Speed Pro H116CP pistons drop in with no rebalance?

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mshred

mshred

The Green Manalishi
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Hey guys,

Playing with the idea of changing out the pistons in my 360 IF I can find a drop in that will work without rebalance. I have done some digging, and would prefer a forged piston if I am changing pistons, but I have only been able to find some info on some of the Mopar boards about these Speed pro H116CP pistons.

https://www.summitracing.com/parts/slp-h116cp30

I can't seem to find any real specs on them, other than what is listed in sale ads, but they appear to be a stock replacement piston with similar weight, but a flat top and with 2 valve reliefs. At what they cost on Summit, I would love to spring for a forged set, but again not sure of a piston that will drop in to a 4.00 or 4.030 bore without rebalancing besides these.

Can these be ran without a rebalance? And does anyone know of a forged option that would work in its place? Bonus points if you have a set kicking around you aren't using and want to get rid of
 
I have built at least four 360 engines using those pistons. No rebalancing is needed. I went as far as having my machine shop check them out and he told me that they are the same weight as the stock pistons. He told me what they did was move some of the material from the skirt to the top of the piston to make it a true flat top piston and up the compression. I think the piston pin maybe moved up a bit too because they will be at "0" deck height at TDC. I'm running a set in a 360 with W2 heads that sees over 6500 rpm on occasion. Been beating on that engine for years now. Stock crankshaft with 340 rods just because they are floaters. Rebalancing is always good advice. Mopar didn't always do the best in that department but it is what it is. So with that said they are heavy but damn good replacement pistons. Put then in and run it.
 
Last edited:
mshred said:
Hey guys,

Playing with the idea of changing out the pistons in my 360 IF I can find a drop in that will work without rebalance. I have done some digging, and would prefer a forged piston if I am changing pistons, but I have only been able to find some info on some of the Mopar boards about these Speed pro H116CP pistons.

Speed Pro H116CP 30 Speed-Pro Hypereutectic Pistons | Summit Racing

I can't seem to find any real specs on them, other than what is listed in sale ads, but they appear to be a stock replacement piston with similar weight, but a flat top and with 2 valve reliefs. At what they cost on Summit, I would love to spring for a forged set, but again not sure of a piston that will drop in to a 4.00 or 4.030 bore without rebalancing besides these.

Can these be ran without a rebalance? And does anyone know of a forged option that would work in its place? Bonus points if you have a set kicking around you aren't using and want to get rid of
Click to expand...
Agree with the above post as far as them being stock replacement weight but buy them here,
https://store.nexternal.com/iepgi/chrysler-360-h116cp-kit-available-30-only-p2397.aspx
 
Thanks for the replies guys! This is supposed to be a budget build, but the car is heavy and a 360 isn't exactly a large motor, so a good bump in compression is helpful!
 
Depends on the block. The last two I did came to "0" but one was decked .0.20"
 
dirty white boy said:
.027 in the hole according to this add and my calculations on wallace deck height calculator....DWB
Click to expand...
Nice! Better than the .110" deck clearance I have right now with the dished factory replacements I currently have at .030" over
 
I did a 360 block some years back and the KB-107’s that have a near identical compression height. They were also -.020 in the hole. This will allow a thin head gasket, I used a .027 from Cometic and it still allows for a OK quench and ratio for pump gas. The ratio was approx 10.25-1 with an Edelbrock head.

It’s said that a decent quench starts at .050 but not more. If you end up at .020 in the hole and the .027 gasket, HEY! .047, under .050! Your in! Head milling optional…….

Since, (IIRC) your cam isn’t to large, you’ll create a decent amount of low end torque. I don’t think it’ll be a rocket out of the hole but it won’t be a pig.

What cam did you decide on using?
 
rumblefish360 said:
I did a 360 block some years back and the KB-107’s that have a near identical compression height. They were also -.020 in the hole. This will allow a thin head gasket, I used a .027 from Cometic and it still allows for a OK quench and ratio for pump gas. The ratio was approx 10.25-1 with an Edelbrock head.

It’s said that a decent quench starts at .050 but not more. If you end up at .020 in the hole and the .027 gasket, HEY! .047, under .050! Your in! Head milling optional…….

Since, (IIRC) your cam isn’t to large, you’ll create a decent amount of low end torque. I don’t think it’ll be a rocket out of the hole but it won’t be a pig.

What cam did you decide on using?
Click to expand...

Crazy late reply here, didn't even get notified about this or maybe I missed it.

Budget has been getting tighter due to socialist policies North of the border, so I stuck with all stock pistons. Cam is currently at Oregon waiting in line for a regrind, going from hydraulic to solid.
 
I just installed 2 sets . 1st - 1988 la roller block cut .010" pistons down .004" , 2nd 1977 - 360 block light clean up cut .002"-.003" pistons down .014" . Both sets were within 5 grams from stock , and compression with stockish 360 heads and felpro 1008 came in at 9.6 - 9.7 to 1
 
Just make sure all the pistons are the same weight or close.
 
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