Moparts
Valve relief pockets as gas ports???
Posted By: 1976 Aspen
Valve relief pockets as gas ports??? - 01/10/09 08:26 PM
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.
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/10/09 08:28 PM
Here you can see where it is in the ring land. Sorry for the crappy pics. Good camera, crappy owner
Posted By: dthemi
Re: Valve relief pockets as gas ports??? - 01/10/09 08:34 PM
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.
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/10/09 08:44 PM
It will NEVER see nitrous!!!
Posted By: goldenlancer
Re: Valve relief pockets as gas ports??? - 01/10/09 08:58 PM
Posted By: 602heavy
Re: Valve relief pockets as gas ports??? - 01/10/09 09:07 PM
Better gap the 2nd ring waayyyyyyy bigger than the top.
.
Posted By: Bob_Coomer
Re: Valve relief pockets as gas ports??? - 01/10/09 10:09 PM
There Junk!
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/10/09 11:00 PM
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
Posted By: Leon441
Re: Valve relief pockets as gas ports??? - 01/10/09 11:12 PM
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
Posted By: moderncylinder
Re: Valve relief pockets as gas ports??? - 01/10/09 11:15 PM
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
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/10/09 11:31 PM
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
Posted By: Gumbydammit
Re: Valve relief pockets as gas ports??? - 01/10/09 11:47 PM
$700 pistons vs. a $4000 short block. ( I'm guessing) I'm not a lucky guy, so I'd be changing the pistons now.
Posted By: moderncylinder
Re: Valve relief pockets as gas ports??? - 01/11/09 10:32 PM
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??
Posted By: dthemi
Re: Valve relief pockets as gas ports??? - 01/11/09 10:57 PM
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.
Posted By: MR_P_BODY
Re: Valve relief pockets as gas ports??? - 01/11/09 11:03 PM
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
Posted By: Sport440
Re: Valve relief pockets as gas ports??? - 01/11/09 11:42 PM
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
Posted By: B G Racing
Re: Valve relief pockets as gas ports??? - 01/12/09 12:01 AM
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.
Posted By: MR_P_BODY
Re: Valve relief pockets as gas ports??? - 01/12/09 12:15 AM
Quote:
Mike, he said all 8 had that hole. Why the machinest didnt stop after the first, I dont know.
I just read that he did all 8...... 
Posted By: Sport440
Re: Valve relief pockets as gas ports??? - 01/12/09 01:05 AM
Quote:
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.
76 Aspen, I agree with BG, if you cant afford a new set, find someone who can weld/plug those holes for you. That would be my first route/fix.
I also think that BG is implying that his shop can do it, even though they like to pretend that they are Hillbillies sometimes 
mike
Posted By: 540dust
Re: Valve relief pockets as gas ports??? - 01/12/09 01:40 AM
I know a guy that welded the notches before too, but the hole was thru the bottom not to the ring groove.
Posted By: B G Racing
Re: Valve relief pockets as gas ports??? - 01/12/09 03:16 AM
Quote:
I know a guy that welded the notches before too, but the hole was thru the bottom not to the ring groove.
The ring groove can be re-dressed
Posted By: dizuster
Re: Valve relief pockets as gas ports??? - 01/12/09 03:28 AM
Quote:
Quote:
I know a guy that welded the notches before too, but the hole was thru the bottom not to the ring groove.
The ring groove can be re-dressed
Really? I called Diamond getting ring grooves re-cut and they told me no way....
I'd be worried about warping the ring land groove. Most good pistons today are so tight to start with, it wouldn't take much...
I'd be getting a new set from whoever screwed them up when they cut them.
I mean come on, cutting a hole in 1 is a mistake, cutting all 8 is a joke...
Posted By: B G Racing
Re: Valve relief pockets as gas ports??? - 01/12/09 03:58 AM
What's so hard about cutting ring lands?We have re-cut them to go to a thicker ring and have also relocated the ring lands.The rings is what conforms to the bore.The top portion of the piston is smaller than the bore.Many pistons are cam ground with only the skirt or thrust sides conforming to the bore,with specific clearences.
Posted By: Anonymous
Re: Valve relief pockets as gas ports??? - 01/12/09 04:09 AM
i wouldn't run them. adding radial clearance is one thing, but milling .065 deeper should give you enough room for an .800 lift cam. they look a lot deeper than that.
i know it's not what you want to hear but, i think you have 8 new paperweights.
Posted By: B G Racing
Re: Valve relief pockets as gas ports??? - 01/12/09 04:19 AM
If your going to toss them,send them to us,Curt Jr and Chaz can practice their barnyard techniques.
Posted By: dizuster
Re: Valve relief pockets as gas ports??? - 01/12/09 01:12 PM
Quote:
What's so hard about cutting ring lands?We have re-cut them to go to a thicker ring and have also relocated the ring lands.
That is exactly what Diamond said they would not do. I called them because I was thinking about buying a set of pistons a guy had, but they were metric rings, and I wanted standard 1/16" stuff. I told Diamond I already had the pistons and I wanted to send them back to get the rings re-cut. They said they absolutely would not do that?
Should have bought them and sent them to you!
Posted By: B G Racing
Re: Valve relief pockets as gas ports??? - 01/12/09 01:39 PM
Quote:
Quote:
What's so hard about cutting ring lands?We have re-cut them to go to a thicker ring and have also relocated the ring lands.
That is exactly what Diamond said they would not do. I called them because I was thinking about buying a set of pistons a guy had, but they were metric rings, and I wanted standard 1/16" stuff. I told Diamond I already had the pistons and I wanted to send them back to get the rings re-cut. They said they absolutely would not do that?
Should have bought them and sent them to you!
Some pistons are not concentric enough to chuck up with out the centering plug left on the top of the piston,once the piston has been machined the stub is knocked off and the top is finished.To re-chuck it can be a pita on some but with a little effort anything can be done.
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/12/09 11:18 PM
Well, despite everybody's advice and opinions, I've decided to run it the way they are. My machinist said he's done this many times with big block chevy's and we all know they're alot more prone to detonation than our stuff. Thanks for all the reply's and I'll keep you updated on when it makes a mess of things
Posted By: dartman366
Re: Valve relief pockets as gas ports??? - 01/13/09 01:00 AM
Sorry, I would have a serious problem with those slug's,,,,I just hope I am never in the other lane against you.
Posted By: Anonymous
Re: Valve relief pockets as gas ports??? - 01/13/09 01:11 AM
here's a silly question. it's clearly obvious that one of the holes connects with the ring land. where does the other one go??? it's too far inward to connect to the ring land. it looks like it would just go through the top and come out the bottom of the piston near the pin.
in any case i do find it interesting that even with all the people telling you all the bad things that can happen, your still willing to chance trashing a motor.
Posted By: dthemi
Re: Valve relief pockets as gas ports??? - 01/13/09 01:25 AM
There are tons of motors out there running way worse than that, and they just don't know it yet.
Obviously it would be the right thing to do to get new ones, and had we done that to a customers pistons, we'd buy you a new set along with an apology for delaying you. but if that were all that was between me and going to the track because of time, or budget constraints I'd pound'm in and head on out.
Alright I'm ready for my beating now
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/13/09 01:56 AM
Dartman- It's not like my motor is going to saw itself in half going down the track
DRAM- There is only one little hole. I have .187 in the thinnest spot to make an actual hole in the top of the piston. And no offense to you or anybody else, I've learned to take most information, advice, and opinions with a grain of salt on this board.
dthemi- I can understand where you're coming from. I'll keep everybody posted when, or if, it decides to break.
Posted By: Anonymous
Re: Valve relief pockets as gas ports??? - 01/13/09 02:12 AM
maybe i'm just seeing a reflection or something. it looks like 3 different holes.
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/13/09 02:14 AM
DRAM, you're seeing a reflection. The only hole is on the intake relief furthest to the left. The others are just camera glare. Whatcha think about it now???
Posted By: Anonymous
Re: Valve relief pockets as gas ports??? - 01/13/09 02:22 AM
Quote:
DRAM, you're seeing a reflection. The only hole is on the intake relief furthest to the left. The others are just camera glare. Whatcha think about it now???
what's the depth of the valve pocket and were they shelf stock CP pistons you started with?
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/13/09 02:27 AM
The pocket depth from the top of the piston to the deepest part of the pocket??? No, they were custom CP's ordered from SDSS when he did my stroker kit last winter.
Posted By: Anonymous
Re: Valve relief pockets as gas ports??? - 01/13/09 02:29 AM
Quote:
The pocket depth from the top of the piston to the deepest part of the pocket???
yes, and if you know, how deep were they before they were cut?
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 01/13/09 03:15 AM
They're about .250 deep now and they were like .190 deep I think.
Posted By: Anonymous
Re: Valve relief pockets as gas ports??? - 01/13/09 04:43 AM
i'm not 100% positive but i think their std. smallblock valve reliefs are something like .230 intake and .190 exhaust. being a custom set they might have been deeper than that already.
to answer your other question, no, i still wouldn't run them. that's a very large hole. eventually the ring gap will line up with that hole and may actually get stuck there due to the pressure escaping. it's not anything like a normal gas port. good luck with them, i hope it doesn't cost you a motor down the road. no doubt it'll run, for how long is the question.
Posted By: RyanJ
Re: Valve relief pockets as gas ports??? - 01/13/09 01:43 PM
My CP spec sheet shows them being .280" intake .250" exhaust when I had them made
Posted By: dizuster
Re: Valve relief pockets as gas ports??? - 01/13/09 03:55 PM
Quote:
My machinist said he's done this many times with big block chevy's and we all know they're alot more prone to detonation than our stuff.
So the guy that screwed them up, and really should buy you a new set says they're fine huh?...
I guess that's the part of the story that I don't get the most? Why isn't he just buying you a new set? I know you're not racing in MN yet!!
Posted By: JohnRR
Re: Valve relief pockets as gas ports??? - 01/13/09 06:19 PM
Quote:
in any case i do find it interesting that even with all the people telling you all the bad things that can happen, your still willing to chance trashing a motor.
That's because he was FISHING for someone to agree with what he wanted to do .
Posted By: B G Racing
Re: Valve relief pockets as gas ports??? - 01/13/09 07:19 PM
Here is best advise I can give you.Don't run them.If that is the exhaust pocket(constant high heat) and the material is fragmented it will continue to burn away causing failure that may damage the cylinder wall.Machinist arn't always the best engine builders.I tell our machinist what I want and will never let him build an engine.Was it his fault or was he told how much to cut?Did anyone varify the thickness or location?
Posted By: Discoquik
Re: Valve relief pockets as gas ports??? - 01/13/09 07:22 PM
They are going to lead to trouble. There are many reasons not to recut, redress, or alter grooves.
The pocket can be altered but with caution as proven here. The manufacturer would have known if the part could be cut for the desired pocket if the diameter of the valve was given. I don't know the details but in our cases we typically look at the computer model and can actually "measure" the changes and know if it is ok. But this is dependent on accurate information and communication of what is going to be done.
I would look into a new set of pistons and order them with the ring stack moved down on the part.
Vic Ellinger
vellinger@wiseco.comWiseco Performance Products
Posted By: ssdart3360
Re: Valve relief pockets as gas ports??? - 01/13/09 09:11 PM
I have a set of BRC pistons with the same deal. .031 top ring --I have run them off and on for years. They probably wearout the ring a little faster but no big deal. 360 low comp. ss car.
Bruce
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 10/16/09 04:03 PM
Well, for all you gurus who thought my pistons were junk, they made it through the season and I'm going to run another one on them. I got 212 1/4 mile passes on them and oh, did I mention, I won the track championship with them??? So to all the newbies on here, take all the advice on this board with a grain of salt
Posted By: JoWeTu_6
Re: Valve relief pockets as gas ports??? - 10/16/09 04:26 PM
Quote:
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.
Posted By: dizuster
Re: Valve relief pockets as gas ports??? - 10/16/09 04:30 PM
You know, if you're a good enough racer to be the track champion, all the more reason to do everything you can to prevent an untimely failure.
If Joe Schmo breaks a motor in the 1st round who cares. But I would think someone chasing a championship would care.
Glad to hear that even though your machinist screwed up your pistons, and talked you into using them anyway, that you didn't get burned from it.
Newbie lesson... "Everybody get's lucky sometimes."
Posted By: Hemiroid
Re: Valve relief pockets as gas ports??? - 10/16/09 04:43 PM
Quote:
Well, for all you gurus who thought my pistons were junk, they made it through the season and I'm going to run another one on them. I got 212 1/4 mile passes on them and oh, did I mention, I won the track championship with them??? So to all the newbies on here, take all the advice on this board with a grain of salt
Hmm, so you're saying that because your machinist ruined a set of pistons and you decided to run them anyway and got away with it that you got bad advice?
You probably would have been the first guy to come back and complain about those that said it's ok it the piston shattered, lost the pin. Then the rod sawed a hole in the liner in that hole and cut the cam in half. Then the rest of the motor came apart and oiled down your slicks and you stuck it in the wall or in the side of someone else's car.
You took a chance, disregarded the advice of a lot of good engine builders and got away with it. Doesn't make you smart, just lucky. You were given the right advice, whether you realize it or not.
Congratulations on your championship.
Posted By: emarine01
Re: Valve relief pockets as gas ports??? - 10/16/09 05:01 PM
Seems like you took the risk and faired ok, I would not have run them myself, as for taking the advice of board members I think the info shared is for the best, and should be interpreted as you think fit, congrats on your win
Posted By: blownzoom440
Re: Valve relief pockets as gas ports??? - 10/16/09 05:08 PM
i am glad it workedout for you.
1Q tho,could thay have been tig welded a little?
Posted By: HPMike
Re: Valve relief pockets as gas ports??? - 10/16/09 05:19 PM
That's great that it worked out. I would find someone with a borescope and take a peek inside the spark plug hole at the area to see if anything looks like it got worse.
MB
Posted By: JohnRR
Re: Valve relief pockets as gas ports??? - 10/16/09 09:29 PM
Quote:
Well, for all you gurus who thought my pistons were junk, they made it through the season and I'm going to run another one on them. I got 212 1/4 mile passes on them and oh, did I mention, I won the track championship with them??? So to all the newbies on here, take all the advice on this board with a grain of salt
If you and your machinist are smarter than everyone else why did you even bother asking in the first place ?
Have you pulled a head to see how much bigger the hole is? With your razzing I'm guessing you would have posted the picture to further your case. 
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 10/17/09 03:32 AM
Dizuster- Sorry, but new pistons were not in the budget at the time
I'm not gloating, razzing, or saying I'm smarter than anybody else. 75% of you probably know more about this than me. I just figured everybody would wanna know how it ended up. I'm pulling the heads to redo the valve guides and I'll be sure to post a picture at that time. Stay tuned!!!
Posted By: JohnRR
Re: Valve relief pockets as gas ports??? - 10/17/09 03:20 PM
Quote:
Dizuster- Sorry, but new pistons were not in the budget at the time
I'm not gloating, razzing, or saying I'm smarter than anybody else. 75% of you probably know more about this than me. I just figured everybody would wanna know how it ended up. I'm pulling the heads to redo the valve guides and I'll be sure to post a picture at that time. Stay tuned!!!
You're not ???
Did someone else post this using your account ?
Quote:
Well, for all you gurus who thought my pistons were junk, they made it through the season and I'm going to run another one on them. I got 212 1/4 mile passes on them and oh, did I mention, I won the track championship with them??? So to all the newbies on here, take all the advice on this board with a grain of salt
otherwise waiting for the pictures 
Posted By: Crizila
Re: Valve relief pockets as gas ports??? - 10/17/09 08:36 PM
Quote:
Here is best advise I can give you.Don't run them.If that is the exhaust pocket(constant high heat) and the material is fragmented it will continue to burn away causing failure that may damage the cylinder wall.Machinist arn't always the best engine builders.I tell our machinist what I want and will never let him build an engine.Was it his fault or was he told how much to cut?Did anyone varify the thickness or location?
I doubt you will have to wait for anything to burn away.
Posted By: 1976 Aspen
Re: Valve relief pockets as gas ports??? - 10/05/10 08:23 PM
Well, another season has ended with these same pistons and I got a third place finish with them. I have new Diamond's on the shelf for the freshen this winter care of RyanJ @ SDSS. The pistons made it another 191 1/4 mile passes and still holding strong. I'm starting to get a little blowby so I think it's time. Once again, I'm not gloating, razzing, or anything. I just promised I would update if something went wrong or when it was time to switch...
