I know this has been discussed many times but ive search at least twenty threads from many forums and I've got many different answers. Some say there shorter at the cup and need longer rods, some say there longer so shorter push rods. And then I've read that the cup is a little taller but it allows for more compression room and that the stock 7.4 are still meant to be used.I then go on to read that with stock gaskets .054 and stock deck heights people have used 7.300 , 7.350, 7.375 , 7.400 and 7.425 and with all these different rod lengths people have had similar results and everyone recommends the length they used. I even heard that high lift cams over .600 lift have smaller base circles that's why u should use 0.025 longer to compensate.i trying to get this top end open and closed the same day and I know the only way to be sure is to use a length checker. But what is the recommended length.I'm doing 243 heads with the TBSS intake and a 220/224 cam with 6xx,6xx lift. Please point me in the right direction???????

 

The LS7 lifter is the replacement used from GM for the LS series engines, I dont see anything from GM indicating to use anything other that the stock push rods when swapping the lifters.

 

They are taller then the old style lifters. However only by a very small amount. They are used AS A DIRECT REPLACEMENT for these engines, nothing is said about needing a shorter PR. However the standard length PR is 7.38, not a 7.4 like alot of places sell. If the cam you are running has a smaller then stock BS then you will need a different then stock length PR's. best bet is to put them in, get a PR checker, measure what is needed. They are hydraulic, so they will be able to adjust to some degree..

 

Maybe I'm reading to many threads but there is pictures showing the cup of the ls7 lifter being more shallow then the old style. And I know there direct replacement but people have checked there length with stock gaskets and stock deck height and got length from 7.300 to 7.425

 

The LS7 lifter has a different cup which makes it's effective length 0.050" longer than the stock lifter, therefore you need a shorter pushrod for the same preload. I am using 7.350" pushrods with mine. I've heard of people using 7.400" rods too without issues as well.

 

So most are running 7.400 PR ?

 

7.35 here with the LS7 lifters, I had 7.4s but after measuring with pushrod measuring tool I went with 7.35 to keep the preload at about .080

 

Ditto! Although my preload was slightly less, maybe 0.07" or so.

 

You are gonna get the same inconstant answers as you found. Everyone's lengths are gonna be pretty much different because of combos they are using. If you want to just throw some in there and hope for the best, I would put 7.4's in. Personally I would just take the extra time to measure it out and get the correct length. The few extra days you wait for the pushrods is nothing compared to the replacement of the stuff you can destroy with the incorrect length.