I'm gonna replace the PR when I do the cam swap for my LQ4. The heads, gaskets, deck height, and rockers are all staying stock. I'm simply changing the cam and springs right now. The cam is a small Comp 216/226 .526/.535 112+4. Its a very similar grind to the hot cam.

Anyways, could I safely pickup a set of 7.400" pushrods? I was thinking about measuring the base circle on the stock cam and the new Comp, and then splitting that difference in half, adding it to the overall pushrod length. Should I go ahead and do this or will 7.4" pushrods be fine?

 

You can measure the base circle like you said, that is a good way to do it. Or to be 100% sure and get a desired preload you can buy a pushrod length checker and actually measure what you need.

 

Yeah, you need to know teh difference in base circle radius between teh stock and new cams. Most likely itll be 1.550 to 1.450. In which case a 7.425 pushrod will be within .005 of the stock 7.380 pushrods. 7.400 will also work, but not quite as on target.

 

You need to buy a pushrod length checker to be 100% sure, don't half *** it because you can cause premature valve stem failure if you're not centered.

 

Correct me please if I am wrong, cuz I am near putting mine back together.
If he has stock valve train, wouldn't the rocker wipe be the same if he used the wrong lenth PR? The rocker geometry is not a variable. Wouldn't the wrong length PR just preload the improperly?

 

This is a greatly debated topic. Im with you on this one. I feel the wipe would only change if the rockers were shimmed to adjust for preload. Other people will disagree on this topic to the death...

 

IMO, no. With a near stock setup though, I do not see how you could end up with the proper preload but have the swipe pattern too off-center. I did not bother to check swipe when I did H/C. All I was concerned w/ was selecting the push rods which gave me the desired preload. Correct me if I am wrong, but if all you change are cam and pushrods, you cannot achieve proper preload without having a proper swipe pattern. This was taken into account during design of the engine and components, was it not?