piston for high rpm

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Mark O'Neal
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Re: piston for high rpm

Post by Mark O'Neal » Wed Oct 25, 2017 5:51 pm

Straight8 wrote:
Wed Oct 25, 2017 9:32 am
Mark O'Neal wrote:
Wed Oct 25, 2017 3:10 am
Is there any way to come up with a 10.000 aftermarket block?

It's a lot of RPM, but it's a puller. Running components that are too light will hurt, it would seem to me. You want to store all the energy you can to help you at the end of the pull.

There is nothing wrong with the rods you have, they'll move a lot of weight off the piston and move it toward the crankshaft.

Dome, dish, or flat?

I'll only complain about the pin when I know how much compression you're running. What wall pins have you been running?
Would a block .300 shorter deck really be a big plus? I know that would lighten the rod a little but I've been involved with the BBC crowd where the tall deck has ran successfully with short deck stuff. Personally I haven't had an engine operated at this kind of rpm,8000 or so with bigger cid and never ran a small .927 pin. I would " think" that pin in a little thicker wall would be ok even for high rpm NA deal,but that's why I'm asking. :D it's gona need all the dome I can get with that short stroke for hopefully 14.1 or more.

Pins used to be a great way to save weight, but not so much anymore, Cylinder pressures are a lot higher today than they were in the 1980s. A .927 will with a thicker wall weight as much as a .990.....so all you're getting is a pin that is more likely to deflect.

Other than that, I don't see anything wrong with your combination. ROSS, CP, JE, Diamond will all build a piston for those parameters and you don't need anything way weird for 8,000 rpm. I don't know what head you're running, but a normal open chamber dome will max out at close to 51ccs, so you will be chasing compression.

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Re: piston for high rpm

Post by Straight8 » Wed Oct 25, 2017 6:21 pm

stealth wrote:
Wed Oct 25, 2017 4:43 pm
Straight8 wrote:
Sun Oct 22, 2017 2:06 pm
What qualities would you look for in a max effort 4.6 bore piston looking at 8800-9000rpm.small inch pulling class with 3.6 stroke with long rods.
Look at NASCAR pistons & rods listed on eBay for inspiration...ro7, sb2.2., etc

They run 9000 rpm for hours....pretty sure the have a handle on design criteria to accomplish your request.
I'm not sure but I don't think they run 4.600 bore. My experience with the large bore is piston rock and skirt failure. This short stroke " shouldn't " be as hard on skirts IMO but the big bore is still the question. What's acceptable for rock in a bore that size?

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Re: piston for high rpm

Post by Straight8 » Wed Oct 25, 2017 6:29 pm

Mark O'Neal wrote:
Wed Oct 25, 2017 5:51 pm
Straight8 wrote:
Wed Oct 25, 2017 9:32 am
Mark O'Neal wrote:
Wed Oct 25, 2017 3:10 am
Is there any way to come up with a 10.000 aftermarket block?

It's a lot of RPM, but it's a puller. Running components that are too light will hurt, it would seem to me. You want to store all the energy you can to help you at the end of the pull.

There is nothing wrong with the rods you have, they'll move a lot of weight off the piston and move it toward the crankshaft.

Dome, dish, or flat?

I'll only complain about the pin when I know how much compression you're running. What wall pins have you been running?
Would a block .300 shorter deck really be a big plus? I know that would lighten the rod a little but I've been involved with the BBC crowd where the tall deck has ran successfully with short deck stuff. Personally I haven't had an engine operated at this kind of rpm,8000 or so with bigger cid and never ran a small .927 pin. I would " think" that pin in a little thicker wall would be ok even for high rpm NA deal,but that's why I'm asking. :D it's gona need all the dome I can get with that short stroke for hopefully 14.1 or more.

Pins used to be a great way to save weight, but not so much anymore, Cylinder pressures are a lot higher today than they were in the 1980s. A .927 will with a thicker wall weight as much as a .990.....so all you're getting is a pin that is more likely to deflect.

Other than that, I don't see anything wrong with your combination. ROSS, CP, JE, Diamond will all build a piston for those parameters and you don't need anything way weird for 8,000 rpm. I don't know what head you're running, but a normal open chamber dome will max out at close to 51ccs, so you will be chasing compression.
Compression is always the issue with short stroke and big valves/ chambers. I have tfs A460 so I need a decent size dome but not really BBC size. Thanks for your input, 8)

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Re: piston for high rpm

Post by Mark O'Neal » Fri Oct 27, 2017 5:07 am

The BBC has the advantage here (just referring to pistons) in that everyone has a hollow dome forging for them The Fords don't use as much dome, but you're always stuck with a solid dome. The truth be known, you're probably getting a BBC flat top forging. The volume on the BBF is low enough that most don't have Ford specific forgings. They just make the valve pocket pad accommodate the Ford relief....or make the piston thicker.

So, if you want light parts, you have to go to someone like Patterson. Window milling the skirts and running an end mill under the dome just won't do enough.

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Re: piston for high rpm

Post by Newold1 » Fri Oct 27, 2017 10:41 am

Might want to talk to and consider some machining from someone like Rebco

www.rebco-machine.com

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Re: piston for high rpm

Post by DaveMcLain » Fri Oct 27, 2017 11:04 am

What if you angle mill the heads to drop the size of the chambers? I think that might help the piston situation a bunch.

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Re: piston for high rpm

Post by Straight8 » Fri Oct 27, 2017 9:23 pm

DaveMcLain wrote:
Fri Oct 27, 2017 11:04 am
What if you angle mill the heads to drop the size of the chambers? I think that might help the piston situation a bunch.
That's always a possibility but the valve clearance becomes an issue even with angle milling. The valve reliefs make for some ugly Pistons but that's not as big an issue with a NA deal. wouldn't angle milling cause a lot of other issues?

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Re: piston for high rpm

Post by stealth » Sun Oct 29, 2017 12:53 pm

Straight8 wrote:
Wed Oct 25, 2017 6:21 pm
stealth wrote:
Wed Oct 25, 2017 4:43 pm
Straight8 wrote:
Sun Oct 22, 2017 2:06 pm
What qualities would you look for in a max effort 4.6 bore piston looking at 8800-9000rpm.small inch pulling class with 3.6 stroke with long rods.
Look at NASCAR pistons & rods listed on eBay for inspiration...ro7, sb2.2., etc

They run 9000 rpm for hours....pretty sure the have a handle on design criteria to accomplish your request.
I'm not sure but I don't think they run 4.600 bore. My experience with the large bore is piston rock and skirt failure. This short stroke " shouldn't " be as hard on skirts IMO but the big bore is still the question. What's acceptable for rock in a bore that size?
Very true...yours are 4 tenths larger diameter...nothing will apply.... :wink:
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.

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