what`s the deal?

[Detroit Whitey]

Can someone tell me on 3cly omc 49`s why a cast crank is better than a forged crank is it just balance,weight,?

[Roy Hodges]

Can someone tell me on 3cly omc 49`s why a cast crank is better than a forged crank is it just balance,weight,?

.......
.................................................. .....................................Rapido Frederico should have the answer to that & supply the true facts ?

[Detroit Whitey]

i'm sure he does but he no speakie. there's a 1.5 lbs differance between the two i mean forged is lighter but that's all i got

[Roy Hodges]

If you were talking about a 4 cycle crank, like for a car engine, the hot rodders , racers always prefer forged cranks , they are stronger . the omc's ? I know that the local feh guys run "whatever junk they can scrounge up" is what they told me. and, they didn't balance them . Some builders claim a 3 cylinder cannot be balanced . UNTILL it's proven without a shadow of a doubt , i don't believe that .

[Detroit Whitey]

i think there pretty well balanced from the factory.or at least i hope they are but that could explain why i have chunks of my block in my helmet from last year.o well if anybody come's up with anything let me know i have both crank's

[Fast Fred]

the forged crank, the beefy one, will store more anersha, this would be best on top end.

the cast , lighter one, is easer to turn, so it spins up quicker.
thats how i look at it.

run the big A fraim rods, late model 49 or 56 rods.

my $$ is on the beefy one.

[David Mason]

Cast 49" cranks shake a lot. Forged still shake, but not as much. OMC tolerances are perfect for stock fishing engines. Spin them at race RPM's and they will create a James Bond Martini in no time at all. You have to reach 8000RPM and above for the shake to go away. When I am milling in SEH I never hold onto the wheel down the straight away as it is vibrating so badly it can make your hand anr arm numb.

You can balance these, but not cheap. You would need to add another case, and crank with a pulley and belt that offsets the shaking. Lot of machine work, and money. Run it like it is. It will last a couple years shaking if you don't run it every day.

You can creat a full circle crank in these to help with the balance. It has ben done, and no performace advantage was seen, so why bother with the expense ? Send it off to a reputable auto crank balancer and have them do the best they can, it will help, but not eliminate.

After quite a few years dealing with this engine (49") we have tried a lot, and I meana lot of things to improve performance. About the only one that has come close to us on experiemnts and speed is Ralph Cook. This means staying within the rules of a anctioned organization, not for fun mods. For fun Mods, I am certain we could get well over 120MPH out of one of these on our rig.

Don't ask, I ain't telling. I still race the class in NBRA. I give away a lot, but still want to win, and I feel we work hard to be where we are at. Hardly a day goes by all year we are not in the shop working on something for our boat racing. I am serious, I spend the holidays in the shop, cause it means we can work all day on engines and boats instead of only after work.

[Detroit Whitey]

thats good info Dave. thanks
i konw all about the vribrate you to death thing.we tiller these so i lose feeling alot.Dave i like to share ideas on these motors if you want to chat you can call me up. i work at the oldest jhonson dealer on the planet and we are in michigan call me up sometime if ya need parts or gaskets.
Eric
lockemans hardware&boats
detroit michigan 3138420101

[Fast Fred]

the piston and rod, the piston mostly, is far more refined than stock, and lighter,
all Modas have a high and a low speed imbalance,

[Fast Fred]

Mod50