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WTB Forged BBC crankshaft

PlumLoco

Vintage Jawa CZ motorcycles
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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

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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

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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.
 

74 spectra20 v-drive

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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

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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

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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

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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

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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?
 
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