So I’m getting all my parts ready for a weekend cam swap on my LQ4 in my 1500HD. Main questions are LS7 lifter seat height and pushrod length. I know I know I should always double check length. I do have a comp push rod checker and plan check prior to dropping in the pushrods. I’m needing some help so I can get pretty close. My build specs are below.

Stock bottom LQ4
862 heads ported and milled for flatness (.007 off)
Comp XR269HR 216/220 .525/.532 lift
Summit LS7 lifters (wanted morel 6504 but worried about preload being tighter)
Felpro .041 head gaskets

Stock pushrods are 7.38. I’m taking .020 off that between the head gasket and milling the head which brings me to 7.36. From what I can find my cam base circle is .040 smaller than stock. This would put me at a 7.4 pushrod. I’ve heard mixed stories of LS7 lifters needing a .050 shorter pushrod due to cup height. I have no idea about these summit lifters. They have said that stock pushrods work and reviews claim to use them in stock motors. But to me neither could be correct. My problem is I’m not sure if 7.35-7.375-7.4 would be correct or even close for a roughly .080 preload. Really hate to order all 3 sets as this is a weekend project and I need all parts on hand. Hoping someone has used these lifters or similar cam and has input. Thanks

 

Whatever lifters you use should come with a recommended preload. OEM, i think, you should just aim for mid travel, iirc they have the OEM lifter travels posted somewhere. That being said...

It is certainly possible to calculate from base circle, lifter dimensions, head measurements, etc, but it's so much easier to use a pushrod length checker tool and a pair of digital calipers.

Find length at zero lash, then add preload. EZPZ.

 

I couldn’t agree more. But with this being a daily driver and needing to finish it in a weekend I’m trying to get close. I don’t mind if I have to get two sets. I just want to be close. I’ll use the checker before I install them to confirm which will be closer. These should have the same preload as ls7’s which is recommended .050-.1 preload

 

Just get the tool. $30 or whatever, done. You can't buy enough bottles of aspirin and Tums with that little coin to make up for that.

LS7 lifters like about .075 - .080" of preload, but have a wide band of forgiveness. They have about .150" of total travel. Dread is right on the money, as are you. Take a deep breath, gain some confidence in yourself, and jump in there and do it. You've got the right idea. It's just pieces of metal and a measuring device.

Stock pushrods BTW are 7.400", measured by the method most widely used in the aftermarket. GM measures them a different way so IGNORE what they say they are. Not that they're "wrong", just, you can't compare their #s to anybody else's.

 

I appreciate the help but like I said previously I already have the tool. Used it on previous builds but this one is needing to be done in a day. So I don’t have time to install the cam then take measurements then order. I need to order up two sets and use the one that fits the best. I understand that gm doesn’t include the ends like the aftermarket does. I called comp but they refused to tell me what the base circle is. How nice of them. Since I can’t get the lifters in gm ls7’s like I wanted and I’m having to go with a summit brand, it appears these are more of a stock type ls lifter without the higher pocket that I was worried about. I’m going to order up some 7.4’s and 7.375’s. Since stock is 7.4 and the head and head gasket should make up the difference for the smaller base circle. Either should be fine with preload. I’ll still measure before install.

 

Ok I'll add this.
I'm getting ready to do pushrods soon, and I read that about the ls7 lifter cups being at a different height. I also read on this site that the ls7 lifters are the same height as the ls1 lifters. They only appear a different length because of the cup height.

I did a search comparing ls7 to morels and pushrod preload.