After browsing some of the supporting tuners and vendors sites I thought 7.4" was stock length. After all that is what they are advertised as. Then I looked up the part number for a stock LS1 pushrod and found the stock length. It was 7.318". I know there is great variance in pushrod length depending on endcap size, style, and manufacturer measurement standards. It caused my eybrows to shoot up, because I just replaced my stock pushrods with TR 7.4's. I have had them in the car for about 1000 miles now and have been to the track a few times and nailed it a few more. Zero problems, and valvetrain is quiet as stock. When I installed them I didn't check for lash, because I thought they were 'stock' length. Are my lifters making all that length up? After the install I read a post that someone had measured the TR pushrods and found them to be 7.424, I think. I thought I understood this stuff, but the more I learn, the less I know.

 

 

Nominal stock pushrod length is 7.400" but manufacturing tolerances have to be factored in. Without a machine drawing, you'll never know the manufacturing tolerance for sure.

My heads were milled .030" so I went with 7.350" pr's since they generally come in .050" increments. They rest is made up by the travel in the hydraulic lifters. Some tuners use shims under the rocker bolts to make up some of the preload.

Check out one of CompCam's tech pages on pushrods:

http://www.compcams.com/Technical/Products/Pushrods/

 

Here is a little Insight as to what I have found out since Im dealing with the same Push Rod Length issue, only that its with an Old Small Block Chevy. The stock length on an Old Small Block is the 7.40. But, the stock pushrod length for the LS1 is like you said the 7.318. This shorter length is due to the fact that your car (If stock LS1/LS6) has a "Roller Cam" which means you have "Roller Lifters". Roller lifters are a "Taller" lifter than a Flat Tapped lifter, which means the pushrods need to be shorter. You say that the car is running fine. Might be good or bad. Im not sure. If your truely concerned, they make a adjustible push rod kit, that gives you an adjustible push rod and a plastic Mock Up rocker arm. If all is stock, you bring the cam to the bottom of the lob circle so the valves are both closed in one cylinder, install a good lifter, place the plastic Mock up rocker arm on the stud, put the adjustible push rod in and adjust it until it barelly touches the plastic rocker. Pull the pushrod out and measure it. Its a trick deal. I just got done using one. They work great.

Good Luck



Tony

 

stock length of ls1/ls6 pushrod is 7.400

 

what is it??? 7.31 or 7.4???

 

The latest info from ls1tech indicates the stock length is 7.380, so 7.4's can be accomodated by the stock hydrualic lifter (.020 difference). If a cam change is done at the same time, many aftermarket cams have a base circle .030 smaller in radius, so the net change is .020(extra pushrod length) -.030(smaller base circle)= -.010(pushrod shorter than nominal), once again, within the range the lifter will tolerate. If the heads are milled, then within .010-.020 milling, you are still in a good range fom the calculations above.


Hope that helps