BBC 2 Bolt main block hp limits?
 

A friend purchased 2 454's with small B&M 250 blowers for his 35 cigarette that was converted to a bravo boat. One of the engines ate a cam and upon looking it over it is a 2 bolt main block. The engines are very similar to the 525 Mercury or Hawk.
The current plan is to put in some very mild Hydraulic rollers RM supplies and turn it 5300 RPM.
Any input on the blocks abilities or short coming would be appreciated.
Thanks
Steve

I have always heard 500-550hp on a 2 bolt is about max for reliability. The other big issue is how many rpm's. I think the 5300 is about all you would want to run.



Darrell.

Fixx
 

a friend use to build 550 hp 2 bolt main 454's all the time wqith good luck..and that was with a cast crank:eek:

A friend of mine had a 427 with a 2 bolt block in his drag boat and he would turn that thing 8500 rpm with a steel factory crank and aluminum rods and light pistons. we just reringed it after sitting for 10 years and it went into a flat bottom boat he just bought so with the right parts it can be done.He all so ran it on alcohol and 400 shot of nitrous

6500 rpm and 650 hp on a continuos WOT not a short burst like a dragstrip or so with a LS-6/7 steel crank and factory 7/16 rod bolt rods. The cast crank and 3/8 rods never over 5800.. learned that the hard way with a Stock class NHRA record holder. Instant Kaboom at 6000...on a boat 53-5400 tops.

2 bolt main
 

the 2 bolt main actually has stronger webbing in the bolt area...we used to look for 2 bolt blocks and convert them to 4 bolt. I have one in a blown drag car making over
1,000 hp at 7200 rpm.
For what you are doing, the 2 bolt unit will be fine, just use ARP studs instead of the bolts.

I think some of the older 2 bolt blocks were stronger than the newer 4 bolts. Good friend of mine ran a 2 bolt in a jet boat with a 8-71 for many, many years. Block now is in my boat for 9 years now as a 496, 5500 rpm, 10 to 1....trouble free.

I would never do it. That crank flex's alot under load for a long time.

At a Minimum I would have ARP studs for the caps and have it line honed.

It dosent cost that much to have new caps with 4 bolts put on.

Ok, what about a 2 bolt with splayed caps???? Is this a myth or are they stronger???

State you case! :)

probably more than the bravo can handle...raced 2 bolt main blocks at a lot more power in a drag car than boat will see, never a failure !!!