Plugged compression release holes

[philrock]

I have located a pair of McCulloch 101MC engines that I’m thinking about buying. They are set up for alky, and have zero hours on rebuilds by Hanson Duncan. They also have plugged holes where compression releases used to be. The plugs don’t go all the way in to the bore diameter – they come up about ¼” short of the bore wall, leaving a dead space near the top of the combustion chamber about ¼”diameter x ¼” deep. This amounts to about 1/5 of a cc.

How will this small dead space affect performance, reliability, and longevity?

[steveohara]

Philrock,

They will have no effect on reliability or longevity and the effect on performace is so small that it is of no consequence for vintage karting. If the motors are otherwise in good shape you should not pass them up due to the plugged up compression release holes.
I am curious about the meaning of "setup for alky".... Do you know any specifics? Are the motors equipped with the double pumper carbs? What other changes have been made?
Steve O'Hara

[philrock]

Steve,

Thanks for your reply. One engine has .008" oversize bore. Both have double pumper carbs and Mac 101B crankshafts. Air/fan shrouds might not be standard for Mac 101MC. I'm not aware of any other changes. Seller says condition is stock other than these items.

By the way, both engines have pull/recoil starters that appear to be in mint condition; these will be up for sale soon.