I needed more piston to valve clearance so I had my existing CP pistons milled. CP told me I had .287 of material left and had plenty of room for machining. I'm sure I still do but not at the ring land. On the existing reliefs we went deeper by .035 on the exhaust and .065 on the intake and .100 more radial clearence on both as well. On the intake relief on all eight pistons it broke into the top ring land area just a tiny bit. I'm not talking about the side of the piston now, it still has the complete top to it and the milling doesn't go over the edge. I'm trying to explain how the cutter broke through at the deepest part of the relief. I bet maybe a 1/16" drill bit could maybe go through. This shouldn't hurt anything right??? It should just act like a gas port piston I hope??? You can see the light shining through on both pics.

Here you can see where it is in the ring land. Sorry for the crappy pics. Good camera, crappy owner

The problem is that it's thin further than where it broke through, so when it gets some heat on it it will burn out wider. That being said I've seen nitrous motors burn that area out even when there was no hole to start with but since it was the thinnest part of the piston when things started to melt it went first. The funny thing is they still ran fine and leaked like nothing had happened. So what I'm saying is if it's not going to get sprayed, or ran too lean, it'll probably be ok, but it'll eventually load up some carbon in the land. Also if it ever detonates hard it'll pinch the ring right there.

It will NEVER see nitrous!!!

I've run them like that before. they ran about 2 seasons then chunked out where the top ring land had a hole. (JUST LIKE YOURS)as long as you don't get crazy with them you'll be ok for a while....

Better gap the 2nd ring waayyyyyyy bigger than the top.



.

There Junk!

They're junk??? I see no difference between this and vertical gas port pistons. My machinist has done alot of pistons like this for roundy round motors and never had a problem. Any other opinions??? The motor is going together tomorrow so speak now or forever hold your peace Plus, a $700 set of custom pistons, new rings, and a hone job aren't in the budget right now

I wouldn't run that junk. You pressurize the land between top and second ring. This is going to happen. The hole in your picture is larger than all the holes put together in a gas ported piston. When you gas port you do not drill holes near the intake valve releif as it is the weakest area in the top of the piston. Like someone said you would want to gap the heck out of the second ring because you will want to blow all that pressure out of the land. If you run it and get away with it fine. If you don't. What will happen is the top of the piston next to the valve relieg will bend up from pressure. Then it will finally reach the head. When it does the piston smacks the head bended this problem back down. This process will continue until the piston breaks sending this chunk into your ports bending valves. If you are lucky it will shoot out of the exhaust. If you are not so lucky it will go by an intake bend it, [Edited by Moparts - Keep it clean] the seat and get into the intake manifold and find another cylinder or two to screw up. Don't do it.

Leon

why did you need .100 more radial clearance? did you punch the piston 10 degrees down on the guide centers then see what you had? or just make the notch huge so you didnt need to worry about it? i think that was your problem

id run them,, though you took a sey of pistons that might last 400 runs and now they will last 50 or so

I previously had Eddy's on them with 2.02/1.6 valves and now I have Indy's with 2.100/1.650 valves. So now it has .050 per side radial clearance. We found the least clearance at seven and ten degrees and made our mark with the punch through the guides. So you think these will only last 50 runs??? That's only quarter of a season for me I'm hoping they'll last two to three seasons

$700 pistons vs. a $4000 short block. ( I'm guessing) I'm not a lucky guy, so I'd be changing the pistons now.

yes it will start to lift the land at about 50 passes or so,,, usually pistons come with large enough pockets to fit that large of a valve,,, you made the pocket 2.150? or 2.200? i still think you have way too much radial clearance,, and thats where your problem came from,,, and if the guy notching them didnt know that was going to happen until he seen a hole,, dont go back to him.... how does that go??? measure twice cut once??

I like the "measure it with a mic, mark it with chalk, then cut it with an axe" method myself. That's right about the guy should have known, and plotted where he was cutting first, but it's too late for that. It is what it is now.

I'm thinking this is only 1 piston, so IF you did
go greater than needed on the radial clearance you
would be lucky.... and only have to buy 1 piston

Mike, he said all 8 had that hole. Why the machinest didnt stop after the first, I dont know.

As stated before the hole you see now is only going to get bigger. Close to the hole its paper thin I bet. If you stuck a pointed tip in the hole it would probably slot out abit pretty easy.

Depending on the combo, you could be okay for awhile. Mild/longer Wild/short JMO mike

I know a cheap guy that runs a stable of Maxwedge cars that had some hillbilly shop weld up a couple similar to that with some high silicone aluminum rod and the lasted longer than his engine did.If it's affordable buy a new set,if not find a hillbilly shop like the other guy did.I would not run them like that,the hole would only get bigger.It's not like a gas port that is a small hole that is in the meaty part of the piston.

I know a guy that welded the notches before too, but the hole was thru the bottom not to the ring groove.