joshua022

iTrader: (12)

going on in a few weeks after I get a valve job done on my heads ( I heard you can gain some flow at the lower lifts ie.. .200, .300, .400)

-243 heads off a 06 corvette, P&P'd, milled .055, and with the valves unshrouded, w/ sodium filled valves
-6.0 stock head gaskets
-8.1 injectors
-7.300 hardened pushrods

I put my new se-tup and specs into my GM engine analyzer program and it said the compression ratio would be 10.66:1.

I'm hoping for a good improvement.

What kind of numbers difference do ya'll think this will make??

Yogi Bear

The 7.300 pushrods sound a little short. I think that they need to be at least 7.345"

joshua022

iTrader: (12)

I was doing some reading on LS1tech and found out that if you reduce the length of the pushrods a tiny bit it takes some of the pre-load off of the lifters, and reduces the sewing maching noise at idle.

I did all the calculations and that is what size I need to both; accept the milling of the heads and to reduce the preload some.

Yogi Bear

Preload eliminates clearance in the valve train and reduces noise. Can you post a link to the story you are referring to?

joshua022

iTrader: (12)

it doesn't reduce any clearances, because they are hydraulic lifters and they take up for any slack in the valve train. This just reduces the amount of preload on the lifters.

I'll see if I can find it. I just did a search on "sewing machine noise" the first time if I remember correctly.

I believe it was the sponsor "wheel to wheel pwertrain" that figured it out.

Yogi Bear

Hydraulic lifters will NOT "take up for any slack in the valve train". They have to be adjusted properly to take up slack. By changing the pushrod length, you adjust the lifter to eliminate clearance, which causes noise. All hydraulic lifters have a range of adjustment on the preload, and you may get away with reducing the preload some, as long as it is within the range of preload for the lifter. Reduce the preload too much and you will definitely have valve train noise.

Generally, the only reason to reduce preload is to reduce the likelihood of valve float cause by some lifters that "pump up" at higher RPMs.

joshua022

iTrader: (12)

Well, If I have time later I will try to find that thread for you to show you what exactly I am talking about.