valve clearance

[underdog]

If I measure the valve travel to the piston at TDC is there a way to calculate how much lift I can get away with ?

I have the rockers off and the heads still on the block. The Intake valve will drop down 3.069, the exhaust is 2.055, before it hits the top of the piston at TDC.

I tried the clay on the piston thing but when I pull off the clay it distorts and I don't trust the measurement. I have misplaced that reading in all my notes and really don't want to do it again if I don't have too.

I'm tring not to remove the heads again, that's why I ask?

This learning curve is killing me ! :eek:

[lun40119]

The piston isn't at TDC when you are at max lift. I am suppose there could be a way to measure it that way, but I don't know how. I guess I like to play with play-do, and I use the back of a caliper. I don't take the clay off the piston until after I measure. Good luck.

[underdog]

I wrote that wrong it's .255 and .369 I guess I'll take the heads off AGAIN !

[want-a-be]

The exhaust valve minimun P-V clearance is measured at around 10° beforeTDC. I usually start at about 16° before TDC and check every 2° until I get to about 4° Before TDC in order to graph how the valve sweeps through minimun P-V clearance.

The intake valve is closest when the piston is at around 10° after TDC. I usually start measuring at about 4° after TDC and check it every 2° to about 16° ATDC in order to graph how the valve gets closer then farther away from minimum P-V clearance.

I have a great tool I made for this job. There are others out there for sell. They are a great investment.

Hope this helps. Any more questions let me/us know.

Don

[underdog]

Don

You are checking with the lifters and rocker - push rods in place right ?

I was trying to get an idea of the clearance before I order my parts.

[want-a-be]

Yes,...sorry about omitting that. Yes I use pretty much everything I'm going to use. I have a tool made that grabs the rocker arm and allows you to move it through it's range of movement. I put a Dial indicator on the retainer so the movement can be properly measured.

If you're going to get a new cam. The cam guys will be able to use the specs of the cam you use to get a close proximity of what the limits are. From there they can get you a cam thats pretty close.

Once I get my new shop moved in to I'll persue marketing my valve spring tools. Like the one I'm talking about in this post. I've already had good luck with the gas porting tool that I've brought to market. Just no time to invest on the other tools I have.

Don

[Awesome Bill]

what Don does is what most do. Just use a dial indicator vertically positioned over the valve angle and every 2 ° from 20 btdc exh, to after 20aftd for intake. You can just push the retainer going threw the movement. Have you head gasket your using on, you do not have to torque this. You can also omit the gasket to always give you a little cushion of clearance until you get it figured out. Put a degree wheel on the camshaft first, get it where it needs to be and then run the pv. In real tight areas, we will move the cam 2° either way to avoid fly cutting if the customer is on a budget. Play doooo @ best is a very bad way to do it but if you have to you have to.

[want-a-be]

what Don does is what most do. Just use a dial indicator vertically positioned over the valve angle and every 2 ° from 20 btdc exh, to after 20aftd for intake. You can just push the retainer going threw the movement. Have you head gasket your using on, you do not have to torque this. You can also omit the gasket to always give you a little cushion of clearance until you get it figured out. Put a degree wheel on the camshaft first, get it where it needs to be and then run the pv. In real tight areas, we will move the cam 2° either way to avoid fly cutting if the customer is on a budget. Play doooo @ best is a very bad way to do it but if you have to you have to.


OOPS,...:o...thanks for the light rap on the knuckles there Bill. yea I forgot to mention that I'll either have a degree wheel on or an ATI dampner that's fully marked installed. Of course when I use the dampner I have already checked it with the wheel.

Also they way I was checking would be with the actual springs that are to be ran. As Bill is saying this method can be done with checker springs or without. Usually it is on the safe side as I've usually seen a difference between it and checking with the springs you're going to run. But the error is in your favor. If you clear with checker springs then you'll gain more p-v clearance with the regular springs. Only because of where you are doing the checking though. With the heavier spring installed the loads are closer to what it will be when it's actually running....lol...minus the flex of everything that is.


I'm totally with Bill in the clay method.

Don

[Awesome Bill]

Don is right, the actual springs are better because it load the camshaft and stretch can be factored. But if you don't have all those fancy spring checkers, you can just use a inner spring and do it by hand and feel the air gap every 2°. Play dooooo can actually get into the ring lands also, be careful.