Correcting squish on McCulloch cylinders

[Mastermind]

I'm sending my 450 rancher

MS390 in the mail Monday.

 

[farminkarman]

MS390 in the mail Monday.

Shoot…I’m gonna need a bigger garbage can.

 

[farminkarman]

Finally had a chance to get back to this Mac cylinder. I cut the pockets 0.032” deeper to match the amount I removed from the cylinder base. Then I swapped out the boring bar for a groove cutting tool. I then re-cut the retaining ring groove for the flywheel side bearing.

 

[Mastermind]

Finally had a chance to get back to this Mac cylinder. I cut the pockets 0.032” deeper to match the amount I removed from the cylinder base. Then I swapped out the boring bar for a groove cutting tool. I then re-cut the retaining ring groove for the flywheel side bearing.View attachment 376647View attachment 376648

I love it.

 

[farminkarman]

I love it.

Hopefully all the fuss is worth it. It has been a learning process for sure.

 

[farminkarman]

Here is what the finished product looks like. If you look closely, you can see several pocket voids in the casting that showed up after doing the base cut. Both cylinders I did were like this…I thought it was noteworthy as I haven’t seen that on any other cylinder I have cut. Anyway, these are now with @Stump Shot for the port work.

 

[slackinoff]

For mine, I welded the used bearings solid onto a shaft. Then I simply dipped the bearing in toothpaste and re ground the pocket using a string bow from my boy scout fire starting kit.

 

[slackinoff]

Excellent work btw. I can't wait to see more pictures. I still have a Pro Mac 60 to get to one day. It's cleaned and ready to tear into though.

 

[Stump Shot]

View attachment 380629
Here is what the finished product looks like. If you look closely, you can see several pocket voids in the casting that showed up after doing the base cut. Both cylinders I did were like this…I thought it was noteworthy as I haven’t seen that on any other cylinder I have cut. Anyway, these are now with @Stump Shot for the port work.

Going to be a bit before I get after 'em, I will update here when I do.

 

[farminkarman]

For mine, I welded the used bearings solid onto a shaft. Then I simply dipped the bearing in toothpaste and re ground the pocket using a string bow from my boy scout fire starting kit.

How long did that take?

 

[slackinoff]

How long did that take?

FOREVER! I can't even look a string bow drill in the eye or I will break into a cold sweat.

 

[drumbum]

Who saw Captain Spaldings 610 build for Mr. Absolutely?

awesome stuff.....lol

 

[Woodslasher]

View attachment 380629
Here is what the finished product looks like. If you look closely, you can see several pocket voids in the casting that showed up after doing the base cut. Both cylinders I did were like this…I thought it was noteworthy as I haven’t seen that on any other cylinder I have cut. Anyway, these are now with @Stump Shot for the port work.

Outta curiosity, would a bigger jug (like one off a SP81) be viable for this sorta treatment?

 

[farminkarman]

Outta curiosity, would a bigger jug (like one of a SP81) be viable for this sorta treatment?

Ya know, I don’t know for sure, but I think it might.

 

[drf256]

Wouldn’t a 2 piece head be easier?

 

[farminkarman]

Wouldn’t a 2 piece head be easier?

I have never done a 2-piece head, so I can't say. I'm not sure there would be a good way to hold a removeable head down on a mac jug. As it is, there isn't much extra meat on the bearing pockets, so I am pretty much limited to getting the squish set to a respectable value.

 

[Stump Shot]

Wouldn’t a 2 piece head be easier?

Not feasible, the exterior frame bolts right to the top of the cylinder head, so there isn't any extra room to speak of, that and you can't just use long bolts as it doesn't go together that way.

 

[Al Smith]

In theory about the only method to hold a head on that model would be to use "banjo bolt " design .This method was used decades ago on kart engines like the AH 47 Power Products engines which were an "entry level " engne.
As far as the Mac engine in stock form they are almost bullet proof .However if the bottom end would hold up at much higher compression remains to be seen .

 

[drf256]

Not feasible, the exterior frame bolts right to the top of the cylinder head, so there isn't any extra room to speak of, that and you can't just use long bolts as it doesn't go together that way.

I was thinking studs. There is room on the bottom flange for that. Inside the clamshell clamping bolt perimeter.

 

[Stump Shot]

I was thinking studs. There is room on the bottom flange for that. Inside the clamshell clamping bolt perimeter.

Possibly if one could get them recessed in the head. corners of the cooling fins would have to go. then the whole thing be the same length and a couple of 1/4"-20 threads tapped into the top of the head on either side of the sparky hole to mount it up to the chassis, as well as it not be too big around to fit inside, might be square would be easier to work with.
For now I have to see where this path taken leads me and the end result. The fat lady's not even in the building, let alone warming up, so it ain't over yet. Good news is, what ever wrangaboo I got myself into, I get to do it twice, for a second shot at redemption.