Help! How do I adjust lifter preload?

[Rhino79]

And we just remeasured with our newer lobe design, and yes with his heads milled they will be .018 with a checker spring. Now when you factor in spring pressure, defelction in the pushrod and rocker, you will have in the .050 range.

We have ran this setup before, why do we not do it all the time???

Because of situations like this. All we can do is tell people the right way to check and make sure preload is correct.

We also sent this gentleman modified stock lifters that are solid so he can check with.

Will it need 7.425? Probably not, but we can exchange those when you determine what length you really do need.

There is no way to forecast what you milled heads, and cam combo is going to need exactly with pushrods, because each engine will vary some.

[Rhino79]

Originally Posted by Russell James

You may want to ask clarification, are they really saying only .018" (18 thou) PTV clearance?

If so, that is wayyyyyyyy too close. That note makes no sense. 18 thou, and you'd even be OK with valve float? That's mind boggling f'd up.

Ask if they really meant .180"

Most builders like to see a min of .080 intake and .100 exhaust PTV. A builder that really knows what they are doing could possibly go a hair tighter. An amateur build...spec out a cam/head combo that is known to have plenty of PTV.

LS1Tech is a really good website with tons of LS Technical info and some really good builders that chime into the threads.

.080 and .100 is rediculously conservative. And .080 and .100 is assuming thats the amount with the lifter/springs used with the combo NOT Checker springs.

So with .018 on a check setup, near .050 in dynamic run environtment, .030 preload, the engine grows about .015 when warm so you lose .015 of the .030 and you end up with .015 hot preload.

.015 hot preload, .040-.050 clearance when engine running, if lifter ever pumps up and valves float, you still have clearance with no interference....

LS1Tech is useless now, it used to be good.

But to discredit us and recommend ask for a second opinion? Why? Because its not what you have seen done before? lol

We have several good minds in our program with many years of experience.

[Rhino79]

Originally Posted by Russell James

I'd get a second opinion on the build.

PTV so close that lifter preload is to be shorted? Never heard of that as a PTV assurance strategy.

Lifter preload should be based on the lifter manufacturer's recommendation. Generally 50% of total travel. Most are .120 travel, shoot for .060 preload. Racing short travel .060 travel, shoot for .030.

PTV clearance needs to be sorted out in the cam specs, not preload fudging.

Its sorted, all he needs to do is get the right length pushrod, put it together, and make sure the cam is dot to dot.

[Rhino79]

OK, just checked with Aaron. Pushrods were sent with the heads....All you need to do is find 0 lash and check piston to valve clearance using the SOLID LIFTERS we sent to check with.

[Rhino79]

Here is what was sent with the heads, to detail how you check your piston to valve clearance before final assembly. Also shipped were checking lifters, and a set of 7.350 at no charge....


Measuring PTV in chassis without a degree wheel

1, Make a piston stop. A piece of steel with a threaded hole in the center attached diagonally over the cylinder by the head bolts works great. Fine thread with a 1/4 “ bolt so you can attempt to stop the piston just before TDC.
2, bring the #1 piston to visual TDC. Install a piece of masking tape on the balancer. Turn the crank clockwise until the piston contacts the stop and prohibits further movement. Mark the tape and reference with timing cover. A piece of wire attached to a bolt works good for a pointer. Turn the crank counterclockwise until it stops again. Mark that point. True TDC will be midway between the two marks you made. You can now make 5 deg marks by measuring .327 from the TDC mark. 10deg would be .654 from TDC. The 10 deg mark + or – 2 deg will be your point of closest contact.
3. Install the 2 supplied test lifters. These lifters are not to be ran as they have been modified to test for PTV.
4. Install 2 check springs on #1 intake and exhaust. If working on a L99 the exhaust could be omitted as an exhaust relief is already present.
5. Install head gasket and head with 2 to 4 bolts snugged. Install pushrods and an intake and exhaust rocker arm. With one valve, partially open set the other one to zero lash. With a dial indicator on the retainer and the crankshaft at 9 to 11 deg ATDC depress the intake valve until it stops and record the measurement. Rotate the engine a few degrees either direction and verify the point of least clearance.
I figure you should have around .018. The block grows .015 when its warm, you will lose .030 in valve train deflection at RPM so you should be fine. I would run the intake lifter preload towards the light side so if you ever float the valves the plunger can only pump up a limited amount. 1 turn = .079, ¾ turn is .059. I would want to be close to that on the intake side.