Last race days: Tomorrow and Sunday at Bremerton

stock50LX · Oct 23, 2006

gospeedgo said:
The Hyperut's need a TON of clearance. What was he giving you?

You are referring to top ring gap clearance, right? Mine was .032! The piston should fit pretty tightly in the hole for hypers -at least that is conventional wisdom. There are pictures nearly identical to mine on another site from a guy running the same KB 151 pistons. Except he has pictures of his other pistons with cracks in the area where the other pistons broke. I will look at the remaining "good" pistons when I get home... Live and learn. -Forged hereafter.

gospeedgo · Oct 23, 2006

The top rings on a KB grow a ton compared to a typical forged piston. Dad had a similar problem on a couple early KB piston'd motors he built years ago.

stock50LX · Oct 23, 2006

gospeedgo said:
The top rings on a KB grow a ton compared to a typical forged piston. Dad had a similar problem on a couple early KB piston'd motors he built years ago. Our track record holding motor at the local speedway is running a full .100 ring gap on hyperut's!

I guess that's what I needed to do. Take their specs and triple 'em. I'm just going to buy a kit.

MyFordsFly · Oct 23, 2006

That really sucks John. That thing was starting to run really well.

Tylerb59 · Oct 23, 2006

Dang, John!

stock50LX · Oct 24, 2006

There's a guy on another site that related a near identical story to mine. He has the same KB 151's. He replaced a piston after the first time, then they failed again. I don't think they take much abuse.

stock50LX · Oct 24, 2006

MyFordsFly said:
That really sucks John. That thing was starting to run really well.

Crank looks fine, not much damage to the block. Oh well, needed to replace the rack and pinion anyway. It will make the job easier with the engine out

gospeedgo · Oct 24, 2006

stock50LX said:
I don't think they take much abuse.

I still think your blaming the wrong part. Its like blaming the nitrous bottle for incorrect jetting. If you were running a tight ring gap, the things expand and bind, freezing in the bore. It aint a forged piston, you cant set them up like one.

stock50LX · Oct 24, 2006

gospeedgo said:
I still think your blaming the wrong part. Its like blaming the nitrous bottle for incorrect jetting. If you were running a tight ring gap, the things expand and bind, freezing in the bore. It aint a forged piston, you cant set them up like one.

I followed their instructions and even added a little gap. Sure, I could have tripled the gap -which is what your father did. Maybe that would have eliminated the problem. I'm just not going to take the risk again. The owner of CHP looked at the photo of the piston and wrote that the car ran lean. Others wrote that it looked like detonation. It was probably one of those three. My KB 151 pistons, and those of other racers, have broken in the same spot indicating a weak area. Could this have been avoided? Probably. Are there much stronger pistons on the market that could take this abuse and survive? I think there might be. Next time I will be sure I am running richer too. And I'll probably buy some dyno time to get the timing sorted-out before I hit the track. Hopefully covering all three possibilities will solve this issue.

KyleL · Oct 24, 2006

You don't see many pictures on the boards of forged pistons with the top ring lands broken off, but you see many hypers with that condition. That should say something about the relative strentghs. I'll be getting rid of mine before getting back to the track. John- I think going lean=detonation. Where was the piston piece? Good thing it didn't get the head.

By the way, my car ran it's best MPH on Sunday, 119.97. That close to 120! Grrr...

gospeedgo · Oct 24, 2006

They are NOT a replacement for a forged piston, they are a upgrade for a cast piston. Forged is obviously the answer if it is in the budget. Hypers are still new technology- and builders are still learning about them and how they react. Dad learned how to gap them the hard way and since then has not had one issue. He uses them on quite a few circle track builds and has had great luck. Personally I think they get a bad rap but most of it has to do with the lack of "public" knowledge that the ring manufacturers as well as the piston companies have using them in performance applications.

stock50LX · Oct 24, 2006

gospeedgo said:
They are NOT a replacement for a forged piston, they are a upgrade for a cast piston. Forged is obviously the answer if it is in the budget. Hypers are still new technology- and builders are still learning about them and how they react. Dad learned how to gap them the hard way and since then has not had one issue. He uses them on quite a few circle track builds and has had great luck. Personally I think they get a bad rap but most of it has to do with the lack of "public" knowledge that the ring manufacturers as well as the piston companies have using them in performance applications.

Companies like KB could help their cause by specifying the correct top ring end gap. If your Dad had success at .10 and not the .030 KB recommends, changes need to be made. I ran factory cast pistons for a couple seasons and had no problems. In fact, I ran them with the same components that were on the car when the hypers failed (the first failure). Same heads, cam, intake, headers, trans, gears etc. Other manufacturers of hyper pistons do not specify the increased end gap that KB specifies. I think the 151 models have a flaw.

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