O'Neal's new piston for the nitrous guys

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itey

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Hmm, not much interest in a pretty cool deal.

Steel top for the rigors of combustion and aluminum bottom for weight.
I like it...
 
Yeah, we were going to make them for them, back in the day, but the investment was more than it was worth. Diesel piston are far more accurately manufactured than hot rod pistons are ... and hot rod pistons are pretty accurate.
 
Steve439 said:
I do not recall... can the top part be round?
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The top part is the only part that is round, and sorta square, depending.

Having said that, The correct rod ratio is always 8 to 1... 8 rods to 1 crankshaft. Rod ratio is about the 95th thing you should be concerned about when you're building a motor. The only advantage I can see to that thing would be that you wouldn't need an oil rail support.
But I think it would add more weight to the piston, that I'd rather have gone, than worry about having an oil rail support.
 
Oddly enough, I'm rereading Billy Godbold's cam book and he thinks rod ratio is a big deal.

He also has a bunch of graphs comparing things and I'd have to get a magnifier out to see the difference in some of the curves... :LOL:
 
What are the negative aspects for making a 100% steel investment cast piston?

My dad's '41 Chevy 3/4T PU I drove to high school had cast iron pistons and #5 had a collapsed skirt that rattled so loud it sounded like a one cylinder diesel. I drove it like I stole it nearly every day for 2 years and in the 10 years experience I had with the faithful old rig the piston rattle never changed, so the iron was tough enough to stand up to the abuse I gave it power shifting a 4spd crash box (granny low, no synchros) with 4.56 R&P.

My point is, a steel piston is no doubt strong enough and much more resistant to melting and destruction from detonation and preignition, so how close can steel come in weight and still be practical for big boosted applications that don't require sky high RPM because they can turn up the boost?

Have you ever calculated the possibility, stress vs. strength vs. weight? All the advancing tech with AI might make it a lot easier to run a "what if ?" computer prototype exercise.
 
Steve439 said:
Oddly enough, I'm rereading Billy Godbold's cam book and he thinks rod ratio is a big deal.

He also has a bunch of graphs comparing things and I'd have to get a magnifier out to see the difference in some of the curves... :LOL:
Click to expand...
Obviously, combustion chambers, valve timing, VE, etc, a lot more than rod length ratio involved in this, but just a hunch from 60+ years of playing with distributor machines and seeing how engines respond to the advance curves they like best, the "short rod" engines seem more likely to appreciate a curve that gives them ideal timing at both torque peak RPM and HP peak RPM. Short rod engines seem to want more advance from TQ to HP.

The timing that makes best HP is almost always too much for best TQ, even if the fuel doesn't knock. This is so for all engines, but seems more so for "short rod" engines.

Some of this "hunch" is from comparing OE advance curves for pre-smog engines and seeing this trend, and some from seeing "all-in at 2500" setups hurt performance compared to the original curves that didn't total until well past the peak TQ RPM.
 
Mark O'Neal said:
Yeah, well, he did create the Xtreme Energy cams to beat the shit out of our valvetrain ... so that's that.
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I don't know who was responsible for it at Comp, but I got a .480" lift rule cam from them for a 305 Chev A/S SCCA spec engine that needed so much valve spring pressure (and still floated the valves at 5500 anyway) it lost 35 Ft.lbs. at the torque peak. GM "140" cam will turn crazy RPM with such low seat pressure it has to be lofting but yet causing no damage. Decades ago Crower had some crazy short duration high lift everything TQ and HP all in one cam that needed crazy spring pressures. After the first experience with the 140 in about 1969 I had some enlightening discussions over the years with T Willy Hutchins about the light spring 'lofting' phenomenon of the 140 cam and I have used at least 20 of them since, Crane, Melling, Wolverine, etc, copies to build low buck engines for entry level oval track racing and always had good luck. According to a lot of cam experts the 140 cam is obsolete junk "not enough lift and too much duration" but it works good in spite of their opinions.
 
Mark O'Neal said:
Yeah, we were going to make them for them, back in the day, but the investment was more than it was worth. Diesel piston are far more accurately manufactured than hot rod pistons are ... and hot rod pistons are pretty accurate.
Click to expand...
Why is that? What are the differences between the two? Just curious, I have no clue what the difference is between the two.
 
Mike Beck said:
Why is that? What are the differences between the two? Just curious, I have no clue what the difference is between the two.
Click to expand...


We'd have had to add a couple of million in machines, and the contract was iffy at best. Believe it or not, the tolerances are far tighter on those things than they are on anything we run.

Probably should have done it. This industry is going away. I expected it, but not this quickly.
 
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