piston help... identify please.

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abodyjoe

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so 8m thinking about throwing together a mild 360. got these pistons years ago and when i look up the number i cant find it. i can find the H405CP by speed pro but dont see the H405P assuming also by speed pro. so i guess my question is what exactly do i have here? are these speed pro hypereutectic?

thanks for any help in advance.

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What's the top look like, dished, valve relief cuts? 65'
 
Summit lists them as a "cast" piston, then in the description lists them as hyper, and says they are 16% silicone. So, I guess ,hypereutectics.
Not much compression ratio, though.
 
here is the h405cp which is all that comes up when i google h405p. not sure if its just a new part number or an entire different piston,...

Speed Pro H405CP Speed-Pro Hypereutectic Pistons | Summit Racing

View attachment 1715859425
Theyre a cast hypereutectic piston. I just built an engine with them, .020
9.1 type. I'm surprised more people don't use them for the price too. I find them on eBay brand new for 160 bucks. I also find my main and rod bearings on there for 54 bucks for both sets.
 
Theyre a cast hypereutectic piston. I just built an engine with them, .020
9.1 type. I'm surprised more people don't use them for the price too. I find them on eBay brand new for 160 bucks. I also find my main and rod bearings on there for 54 bucks for both sets.

so are the H405P and H405CP the same thing? they aren't 9:1 are they? thought they were like 8:5 to 1.
 
ok. that makes sense. thanks. at that price i should just buy new ones and know exactly what i have. lol

Right?.lol
When people say it cost a lot of money to build a decent street motor.. I have to laugh.
It's not that much money to make 375-400 hp with a 360.
 
yea lower compression is fine. want a mild motor that can run cheap gas.
My 11/1 360 runs at a tic under 180 psi, with full-timing, full-time, on 87E10 ......... with alloy heads. With a small cam, overdrive, and a modest hiway gear, I think it could make hiway fuel-economy deep into the high 20s and still go 12s. Oh wait, it already did.
The point is, if yur gonna do pistons anyway, you don't have to lower your expectations. I mean you can but, you may be leaving economy in the back-room.
But if you have to run iron heads, for whatever reason, I get it.
However, IMO
running a lower compression and running cheap gas is a kindof loosing battle.
Assuming a price difference of 5% between 87 and 89;
If your car drives just 5% further on hi-compression and 89 gas, than
with low-compression and 87 gas, that is a break-even. 5% is just 10 miles on a 200 mile tank. If i goes 6% further, just 12 miles on that 200 mile tank, it's actually costing you less per mile even tho, more at the pump..
Furthermore; you only need just enough octane to suppress detonation.
If yur going down the highway with an 8/1 engine throttled down to an effective Dynamic cr of 5/1, it will burn any old skunk pee. So 87 is already a luxury gas. So you may as well bump the Dynamic compression ratio up closer to 8/1, which is what 87 will support with iron heads.
You say mild engine. If that means 2bbl, then the engine may never get past 70% Volumetric efficiency anyway, and so you might be able to run the Dynamic cr all the way up to 8/1 or more! still on cheap gas.
Jus tossing it out there
 
My 11/1 360 runs at a tic under 180 psi, with full-timing, full-time, on 87E10 ......... with alloy heads. With a small cam, overdrive, and a modest hiway gear, I think it could make hiway fuel-economy deep into the high 20s and still go 12s. Oh wait, it already did.
The point is, if yur gonna do pistons anyway, you don't have to lower your expectations. I mean you can but, you may be leaving economy in the back-room.
But if you have to run iron heads, for whatever reason, I get it.
However, IMO
running a lower compression and running cheap gas is a kindof loosing battle.
Assuming a price difference of 5% between 87 and 89;
If your car drives just 5% further on hi-compression and 89 gas, than
with low-compression and 87 gas, that is a break-even. 5% is just 10 miles on a 200 mile tank. If i goes 6% further, just 12 miles on that 200 mile tank, it's actually costing you less per mile even tho, more at the pump..
Furthermore; you only need just enough octane to suppress detonation.
If yur going down the highway with an 8/1 engine throttled down to an effective Dynamic cr of 5/1, it will burn any old skunk pee. So 87 is already a luxury gas. So you may as well bump the Dynamic compression ratio up closer to 8/1, which is what 87 will support with iron heads.
You say mild engine. If that means 2bbl, then the engine may never get past 70% Volumetric efficiency anyway, and so you might be able to run the Dynamic cr all the way up to 8/1 or more! still on cheap gas.
Jus tossing it out there

pistons i already have, iron heads are going on... it will have a 600 holley on it since i have a few of them laying around and have the intake here...
 
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