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Piston Design Questions

General engine tech -- Drag Racing to Circle Track

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skinny z
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Re: Piston Design Questions

Post by skinny z »

That'll be the plan more or less.
But it'll be more of case where the builder will take of that. Good shop and they've, like you suggest, have probably encountered this before and will have a remedy. There is an element of a time restraint and over the counter is what will be needed.
This is more a case of my due diligence so at least I'm informed.
Thanks.
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frnkeore
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Re: Piston Design Questions

Post by frnkeore »

I re-read this whole thread and I haven't seen why you couldn't use the dished pistons and mill the head, to get where you need to be. You could also decrease, the amount taken of the heads by 1.14cc, by decking the block, to get .035 PTH.

From what you said about the 355, with it's 10.4 CR, you needed more cam for it. If your looking for more cubes, and better street manners, than the 355 and pump gas, I think you'd be better off targeting 10/1 CR. But, you have to get the cam timing right, to go with the CR, no matter what.
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Re: Piston Design Questions

Post by Bill Chase »

Find someone that is a race tec/wiseco dealer, and just have pistons made. Or, others that do not charge an arm and a leg for a custom piston. If you want it that precise (it sounds like you do), and if you want shelf stock piston prices (it sounds like you do)

I mention wiseco because I've seen some of their pro tru stuff made for skip white and they were reverse dome d cup pistons with around 12 cc, and I believe he has them for 5.7 and 6 inch rods. As well as slightly taller compression height. So you could buy them at shelf price and mill the dish or quench pads to bring your dcr into a more precise spec. And they are a quality 2618 forging.

My question is for all that will cost, why not just step into an aluminum head. There are far to many as cast heads out there now days that are good quality and will flow the number your current iron heads have. It sounds like you want a fast street car, or a track car that will be driven on the street and must survive on pump gas. Why fight the iron heads? Heads are cheap now days, almost throw away prices.
skinny z
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Re: Piston Design Questions

Post by skinny z »

frnkeore wrote: Mon Jan 11, 2021 2:42 am I re-read this whole thread and I haven't seen why you couldn't use the dished pistons and mill the head, to get where you need to be. You could also decrease, the amount taken of the heads by 1.14cc, by decking the block, to get .035 PTH.

From what you said about the 355, with it's 10.4 CR, you needed more cam for it. If your looking for more cubes, and better street manners, than the 355 and pump gas, I think you'd be better off targeting 10/1 CR. But, you have to get the cam timing right, to go with the CR, no matter what.
Going back over the thread myself, I see that I neglected to mention that the heads have been cut already. I believe .012" so as to pull a couple of cc's out of the chambers as they were modified as part of the 355. I'm not certainain if there's too much left to remove. At .006" per cc, I might gain a little but it would be a tenth or maybe slightly more in CR. (Those milled values are from memory so they may be off a little).
Ideally, I'd like a .035-.040 PTH clearance.
I agree that 10:1 is a reasonable target. And having that determined is what's needed before I proceed with finalizing the cam spec.
I did a little investigating on the profile of the 19cc Icon piston and it's a stepped dish. It appears to leave little to no quench. In my estimation, it's a poor choice.
I'm liking the Ross D-shaped dish at 15 cc.
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skinny z
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Re: Piston Design Questions

Post by skinny z »

Bill Chase wrote: Mon Jan 11, 2021 4:06 am Find someone that is a race tec/wiseco dealer, and just have pistons made. Or, others that do not charge an arm and a leg for a custom piston. If you want it that precise (it sounds like you do), and if you want shelf stock piston prices (it sounds like you do)

I mention wiseco because I've seen some of their pro tru stuff made for skip white and they were reverse dome d cup pistons with around 12 cc, and I believe he has them for 5.7 and 6 inch rods. As well as slightly taller compression height. So you could buy them at shelf price and mill the dish or quench pads to bring your dcr into a more precise spec. And they are a quality 2618 forging.

My question is for all that will cost, why not just step into an aluminum head. There are far to many as cast heads out there now days that are good quality and will flow the number your current iron heads have. It sounds like you want a fast street car, or a track car that will be driven on the street and must survive on pump gas. Why fight the iron heads? Heads are cheap now days, almost throw away prices.
A custom piston is entirely likely and I'll check Skip White's website to see what's there.
I had mentioned I like the Ross D-shaped dish at 15 cc. It seems a decent fit and should let me get close to 10:1.
As for the heads, therein lies the rub. I've got too much invested in these and would like to incorporate them into this 383. It is proving problematic though and the thought of a total rethink isn't outside the possibilities.
As for precision, I'm sure there are many here that would argue that it isn't necessary given what this will be. Nothing special in terms of a result. But I figure if I an get a little here and there, the end result might be step over and above an average result.
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Re: Piston Design Questions

Post by rebelyell »

I have a set of off the shelf Wiseco Pro-Tru pistons for a 6" rod 406; they did Not come from Skip White. Mine are Not 2618; they are 4032. It's been my understanding that Wiseco's Pro-Tru piston Line are essentially a street-hipo piece (thus lower-expansion forged 4032 alloy) versus the higher priced all-out race pistons (2618) from Wiseco.

I've never bought anything from Skip White and likely won't; including his over-hyped ad BS. I know folks who bought into SW who got scheisse in return.

FWIW, built a stroker harley back in 70's w/ "forgedtrue" pistons ... IIRC, those were 2618
skinny z
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Re: Piston Design Questions

Post by skinny z »

I had a look at the Wiseco catalogue the other day. It's not something easily done on a phone I can tell you that. I'm going to dig a little deeper.
I've mentioned the Ross piston but I've no idea if my machinist works with them. Being an old school Pro Stock team (from the 70's) I'm sure they've had their hand on just about everything. Wiseco most certainly.
Thanks for the heads up too. I've heard of Skip White horror stories but then I've also heard there's more than one Skip White? Beats me. I tend to stick with mail order or what comes over the counter from the local speed shop or whoever I'm doing business with.
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Mark O'Neal
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Re: Piston Design Questions

Post by Mark O'Neal »

skinny z wrote: Fri Jan 08, 2021 2:04 pm
Mark O'Neal wrote: Fri Jan 08, 2021 12:46 pm Run the flat top and a .080 gasket.
I take it then that you've little concern for an excessive gap between the piston and the head? Seems the conventional thinking is that it deserves attention.
This is part of the reason for my wanting to stay away from a full dish as opposed to something with a D shaped dish. That would be to take advantage of that tight squish area.
Depends on what you're doing, I suppose but I have no concern at all.,
skinny z
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Re: Piston Design Questions

Post by skinny z »

Fair enough Mark.
I can see that you're not alone on that.
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