2 bolt vs 4 bolt?
07-10-2006, 06:01 AM
#1
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2 bolt vs 4 bolt? I am really interested in knowing the difference, and what makes which better. I always thought the 4 bolt would be a stronger application, but a lot of people around me say the 2 bolt would suffice, and I wouldnt be spinning the motor that high. Plans are a forged 383 stroker, with a decent shot down the road. Anyways any guru that can chime in thanks!
07-10-2006, 06:13 AM
#2
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The way to go is 4 Bolt the corvettes had them and lots of engine builders make a 2 Bolt a 4 Bolt. But the ones from the engine builders are better because the holes get bored in an angle to handle more power. I got me a corvette 4 Bolt two weeks ago really like my first V8 engine block but its straight bored.Also the guy that had it before me had it line bored 0,40 over and it was a 396cui but I am not a fan of stroking. Ill have it honed because it seemed to throw a lot of thrust on the outside cyl. wall. Hope I could help you
07-10-2006, 09:22 AM
#3
What are you going to do?
FWIW I don't build anything unless it's a 4 bolt, it's just not worth all the work in the motors to not do it the right way at power levels over 500hp. I'd rather put a prepped cast crank in a 4 bolt block than a forged crank in a 2 bolt block.
Bret
FWIW I don't build anything unless it's a 4 bolt, it's just not worth all the work in the motors to not do it the right way at power levels over 500hp. I'd rather put a prepped cast crank in a 4 bolt block than a forged crank in a 2 bolt block.
Bret
07-10-2006, 11:08 AM
#4
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Well I plan on looking at heads first, then will build my motor around the heads. I was just curious ... I had 3 very well respected drag guys all tell me that the 4 bolt is really a myth, and in the 383 I wouldnt be spinning the motor high enough to hurt the 2 bolt. I am in the market for a lt4 block, but I am always asking questions. I like to understand it all not just buy something because people say too :] I know I want to go 383 since the rotating assembly is a nice package from eagle, in a lt4 block .030 over. I plan on telling my head guy the motot I want, and I will more then likely go with a custom grind cam as well, so everything flows flawlessly together. I just want to be another big motor big shot nice stall lt1 thats all ;]
07-10-2006, 03:31 PM
#5
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My gut tells me that a 4Bolt is definately the way to go. However, I have heard of more than one machinist who thinks that the extra holes for the two other bolts can significantly weaken the bottom of the block and can cause problems. That being said, I am sure you can frag any motor if you run it hard enough. But I've always had that in the back of my head.
07-10-2006, 03:43 PM
#7
N/A the factory crank and two bolt mains won't be a problem until you make some really high HP numbers. For power adders I would think that the extra stresses on the bottom end would require a four bolt main and forged crank a lot earlier. If I wanted a four bolt main I would modify a two bolt block with splayed caps before I would use a Corvette block.
Daren
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07-10-2006, 08:00 PM
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I wouldnt mod a 2 bolt block to be a 4 bolt. If I wasnt building something radical like a 391 stroker with a 400 shot, a true 4 bolt would be a waste. Dont take that to heart, but if your plans are something like a 400hp daily driver dont waste your money on a 4bm.
07-10-2006, 08:18 PM
#13
The LT1 4 bolt blocks are the same casting as the 2 bolt so the "4 bolt conversion weakens the block" argument that DID apply to some of the Gen1 stuff DOES NOT apply here.
That said the 2 bolt LT1 block can handle a lot I know of a couple stock shortblock b-bodies in the 10s and a bunch more in the 11s. Remeber FEW local shops will have any meaningful experiance with this block so don't rely on them, while I disagree with some of the folks here this is till a better source of info than most locals will be.
On a full build though and if looking to spray a motor making serious power off the bottle I would consider an aftermarket splayed 4 bolt conversion NOT the Vette block setup.
Far as an LT4 block see the comments a few of us have made about the LT1 Vette block, it is the same.
That said the 2 bolt LT1 block can handle a lot I know of a couple stock shortblock b-bodies in the 10s and a bunch more in the 11s. Remeber FEW local shops will have any meaningful experiance with this block so don't rely on them, while I disagree with some of the folks here this is till a better source of info than most locals will be.
On a full build though and if looking to spray a motor making serious power off the bottle I would consider an aftermarket splayed 4 bolt conversion NOT the Vette block setup.
Far as an LT4 block see the comments a few of us have made about the LT1 Vette block, it is the same.
07-10-2006, 08:42 PM
#14
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Thanks for all the opinions, and It seems there really is a difference in opinion here! It will be a dd, and I am hoping for a good 410-450rwhp n/a, for nitrous I am going to start small and go bigger over time. The crank will be forged, along with other internals.
07-10-2006, 08:48 PM
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FWIW, another splayed 4-bolt main user here (with studs). My shop said that they don't even mess with 2-bolt, or straight 4-bolt mains anymore. They just install splayed 4-bolt mains in every buildup they do, so that they know it will handle whatever is thrown at it. I would imagine that the strength of the caps would make up for some of the weakness created in the webbing due to drilling for splayed bolts, but I'm no expert.
If sticking with a 2-bolt main, you might at least consider upgrading the nodular main caps to a billet steel cap & getting an align-bore. I'd recommend Pro-Gram.
Again, take that with a grain of salt, because it seems this is a fairly subjective subject.
If sticking with a 2-bolt main, you might at least consider upgrading the nodular main caps to a billet steel cap & getting an align-bore. I'd recommend Pro-Gram.
Again, take that with a grain of salt, because it seems this is a fairly subjective subject.
07-10-2006, 10:28 PM
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Originally Posted by Honda Hunter
I think it's one of those questions. You would be fine with the 2.
07-11-2006, 01:24 PM
#20
I would go with a 4 bolt like Bret said. The question of straight vs played gets a sticky. Some guys like one and some the other. I have seen a few major (1000+) LT1 builds, including mine, that are using straight 4 bolt corvette blocks. Granted the caps are premium quality aftermarket units but they are not splayed. It all comes down to proper engine prep and build.