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Old 01-12-2009, 09:45 PM
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2 bolt vs. 4 bolt main 454

Question for you guys. I am starting to piece together my 454 for my coupe. I intend to run this engine to 6000 rpm (6500 maybe but i really doubt it). All things being equal, will it make that much of a difference if I purchase a 2 bolt main instead of a 4 bolt main? A guy I met here locally told me that he has a 2 bolt main 427 that he revs to 8k rpm in his dragster (has forged rotating assembly) without an issue.

I understand the internal workings of the motor will probably need to be beefed up (rod bolts, will probably go with forged rods and maybe a forged crank), but I really want to know if the 4 bolt main is just overkill for this desired rpm range or no.

I can pick up a complete 2 bolt 454 for $275 locally or I can pay $450-$500 for a 4 bolt main short block. I figure I can save the money on the block and throw it into the rods, crank, etc. if necessary if I go with the 2 bolt main set up.

Thanks in advance for any replies.

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Old 01-12-2009, 10:35 PM
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The 2 bolt block will be fine for revs to the 6000 range. 2 bolt blocks are fine for horsepower levels up to 500 horses. However, even so I`ve delt with small blocks (poor mans engine) and not big blocks I can say I have never seen a small block, or big block for that matter fail through the main caps. But I have seen I don`t know how many fail from the rods. If you still feel uncertain you can have the block line honed and use Studs in place of the bolts for better insurance.
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Old 01-12-2009, 10:41 PM
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Thanks for the reply DV. The input is appreciated.

Last edited by 31fordcoupe; 01-12-2009 at 10:50 PM.
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Old 01-13-2009, 12:00 AM
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doublevision is right, i've never seen any engine (BBC, SBC fords or chryslers fail through the mains. it's always the rods that go long before the mains ever think about it. get the 2 bolt and "get er done"--->
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Old 01-13-2009, 05:07 AM
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block

The big block chevy 2 bolt block is very different in strength compaired to a small block 2 bolt. The size of the caps, registers,bolts etc makes them a strong piece ,even the 2 bolts.

I would not even think twice at running a big chevy 2 bolt block in your application.

Keith
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Old 01-13-2009, 05:53 AM
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Thanks again guys for confirming that. I'll be picking up the 2 bolt this evening.
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Old 01-13-2009, 04:05 PM
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2-Bolt big block are pretty strong, but it's "nice" to have the extra insurance (strength wise) with the 4-bolt. You can retro-fit a 4-bolt main caps to a 2-bolt block. You could probably find 4-bolt caps on eBay semi reasonable, then all you need is a bolt or stud kit and then take them into you favorite machinist and have him fit it up. Good Luck!
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Old 01-13-2009, 04:15 PM
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OK ... I will be DIFFERENT

I always use a 4 bolt main block ... ALWAYS

As a fellow who worked in a automotive machine shop years ago, I believe that the 4 bolt main blocks are better blocks. When looking at them, I believe they have less core shift, the camshaft is in the center of the block better and it seemed like they were a little harder to bore ... because of the metal content. I do know that they " sonic " checked better than 2 bolt main blocks. Whenever Chevrolet installed a mechanical lifter camshaft in a BBC ... from the factory ... it was always a 4 bolt main block. The solid lifer engines had better heads, better crankshafts and made more Horsepower. It stands to reason that they would have the BETTER blocks also.

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Old 01-13-2009, 05:38 PM
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11echo thanks for the tip. I will consider that.

Deuce,

With all due respect, I think you could always build a "better" or "stronger" block. And there is no doubt the 4 bolt would be the "better" option. If I had $15,000 to spend on a motor we wouldn't even be having this conversation.

All I want to know is will a 2 bolt main 454 stand up to 6500 rpm on a semi-regular basis, or will I have to worry alot about the mains failing. I know it's always possible, and less probable with a 4 bolt main, but just trying to get the general feel out there. I rans SBC's in high school to 6500 (and saw friends run SBF's to 8,000 rpm) on stock rods and never once saw one fail at the main caps.

If it is that critical, I will spend the extra $200 dollars and I will get the 4 bolt. If most folks here feel its overkill, then I can use the money for some forged rods, pistons, etc. The general consensus that I am getting so far is that the 2 bolt main will get the job done without any problems.



Thanks Deuce for your comments and input. Anyone else have any input about this before I drop the cash?
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Old 01-13-2009, 11:18 PM
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Ok guys so I went out to look at this 2 bolt 454......

The casting number on the block was 361959 (73-90 2 bolt main 454) and it's bored .030 over now and rusty.

The heads were in decent shape, oval port . I believe they had a casting number of #346286, but the closest thing I could find to that online was #346236, which is a 75-87, 120 cc, 454 head.

The rods and pistons were cast and so was one of the cranks.

However..I believe the other crank he had for it was forged. It had the real thick casting line (about 1/2 to 5/8 inches wide) that looks it has been ground down. I know I missed the casting number on the crank (it was dark, late and I didn't want to keep this guy up all night looking at stuff in his garage), but I believe I wrote down what would be the date code (B579 = Feb. 5, 1979?).

Is there anyway to guess at what the casting number may be for that crank given the date? I'm guessing not but any help would be appreciated in identifying that crank.

He also had a complete 348 if anyone is interested in it. He said it was not seized and it looked like it was all there including flywheel, intake, etc. He wanted $650 for it.

Thanks in advance for any help on identifying that crank. If I buy the motor, it will be only for the purpose of getting the crank if it is in fact forged. Deuce has made me paranoid enough to get the 4 bolt main 454 instead of the 2 bolt main.
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Old 01-14-2009, 04:49 AM
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block

With all due respect to Duece,

The castings that they use for the 2 bolt and 4 bolt blocks are the exact same castings, core shift,hardness etc is more of a crap shoot then anything relation to a 4 bolt/2 bolt.

I own an automotive machine shop and i can say the exact opposite, I have seen just as many 2 bolt blocks that are much better centered then 4, also I have bushed lifter bores in alot of big blocks and i can tell you that all of them are way off, not just the 2 bolts.

31ford,
I will promise you that a 2 bolt block will NOT fail in your application.When was the last time anyone on this forum seen any engine blow the crank out of the block because it was a 2 bolt main????

Once you get away from the Chevy's and into the Fords and Mopars there really arn't any 4 bolt blocks to speak of. The Chevy guys are stuck on the 4 bolt deal because GM made a bunch of them in production engines. I am not saying that a 4 bolt is a bad thing, but it is not necessary at all in your application.

I just finished a 450CI big block Mopar that made just shy of 700 hp. it's a studded 2 bolt block. I have zero problems sleeping at night becasue i am worried about a failure.

In one of my own personal cars i have a .070" over 454 block thats a 2 bolt. It's in a 4 speed 68 chevelle. I beat the crap out of that car every time i drive it. 6500 rpms no problem,also no issues.I have not had it on the pump but it makes 500hp easy.

The 4 bolt caps only really do 1 thing, Stop cap walk. This is an issue in the small block 350 engine because of the register, bolts, etc. The big blocks have a different contact area in the register, larger bots. It's never been an issue with the 2 bolts being able to hold the crank into the block, like i said you just don't see engines blowing the cranks through the pan. It's an issue with cap walk. Big chevys at your power level do not walk the caps.


Keith
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Old 01-14-2009, 07:36 AM
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if you plan to use stock heads then get the engine that has 049 or 781 heads.

the 4 bolt block may have a forged crank. yes, the wide casting marks indicates a forged crank. But it could be a 427 crank.

The block just needs to hold in the crank. I never had a block fail (2 or 4 bolt).
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Old 01-14-2009, 10:35 AM
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If you are in VA this summer look me up....I got a 396 that sees at least 7500 everytime I run it....it is a studded 2 bolt block, stock steel crank and stock rods. She will be getting a new set of bearings before the season starts though..........as stated before big blocks and small blocks are different animals. I expect the rods will go long before the mains.
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Old 01-14-2009, 12:59 PM
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According to "how to hotrod Big Block Chevy Engines" by HPbooks. The 2 bolt Big Block Chevy blocks are fine for anything up to 6500 RPM and 600 HP.
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Old 01-14-2009, 05:21 PM
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Ok. That settles it. I'll buy the 2 bolt block tonight. The heads that come with it are 346236 castings. Does anyone know if this series of heads came with screw in studs and push rod guides? The heads that I looked at last night had them. Just curious.
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