KB hyperutectic pistons

[redmt]

I know the hyperutectic pistons have a bad rap. Were they all junk or was there a certain series or type? I'm working on a a 410 W motor built in the early 2000's. Wondering about the longevity of the pistons that are in it. I'd like specifics if anybody has some info, not that they are junk in general.(unless of course they are)

Thanks,,,,,,,,,,,,,

[blykins]

They have their place.

Most of the issues was because of the way that KB has the top ring spaced from the top of the piston....it's a lot closer than normal, which requires a wider top ring gap. A lot of guys would file the rings like they normally would and then they would have issues.

For a budget build, they're absolutely fine. But for an engine that's going to see some abuse, forced induction, extreme rpms, etc., I would upgrade. Forged pistons aren't that much more expensive in comparison.

[redmt]

That's pretty much what I got from my buddy that used to do all my machine work. He said they expand more than normal and that the ring gaps should be about double the .004 per inch formula.

Problem I have right now is I've got this engine down to it's underwear and I'm trying to decide where to stop. The comp and leak down #'s were acceptable for an engine that hasn't run for a few years.

[blykins]

If it an't broke.....

[redmt]

Originally Posted by blykins

If it an't broke.....

I agree! BUT!!!! If there is some info that needs to be considered, now is the time to find out. There has been bad runs of nearly everything. This ain't the good old days when you could trust the quality of parts on the market. Believe it or not, you used to actually be able to buy things that weren't made in China, or Taiwan or Mexico or,,,,,,,,,,,,,,,.

[joyridin']

I had them in a Chrysler 440. I ran 11:1, had a pretty big cam, ported heads etc and never had a problem.

I followed the directions and gapped the rigs accordingly. I wouldn't run boost with them, but never had a problem otherwise.

[DAVID GAGNARD]

Originally Posted by blykins

If it an't broke.....

Yep, back in the mid 90's I built a 351-W "street cruiser" engine for my 65 Fastback which at the time was going to be driven very little and shown a lot..Used the stock crank/rods,bought a set of cast flat top,4 valve relief pistons for all of 99 bucks.....hydraulic flat tappet cam, nothing fancy, just a basic budget engine....
A couple of years later I got fed up with the "show car" scene and began driving it a lot and driving it hard. Then began drag racing,made well over 100 passes, probably closer to 200, shifting at 6,000rpms, then began tracking it, ran on 4 different road courses, putting 2,000+ miles running the motor from 3,000 to 6,000 rpms.....throw in 30,000 "street" miles and now that very same engine resides in a mid 80's Bronco 4x4....all I ever did to that motor was change the oil and spark plugs......During my open track days, I was hoping it would blow up so I could build a hot 331 or 347 to replace the 351-W, dang thing would just run and run and run and never gave me a minutes trouble,all with stock/OEM parts and an el-cheapo set of cast pistons!!!!!!!!!!!
So,iffin the motor is running good and your satisfied with it, leave it alone......

David

[ERA Chas]

^^That is a great testimonial for all of us.

[bobcowan]

Those pistons got a bad rep for the same reason a lot of new technology got a bad rep - people don't understand it.

The goal was to find a piston material that was stronger than cast alum but less expensive and with less expansion than a forged piston. Life's full of trade offs. It's definatley a step above a stock replacement part. It can take moderate to high cylinder pressures and moderatly high rpm's for long periods of time. But they can't handle true racing abuse, and can't handle power adders.

There are also some special ring set up specs that you need to know during assembly. Failure to follow those specs results in bad stuff happening. Who is the average shadetree mechanic going to blame? The new part? Or his own skill level?

United Engine & Machine Co. Incorporated

[Rick Parker]

I seem to recall some of the Ford Racing Crate Motors that had issues near where the valve relief area met the outer diameter of the piston. The area near the ring land was poorly supported and chunks of the outer diameter of the piston would fracture causing serious consequences.

[blykins]

Red, you can get a set of Probes for $450-500. They are forged.....

[Tony Ripepi]

Hey John,

In for a nickle- In for a dime.......Ron will push the Hell out of that motor.

If I had it to do over I would not have used the hyperutectics in that engine.

TR