Need help ID ing Mcculloch motor. Mc100?

[carl haydt]

Dean,looks to be an 101B. 5 fins above the exhaust port & counterweights on crank plus copper o-ring head gasket are what I can see in pics. Should have had a metal tag riveted on with a prefix of 17 or possibly a replacement block.

[Dean Richards]

The block does not have a serial# and the crank is right hand thread. From what I can tell from the super series chart it appears to be between a 101AA and 101B. Chart shows 101AA does not have serial #'s.

[Vince Rosanelli]

Dean, glad to see you had a chance to post some photos. If you get a chance, take and post a clear photo of the stuffer opening with the stuffer removed. The recess for the connecting rod bolts will help determine what you have. Also, in your first photo the fan shroud is resting on its bottom; take and post a photo of that part of it to view.

The 101AA came with both left and right handed pto threading. The chart states the 101B only came with left handed threading. Also, I t could just be the photo, but it does not appear to have a recessed exhaust gasket surface. Perhaps a clearer photo of that area cleaned up might help too. Again, it could just be the angle of the photo or the grime on the block, but it almost seems like there is a stamped number on the block just to the right and below the oiler nub when using he zoom feature. Double check that if you can. As for the serial number ID tin that usually goes missing, the 16 prefix is for the 101AA and the 17 prefix is for the 101B. They both use the copper head gasket. Although most 101B engines came with a blue and red color scheme, the early ones were available with chrome shrouds.

I have a 101AA that was positively identified by Chuck G. (StrokerAce) soon after I initially posted photos of it and later confirmed by Steve O'Hara. They both helped point out the identifying features and also offered more valuable information on it. I'll try to post photos of it for reference. I'll also post some other reference material below that might lead to identifying what you have. Worse case, you might have an engine comprised of some mismatched parts, better case is you might have an A, AA, or B engine and just came up with a bore measurement that was off slightly.

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The block does not have a serial# and the crank is right hand thread. From what I can tell from the super series chart it appears to be between a 101AA and 101B. Chart shows 101AA does not have serial #'s.

[Dean Richards]

I have search high and low for any numbers on the block and found none. No serial # tag. posted couple more pics. Looks to have casting recess for the crank bolts and recess in piston skirt for crank, no recess in exhaust port, Recessed head gasket, Right hand thread on crank with keyway, 2, finger ports opposite of exhaust, chrome flywheel cover, no 9 port or 3rd port, no transfer port cover, and not a fixed head. The bore is from 2.265-2.277 around the cylinder, and stroke is 1.835. I see from the super series chart that this appears to be a 101A/A since all others have a serial/ block number??

    I want to say Thank you to all that have helped me with this process and look forward to more input.

                                                                                Dean
,

[Vince Rosanelli]

The block does not have a serial# and the crank is right hand thread. From what I can tell from the super series chart it appears to be between a 101AA and 101B. Chart shows 101AA does not have serial #'s.

Here are a couple photos of my 101AA and the notched fan shroud for the same

[Vince Rosanelli]

From your photo, your engine doesn't seem to utilize the high ksi spline bolts for the connecting rod that McCulloch used. From what I've read, engine builders recommend NEW 150-320 ksi bolts...

[steveohara]

The motor is a 101A. Very easy to ID from the first photo.
The 101A is the only model to come with the venturi type flywheel cover that has no depression on the round end for a saw handle. Also the only 101 series model to come with a hole in the spark plug boot. Another identifying clue to the A model as compared to the A/A or B is the partial sphere shaped relief machined on the inside of the block to clear the rod bolts. The later models have a channel cast in for rod bolt clearance.
Steve O'Hara

[Vince Rosanelli]

The Mac Gospel according to Steve O....
-Amen!
Dean, in case you didn't know, now you know. Steve is one of the foremost authorities on Mac engines inside and out; so final answer is you got a 101A. Good luck with it!