wastintime

Hey everyone,

Next weekend we're upgrading the LS3 in our 2011 Camaro SS and it's actually going to be pretty cool, a new, very aggressive, cam is going in, ported heads, new valvetrain, dry sump, etc... As far as I understand it the stock LS3 pistons do not have any valve reliefs machined into them, only the L92 pistons do. I know of at least 3 LS3 Camaros running the cam we're installing with absolutely no issues at all which makes sense to me because it has a 114 LSA and I have the exact p/v clearance numbers on a different cam with plenty of clearance with an almost identical profile, but a 112 LSA, so in theory we should have more clearance. However we still want to check, also we're installing a very slightly higher compression head, so that's kind of a monkey wrench in the equation, as well. I'm REALLY hoping we don't have to flycut the pistons, but at least we'll know from measuring the clearance.

So here's my question. And I know nothing about LS motors, this is the first I've ever touched, but... everyone says it's impossible to check piston to valve clearance with hydraulic lifters. I want to know why. It doesn't make any sense to me. If I know for a fact that the LS3 lifter can compress/extend 3.20mm and preload is 1.58mm, then with no oil pressure and certainly with no oil in the motor, if i spin it over with valve springs installed it's going to compress the remaining 1.62mm or .064" multiplied across a 1.7mm rocker arm is .108" or 2.74mm Isn't it exactly as simple as subtracting this number from our measured clearance to find the p/v clearance at pre-load? I suppose you could argue that the spring is going to absorp a little bit and your clearance reading might be a bit low, but if the valve was already opening, it can't be that far off.

Any thoughts or advice?

Thanks,

RsSean

iTrader: (27)

go to lowes there are checker springs in the nut and bolt section. Clear/blue bag there is two in the bag for 2-4 bucks. There is enough spring tension on the retainer and the locks on the valve, but no enought to colapse the lifter. Roll the motor over with teh clay on the piston subtract the .050 for the lifter preload and you end up with

wastintime

I understand it CAN be checked that way, with the added complexity of having to remove valve springs, and at that point the clay method doesn't make sense, it makes more sense to measure the gap at the rocker/valve with everything torqued down.

My question is what's wrong with simply mathematically subtracting the error you know you should be getting from a compressed lifter? Everyone says you can't check with hydraulic lifters because they compress, well yes, but GM has given us the exact amount they compress, so why can't you just correct for it? It seems like every solution involves investing in tools, parts, solid lifters, etc... but why not just subtract?

3pedals

iTrader: (3)

because it doesnt work.
the lifter may not fully colapse, and you will be left not having any reliable info.

SweetS10V8

iTrader: (4)

Checking spring
Adjustable pushrod
dial indicator

Install checking spring, adjust pushrod to zero lash, roll over the engine with the dial indicator on the retainer. Push the rocker down till it hits the piston. Keep rotating and checking until you find the tightest spot. No clay, just physical measurements with everything bolted together......

Gray86hatch

iTrader: (83)

If you start taking preload into your measurments you are going to have issues. THings change with heat and oil pressure.

Light spring zero lash is the way to go.

Tim