Magnum 360 piston choice

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WacDad Miller

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Im building a Magnum 360, going with a .030” bore and just getting some opinions on a good flat top piston.
 
Speed Pro H116CP. 1.660" CH, 5cc valve reliefs. Sit down the bore 0.027" with a stock block deck height. They are hypereutectic's and they use the ring gap that the ring manufacturer suggests to use. The skirts have a friction coating.
 
Dan the man said:
Speed Pro H116CP. 1.660" CH, 5cc valve reliefs. Sit down the bore 0.027" with a stock block deck height. They are hypereutectic's and they use the ring gap that the ring manufacturer suggests to use. The skirts have a friction coating.
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Hey Dan. Where does this information come from exactly?
 
Any 360 stock stroke piston should work I believe the only difference is deck height on magnums are around .020 shorter. With iron heads you probably going to want something with a little lower compression so pump gas will run fine. I know Icon 741s are close to stock magnum piston wieght for easy balance but your compression will be to much for pump gas
 
Are you sure it needs over bored?

Those blocks are famous for still having the factory cross-hatch pattern after 150,000 miles or more.
 
I'm doing a 5.9 build and just got these. I'm using the MP R/T head. Should be around 9.2-9.5 CR and I can run pump gas.
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YY1 said:
Are you sure it needs over bored?

Those blocks are famous for still having the factory cross-hatch pattern after 150,000 miles or more.
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Mine still had a lot of cross hatch but when we did a hone job we didn't get a good even cross hatch because some the cylinders were out of round a bit.
 
YY1 said:
Are you sure it needs over bored?

Those blocks are famous for still having the factory cross-hatch pattern after 150,000 miles or more.
Click to expand...
Yes, I have a cylinder that has rust in it from sitting to long opened up. I cleaned up that bore a bit with a ball hone and it has blemishes.
 
There are a few .020” over pistons available if it will clean up at that size. And plenty of ring choices at .020” as well. Most are hypereutectic and I know SRP has a forged version as a shelf piston because I ordered a set for mine.
 
If they have a nice flat top or something zero deck with valve reliefs anything but the LA dished stlke LOL!
 
Dan the man said:
Speed Pro H116CP. 1.660" CH, 5cc valve reliefs. Sit down the bore 0.027" with a stock block deck height. They are hypereutectic's and they use the ring gap that the ring manufacturer suggests to use. The skirts have a friction coating.
Click to expand...
Looking at these pistons my only problem that I see is I am running a cam with .050 lift stock arms. Guy I was going to buy these from said I'd probably have to mock it up and possibly adjust with the head gasket running basically a stock EQ heads
 
chris100 said:
Looking at these pistons my only problem that I see is
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chris100 said:
I am running a cam with .050 lift stock arms.
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Could you clear this up for me? I’m missing what you’re trying to say. The cam your running has a valve lift of .500 because the .050 is confusing me. The stock rocker arms are not known to be very accurate at there listed ratio of 1.5. Normally less.

I run those pistons at a zero deck height and a 1.6 rocker arm for a total valve lift of .574. Up top? I’ve had Edelbrock heads, ProMaxx CNC heads (Edelbrock knock offs) and it currently sports Trick Flow heads. I hope that helps.
 
rumblefish360 said:
Could you clear this up for me? I’m missing what you’re trying to say. The cam your running has a valve lift of .500 because the .050 is confusing me. The stock rocker arms are not known to be very accurate at there listed ratio of 1.5. Normally less.

I run those pistons at a zero deck height and a 1.6 rocker arm for a total valve lift of .574. Up top? I’ve had Edelbrock heads, ProMaxx CNC heads (Edelbrock knock offs) and it currently sports Trick Flow heads. I hope that helps.
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I don't mean to high jack the OP thread, but can the sbm's deck surface be safely machined 0.027" so those pistons can be ran at zero deck height?
 
Dan the man said:
I don't mean to high jack the OP thread, but can the sbm's deck surface be safely machined 0.027" so those pistons can be ran at zero deck height?
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Yes. In my engine, it was less. In my other 360, the KB-107’s with a very minor difference in piston height was an even .020 below deck and used with a .510 lift total mechanical cam.
 
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