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Author Topic:   Pistons, hypers or forged.
FS93
Member
posted October 02, 2001 11:11 PM
IS there a significant advantage in a IMCA modified engine in using forged vs hypereutectic pistons. I am getting ready to start on a backup motor for next year. I want to keep the cost down, but dont want crap in the motor. The 406 that came with the car has forged pistons. I am thinking of building a 383 or 377 and am looking for ideas.


WILDphil
Member
posted October 03, 2001 10:52 PM
Unless your on a tight budget , Hyperexplosives should not be used in a race engine . *Just my opinion*


jammin
Administrator
posted October 03, 2001 11:54 PM
The weight is the biggest factor when looking at hypers. I have a couple of motors with Speed Pro's in them and have had no problem. Even had some major carb problems on a motor last year and never melted one. I can say that they are very, very durable. But, on the other hand, they are also heavy. This will affect your acceleration a little, but for a claimer, it is the best alternative. For a better engine though, I would use forged aluminum because of the weight and durability it offers. If you spend the money on lighter internals, then you should spend it on the pistons for a complete package. Dont skimp on hypers if your spending the money. But for basic stock applications, hypers are hard to beat.

jammin


istock59
Member
posted October 04, 2001 08:02 AM
If it's for a claimer motor (IMCA), hypers are hard to beat. Just remember to open up the top ring gap. I exploded a set of Speedpro hypers last year because the machineshop told me to not file the top ring....


smayo964
Member
posted October 04, 2001 09:15 AM
Hey istock59. Question for you concerning your statement about opening up the top ring gap. What gap is recommended and what gap did you have when the engines detonated? Just curious. I've blown a couple this year for some unknown reason. Also, does anyone know what the max compression ratio is for the hyper type pistons? Thanx


istock59
Member
posted October 04, 2001 10:55 AM
smayo964, checkout www.kb-silvolite.com for recommeneded top ring gap. I know that's Keith Black stuff, but I used the same top gap in my second set of Speedpros. 20+ races on them with no problems.

On the set that came apart, I used just the standard drop-in ring gap. Probably around .018 I suppose. I asked the machineshop about the ring gap when I put it together, but they told me that Speedpros didn't need the extra gap like KB's. But, I got the carb a little lean, the engine a little hot, and ripped the tops of a couple pistons off the skirts.... Oops..

Never again. All my hypers get the top ring gap opened up now!

smayo964
Member
posted October 04, 2001 03:45 PM
Hey istock59. Thanx for the web address. Printed out all the pertinant specs. I've had a couple engines totally detonte the pistons out of them. That is why I asked about compression ratios. My flat top 400, had 305 heads on it with a small 268 degree cam and I was pumping 220lbs per cylinder hot. Same thing happened with a "fresh" built 350 with the same heads and a different cam, etc. Don't know if that was due to top ring issues, or just the pistons giving up under pressure.


istock59
Member
posted October 05, 2001 07:56 AM
Personally, I doubt that it's piston pressures giving you problems. I'd bet that it's the top ring gap...

I'd love to run forged pistons, but it's hard to justify a $500+ set of pistons in a $425 claimer motor. Hypers seem to fit in the budget a little better...

ford5
Member
posted November 11, 2001 04:01 PM
If the machine work is done right timing is correct ,jetting is correct top ring gap is correct KB pistons are an excellent choice for most budget racers i have won lots of races with them and they are the best ive seen for the money


jammin
Administrator
posted November 11, 2001 07:27 PM
I personally have had some great luck with Speed Pro hypers. Had some problems with fuel one time, leaned a motor out a few times, never melted them.

jammin


bbracer17
Member
posted November 13, 2001 07:06 PM
I have been running Silvolites in my car for 2 years and I will by another set.


Racer111
Member
posted November 16, 2001 08:43 PM
KBs are real good.Ran them for years ,turned motor 7200-7500 every night no problems.


dirtracers
Member
posted November 25, 2001 01:16 AM
If you run the hypers make sure you have a good carb and fuel line I went through 2 motors this year because of trash in fuel line it made the carb lode up and it melted three pistons in my 400 and in my 350 we bought a new carb and the trash problem was fixed but the carb kept flooding out first and only night I put on it I melted a piston and they were Speed Pro


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