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1,278 Posts
Discussion Starter #1
we all know a 4 bolt main set-up is the best, BUT, will a 2 bolt main set-up work with a low HP application?...say 375-400HP...how much RPM will they handle?

how many of you are running 2 bolt main motors & what kind of RPM's are you turning?

FastRat
 

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Hondo Jet
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120 Posts
I believe a cast crank 2-bolt combo is good for up to [email protected] beyond that cap walk becomes a problem and it's bye bye bearings. My old motor was a cast crank 2-bolt in the 500hp area. I beat the hell out of it (over revved it, over heated the oil:() but when I tore it down the bearing were still good! These are stout motors, they will take 400hp for years trouble free:)
 

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E-7 Sheepdog (ret)
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6,834 Posts
I run over 600 from my 2-bolt, cast cranked, nitrous snorting, 30 year old 454, it's fine.

Keep the cast cranks under 6,000RPM and a good balancer on them.
Make yourself sleep a little easier with a set of ARP main studs in it, beefs it up a bit, and not terribly expensive.

I run a max of 5400 most of the time, untill toggling in the nitrous.
 

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Sit N' Spin
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1,423 Posts
I'm running estimated [email protected] on a 2 bolt main. I did put the ARP main studs in though for some added strength. But I'm running OEM cast crank and stock rods with forged pistons at 9.5:1 compression. Been beatin' the hell out of it this season...unloaded the pump several times on it. I do have a rev limiter set to 6000RPM, which IMO every jet boat should have a rev limiter. But as has already been stated above keep it under 6000 RPM and she'll perform like a champ for years to come.

Just my $0.02.
 

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Cantard
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5,017 Posts
Word is that a studded 2 bolt is as strong as a stock 4 bolt. You have nothing to worry about. My old 496 was a studded 2 bolt and it made 700hp and I turned it 6800 with absolutley no problems. Still running strong today, 7 years later.
 

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357 Posts
my 327 ran for 40 years without having to tear apart any part of the block EVER. 2 bolt main. ended up rebuilding it because of loss of power...which was to due the valve seats being very pitted from todays gas. but the bearings looked perfect, pretty amazing if you ask me.
 

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Choking my .......
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355 Posts
I've been flat footing a 425 HP at 5k -52000 at the circle races for a couple of years now . This motor was old when I bought it and it's all stock shit inside . 600 ponies sounds about right for a safe cieling .
 

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steelcomp was here
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26,512 Posts
Just remember...if you switch to studs, have your main bores checked. The're probably not going to be round any more.
 

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Half a bubble off
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2,467 Posts
Just remember...if you switch to studs, have your main bores checked. The're probably not going to be round any more.
Hey Scott, based on your experiance has the switch to studs on a 2-bolter significantly changed things so you have to take a significant amount of metal out to get them round again or does it "typically" take just a touch up like a light line-hone??
 

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steelcomp was here
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26,512 Posts
Hey Scott, based on your experiance has the switch to studs on a 2-bolter significantly changed things so you have to take a significant amount of metal out to get them round again or does it "typically" take just a touch up like a light line-hone??
Usually just a clean up. Of course, when it comes to tolerances,.001"-.002" is a significant amount...;)
 

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'77 Hondo GT
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390 Posts
we all know a 4 bolt main set-up is the best, BUT, will a 2 bolt main set-up work with a low HP application?...say 375-400HP...how much RPM will they handle?

how many of you are running 2 bolt main motors & what kind of RPM's are you turning?

FastRat
I run a 2 bolt 468bbc, spin up to 7300rpm 8yrs on motor 12.5cp, 700 lift, good parts is a BIG plus.
 

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Premium Member
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5,488 Posts
Referring to post #16 + 17...
Just wondering but, would there be a difference in a 2-bolt 750 HP hi-compression engine that runs the 1/4 every now and then vs a 2-bolt slightly lesser HP/compression boat engine that sustains 5-6000 rpm for several miles every weekend etc?
 

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Just remember...if you switch to studs, have your main bores checked. The're probably not going to be round any more.
One question if I may! why would that make the crank bore centerline go out. the crank saddles do not realize a bolt from a stud:)devilThe saddles and block feel only that they are secure in area they live in. I have ran 2 bolt bottom ends and never had a problem under 6k. I even studded a motor that I built for a friend and during assembly checked crank spin friction and felt no change at all! I personally have ran 2 bolts both ways and 4 bolts for higher RPM apps so I am curious as to why the line hone would be needed?
 

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Sit N' Spin
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1,423 Posts
One question if I may! why would that make the crank bore centerline go out. the crank saddles do not realize a bolt from a stud:)devilThe saddles and block feel only that they are secure in area they live in. I have ran 2 bolt bottom ends and never had a problem under 6k. I even studded a motor that I built for a friend and during assembly checked crank spin friction and felt no change at all! I personally have ran 2 bolts both ways and 4 bolts for higher RPM apps so I am curious as to why the line hone would be needed?
As it has been explained to me, it's not the caps that are the issue, but rather the main webs. While a bolt can only go down so far into the main webs, a stud goes all the way down into the main webs. This pulls the main webs out of round more than a bolt can pull it out of round, so the align bore/hone is needed to put them back in round so that they are in round with the studs torqued to spec.
 
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