LT4 Rocker arm issues

[calvin]

I'm putting together a gen V lt4 for my 56' GMC.

I did a DOD delete on it and used LS7 lifters, stock 7.850" pushrod length BTR rods, and Texas Speed LT4 adjustable rocker arms( i got a great deal on them..didn't look for these specifically fyi)

Anyway, I went to bolt the rockers on and noticed they open the valve probably .020" when tightened down. (yes, on base circle)

So now i'm scratching my head. Got an adjustable push rod and tried to come up with the proper length.

I basically took the rod and set it up for zero lash and then added .070 to that measurement and came up with a 7.70" rod.

Did I go about this right? and is it safe to use the same rod on all valves even when factoring in the lash caps on the intake valves?

Sorry for the long post.





Thanks for any help

[Vimes]

I'm pretty sure GM uses different lobe profiles on the DOD cams, on the same cam. The lobes for the cylinders that shut off are not the same as the lobes on the cylinders that don't shut down as the hardware is differerent. You may need different length pushrods for the DOD cylinders, or just get a different cam.

[calvin]

Sir in the original thread I state I did a DOD delete

[Vimes]

So you're seeing the same across all cylinders? My bad. For some reason I was thinking you were only seeing it on some cylinders, but still Gen5 engines do use different profiles on the same shaft for DOD engines because of the difference between the hardware on the cylinders that shut off and this is what I thought your issue was. But, Gen3 and above engines are more sensitive to pushrod length than the Gen1/2 engines were. Link to the procedure:

https://www.themurdernova.com/post/t...ength-pushrods

[calvin]

Same on all valves. Not sure why

[Big_KID]

Typically an adjustable rocker is not used with a hydraulic lifter as there are no lash adjustments to make like with a solid lifter. However, if you want to keep these rockers and pushrods, you can effectively shorten the pushrods by backing off of the lash adjusters. This will need to be done somewhat systematically to insure the proper preload on the hydraulic lifters. The turns/inch of the adjusters would need to be determined to set the lifter preload after zero lash. Be sure to check the wipe pattern on the valves after setting a few.

[calvin]

Yes. Adjusters were backed all the way out. I ended up going with a 7.675 rod to bring it into spec.

Thanks guys