my afterthought

[river_ratj40]

got myself ahold of a extra block. 91 or 92 omc 3 cyl. 56 cu split port block. wanting to do something extreme. Like to put 3.5 inch piston and stroke it. can it be done? How far can you stroke one? What kind of sleve would you put in it to make it last? and who would i need to get in touch with to construct a monstrosity?

thanks
river rat

[Ed Hatch]

For the effort and $$$ you'll need to fiddle with that 56 cube block you might find it easier to pick up an SST60 powerhead, it is 56 cubes, puts out around 90 plus HP and parts are still available from Sea-Way marine in Seattle.

[river_ratj40]

what would be a better block then, a sst60 or to get a 90 hp yammi?

[Ed Hatch]

Not familiar with rice motors, if you have a tower with the 56 cube bolt pattern why not take advantage of the SST60, if you have to come up with a tower then there is no real advantage going OMC.

[JohnsonM50]

got myself ahold of a extra block. 91 or 92 omc 3 cyl. 56 cu split port block. wanting to do something extreme. Like to put 3.5 inch piston and stroke it. can it be done? How far can you stroke one? What kind of sleve would you put in it to make it last? and who would i need to get in touch with to construct a monstrosity?

thanks
river rat

It seems to me that the motors already used to race would be the way to go for one good reason.. the wealth of 411 about them. Other motors may not have been as studied/tested leaving you on your own to figure out how.. then you risk a dud or a bomb for the $$

[Sam La Banco]

Find a 56 cu. in. short block that was used before the SST 60 engine was released for production. The orginal design for this motor used the "Permenent Mold" method for the block castings. The SST 60 uses the
the "Lost Foam" method for it's block castings.

If looking at each together, you will see a number of features that would be better for performance on the "Permenent Mold" version.
It would be to long of a disscussion to get into all of the advantages here, but the most important is the shape and finish of the transfer ports.

The Hot set up would be to put SST 60 sleeves in a "Perminent mold" early block.

I would also advise against using forged after market pistons, they require more skirt clearence and this engine runs best with tight clearences.

Just my opinion after racing this engine since 1989.

[proprider01us]

[Just my opinion after racing this engine since 1989.]

And quite competetively, I might add!! Hope your doing well Sam.
Joe Schweickert

[Sam La Banco]

Thanks Joe, we keep busy at it.
Doing ok.

[John (Taylor) Gabrowski]

Sam Lebanco: Two summers ago at a neighborhood garage sale I picked up a brand new NOS - OMC 49 inch 3 holer complete block from the factory along with the blown up fishing motor it was to replace where its block had kicked a rod through the side of the block for $200.00 bux. I bought it specifically for a Super E Modified engine. Talking to other people, reading the posts here and elsewhere leaves me confused as there are so many pros and cons from everyone to using the OMC pistons or aftermarket pistons like Wiseco. Reading your post just adds to wanting to do the right thing and I have no experience with these OMC 3 Holers. Will you advise as your experience base is profound?

[Sam La Banco]

Hi John,

Just like everything else, there is many ways to skin the cat. Also, their are some pretty smart guy's with a lot of experience writing on this forum about this engine. All I can do is give you an opinion based on my experience.

I have won a few races, but that does not make me smartter than those guy's.

Here's a few things to think about, the OMC pistons were not designed to go racing, but a whole lot of work went into them. Just ask guys like Jim Nerstrom.

What I have found is that all the stock pistons go out of round after runinng them, which is the common complaint, that does not mean at running temp they are that way (can't measure them then.) I do know that some years, they were worse than others, but that was when they were measured out of the motor.

I do believe the ones we have been getting in the last 2 years measure better after running, but I don't know if that really means anything in the motor.

There seems to be a lot of misconception about forged parts by people that they are always stronger than castings. In very general terms this can be true because of the post forging grain structure and all that stuff they talk about, but there is a quite a bit more to it than grain structure.

I am not saying forged after market pistons are not good by any means, but I would like to see "real" evidence that in this motor they are any better.

(maybe I've been a engineer to long)

I do know because of the difference in the physical properties of the cast and forged materials, you need to run more clearence with the forged ones.

I also know that these motors run best when tight and after .0045-.0050 skirt clearance they don't win races, they still turn up good till about
.006-007, they just don't come out of a corner the way you need them too in a real race.

Do the forged pistons fit just as good under dynamic conditions running in the motor, maybe, they don't do a bad job thats for sure.
Just show me the dyno sheet . The cast ones have done pretty good for us under racing conditions.