Get out the straight jacket

When I started the last engine re-build I went looking for sheets of what I used to call emery cloth at the local hardware stores and couldn't find any. Hardware stores aren't what they used to be.

A little late for plastigauge. lol

I could get some just to see how far out it might be and find out how close the Molnar journals are to what I figure are Standard because the crank is new. I'll get a rough diameter with a caliper tomorrow on both cranks for grins and see how the numbers compare to what the manual I have says standard for a 750 should be.

On to more fun topics. The Molnar barrels don't actually fit on my old cases without a little modification. I have to remove some material from the edge of the barrel at the flange on the timing side. Since I don't have a Bridgeport in my garage I'll use some barnyard Dremel metal trimming technology. It is a minimal skim but will take me 2 hours to do like a drunken woodworker. Lots of test fitting. Now that I think a little more about it, I may do it caveman style with hand file for aluminum. Might have better control with a file.

The Molnar cases are starting to look better all the time.

Low cost mill for aluminum. Works great.

Mine is so old I wore Nicholson down to just the N at the end of the name. I wore it down with my thumb.

The Molnar crank is within spec for standard shells. That is what is going in the engine, so I think I'm good this time around.

The Norton crank was -.010, but a little out of round. I had +.010 shells in it, but a wiser man would have gotten the crank reground -.020 and gone from there. I'm not a wiser man though, and knew I was going to get a lighter theoretically stronger crank before I was done playing around with this old Norton.

The modifications I had to make to get the Molnar barrels to seat on top of the P11 cases.

Before the modifications, it was a no go.



Got out the Dremel and a metal cutting bit I use for this and that. Filing it would have been a real PITA.
Here is the cut I made.





Das tight fit:



It sits flush on the case surfaces. I wanted a close finish fit against the timing chest as well. I ran the through bolts into the existing 3/8-16 holes to clamp it down for a minute. Sweet Job's done.

Anywho, another hurdle cleared. I'm sure there will be some more.

Schwany said:

Hmm, maybe I should have had the journals ground -.010 and polished them.

Weighed the cranks and barrels today. The Molnar crank is 3lbs lighter at 20lbs than the 23lbs crank that was in my P11. The Molnar barrels weigh 9.5lbs less than the iron barrels. Chasing threads and getting mentally prepared to do the inserts. Fun times ahead.

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Are those stock AN bearings on the stock crank? If so I've got the same setup. Tried the plasti-gauge but couldn't get it to work. I did mike the journal and rods and it seemed to be within clearance using the stock bearings so I guess fingers crossed cause I doubt I'll be tearing it down anytime soon

Cylinder fit looks very nice Wonder if @Junglebiker had a similar experience with his cylinders?

Schwany said:

The modifications I had to make to get the Molnar barrels to seat on top of the P11 cases.

Before the modifications, it was a no go.

Click to expand...

I am surprised there is a clash in the deck/timing chest area, but easily sorted. Andy told me there is a need to open up mouth of the crankcase in order to fit his barrel.
I guess this applies to the 850 barrel only.

- Knut

Schwany said:

I could get some just to see how far out it might be and find out how close the Molnar journals are to what I figure are Standard because the crank is new. I'll get a rough diameter with a caliper tomorrow on both cranks for grins and see how the numbers compare to what the manual I have says standard for a 750 should be.

Click to expand...

I made a discovery while trying to measure my freshly honed Molnar barrel: Caliper readings are done in vain. They are much too inaccurate. So I had to invest in a calibrated micrometer and a bore gauge. I guess the same applies to attemted measurements of journals.

- Knut

mdt-son said:

I made a discovery while trying to measure my freshly honed Molnar barrel: Caliper readings are done in vain. They are much too inaccurate. So I had to invest in a calibrated micrometer and a bore gauge. I guess the same applies to attemted measurements of journals.

- Knut

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I've got a bore gauge, but need some micrometers. Using a caliper on the journals was as you say useless in reality. Plus calipers can scratch the journals. Micrometer is the right tool for measuring the journal diameter. Although there could be something better I'm not aware of.

The Molnar crank is good, so is the stock Norton crank. I checked the old bearing shells to see what they looked like. The old bearing shells appear to be a lot tougher material. Could just be they are aged and hardened a little. They looked ok which is why I just bought new bearings of the same size. What I did not do was polish the journals a little. I think it would have shown better results. Doesn't matter. It's water under the bridge.

My Molnar 750 barrels are iron lined and use less material around the bore according to Andy, which is why they fit in the old cases, and why I bought them. Andy said 750 Nikosil barrels would not have fit in my cases, because they use more material around the bores. I would have had to use Molnar cases to go up to an 850 or larger bore with Molnar barrels.

TomU said:

Are those stock AN bearings on the stock crank? If so I've got the same setup. Tried the plasti-gauge but couldn't get it to work. I did mike the journal and rods and it seemed to be within clearance using the stock bearings so I guess fingers crossed cause I doubt I'll be tearing it down anytime soon

Click to expand...

The shells are whatever Andover is selling as +.010 shells for a Norton crank. If your journals looked smooth and measured in spec they are probably good. Mine really were not perfect, and I took a chance with the crank as is since the old shells did not look that bad to me. Not recommended if even the slightest amount of doubt exists. I actually knew better but was foolishly optimistic.

Schwany said:

The shells are whatever Andover is selling as +.010 shells for a Norton crank. If your journals looked smooth and measured in spec they are probably good. Mine really were not perfect, and I took a chance with the crank as is since the old shells did not look that bad to me. Not recommended if even the slightest amount of doubt exists. I actually knew better but was foolishly optimistic.

Click to expand...

Whew, it sounded like you had stock bearings and needed to mill the journals -.010. Looks like you might have been good with stock dimension bearings

TomU said:

Whew, it sounded like you had stock bearings and needed to mill the journals -.010. Looks like you might have been good with stock dimension bearings

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The crank had been turned down -.010 in the 1990's when I got it rebalanced. The engine had +.010 shells in it when I rebuilt the engine then. Didn't remember that was done. I did not do the crank mysef back then. I was working at the time and flush with the legal tender. I had it rebalanced and assembled with the rods on it through Bob Raber. +.010 shells are what I took out of the engine when I rebuilt it a few months ago, and +.010 shells are what I put back in.

If I had put standard shell bearings in it, it would have been too loose and started making a bunch of noise in less than 100 miles. Plus, I'd really have to be further into dementia than I already am to not have looked at the shells I took out of it when I replaced the rods and such.

Longtimegone said:

Cylinder fit looks very nice Wonder if @Junglebiker had a similar experience with his cylinders?

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There was no mention of having to do it in his thread. Andy was not surprised that I had to do it. It won't be the last thing I have to do to make the barrels work on a '67 P11 set of cases.

During my 7 decades plus on this rock I have spent a significant amount of time making performance bolt-on parts bolt-ons. lol

JSM through bolts with dirty coffee cup back.

Lighter weight than the stock through bolts (55 grams vs. 71 grams per bolt).

The radius on the heads of the stock bolts was not equal and when mockup installing them they rubbed against the edges of the pockets in the Molnar barrels. I could have taken a grinder to them, but these ARP bolts are a nicer product all around. Not cheap.


I might get something done today or tomorrow on the motor. Although it is friggin cold in my garage. That won't mean anything to the young guns or keyboard tough guys out there, but it's not fun for older folk with paper thin skin. lol

Decided to make a modification to the JSM lifter blocks. Theory behind the mod is get oil to the cam lobes a little quicker in a straight up motor. The lifter blocks are angled in the barrels in a way that puts the oil holes in the lifter blocks in a high position in the bore. Higher than it would be in a canted forward Commando engine. Oil has to fill above the top of the lifter to overcome the angle before it starts flowing down the oil holes. So I figured I'd do something to help get a few dribbles flowing sooner. Could be a big waste of time, but it didn't take long. The little troughs are hand ground with a Dremel, so not quite asymmetrical. I don't think the oil will care. I might make the cut larger more like a triangle in front of each hole.

Feel free to pooh pooh the idea and blind me with science.

Should have the bottom end and barrels on tonight if I don't get sidetracked on some other barn yard modifications.




This might be better.

Schwany said:

JSM through bolts with dirty coffee cup back.

The radius on the heads of the stock bolts was not equal and when mockup installing them they rubbed against the edges of the pockets in the Molnar barrels. I could have taken a grinder to them, ....

Click to expand...

How are JSM through-bolts tightened? I was kind of surprised to see the 12pt bolt head on them, as there will hardly be room for a socket in either iron or alloy barrel. Did Jim specify a turned-down socket?
Bolt heads (or rather, the built-in washer) may rub, as long as no swarf is produced, possibly leading to poor seating of the bolt head within the barrel.

- Knut

You just need a set of long series sockets (like those linked below), they fit without issue.

mdt-son said:

How are JSM through-bolts tightened? I was kind of surprised to see the 12pt bolt head on them, as there will hardly be room for a socket in either iron or alloy barrel. Did Jim specify a turned-down socket?
Bolt heads (or rather, the built-in washer) may rub, as long as no swarf is produced, possibly leading to poor seating of the bolt head within the barrel.

- Knut

Click to expand...

Couple of things:

The pockets for the through bolts in the Molnar barrels are flat and I'll use Carrillo fastener grease under the perfectly flat JSM shouldered bolt heads and on the bolt threads. Now hold onto your butts, I'm considering putting used copper crush washers under the bolt heads because they are the perfect size for the job. Jim says washers are not necessary though.

To get those through bolts tightened down I have one set of 1/4 inch drive 12 pt sockets that will do the job on a 3/8 to 1/4 adapter for the torque wrench. I think those bolts are only 25 ft lbs of torque. If I did not have those sockets I would grind on one of my 3/8 sockets until it fit.

Don’t use copper washers under those !

You’ll be adding a soft material into the joint. The design intent is for those through bolts to clamp up 100% solid because you cannot re torque them.