Yamato 80 break in procedure

[Steven27jack]

What does RB stand for? These are the only good pics I have, and they're not great, but the pistons are not flat top, they're a little round

[DeanFHobart]

What does RB stand for? These are the only good pics I have, and they're not great, but the pistons are not flat top, they're a little round

If I am not mistaken, RB stood for ‘Restricted B’… The ‘Restricted’ part meant that the power head remained stock, except the block could be blueprinted to max / min specifications, meaning the head could be machined to minimum CC’s to increase the compression, and the ports could be machined to max specs. Also, the motor could be converted to run on Methanol. That is why there is a Bing carburetor on it. The ‘B’ means 20 cubic inches or in metric 350 cubic centimeters. This was in the ‘Pro / Alky’ outboard division of APBA.
Yamato later on would also manufacture total complete ‘Alky’ motors without any Restrictions except cubic centimeters.

Some of the other guys here should be able to add more information on this.

[dwhitford]

15 cubic-inch engines could also run in the RB class almost without any restrictions. For example a 20 ci RB engine could have only one carburetor, and that one was restricted in size. Mike Schmidt was quite successful in RB running my 15 ci Quincy Z engine with two 36 mm Mikuni carbs on it. Mike won with my engine most of the time.

[raceright]

Break in race motor. Squeeze throttle.

[Steven27jack]

Looking into 18mm to 14mm spark plug adapters, brass or steel?

[ZUL8TR]

Brass but if you can get aluminum has better thermal conductor and best. I was given steel from Tom Cronk and required 1 range colder plug since less thermal conductivity much less than brass or aluminum. Make sure final 14mm plug threads are level with end of adapter (I trimmed adapter 18mm end) and the adapter fits in the head with same plug reach as the OEM 18mm plug. To achieve this I used the thick copper spacer from the OEM 18mm plug on the trimmed adapter into the head and no squish gasket on 14mm plug into the adapter. I am using NGK B10EGV fine wire gold palladium tip electrode, NGK part #5927. The adapter you get might require different trim adjustment and spacer(s)?