Do these valve/piston clearance numbers sound right?

I am getting .230 on exhaust, and .270 on intake. That seems kinda high, doesn't it?

Procedure used was to set preload to 0, rotate engine until i started getting overlap. Then measuring the distance the valves traveled before they hit the piston. Did this for both of them. Then to double check, I left the feeler gauges in there at the above settings and rotated it all the way around a full intake/exhaust stroke and it didn't bottom out. (I actually got .240 but hit on the way around, then set it at .230 and cleared).

These pistons have pretty deep notches in them, so maybe they are working...

 

Did you use solid lifters when you checked it?

 

no, but I watched the lifters to make sure they weren't loading.

I have a pair of converted solid lifters. I will try it again with them.

 

Yep, solid lifters and you need a degree wheel to check the clearance at 5* increments from about 20* BTDC to 20* ATDC to find the closest point for each valve. At the point where each valve is the closest to the piston use a dial indicator on the spring retainer to measure the clearance when depressing the valve. If you are using soft check springs they often show slightly less clearance than what you will actually have with the real springs installed.

 

Used solid lifters and still same clearance. I am using the COMP degreeing kit and have the soft springs on it. I will do the 5* check and see if it gets any tighter.

 

YUP, little bit different numbers. intake hit .230 near 10* ATDC, and exhaust hit .195 at 5*ATDC. Still a pretty good bit of clearance...

Used the dial indicator this time rather than feeler gauges.

Guess I can safely mill .010 off the bottom...

 

Why only cut .010" off? You can go .030 before you have to worry about intake manifold alignment.

 

Oh yeah? Maybe I better call those guys Monday morning and tell them to take off .030.

Or should I be a little conservative so the next person to use them will have some material to work with?

Isn't it approximately .1 CR to each .010 milled off?

 

That depends on your combination of parts, size and shape of your combustion chamber, etc. But you're right, it wouldn't make that big of a difference.

 

Then I will just leave it at .010. Then the next guy can do another .010 and not have any problems...

I just want the bottoms flat so they seal well.

 

You have flat top pistons. depending on the heads you are using you could already have over 10:1 compression or you could have only 9:1. If you go too high you are going to find it hard to get gas that will run in it. If you are using E85 you need lots more compression....

 

Just using regular, maybe super at the pump if I get any issues.

Are these considered "flat top" pistons, even though they have the valve reliefs cut into them? Seems like you lose a bit of compression having those cut in there. Any idea how much?

 

...flat top...
there are...Dish...flat top...popup (dome)

......

 

Mr. Obvious speaks. Read the rest of his threads and you will see which heads he is using.

You're the one using stock pistons.

 

It was just a question. I am not searching for more compression at this time with this motor. Just wondering...