crainholio

iTrader: (2)

Using a Comp 6.800" pushrod measurement tool, I have measured two intakes and two exhausts, got 8-1/2 turns to zero lash each time.

The engine is an LS1 long block with the following modifications:

'02-04 LS6 camshaft (brand new from GM dealer)
243 heads with 0.004" milled off (deck height was 1.608" factory, now 1.604")
LS6 valves (taller than LS1 valves)
Morel link-bar lifters (cup is 0.050" higher than LS1 lifter)
Stock rockers
GM MLS head gaskets

The measurement puts me at 7.225" length, plus 0.030" preload the Morel lifters want gets me at 7.255" net pushrod length.

Morels seem to like less preload than more, so I'm looking at 7.250" pushrods.

Can you guys check my math? This is basically a stock setup with a few known changes, but I can't account for the pushrods being so short.

Morel lifters have the cup higher than stock: 0.050"
Heads were milled: 0.004"
LS6 valves taller than LS1: 0.014"
------------------------------------------------------------------------
net difference: 0.068"

Stock pushrod is 7.385" and includes some amount of lifter preload.

7.385" - 0.068" = 7.317"
7.317" - (lifter preload from factory) = X

What am I missing?

A.R. Shale Targa

iTrader: (2)

LS6 valves are 0.6 mm longer or 0.0236" to allow for smaller base circle
of factory cam and still use 7.385 push rods of LS1

crainholio

iTrader: (2)

Thanks for the number, but let me explain my math.

I used 0.014" in my math above, based on the fact that the 0.0236" is on the long side of a 1.7:1 rocker and therefore:

0.0236" / 1.7 = 0.01388" or 0.014" at the pushrod cup.

Is this the correct geometric approach?

A.R. Shale Targa

iTrader: (2)

I see what ya mean. I was talking actual valve length and your thinking was
pushrod simulation. Also milling the head simulates a .004 longer pushrod but
the valve tip height lowers the same. Pray for quiet valvetrain !!!!

crainholio

iTrader: (2)

Prayers, animal sacrifice, whatever it takes.

If nobody chimes in with something I missed, I'll grab a set of Comp 7.250" pushrods in the morning.

The irritating thing is that I can't find any indicators of lifter failure on my old stock #8 or #2 intake lifters, the two noisy ones that the valve tips got hammered on. They won't compress w/ a pushrod by hand one bit. I expected them to be squishy. The cam lobes and lifter rollers showed small grooves, most likely caused by the ablated valve tip material washing onto them while in motion.

vettenuts

iTrader: (4)

I ran my Morels at different preloads and have found them most happy at 0.050" preload.

Not sure of what you are doing at the end of the post but a couple of things to think about. LS1 and LS6 use the same pushrod. LS6 taller valves must used the rocker ratio to figure out preload change. So the 0.014" taller valve stem will result in a 0.014 X 1.7 = 0.024" change in preload. Not sure if that helps resolve the difference. Also, not sure if you included the difference in preload that you are using vs. stock. I have measured a few stock vehicles and they come in close to 0.100" so that is approximately 0.070" difference as well.