starting to open each valve you check to see valve stem face is contacted by rocker in/on the centerline. As valve goes to full open the rocker face contacts the valve face in a new place or moves off centerline. If your rocker moves too far from centerline of valve it imparts a great side load on valve to valve guide in head (very BAD). This is corrected or fixed by altering the pushrod length. I have a threaded pushrod in toolbox that I can screw in or out to perform tests and then order proper length pushrods. On my old hemi drag engines you use adjustable P. rods to set lash because rocker shafts were not adjustable!
This should be checked on every engine built !! as you never know if somebody machined the hell out of something before it came home with you. Adding a big cam and different rockers ratios also changes this contact point. Your builder knows this and checked during assembly so do not worry about your engine IT WAS checked during build if a good builder and it will put up with some error anyway. Vettestr

69 Mach I · #5 (**permalink**) 07-11-2005, 08:44 AM

Quote:

Originally posted by vettestr

Hey 69,

This should be checked on every engine built !! as you never know if somebody machined the hell out of something before it came home with you. Adding a big cam and different rockers ratios also changes this contact point. Your builder knows this and checked during assembly so do not worry about your engine IT WAS checked during build if a good builder and it will put up with some error anyway. Vettestr

All of that aside, would it even be possible to fit an 8.6 inch push rod in a 351W that normall takes a 8.150 inch push rod?

vettestr · #6 (**permalink**) 07-11-2005, 09:06 AM

69 Mach,
What ever it is the big issue is has it been set up with all working relationships. does it work or are you breaking stuff? A difference of .450 does seem to be way out there and noy likely.
Not being a wise a$$ here but anything is possible. You would not believe what has been brought to my machine shop over the years.
It would seem the P rod would be about 3/8 " too long and that does not seeem feasable but a .250 long P rod and a .200 SHORT valve stem etc.... it might run?