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Author Topic: PREDATOR 420CC ENGINE  (Read 22717 times)
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Chris Matuschka
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« on: July 22, 2011, 10:32:11 PM »

Hi, has anybody experimented with the new Predator motors at Harbor Freight. It looks very similar to the GX390 on the outside but I am wondering if the ARC parts will fit and gasket availability.
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zach87cp
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« Reply #1 on: July 23, 2011, 06:24:46 AM »

I dont have any experince with a clone but i heard that the block are weaker than a honda and they crack.
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Zach Rupert
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« Reply #2 on: July 23, 2011, 07:48:14 AM »

We run the clones and have great luck with them. No problems so far and all the hopnda ARC parts fit.
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George Herrin #6
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« Reply #2 on: July 23, 2011, 07:48:14 AM »

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Chris Matuschka
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« Reply #3 on: July 23, 2011, 08:05:06 AM »

I know alot of guys had good luck with the older blue ones from Harbor Freight but didn't know if the new black Predators were still the same. I'm hoping the only diference is the bore.
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George Herrin
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« Reply #4 on: July 23, 2011, 09:17:49 AM »

ours been red n yellow and 1 blue i think oh 1 black too but it was a 390 clone. we got one of the 420 here in BTMRA and its stroked. been a whole season and starting half way thru the second so far so good
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George Herrin #6
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« Reply #5 on: July 23, 2011, 03:48:34 PM »

Honda blocks will crack as well, they really need supported.
The 420 has a bigger bore, same stroke as a 390.
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« Reply #6 on: July 23, 2011, 07:26:42 PM »

Same rod dimensions and flywheel as well?  A big bore 390 sounds very attractive!
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Chris Matuschka
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« Reply #7 on: July 23, 2011, 07:34:07 PM »

Thanks guys, they are on sale for $350 plus 20% off with coupon. Was hoping to use an Arc rod and flywheel and a cam change. Was thinking to only mill the head a little to keep compression reasonable. I want to build something mild and reliable until I get some runtime on the chassis.
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« Reply #8 on: July 23, 2011, 07:46:12 PM »

Call Mike at precision he built my clone and its stupid fast. He can fix you up on anything you need for it. ALL ARC parts fit too.
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George Herrin #6
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Ron Atchison/A.C.E. Race Engines
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« Reply #9 on: August 01, 2011, 12:14:17 AM »

All of the block will eventually fail if they are pushed beyond their limits! We have built several of the 420 clone engines. Over the last couple years we've came up with a good forged lightweight piston, cyl head, billet flywheel & cam package i sell that makes around 35hp with good reliability. If you run the Arc rod and spin engine over 6500 rpm you'll need change the rod in 12 or so nights. The alternative to the Arc rod is to buy a $290 4340 steel rod. We turn our 420's around 72-7500 rpm with no problems when built right. Here's a couple pics of a 38hp 390/420 where the block didn't survive the dyno run.




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DanW
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« Reply #10 on: August 01, 2011, 07:42:27 AM »

LOL... pass.  Who makes the steel rod btw?
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cubcadet70
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« Reply #11 on: August 01, 2011, 11:27:27 AM »

Honda makes the stell rod. You will have to buy the bearings. Do you know which color bearings I should buy for standard size? They go buy color coded and I don't know which is which.
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Ron Atchison/A.C.E. Race Engines
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« Reply #12 on: August 01, 2011, 03:26:52 PM »

Honda makes the stell rod. You will have to buy the bearings. Do you know which color bearings I should buy for standard size? They go buy color coded and I don't know which is which.

The steel rod i'm referring to is not the casted Honda steel rod but, it's a forged custom made 4340 h-beam design.
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« Reply #13 on: August 01, 2011, 04:01:09 PM »

Who makes it?  I've gotten quotes on custom forged rods and it comes out to $500 per rod if the production is low.

I would be very interested in having them make h or i beams for a Vanguard if they are in the ball park of $290.
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Ron Atchison/A.C.E. Race Engines
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« Reply #14 on: August 01, 2011, 11:14:38 PM »

Who makes it?  I've gotten quotes on custom forged rods and it comes out to $500 per rod if the production is low.

I would be very interested in having them make h or i beams for a Vanguard if they are in the ball park of $290.

ok, contact these people  http://pacrankie.en.alibaba.com/product/290289603-200240948/CC131mm_8A_Connecting_Rod.html.    To have domestically made they wanted a min. order of 100 at $200 each!
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