How much valve clearance should I have?

Muddin_dude06

Muddin_dude06

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I am finally at the point I can mark my pistons for the center of valves so I could have them flycut.

The reason I am rebuilding my engine in the first place is because my intake valves started to slap the pistons, BUT I believe it was due to the cam gear walking off about a 1/2".

I now have the camshaft drilled and tapped for a billet gear retainer I got through PDP. It is a PDR cam that Hamilton measured out for me to be 176degree .255" lift intake 206 degree .298" exhaust and a 104 LSA.

I have a standard thickness HG and the block was milled .006" and I have Mahle 286210 pistons that are .040" OS. I will be using Common Rail tappets that I have as well.

With that information can anyone figure out about how much piston to valve clearance I should have? Maybe even my CR? Should I get some flycuts in my pistons .050"-.060" anyway just in case? Or should I have nothing to worry about?

I appreciate any help you guys! I just don't want another valve to break! Thanks
 
it depends where u install the cam

the more you adv it the less has on the ummmm. lemme think - ex opens on the power stroke n closes on the intake stroke/intake opens on the ex stroke and closes on the comp stroke - so yea, adv the camshaft is gonna decrease intake valve to piston clearance

when i am doing what you are doing i usually take a old valve and grind the head off of it. then i grind it to a point. then, with the bottom end together, i set the head on the block (with dowels in place to align it) and one cyl at a time i put the piston on tdc and run my home made center finder (lol) down ea guide for that cyl, lightly tapping it with a rubber mallet to locate the center. that should be good enough for any good machine shop to flycut them.

with the numbers u posted it is hard to believe it did not have clearance
 
Its a reground cam and I just have the factory gear installed at original cam to crank relationship and the keyway on the cam snout is factory.

I think they started making contact as the cam gear started walking, I had abut 5-6k miles on the cam when it happened, I was thinking if they were making contact from the get go it would have happened sooner.

Thats what I was going to do to mark the center of the valve, I have a friend with a lathe we can use to grind them to a nice point perfect center. If I have them cut I'll be sending them to XlR8's shop.
 
From what i read its sounds like you havent degreed in your cam? I would reccomend doing so, i have seen the intake centerline move substantially on regrinds. And then the only way to know your p to v is to check it yourself, guys on here arent going to be able to give you more than a guess.
 
No I have not degreed it, didn't think I would need to? I suppose I can, I could just install the crank, #1 piston/rod and the head to do it. However it is degreed with just putting it all together it ran really really well.

I suppose I could just put some plumber's putty or something ontop of a piston bar the engine over and see what I have for clearance...
 
The best way I have found the check valve clearance is with a dial indicator and a degree wheel. Use "checking springs" or any other light duty spring you can compress easily. 15-20* before to 15-20* after TDC on the overlap is where you want to check. Just push each valve down untill it hits the valve every 5* and record the measurements. Then you know what you have. You woudn't even need a degree wheel. You can just layout some marks on the dampner.
 
or forget the checking springs and just run the valve adjuster down until the valve hits the piston. Set up the dial indicator to measure off the retainer. Set the rocker up with zero lash. Zero the gauge, run the valve down until it hits and record the reading, put it back where it was. Rotate engine 2 degrees, check again. When you are finished, reset your valve lash to where you had it before.
 
I just got my clearance measured out using putty, .015" on the intake valve and .050" on the exhaust. Looks like I'll need reliefs cut? I don't get how this towing/street cam would have such little clearance unless when my head was decked they didn't sink the valves deeper? Granted the block was machined down .006" to get flat I would still think this cam would have more clearance...
 
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