WTB Forged BBC crankshaft

[PlumLoco]

I bought a motor to build for my day cruiser. It has the small port, small plug heads but it is a 4 bolt main with a cast crank. Kinda weird or at least not what I was expecting. Does anyone in so Cal have one laying around that you would be willing to part with?

 

[motormonkey]

I bought a motor to build for my day cruiser. It has the small port, small plug heads but it is a 4 bolt main with a cast crank. Kinda weird or at least not what I was expecting. Does anyone in so Cal have one laying around that you would be willing to part with?

Might want to post year of engine and stroke to help you out.

 

[PlumLoco]

I don't speak GM. It looks to be a mid-80's truck motor. Peanut plugs, small ports, but a 4 bolt main block with a cast crank. The motor is not at my house so I can't look for more details easily. I will likely be replacing the heads with some 049s but as it will need new pistons anyway, maybe a stroker combo is the smartest way to go. So far the heads were easy to find but a stock crank has been. more elusive.

 

[n2otoofast4u]

If you’re already buying pistons, and you need a crank, I’d look at a complete rotating assembly rather than bits and pieces.

 

[74 spectra20 v-drive]

You will be ahead of the game buying a good rotating assembly all together unless you have experience building, Scat and or Eagle have a good name. You will also be ahead of the game dumping those heads, some good stock replacements would be 049 or 781 casings. I run 049's with the bigger valves in my Day Cruiser, 990 square ports in my flat and they run great. Just my two cents. I stayed away from aluminum for cost as well as I don't get much heat in my engines on the boats. Some very good builders on these pages, Obnoxious usually chimes in on these.

 

[69hondo]

you need to find out if its a Mark4 (two piece rear main seal) or gen 5-6 (one pice rear main seal)
If its truly an 80s its probably a Mark 4 but you neve know. Casting numbers on block where bellhousing bolts up will tell you

 

[obnoxious001]

I bought a motor to build for my day cruiser. It has the small port, small plug heads but it is a 4 bolt main with a cast crank. Kinda weird or at least not what I was expecting. Does anyone in so Cal have one laying around that you would be willing to part with?

Depending on what power you plan to make, the cast crank, or even a new aftermarket cast crank would work. I probably have a GM steel crank here, but I am in Parker.

By the way, a bunch of the 4 bolt blocks had cast cranks in them, that's not at all unusual in a truck or motorhome.

 

[PlumLoco]

Depending on what power you plan to make, the cast crank, or even a new aftermarket cast crank would work. I probably have a GM steel crank here, but I am in Parker.

By the way, a bunch of the 4 bolt blocks had cast cranks in them, that's not at all unusual in a truck or motorhome.

Thanks for your input on this. I had a long conversation with my builder yesterday and he agrees with you on the ability to use the cast crank.
My goal is close to 550 ft/lbs at a low range as it is going in a very heavy jet boat. I couldn't sell him on using the small port heads but if he is sold on the 049s at a great price, why should I complain? He is very old school and has a general combo that he really likes. I discussed some stroker combos and he really wants to stick to a simple 30 over bore 454 with a roller cam. He has built a lot of boat engines and seems to be very aware of their special needs.

 

[obnoxious001]

Thanks for your input on this. I had a long conversation with my builder yesterday and he agrees with you on the ability to use the cast crank.
My goal is close to 550 ft/lbs at a low range as it is going in a very heavy jet boat. I couldn't sell him on using the small port heads but if he is sold on the 049s at a great price, why should I complain? He is very old school and has a general combo that he really likes. I discussed some stroker combos and he really wants to stick to a simple 30 over bore 454 with a roller cam. He has built a lot of boat engines and seems to be very aware of their special needs.

That's good. I have been building performance and race marine BBC engines since my first turbo engine that I did on my own in 1981.

There are a few guys posting that they make good power with ported iron peanut port heads, but why spend the money on porting?