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2-Bolt Main vs. 4-Bolt Main - Throw Down and State Your Case!

 
55Guy
Administrator
Posts: 1153
Joined: 07/06
Posted: 06/27/08 08:01 AM

Taking a suggestion from a post in our 350 vs. 305 thread, lets talk about the debate people have, 2-bolt main blocks versus 4-bolt main blocks.

I'll go ahead and ask, which one is better?

But, I'll also ask, how much horsepower have you built out of, think it'll handle, a 2-bolt main block?

Fire off everyone!  

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LOVEmyCHEVY74
V-6 Camaros rule!
Posts: 89
Joined: 02/08
Posted: 06/27/08 09:01 AM

I think 2-Bolt Mains are perfect for street cars up to 600 horses that can rev maybe 6000 rpms. Anything more than that in either category than the block should be changed to a 4-Bolt Main block. Obviously a 4-Bolt Main is better because it provides more strength to the bottom end of the block, but at top speeds and high rpms there are 8 more bolts you have to worry about coming out of the threads that you so dearly need them to hold on to.  

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bdrat
I love my Chevy Chevette!
Posts: 11
Joined: 04/08
Posted: 06/27/08 03:59 PM

really unless your going be revving the thing over 6000 rpm on regular basis,or throwing a boat load of nitrous at it,a 2 bolt main block is great.you can add main studs instead of bolts and be safe well into 500 horsepower. the 4 bolt blocks are for the guys that can't sleep at night.  

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kev0077
I love my Chevy Chevette!
Posts: 8
Joined: 06/08
Posted: 06/27/08 05:12 PM

Well I guess since this was my idea I should post and stir everything up so here goes.... I cant belive that in a Super CHEVY forum you guys are telling everyone that every other V8 motor ever built was better than the 350 chevy 2 bolt.... well maybe not every motor but a few notables.... LA 340 mopar I and many others have turned these stock to 7000 with no trouble and lets not forgot the dare I say SBF 302 that will turn RPM all day I think we have all seen plenty of those motors make a ton of horsepower and not pop main caps. Out of curiosity how many people have actually broke a main cap or even seen a broken main cap? I really think this is bogus information I'll take all the 2 bolts you want to throw away.  

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LOVEmyCHEVY74
V-6 Camaros rule!
Posts: 89
Joined: 02/08
Posted: 06/27/08 06:01 PM

My uncle had a 327 small block in his 57 Chevy Bel Air with 11:1 compression and he threw a main cap on the drag strip it had 520 horses and ran beautifully on the street. The 2 Bolt Main is just not strong enough to hold all the pressure above 600 horses and 6500 rpms, even with studs you are definitely risking a blow out. I agree with the fact, even though I am a big chevy fan myself, the LA 340 motor and the 302 Ford motors are awesome, I would still go with the ford motor, who wouldn't want the know they are getting the most stability at one of the most important spots in the motor?  

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kev0077
I love my Chevy Chevette!
Posts: 8
Joined: 06/08
Posted: 06/27/08 07:53 PM

Thayts odd being the 327 L84 was the highest horsepower N/A SBC ever built until the LS6. Also I'd be interested to know if it was a early 2.30 main block or the revised 2.45 block.  

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v8alltheway
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Posts: 14
Joined: 04/08
Posted: 06/29/08 12:14 AM

I think it is about more than just breaking a main cap when it comes to this discussion. The bolts stretch before they ever break, so maybe damage can be done just by too much main bolt stretch and therefore drastically increasing main bearing oil clearance and crankshaft distortion. Also, I believe the Boss 302 Ford motor was a 4 bolt main block and i'm sure they knew what they were doing. I have also heard of 4 bolt Chevy motors that have had cracking problems in the main webs because they are 4 bolt main. I don't know if that is true or not, but I have heard it many times in the past. I have a 2 bolt main 355 in my car now, but I bought the car like that. I would never build a motor with a factory 2 bolt block. I plan on building a new motor this coming winter and I plan on buying an aftermarket splayed 4 bolt main block with steel caps. Not that I really need all that, but it gives me piece of mind when putting 5,000 bucks or so into a motor.  

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leviakashock
V-6 Camaros rule!
Posts: 64
Joined: 04/08
Posted: 06/29/08 07:14 AM

for a couple hundred bucks you can buy splayed four bolt main caps and for 30 bucks you can buy the threading kit to tap the bolts or studs yourself. n so whyu wouldn't you go with 4-bolt mains.it would make no sense if you don't.  it is obviously stronger and just gives you peace of mind.  that is like not wearing safety glasses at work.  you don't have to and a lot of guys don't but after i got shot in the eye with a nail gun...now i wear them all the time.  you can learnm the hardway or you can be precautionary in advance.  

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v8alltheway
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Posted: 07/14/08 04:51 PM

An excellent point leviakashock.  

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race4ever9
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Posts: 1
Joined: 07/08
Posted: 07/15/08 02:12 PM

I have personally had to 4 bolt blocks brake from the outer bolt right into the cam jurnal. I went to a 2 bolt block with splay caps and haven't had a problem since.  

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regs66malibu
I love my Chevy Chevette!
Posts: 2
Joined: 07/08
Posted: 07/21/08 09:19 AM

I have a 355 with a two bolt main that had ten years of shifting at 6900 to 7000 rpm all day and never had a problem with it.  

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BrandonMski
I love my Chevy Chevette!
Posts: 1
Joined: 01/09
Posted: 01/15/09 07:03 PM

Okay well you all seem to know what your talking about so help me out here. I have a 1993 z28 camaro that im going to turn into a daily driver\racer (i want to go fast but who doesnt??) Basically what I'm asking is what should I get here? Confused  

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chevelle83
I have an SS396 tatoo
Posts: 442
Joined: 10/08
Posted: 01/17/09 08:23 PM

I just use which ever block is laying around, I have never had trouble with 2 or 4 bolt. My next build is a 383 because they are easy to build strong motor. They have lots of bottom end torque and are good for everyday drivers.  

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heshtesh
V-6 Camaros rule!
Posts: 75
Joined: 02/08
Posted: 01/18/09 08:09 PM

Well for me i had two 400 small blocks one 2 bolt one 4 bolt i kept the 2 bolt and installed Howards splayed caps with studs down the center i plan on being able to sleep at night especially when pushing a little over 700 hp.My 383 is approx 500hp on a older two piece rear main seal block and have had zero problems i just tore it down at around 50 thou miles for a refresh bearings,rings,timing set and everything looked excellent.  

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cathleen
My first time was in a Chevy
Posts: 161
Joined: 11/08
Posted: 02/01/09 10:21 PM

You midas well start with a newer 4bolt rollerblock if you don't have one  

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