Forum: HoseHeads Sprint Car General Forum (go)
Moderators: dirtonly  /  dmantx  /  hosehead

I have a question regarding pistons.

We are using KB Hypereutectic flat top pistons in our 305. They have 31 show on them over two and a half years and they seem to measure fine and look really good. We are in the 10:1cr neighborhood with Dart Iron Eagle heads. We over-reved them once at 7,700rpm and have not been over 7,400 at any other time. The engine has gotten hot twice over this period of time (260 degrees).

There are people that have told me that these pistons need to be changed yearly. Then there are others who are saying that theses pieces should last in this enviroment for some time. I have tried to contact KB twice and I am not getting any response. Due to funds I kind of need to re-ring them and run another year, but if I need to replace them then I guess that I will have to deal with it. Most of the folks that I have spoken with are in the same boat that I am and really don't know.

If anyone out there has any suggestions I would GREATLY appreciate some assistance.

Thank You ahead of time, Jim

Never hit stationary objects!

Member of this message board since 1997

79, I would have them zyglo'ed to check for cracks. Generally they will crack down in the wrist pin area, but those cracks are generally heat cracks and can be sanded out with a cartridge roll. Other than that I would check your piston to wall clearance to make sure you don't have too much. If you do then expect the skirts to crack and eventually break. Other than that let er rip!!

I ran the same set up but racesaver heads and i can tell you from expeirance they will break like he said at the wrist pin! Cost me a good cam from higgins and ruined pretty much everything in the motor. The pistons had two season probable 20 races. Change the rods also. The ones i used where only good for one year. I ran the motor around 6700-6900. It actually broke the skirt in our driveway.

I did the same thing to save money rings and bearings and i broke the motor. If you look on ebay there is complete kits that are scat or eagle parts.. Can get them with H-beam rods as well.. Take a look they run for about $1000.

Zyglo'ed?????????? Got me there.

Thank you to everyone who has responded.

Where would one go about having them Zyglo'ed and what should it cost????

Never hit stationary objects!

Member of this message board since 1997

zyglo? , doesnt sound that difficult for a back yard wrench to inspect? would a a F40t-12 florescent lamp (black light) do the illumination?, or is there another fixture (and wattage) utilized? what is the chemical ? and, or, would 100% glycol work? this piston reuse is a good question,, , just curious, everyone ive talked to has a different opinion on reuse of pistons, Im kinda in the same situation but, more costly forged pistons, and larger compression . Thanks for the info ..

Member of this message board since 1997

Here you go.....

http://www.magnaflux.com/Portals/0/operatingInstructions/Zyglo~reg_Bulk_Operating_Instructions.pdf

Check you local yellow pages or do a Google search for local Magnaflux/Zyglo shops

Chuck.....

I've got a decent set of rods ($400 H-beams) And forged pistons that are 5 seasons old and still going strong, and I generally turn my 305 in the 72-7500 range. For ~1k you can have a darn near indestructible bottom end for what you're doing. I run a stock crank as well, they can usually be had fairly cheap.

I had some KB Hypereutectic in a 305 and after about 15 races one let go at the wrist pin and destroyed everything in the motor. I would recommend finding something different. Its a lot cheaper to buy pistons than a whole new motor. Good Luck

I've had good luck with the KB forged pistons, KB forged is Icon now part number is ic-830 and they are very reasonably priced.

Thanks, you learn something new every day!

Never hit stationary objects!

Sprinter 79, I would definately change them to forged. I ran a set of Speed-Pro hypers in a limited 360, and one of them broke part way through their second season. The motor was tuned right, never overheated, and never turned over 6500. (I run a rev limiter) Looked like it broke around the wristpin, and it also killed the block, the crank, the cam, 1 head, several rods, the oil pan, and even the mag. Yup, bent the shaft. I'm the low-buckest racer ever, so I'll never criticize anybody for trying to save money, but I'll never run them in a race motor again. You can probably find a good used set of forged for about what the hypers cost new.

Good luck,

John

Thanks John,

I am seeing that there are more folks in the "Blew it up" catagory then not. Guess I will be spending some money!

Perhaps we have just been really fortunate and dodged a bullet.

Never hit stationary objects!

FYI
Goodson sells a zyglo kit.
http://www.goodson.com/store/template/product_detail.php?IID=6335&SID=0147e02537039b0bf2a67b777a8c3b24

Race Engines shouldn't use hypereutectic pistons. Hypereutectic pistons are for street cars.

I know that some pistons manufactures say you can use them but if you want something that will last use a forged piston.

My Signature

Jim

I ran the same piston you are running put 37 nights on the motor got it hot every night and by hot 260 was average. I put a good light weight set of JE in and lost the motor 3 nights in. The motor I ran the last night had a cast crank and cast pistons in it and came from 20th to 6th with it so I think luck is the biggest thing. I'm putting a motor together with the KB in it but I'm also putting to motors together with some light weight JE piston in it.

Nick

Yeah, I think luck has something to do with it as well. The pistons look o.k. and measure alright, but I am thinking that for another $220.00 + change I could get another set from speedway and not have to run the risk. Once you start having to pay someone to check them, you may as well just replace them. Besides, if I get them checked and a couple of them are bad, then I have thrown away money that I could have spent just replacing them. It is a viscious circle. Unfortunately Destini and I only have one engine, so we need to make every effort to make it last.

See you at the races

Jim

Never hit stationary objects!

And people wonder why engines are as expensive as they are. Perfect example by 79, went with cheapy pistons and is going to spend $220 to upgrade to a better piston so he can avoid blowing an engine up. Pistons aren't the only parts in the engine that can be upgraded to a better piece, i.e. crank, rods, oil pans, oil pumps, injectors, gear dives, etc..... and in the end you have the price tag that we have now a days.

Like 79 said at the end of his post, "it's a vicious circle"

I hear this is a good part to use. Has thin rings and slipper skirt.

http://www.jepistons.com/Catalogs/SRPPRO/Chevy_SB/305_Sprint-pro.aspx