Piston choice: hyper or forged???

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360duster said:
Hi Guys, one more question:

i read in the book "how to build big inch stroker SB´s" that the Pistons (for example the KB 356) will stick out of the deck a little and will require machining to clear a closed chamber head. This build was with a block that was not the standard deck height, but i calculated his measurements with my block and think the same will happen with my production 360 block. Did anybody use the KB 356 or IC 745 Pistons in a similar build and can tell me if it´s true that the pistons stick out of the hole? Want to use magnum heads, dont want to run into trouble, machining the pistons will require new balancing........can you help me again???

regards Michael
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Can't say anything about them sticking out of the hole but if they do you should be able to run a thicker Cometic gasket that'll give you the clearance needed. That'd be cheaper than machine work and easier too.
 
360duster said:
Hi Guys, one more question:

i read in the book "how to build big inch stroker SB´s" that the Pistons (for example the KB 356) will stick out of the deck a little and will require machining to clear a closed chamber head. This build was with a block that was not the standard deck height, but i calculated his measurements with my block and think the same will happen with my production 360 block. Did anybody use the KB 356 or IC 745 Pistons in a similar build and can tell me if it´s true that the pistons stick out of the hole? Want to use magnum heads, dont want to run into trouble, machining the pistons will require new balancing........can you help me again???

regards Michael
Click to expand...



I run the KB356 and yes you would cut them for desired clearance.
I run open chamber heads, the quench domes on the pistons pop up 'around'.100 above the deck, so being after cc'ing the heads and having a chamber depth of .039-.041, I measured all at tdc and milled of the amount needed to zero with a compressed .039 felpro head gasket or .039 above the deck.

If you wanna run closed chamber just mill them for .005 above the deck or zero deck.

Always measure at all cylinders.
 
Sounds like you made three wrong choices...lol. I have seen some failures, but never had any of my own. Again, the right piston for the worst case scenario and you wont break one due to materials.
 
I've had hyper in with 8 thou clearance and didn't have any issue or failure.
They made a lil noise, more cold, but you could rock'em back and forth in the bore with you're fingers.
 
i'm not to worried bout a piston letting go at 6000+rpm. the only flaw i can see with hypers is that any cast piston
will tend to shatter when hit by something IE: a dropped valve. whereas a forged piston will tend to absorb the impact.
or extreme temp changes.. like when your using alot of NOS.

so if your using NOS/turbos/supercharging/peace of mind go with forged. otherwise hypers are good and will prolly last
just fine.
forged do tend to be noisy when cold and depending on which ring with you use, consume more oil then hypers/cast.
 
yah but they don't tell you the level of nos or boost it can handle. guess when it goes boom you'll know lol.
factory stock "tin coated" pistons can go 75-100hp shot. and about 3-4psi boost so i guess hypers could handle a little more.
 
360Z28 said:
yah but they don't tell you the level of nos or boost it can handle. guess when it goes boom you'll know lol.
factory stock "tin coated" pistons can go 75-100hp shot. and about 3-4psi boost so i guess hypers could handle a little more.
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Yeah they should, but I had to call and ask=200 shot safe, after that... it's 'find out for yourself' ha ha

and then again what comp is that with.....
 
ran kb191hypers in stock stroke 360 for 5 yrs ....ran a best of 10.77 in 69 barracuda....
 
360Z28 said:
200?!?! thats some funny ****. mabey before I pull my engine i'll do just that then posts pics of an EPIC engine failer lol.
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Like I said, what compression is that with to start?

Btw, if a stock 318 pistons can handle 100 shot a few or so times I find nothing unbelievable about a KB hyper being 200 shot capable but hey...

When questioning hyper piston capability, claimer engines come to mind.....
 
they (stock pistons) can handle that shot becouse the tin coating does a remarkable job of controlling thermo expansion.
not saying that hypers will fail with a 200 shot.. but as you pointed out, they don't specify what cr/timing/fuel pressure/etc.
i'm sure one can kill a stock engine with a 50 shot no problem. the way my engine is built, 200 would be a killer even with
forged pistons.
 
moper said:
Sounds like you made three wrong choices...lol. I have seen some failures, but never had any of my own. Again, the right piston for the worst case scenario and you wont break one due to materials.
Click to expand...

They were dads engines, work truck motors. All three came apart at WOT climbing hills with heavy loads.

I always ran the heavy TRW's in my Mopars, until the 390 with the Ross's.
 
Yeah.. one thing I noted a while ago... the ring gaps for heavy use and towing are larger than "hi perf pass" in the instructions... I've used them in towing engines but the ring gaps were something like .030" going by memory.
 
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