I'm in the middle of an LS1 build.

I have AI ported 243s milled to stock specs.

A custom cam from FlowTech.

Stock head gaskets.

Morel 5206 lifters.

I am at the pushrod measuring stage, and I keep coming up with an average of 8.5 on my adjustable pushrod which, with lifter preload, only brings the rods I need to 7.3.

This seems short to me and Ed at FlowTech.

What am I doing wrong? I've measured a dozen times now on multiple cylinders.

 

There are a half dozen variables that affect the pushrod length you need - lifter plunger height, cam base circle diameter, deck height, installed spring height in your heads, compressed gasket thickness, etc. etc. It's possible that you're not doing anything wrong.

 

Not sure which Morels you are running, but when I installed mine I took several measurements of the lifter and found that they would require shorter pushrods. I found that the combination of taller lifter and shorter preload resulted in a difference of approximately 0.100" shorter pushrod requirement.

What is the preload you are using?

 

7.3 sounds about right for the 5206s. Are the heads bolted down? Are you measuring at 0 lash and adding the .030-.050" needed for the Morels?

 

Yes, yes, yes.

I talked to Ed at Flowtech a bunch and we agreed it is what it is if that's what I'm measuring it at.

Thank you for your advice, everyone.

I went through the procedure of finding TDC a couple more times just to make sure I was and stuck two of the stock pushrods onto the lifters and watched them to make sure I was on the base circle of the cam. I came out with an average of 9 turns after that to 0 lash. I think I was being a bit lazy with my own thought of 0 lash before. 9 x 0.50 = .45 + 6.8 = 7.25 + .040 (mid range) = 7.29. 7.30 were the closest I could get and they are still within the preload range of the 5206s, so I'm happy with where I'm at.

I went with the 7.3s. Doing the first start tomorrow.

 

Manton allows you to order in .001" increments for no added cost.

 

Yes, but I wanted them same-day. Takes maybe an hour to change them, anyway. I'll order some 7.29s this week and sell these when they come in.

 

I got the same length pushrods last week and have the same Ai 243 prepped heads, Ai cam, .051 stock gaskets and LS7 lifters and figured in .060 preload.

 

I thought LS7s were more like .08-.100?

 

Depends on who you talk to, and actually I did add a little more preload. It was 8.5 turns so 6.8 + .425 + .075 = 7.300.