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Onan JB/JC High Compression Pistons


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  #1  
Old 05-17-2016, 11:24:26 AM
nothingbutdarts nothingbutdarts is online now
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Default Onan JB/JC High Compression Pistons

Well, I'm thinking about seeing if anyone has a set of 4 high compression pistons that they want to sell. Since I can't get full A/C output on my JB I would imagine it will be the same for a JC I have torn apart and think I might go with the high compression pistons because of living @ 8,700'.

Pistons for sale or comments anyone????
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Old 05-17-2016, 11:33:33 AM
KPack KPack is offline
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Default Re: JB/JC high compression pistons

What's the parts number , we can search too.
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Old 05-17-2016, 12:16:32 PM
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Default Re: JB/JC high compression pistons

I think Jim McIntyre milled the head on a JB to raise the compression. What fuel are you running?
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Old 05-17-2016, 12:36:58 PM
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Default Re: JB/JC high compression pistons

Nope. I would if I had an extra JB head to tinker with. I have done this on several CCKs with success...
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Old 05-17-2016, 01:02:22 PM
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Default Re: JB/JC high compression pistons

Piston # 112-0174 Std. bore
112-0174-10 .010
112-0174-20 .020
112-0174-30 .030

I will be using either gasoline or propane, mostly propane but, if I needed too I would run gasoline.
Really looking for STD. bore pistons.
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Old 05-17-2016, 01:06:17 PM
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Default Re: JB/JC high compression pistons

Someone tried it here on the site. Can't remember who.
The only other way I would think of gaining power for altitude loss would be turbocharging with a small amount of boost. Use a small turbocharger like the ones used on the Kubota diesels.
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Old 05-17-2016, 01:10:51 PM
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Default Re: JB/JC high compression pistons

Can't get full AC power?

What happens? What is the indication you are not getting full power? Frequency drop off, voltage drop off?
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Old 05-17-2016, 01:26:14 PM
dalmatiangirl61 dalmatiangirl61 is offline
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Default Re: JB/JC high compression pistons

Quote:
Originally Posted by Motorhead View Post
The only other way I would think of gaining power for altitude loss would be turbocharging with a small amount of boost. Use a small turbocharger like the ones used on the Kubota diesels.
Or get creative and use a supercharger, I know there is a small Mazda supercharger on ebay right now
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Old 05-17-2016, 11:14:03 PM
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Default Re: JB/JC high compression pistons

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Originally Posted by Motorhead View Post
Someone tried it here on the site. Can't remember who.
I'd like to be proven wrong, but I don't think it's been posted here before.

I started a thread on the topic last summer but, since I'm fresh out of spare JB heads to tinker at, haven't tried it yet.

http://www.smokstak.com/forum/showthread.php?t=147438

Anyway, the increased CR isn't going to make up for 9000 feet ASL. Darts just needs a bigger genset...

Last edited by Jim McIntyre; 05-18-2016 at 08:37:36 AM.
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