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Old 10-28-2005, 10:58 PM
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2 bolt vs 4 bolt main 350 small block

I'v got a 2 bolt main out of my 70 Lemans, I have read mixed reviews wether
to spend the money on it or look for a 4 bolt to replace it with. I'm building a weekend cruiser but would like it to have decent power. What usually fails first a rod or a main?

Thanx
Cory

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Old 10-28-2005, 11:45 PM
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Is it a Chevy or a Pontiac engine?
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Old 10-29-2005, 08:40 AM
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It's a Chev 350 small block. But I have a Pontiac also from one of my parts cars.
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Old 10-29-2005, 09:05 AM
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I use to do Mud drags, and I ran a 2 bolt main 350 with no problems. The last engine I ran was 460hp with no problems to the mains or rods. The rods were Scat though and not the originals. But from what I've seen, it's usually the rod that fails. Hope this helps!
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Old 10-29-2005, 09:39 AM
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Don't worry about it being only a 2 bolt.My first blown alcohol engine was built from a 454 2bolt main car block pushing a solid 1200 hp. and I never had a bit of trouble with main cap failure.I relize I'm talking about a different block,just trying to show you that for your application, 2 bolt mains are fine.
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Old 10-29-2005, 10:05 AM
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It is a known fact that if the engine is set up properly and all other things are good, the 2 bolt block is capable of some serious hp. Some literature I have seen put that figure at around 600hp, some around 700.

Vince
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Old 10-29-2005, 10:21 AM
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Thanks it's nice to hear from people that have actually used and ran a 2 bolt and can speak from experience. Have a good one!!!

Cory
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Old 10-29-2005, 02:49 PM
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For a mild street engine you have nothing to worry about. It never hurts to install some high quality rod bolts and a new set of good main bolts though. The first engine I built had two bolt mains and a cast crank. That was almost six years ago and I havent had any problems to date. I turn mine past 6000 frequently and pretty much beat the daylights out of it and it's still going strong.
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Old 10-29-2005, 02:59 PM
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A bolt bolt main is still a strong engine, you can always upgrade the mains bolts to studs and will stiffen it up.

My last 350 was a 2 bolt main with studs and was rated at 420HP. After giving it 250HP of nitrous still held up, eh
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Old 10-30-2005, 10:31 PM
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I've Used 'Em Both With Excellent Results. Its Like The 2 Bolt Is Awesome, The 4 Bolt Is Awesome+, Funny, I Have Seen People Who Had A Perfectly Good 2 Bolt Block Yet Would Sweat Blood Trying To Find A 4 Bolt. I Have Also Seen People Who Sincerely Believed That A 4 Bolt Was Inherently More Powerful. I Prefer To Use New Factory Bolts, Oiled And Torqued To Specs. Using Aftermarket Bolts Or Studs Torqued To The Hardware Manufacturers Specs Is Even Stronger, BUT Requires The Block To Be Line Honed As The Stronger Fasteners/Higher Torque Usually Pulls The Main Journals Out Of Round. I Have Had No Problems With Factory Bolts. Of Course As Power/RPM Levels Increase Especially With The Use Of Juice, Blowers, Or Turbos The Use Of Stronger Hardware, 4 Bolt Caps, Splayed Caps, ETC Might Become A Must. I Have Seen Some Very Strong CHEVIES Running Stock Components Longer Than You Might Believe. Ive Even Torn Down One 350 Out Of A Boat That Sank In A Storm. One Main Bolt Didn't Get Put Back In When The Engine Was Rebuilt. (Some People Shouldn't Get Near Tools!) The Engine Ran Fine And Produced Excellent Oil Pressure. There Was Nothing To Indicate A Bolt Was Missing Until I Pulled The Pan. The Engine Rebuilt Fine As It Had Not Been Running When Sank So No Cracks. It Runs Well To This Day And Is Only Slightly Heavier By Virtue Of Having 10 Main Bolts Instead Of 9! LOL, MD
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