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,?:confused:

[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,?:confused:.......
.................................................. .....................................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:cool:

[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.:cool:

[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, :eek:

[Fast Fred]

Mod50:cool:

[Fast Fred]

thats it,:cool:
Will the 49" cranks fit the 56" motors and vice versa? yes, rods too.

[David Mason]

I think you are on the right path, if I can understand your accent....hehehhe.

We have tried a lot of Mod 50 stuff, and so has Ralph. You want the honest truth ? We threw most of it away. No real performance advantage except for exhaust, and that is minimal. I beat Ralph last year in Okalhoma and Centralia one heat using a stock exhaust opened up a bit. Much less expensive, easy to find, and cheap.

Pistons, I had an orignal set of Mod 50 pistons from Europe. Had the rods to go with them. We fitted them into out 49" and farted around with them. I was faster using stock stuff. So, the expense and hassele of finding Mod 50 parts to run in Mod is a myth. You can make the cheap easy to find stuff run as fast if not faster. Ever find a Mod 50 set of pistons laying in the junk pile anywhere ? Not likley, or any Mod 50 part. You have to get lucky to know someone who knows of someone that had a set and track the stuff down.




Dave,

Do you think that maybe that's because of the weight of the cranks vs the weight of the pistons and rods? Not sure how to word this...... The cast crank is lighter therefore there is a greater difference between the weight of the pistons and rods and counterweights of the crank and the forged crank is heavier so there is less of a difference. ??? Hope that makes sense to someone!

[Fast Fred]

so then did you want to sell that Mo'no go 50 exhaust?

[David Mason]

Fred,

I assume you mean the Mod 50 Exhaust. That is about the only thing that works reasonably well. I have built many a duplicate to it using some angle aluminum, and some tig welding. Not difficult at all. Just easier to whittle on the stock exhaust and gain equal performance. My Mod 50 Exhaust is on its last leg, two ears cracked so I am afraid the next time I try to remove it it shall be the last. To much oil inpregnated in the thin spots to try and weld it.

At any rate, if your rules in SLT allow you to make your own exhaust, I would highly reccomend you make a copy. With your skills as a engine builder, I am sure this will be easy. The only tricky thing is if you want to incorporate a water jacket cover along with it, or just drill some holes like i did and allow the water to flow onto the exhaust plate.

[Fast Fred]

in "X" class the rules are vary simple, 61 cubes or less, exhaust must exit through the mid. thats about it, them guys at the factory made tons of dyno pulls, why try to copy a dunkin donut, any who, hears a tip, reed block IS the LIMITING FACTOR, i guess i'll just buy some new ones, again:eek: :cool:, if you change your mind let me know.:cool:

[Detroit Whitey]

Fred did you look at the 90 yham reed cages and see if they will flow more and fit?

[Fast Fred]

i don't think thay will fit, but, on the 49 reed block, cut the webbin and the center bridges out, two stage reed, top reed is one Big peddle, so what you have looks like a one over one peddle reed block, wach out for a lean sneeze, had them blow apart.:cool:

[Roy Hodges]

Which part blue ?................................................. .......in my not so humble opinion, lean is bad news for 2 strokes. They always blow . maybe not quite so bad for a kilo run .

[Fast Fred]

lean sneeze, happens at low speed, mostly at start up, one cyl only gets a parshall charge,burns lean lights off the in comin charge, burps out the carb, i've had this sistuation blow the tricked out reed block to bits.:cool:

[David Mason]

in "X" class the rules are vary simple, 61 cubes or less, exhaust must exit through the mid. thats about it, them guys at the factory made tons of dyno pulls, why try to copy a dunkin donut, any who, hears a tip, reed block IS the LIMITING FACTOR, i guess i'll just buy some new ones, again:eek: :cool:, if you change your mind let me know.:cool:

You are saying you want one, but the factory teams have them and dyno tested them, so you don't want one because of what they have seen on the dyno. But if one in its stock form comes along, you want one.

Did I get the jist of that right ?

[Fast Fred]

lookin for a set of these hear,
http://img260.imageshack.us/img260/8203/153746481nyczddfsmj3.th.jpg (http://img260.imageshack.us/my.php?image=153746481nyczddfsmj3.jpg):cool:
http://img184.imageshack.us/img184/628/p9190002wu5.th.jpg (http://img184.imageshack.us/my.php?image=p9190002wu5.jpg)

[David Mason]

Exhaust.......

Looking for one, okay... I think I understand what you want... I think. No I still am not interested in parting with mine. Liek I said, it will need to be re-cast and a neww one pulled when I take it off my current race engine. The bottom two ears are broke and are JB welded for now. The original cast part was not made from that great of metal. It breaks easy I think.

You might want to call Phil McDaniels down south. He used to have a passel of Mod 50 stuff. I think he is a member here, or over on HR. You could email him from his BIO.

Other than that, not sure. Lots of current Mod racers have one or two. You might keep an eye out and see if one would sell one. I can tell you one thing, it would take a lot of cash to get one off a engine it is being used on.

[Roy Hodges]

the looks are very deceiving, because that mod 50 exhaust cover don't look any more exotic than an old 55 or 60 horse cover ! is it even tuned ?

[Fast Fred]

it works the best when, "exhaust got to exit through the mid" for what i'm doin.
Yamaha copyed it,To- Hot-Sue, same style. kinda on the 56, but thay got that "S" turn on number 3 hole,3turns back at 1 and 2 then down:eek: cut that right out, fix it.:cool:

[Roy Hodges]

I guess i need a "Fast Fred to English" translator , before I understand anything . it seems he is saying that a "3 into 1 header type flow is what he likes , to me that is throwing out the "pulse tuning" that omc was proud of . But, i guess nothing really matters , as long as what you do......works for you

[Fast Fred]

well,:eek: , what i'm sayin is...OMC, back then, in the Mod50 time, although i was not thare, but readin the owners manual, an the history of how thay performed . i think it's safe to say, that if some other setup made more power, it would be on thare. " exhaust got to exit the mid", thay was workin with them words too i think, i know i have too, thats the rule.

thay had a factory of stuff to work with, mold makers, engineers and $$$$$.
i don't think any body since has got after the twostroke 3cly outboard for the sole purpose of makein the most power.:cool:

best to start ware they left off:eek::cool:

[Detroit Whitey]

seein that we went from cranks to exhast set ups.i have a question what lenght tune pipe to use for a 49? i have heard longer gives more low end and short is good for top end but lose on the tourqe on the bottom.there is No way i can find the mod 50 set up so i`ll just use a cleaned up stock exhaust manifold.But i do have a home made tube style 3 in to 1 header i got from a Dmod guy but it gonna take a lot of cuttin.Need some lenght ideas

[Mark75H]

The exhaust stub for a pulse tuned triple does not have to be any special length, but rather a restriction sort of like the stinger on an expansion chamber.

It should not reduce top speed, but should be small enough that it just barely does not.

Any change in prop, jet impellor or even set up angle can change an OK restrictor to too much or less effective

[Roy Hodges]

Reminds me that Smokey Yunick used to say that ANY change in a stock car engine needed a change in the exhaust headers (tuning) . Repeat .. ANY change !!!

[Detroit Whitey]

Well i was expection a full on tech session. so choke it down like a small megaphone but not to much.Hummm sound`s like i get to do a lot of testin with exhaust YeHaw!:cool:

[David Mason]

Well i was expection a full on tech session. so choke it down like a small megaphone but not to much.Hummm sound`s like i get to do a lot of testin with exhaust YeHaw!:cool:


If you can, use the Stock exit through the tower. Cut the square hole into your tower housing, and under that, place an elbow you can get usually for free in the scraps of muffler shops. Get a big enough diameter so that when you place it in a vice and squeeze it somewhat to fit over the hole, it covers it completely. Next get some thing steel, weld this elbow to it. Now then, to experiment, you sould drill and tap holes into your housing where you bolt the elbow on. You can now make several different lengths to try. All for about $50.00 if that.

[Roy Hodges]

are you talkin about a stock( 15") tower or a bass tower . seems to me it'd make a lot of difference

[Fast Fred]

if it was mine, and i was runnin Stinger exhaust, i'd jam a Alu Bat in the Stinger
tuna and make it longer. Stock FT-19s tuna dumps out right next to the waterpump.:cool:

[Mark75H]

The FT-19s tuner is generic, not optimized

[Fast Fred]

Mark75H
generic,

not sure thats the right word, thinkin wide.
http://img455.imageshack.us/img455/5466/p4010002ow8.th.jpg (http://img455.imageshack.us/my.php?image=p4010002ow8.jpg)
49 addapter W/ alu bat extension:eek: :cool:

[Detroit Whitey]

YO! Fred what do you have hangin on there besides the bat?

[Fast Fred]

just some water deflectors, keepin the flow headin toward the waterpump.
squeesin it down just as it comes in to the pipe. how you lookin up thare:cool:

[David Mason]

are you talkin about a stock( 15") tower or a bass tower . seems to me it'd make a lot of difference

The best is a Parker Pipe Tower. Made specifically for Mod racing. Tim Kurz has the patterns I htink, but won't build them.

I have a Bass tower, we cut the hole into the plate on the tower, and also some of the webbing of the support, and mounted our plate and pipe. We don't use stock parts on the dump tube, and it is not run through the tower like some are thinking. We have also made an exhaust wide enough out to dump straight down into a straight pipe at the bottom of the exhaust never going through the tower. Quick and easy to change pipes for different courses. Not as effecient exhaust as the others though. I think it is to big and you lose some of the pulse tune.

[Detroit Whitey]

dave i have a parker pipe gonna try it out when the water isnt hard.Fred im frozen and sick of it thinkin about going to the romp in the swamp zoller side i could run his fat boy boat seein he`s around and i mean round 380lbs and his old lady is 200lbs that thing is going to really fly with my monkey and me in it. how you doin at the end of the bay? Hey Dave are you guys who make the batteries?

[David Mason]

dave i have a parker pipe gonna try it out when the water isnt hard.Fred im frozen and sick of it thinkin about going to the romp in the swamp zoller side i could run his fat boy boat seein he`s around and i mean round 380lbs and his old lady is 200lbs that thing is going to really fly with my monkey and me in it. how you doin at the end of the bay? Hey Dave are you guys who make the batteries?

Yup. That is my Dad, Mason Battery. Lyle Mason owns it. Actually we are a wholesaler for our brand. Small business that is slowly fading out to the bigger companies unfortuantely. A struggle to keep afloat it seems now-a-days in small business.


The Parker Pipe tower is perhaps one of the best universal towers built. I know Bud, rest in peace, certainly made a ton of them. We run the Parker Pipe tower on all our Mod stuff. I bought the Bass tower to go with the Bass Unit, and kept it when I sold the unit. Nice housing as well.

[Fast Fred]

Detroit Whitey
Fred im frozen and sick of it thinkin about going to the romp in the swamp zoller side i could run his fat boy boat seein he`s around and i mean round 380lbs
ya frozen hear too, No i'm not ketchin that one in Fl., guna wait, Berg will let me know how it goes, at one time thay was makin up new rules or some thing, sayin that i had to weigh in my hull, (not happenin) and some other stuff, i sent a hull down thare two seasons ago to run that race, then thay started with that stuff,
so i did not go, cost about a G to send that hull down,:eek: :cool:
seems thay got a fue happenin down thare see what the word is and i'll go from thare.:cool:

[calvin]

I have a few of the omc 3-holers that I am taking apart to make one...How can you tell which crank is cast and which is forged?

[Mark75H]

Forgings are usually smooth on all surfaces, almost as if they were machined regardless of color. Castings are rougher, not quite as pretty.

If you are not sure you can bring them by and I will look at them for you.

[wolfgang]

following exhaust discussion with great interest, as I am pondering building special tower for my Chrysler/Force 4-cylinder. I think tower volume and lengths of tuner pipes (inside tower) are crucial here. For an in-depth study I recommend Alexander Graham Bell`s (I think it ia a collective of Australian tuners) "Two Stroke Performance Tuning" by Haynes Publishing, second edition ISBN 1 85960 619 9. If somebody has experimented with tower housing volumes, please let us know.

[Mark75H]

On an inline 4 the important thing is to divide the 4 into 2 pairs; there is some advantage in having the pairs together for some length and a favorable volume ... but it is a lot of work for minimal power increase on a system restricted to internal plumbing

I have read Bell's book as well as Jennings' book and another by an Italian

[wolfgang]

thanks, Sam. I am well aware of that. I was actually hoping (fishing) someone within the forum might come up with some research-based recommendations. I am sure the manufacturers have done work in this regard - i.e. optimise tower housing material/fabrication input vs. performance improvements/aesthetics.

[Detroit Whitey]

Had a pile of 3cly cranks and some how i got stuck with a 65hp crank wich uses point so to any of you guys bulidin omc 3 cly`s look out for those dam thing`s they have the cam lobe bulit right on the crank.Hek! i even knew this and it still got me.:(

[RichardKCMo]

Is this not good ? Is it because of flywheel weight , or something else?
RichardKCMo

[Tomtall]

Richard - The crank that has the points lob built into the crank cannot run a inductive ignition pick-up under the flywheel. The Inductive pick-up crank has a recieving slot in it to accept the slip on timming ring used on the inductive ignition.;)

[Fast Fred]

http://img300.imageshack.us/img300/3373/p7100008ya2.th.jpg (http://img300.imageshack.us/my.php?image=p7100008ya2.jpg)
cast is on the right side:cool: