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McCulloch Rod Bolt Variations
#1
Good afternoon, gentlemen. I was hoping to get a some clarification on the different types of connecting rod bolts for the Mac 101 series engines. Up front, my simple question is; do the splined rod bolts fit in and can they be used in all of the following 101s (A, AA, B, D)?

I ask because, even though guys refer to the spline bolts as "101" bolts, I found the IPL part numbers for the bolts vary from model to model. Although, according to the IPLs, the 101A, 101AA, B, and D all use the same connecting rod (part# 86415) (the 101A is #69250), the same piston (part# 84469), and the same roller needles (part# 69891); the 101B & D use differently numbered bolts (110720) as compared to the bolts for the 101AA (110470). I also found that the 101A uses yet another numbered rod bolt (part# 47819A) as compared to the three previously mentioned. 

So that leads me to a couple more questions...


First, what are the physical differences in the differently numbered bolts?

Second, which of the above rod bolts are the correct ones for the 101AA if indeed there are physical differences in them? I ask because I just want to know for sure that the spline bolts I have are correct for the 101AA.

Man, I sure hope I didn't make that too confusing! Thank you in advance for any help you can provide, thank you for all the help thus far, and thank you for your time and consideration...
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#2
far as i know spined 101 rod bolts fit all mccullochs.
the main reason standard bolts won't work in super motors has to do with stroke clearance.
hope this helps
D Cool
Dave L.
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#3
Thanks Dave, that does help a lot.
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#4
The 100, 101 and 101A came with allen head bolts that had a large chamfer on the OD at the top to provide the clearance so they would not hit the block or stuffer. Different bolt than came in the 91 or 49 series engines.
The spline bolts arrived on the 101A/A as I recall but it may be that they first appeared on the 101B. None of my Mac literature mentions the rod bolt change.
Steve O'Hara
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#5
Steve, I bought a pair of 101A/A's from Brown Motorsports. Seems like they were in Massachusetts. They were to be built into open motors by APPCO. I took then out of the boxes, and removed manifolds and stuffers, as these would be replaced. One had spline head rod bolts, the other had the screws with the heavy taper at the head of the Allen screw. I remember that when I got them back from APPCO, they both had spline head bolts. I sure wish I had them back, they were the fastest 101's I've ever seen! Ted
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