Fast Fred's Secrets of the OMC MOD50's Thread #1

[Fast Fred]

Hay J.T., you out thare, gots that adapter you were lookin for.
seen some biger than 90hp carbs, i'm not sure thay will stack up on the 90hp intake, cuzz thay are so big they may not fit. for sure have to make a new intake.
they are off a 250hp Yamaha so i'm thinkin they will feed 125-150hp.
gots an intake and some carbs to mess with, see what i can see

[Fast Fred]

i'll say some stuff about the bridge, right now getin me some food.

[inshoreracing]

Hi,
where have you find the selva engine in germany?

regards
jm

This SELVA 850 for sale on a German web site
Some resemblance to a Mod50
What are they derived from?

[Fast Fred]

i'm not sure ware BRIAN HENDRICK saw that moda, maybe he will tell us.

on the bridge, ya you can thin it out, but then it kinda looses it's power to cool it's self, and runs at a hotter temp witch makes it grow and come into the cylinder , so you have to push it out of the cylinder .002 thou., then you get to line up the oiler holes on the thin bridge, it will get thiner but not by much.
hows my run on sentence, it's got to be a good one.
pushin it to the out side, the port, and that will help it stay together with the sorta stock width bridge, i'll flash another shot once i tune on it some more

[quty06]

Hi Fast Fred,

interested with 70hp carb mods on pro50, can u share with us how do u fitted it.

thanks in advance

[Roy Hodges]

Hi Fast Fred,

interested with 70hp carb mods on pro50, can u share with us how do u fitted it.

thanks in advance

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I have a question ; for Rapid Freddy - Have you ever given thought about a "rotary valve system " , like that on a Mc Culloch 590-630 for a 70-75 horse 3 banger omc ? it seems to me that removing all reeds & reed blocks would allow more air into the engine and be as good as the mod 50 reeds and carbs . I will not say that the McCulloch had a "true" rotary valve , but what ever you call it , I think it was a good thing, especially in an engine with a reputation of breaking reeds

[Sam La Banco]

There was an experimental rotor valve 3-cyl motor built in engineering at OMC when I was there. I'm not sure it was an "offical" project at the time though.

Because I don't remember if it was an "offical" project or not, I can't name the engineer that built it, and I'm not sure how much power it made. I do know it had to be pitched out of someones locker though.

[Roy Hodges]

There was an experimental rotor valve 3-cyl motor built in engineering at OMC when I was there. I'm not sure it was an "offical" project at the time though.

Because I don't remember if it was an "offical" project or not, I can't name the engineer that built it, and I'm not sure how much power it made. I do know it had to be pitched out of someones locker though.

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Thanks for your input . Very interesting . If anybody ELSE has any knowledge on that motor ,or the rotary valves , how they (might) work on the OMC 75 H.P. , I'd sure like to hear it .

[BRIAN HENDRICK]

[QUOTE=inshoreracing;62276]Hi,
where have you find the selva engine in germany?

Sorry, i can not find my reference to that site, although it is current. Looks like a commercial dealership, so maybe some one in Europe would know who it is.

If any one is seriously interested in acquiring a complete 19S, I have one gathering dust. I paid a lot for this motor , just so i could get a look inside one, when we were racing FEH.

[Mark75H]

I will not say that the McCulloch had a "true" rotary valve , but what ever you call it , I think it was a good thing, especially in an engine with a reputation of breaking reeds

The McCulloch rotors were "true" rotors much like the 1930's Johnsons ... rather than a disk or crankshaft passage rotor, they were externally mounted rotating barrels.

The fishing McCulloch made 75.2 hp. With bigger carbs, a different head with higher compression and better combustion chamber shape, higher porting and the rotors the 630 racing McCulloch made about 88.5 hp at 6,250 rpm instead of 5,200 rpm; so we know that the Mac gained less than 13 hp with by adding the rotor. Probably only 5 or 6 hp.

The thing that generally stops rotors from being big magic is that motors where they really made a big difference also had advanced transfer ports and expansion chambers. It was the whole package that Kaaden developed that made the difference. Remember, Hot Rods had rotors and were basically only peers to the 20H at the same motor size.

Just the same, I think it would be very interesting to see rotors on a 3 cylinder OMC.

If someone wants to know the internal structure details, let me know, they were actually pretty simple and could easily be made for the OMC.