SDPC with the LS7 lifters can you use a stock pushrod length?

 

They are not identical the picture proves that (not to mention measurements)

What is identical is now if you go to a dealer and ask for LS1 replacement lifter you'll get LS7 because GM made it that way.
Physicaly they are same overall length but cup sits higher.

 

Predator Z's post and my post are regarding two different things, they are not in opposition to each other. His is regarding the old stock lifter that you will take out of your LS1 as opposed to the new lifter which will be replacing it with, they are not the same as each other. You can no longer purchase the lifter on the right in the picture. Any stock replacement LS lifter you buy will be the one on the left, be it LS6, LS1, LS7, or any other LS engine. The replacement parts are all the same "LS7" lifter. My post was in regard to the guy saying the newest LS7 design lifter was not the stock replacement and that those of us selling it as such were actually selling replacement LS6 lifters and that "real" LS7 lifters were different.

 

The difference still keeps them in spec. Running them here no prob......

 

I wanna chim in here. The LS7 Lifter plunger depth is shorter than stock LS1 lifter. I ended up using 7.450 pushrods on my Afr 205 milled to 62cc vrx2 cam 224/228/114 and YT 1.7's RR. If this was another lifter like stock LS1 or maybe comp, I would probably go with 7.500. PS I also have 7.250 and 7.350 crane's for sale.

 

Link to info of lifters disassembled and measured:http://forums.corvetteforum.com/c5-t...ic-lifter.html

 

Most people do, but it is not the ideal length.

 

A buddy and I installed a set of LS7 lifters on my recent cam swap. Used stock length pr's and i'm getting that horrible sewing machine noise. We went with a .040 MLS gasket and 1.75 rockers though. Should've known something wasn't gonna work out.

 

Good thread. Thanks

 

No way. You must be doing this comment by deduction not by actualy measuring roller to inside cup area (where p-rod tip lies).

You have nothing stock to point to that. AFR heads, comp cam and YT rockers. All of which will never give you a deduction on your comments.
It is .050 taller at the cup period (actual measurement)

 

Those are just LS1/LS6 lifters, not LS7 and the story is incomplete since early LS1 came with non incapsulated rollers (as my pic shows).

Picture 1:

LS1/LS6 Delphi on right, Eaton on left

Picture 2:

LS7 on right, LS1 on left (non capsulated roller)

Pic 3:

Delphi LS1 on right and Eaton on left. Although LS7 anf Delphi looks close at first glance, take a good look, you'll see that they are not the same, similar but no cigar.

 

How about the Caddy lifters Are they the same cup depth as the LS1 lifters or the LS7 lifters or are they something completely different?

 

You are correct I meant to say taller, which would make for a shorted PR. Which I ended up using.

 

This is a good thread, it gives a good amount of history, pictures, and ideal operating preload for the LS7 lifters. However, Im surprised there hasn't been a sticky made that covers this subject. I feel a moderator should make a sticky that covers all the various questions and concerns people have about LS7 lifters.

 

so if i go to the dealership and ask to get new lifters, they will give me "ls7" lifters? i had my 243 heads milled .006 to clean them up, and have 7.4 comp pushrods. am i going to have a problem here? definately wish i knew changing lifters would alter pushrod length before buying pushrods. oops

 

Measure, there is no way around it if you want to do it right.

 

I think i will buy a couple of different push rod lengths and measure and install the correct one's. I'll just send the one's back that aren't the correct size.

 

FWIW, EVERY cam install I have done using the LS7 lifter with a cam with greater than .600" lift (read smaller base circle) AND stock heads w/GM MLS gaskets has taken 7.425" pushrods for ~.050"-.060" preload. We measure lifter preload on each and every cam install we do. I have never had a lifter failure nor do we end up with the dreaded "sewing machine" noise.

Its very simple, If you change ANY of the following:
valve sizes, valve job, head milling, thinner/thicker head gaskets, decked block, cam with an altered base circle, etc... YOU MUST CHECK FOR PROPER PUSHROD LENGTH.

I have helped countless numbers of individuals with this process over the phone, via email, and PM's. I've posted the process on at least 3 occasions.

Here it is again in a nutshell:

1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.

For an example, if you use a 7.400" pushrod and come up with 3/4 of a turn, you will need at least .025" longer pushrod to get into range. If you end up with 2 1/4 turns, you will need one .025" shorter...

I might not know everything but I will tell you that this method has worked for me year after year cam swap after cam swap. We average 3 cam swaps a week here so you can do the math.

If you are not familiar with the EO/IC method for determining valve events in a 4 stroke engine, its very simple:
For a given cylinder as the Exhaust valve is Opening, the intake lifter will be on the base circle of the cam and lash/preload should be checked for that intake valve.
For a given cylinder as the Intake valve is Closing, the exhaust lifter will be on the base circle of the cam and lash/preload should be checked for that exhaust valve.

THIS METHOD ALWAYS WORKS!!!

I hope this helps someone. I have explained it so many times I think I do it in my sleep!!!

Shane

 

Shane, I tried your method and I ended up being less by half a quarter of 1 1/4 turn.

Should I get worried?

 

That is the most screwed up sentence I've ever read. What exactly is a half of a quarter of 1 1/4 turns?