56ci OMC realistic power

[Mike Wienandt]

The best block for mod engines is the early 56 ci permanent mold block, not the foam block. Bridge port, not oval port . I think about 87-88 I have built with all of them . The transfer ports are shaped better and the bridge port allows you to make wider exhaust port. The port timing of All ports is critical, you must measure, there are many different versions. I have not studied the carbs details closely to see why the three jet carb does not work. But watching the fuel flow and BSFC on the dyno I can quickly see it's wrong for this engine.

[LittleCharger]

The best block for mod engines is the early 56 ci permanent mold block, not the foam block. Bridge port, not oval port . I think about 87-88 I have built with all of them . The transfer ports are shaped better and the bridge port allows you to make wider exhaust port. The port timing of All ports is critical, you must measure, there are many different versions. I have not studied the carbs details closely to see why the three jet carb does not work. But watching the fuel flow and BSFC on the dyno I can quickly see it's wrong for this engine.

Thanks Mike that was what I had thought but always nice to hear straight from a top builder of the 3 cylinders...cheers,

[ferdthe4]

Glad I have a 1987 as well. From my reading on the mod 70 build which heads are better to shave. If my memory serves me correct in the mod 70 build the oval port ones didn't require as much decking to get the bowl depth and volume to around sst60 spec. Or maybe I have it backwards and it was the bridgeport ones that were better.

[Mike Wienandt]

When milling the head, if you make it very tight spec the head will flex and not hold head gasket seal. That is one reason why I weld the thermostat hole. To give the head strength there. Would not recommend tighter that SST 60 spec unless you raised the ex port to high. You do not want more than 8.3:1 ECR It will cause engine to slow down as it heat soaks. And certainly good Fuel is required.

[ferdthe4]

When milling the head, if you make it very tight spec the head will flex and not hold head gasket seal. That is one reason why I weld the thermostat hole. To give the head strength there. Would not recommend tighter that SST 60 spec unless you raised the ex port to high. You do not want more than 8.3:1 ECR It will cause engine to slow down as it heat soaks. And certainly good Fuel is required.

I wasn't going to go extreme on the head decking want to be able to run premium pump gas don't wanna have to buy race fuel for my fishing/hunting boat. So I don't even know if I would go as far as sst60 spec

[Hounddog]

Having Mike Wienandt add posts to this thread has confirmed most of the findings posted on other threads about the 3 cylinder 56 cubic inch OMC. The SST 60 is a spec motor and you must use original OMC parts. You cannot alter or modify parts past the given spec measurement. It is more time consuming and usually more costly to build a 100 plus hp SST 60. You MUST find near perfect parts. The motor that Mike builds will only be as good as the parts he has to work with. That being said. Some motors perform better than others. Plus the motor is only one part of a successful winning boat. Many will say the late 80's SST60 motors produced the same power as Mike's motors. A few may have. But there was a wide difference in SST 60 motors. Mike was able to equalize the motors and even out the playing field.
I do think we will see improvement in the oval port motors. The builders have played with the bridge ports since the 1980's and I do not think they have spent a lot of time...YET! playing with the oval port. For the low budget lake runner we have seen first hand in Canada that it is very easy to get good performance out of a stock oval port by just changing the carbs. We have a few T850 boats running over 76 mph, we only had one confirmed that ran over 80 mph and that was an oval port.

[filthy phill]

I read that the early 56 was sandcast blocks then went to lost foam around 1988 - 1989 when the sst60 with its hand finished lost foam block was introduced.
funny how those that worked at omc building the motors would get that wrong .

be nice to know how they used a permanent mold to do the closed engine exhaust.

[Mike Wienandt]

The early 56 block was not sand cast. It was permanent mold. The surface was smooth and shaped very well. The proto type engine tested for SST 60 was made of this, but when the engine was manufactured, it came out as foam block and did not run as fast as the prototype. The permanent mold blocks were never legal as they are faster. The foam block were cheaper to manufacture and issues like the glue lines slowed them down. Ports in the foam blocks were less consistent.
Most engines that come to me are very worn out. I can rebuild with fresh good parts and make them good. But I you say I need to win, it is much harder because then only certain parts are required to do that. Those are hard to find, impossible to make.
I need a good clean block, not hard to find. I use my own special liners. All with in the rules. I can fix the bad boost ports per the rules. But you still have a missing link.

[filthy phill]

Mike Wienandt

would it be better to use the head from the oval port 56 being as its thicker material ? part no 339221 normal thickness is 0.240 (6.096mm) at thermostat area.
if machined down to sst60 spec it still leaves 0.0150 (3.81mm) at the thermostat area, not as ultra thin like some bridgeport 56 heads.
I measured at the thermostat and at the bottom area to see if both the same and they are uniform from what I could see.

[Mike Wienandt]

Yes, that sounds like good idea.