From: Gord Sent: January-18-16 10:21 AM To: Don Whittington Subject: 56 OMC T850 engine specs? Don, thanks for sending me the T rules. I am not sure if I will race, but, if I rebuild my motor I want to make it legal. I am not an engine guy and the porting is a mystery to me. What should I do?
Gord, I know you visit this site so I thought it best to answer here. First you are not alone.
Your block is a production 1986-7, 56 cu. inch 70 hp fishing motor. It has all the right stuff to be a competitive T850 motor and a long lasting lake runner as well. I have never blue printed one of these. In the test comparisons mentioned, the fishing motor powerheads were all non rebuilt motors I got for $500.00 or less. The only thing I did was run smaller than stock CC heads. The compression readings ranged from 135 to 163 depending on the head and how tired the motor was. Nothing else was done. The powerheads were all raced tested. The best motors were 145 to 155 compression. In that range every motor on any of the T boats ran between 66 to 69 mph. All were competitive. The 66 mph ones accelerated better and got to 66 mph faster than the ones that ran 69 mph. That difference is what you would expect from stock production motors. It also tells you what a good race-prep power head will run...69 to 71 mph with acceleration. THAT IS EXACTLY WHERE THEY DO RUN BASED ON RACERS THAT HAVE RACE-PREP 56 FISHING MOTORS. So my advise is to blue print the motor and just clean up and match the port it to run 145 to 155 lbs compression. No need to do more and it is 100% legal if you decide to race. Sign up to race for a weekend!!!
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