i wasn wondering if i could run 1.6 rockers which would put me at .469 lift and i had my heads shaved .030" . i i think would be like having a .499 lift cam on stock untouched heads

 

It's unlikely that piston to valve clearance would be an issue.

 

thanks

 

That doesn't mean you won't want to check it, though.

 

A bit of play-dough or similar on the top of the piston will let you know where your at for clearance but like Apeiron said, it *shouldnt* be an issue unless your using big domed pistons or something.

 

I just got a chance to check valve clearance on my setup today. It has .150 dome pistons, 68cc aluminum heads, and a 230/236 .571/.596 114lsa cam. I used playdoh. When I pulled the head off, the valves haden't really made an impression in the playdoh. I took it out and measured it, which came out to a little over .300in. Does this sound right? I have the cam installed straight up, with marks aligned. Am I doing something wrong? I thought for sure my clearance would be a little tighter than that. Thanks for your help.

 

How many rotations did you put the crank through?

 

If you have a hydraulic cam then your are probably not getting full lift because the lifters are not pumped up. That would cause you to see more clearance than what will be there when the motor is together and running.

 

Just remember to take out the playdough before running it. Just my 2 pesos.

 

I ran the motor through 4 revolutions. Enough for both the intake and exhaust valves to fully open and fully close. Thanks for the tip ResurrectingZ.
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Sorry, ran isn't the correct term, turned the motor.

 

Valve/piston interference problems are usually caused by cams with LOTS AND LOTS of duration, and high-domed pistons. By LOTS of duration, I mean more than 280° @ .050. By high-domed, I mean 14:1 compression, like an alcohol setup.

Doesn't sound to me like you have either of those things, so I wouldn't expect a problem. .300" of clearance sounds pretty much in line with normal results.

I'd say, you're problem-free, in that one area at least.

 

Thanks sofa, I feel better about the cam now that I know there's no interference.

 

Most streetable cams do not cause valve to piston clearance problems.
it is the valve opening amount at or near TDC (30deg either side of tdc) that is critical. When the valve is at full lift the piston is more than half way down the cylinder bore. Cams with lots of duration and tight LSA ( more overlap) decrease VTP clearance.

I built a motor with a shaved block (.030") (.015"-.018"piston deck clearance) shaved heads (.060"+) thin .015" head gaskets and used a cam with 256-264* @.050 and tight 105LSA installed advanced. valve to piston clearance was right on the minimum required to avoid interference and bent valves at high rpm. (.100") It pays to check.

 

Thanks for the help guys. Now I can get this thing together and hopefully drive it next week.