Johnson 2110's into an LS7: pushrod length?
 

Trying to figure out the math here so that I can better speak to the subject.

Trying to figure out the "theoretical" desired push rod length for a new set of Johnson 2110 SLR drop-in lifters in my LS7 while I have the heads off and swap the cam. Of course, I'll measure to be certain, but given these are the standard 2110's (not the R's with the very short plunger travel) I should be able to get by on just one pushrod length. Heads will not be milled and will use OE GM MLS head gaskets.

The OE pushrod length on the LS7 cylinder heads with the LS7 lifters is 7.800". A lot of folks believe the GM preload is a tad high and like to reduce that length right off the bat and run 7.775" PR's.

The preload on the Johnson 2110's is .035" and it's common to shoot for .040" +/- .010". I believe the OE LS7 lifter preload is around .100" to .125".

I believe that both the 2110's and GM LS7 lifters share a common .842 lifter body diameter and I believe (per Texas Speed's website) the 2110's are .045" taller than the GM LS7 lifter. From what I have gathered on this and other forums, I believe that the plunger travel on the 2110's is about .210" which I believe is also the same as the OE LS7 lifter?

So for starters, what length pushrods should I (theoretically) be looking to start with?

Ok, here's the deal. All this on the same engine:

Stock pushrods 7.385
Cam swap 7.400
Heads and lifter swap including Johnson 2126 7.700
Pulled heads, installed solid lifters, no other changes 7.410

Bottom line. Get a check tool and measure

I agree with you, but with a hydraulic lifter with a .201" plunger travel, I should have a lot more margin than say with the 2110r's. I should be able to get by with just one pushrod length, just like the OE LS7 lifters. I may as well start with one length of pushrods and that is why I'm leaning towards 7.775".

I believe there is a desire to run .080 preload on the LS7 lifters instead of .100, and that is why some will put back in 7.775" PR's on a head swap.

If .100 preload on the OE LS7 lifter gets me the OE PR length of 7.800", switching to the 2110's I would need to account for two things: the .048" taller height of the 2110 and the smaller desired preload of .035" +/- .010".

"Theoretically," does the taller height of the 2110 (.048") offset the roughly half as much preload (.035" +/- .010") it calls for thereby leaving 7.775" a good place to start and at least have on hand?