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2 bolt vs 4 bolt main 350 small block

15K views 9 replies 7 participants last post by  MAHRKEAU 
#1 ·
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
 
#5 ·
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.
 
#8 ·
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.
 
#9 ·
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
 
#10 ·
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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