SC M37

[Elwood]

Now the total weights are matched:

Interesting that you chose to remove the ribs from the bottom ends of the rods in order to balance. More modern rods sometimes have a sacrificial balancing "pad" on the bottom half, but I'm not sure that was the intention of those ribs.

[sturmtyger380]

Taking some of the ribbing off was they only way to reduce weight. I talked to an older guy that built hotrod engines when he was working. He said you can remove a lot of metal off of the bottom of the rods. I showed him the picture and he said they look great. We will see.

[ashyers]

It may be a good idea to find a shop that can shot peen them properly. It's cheap insurance.

Andy

[Elwood]

Agreed with Andy on the shot peening. When I balanced and polished the rods for my engine, shot peening was on the list of things done.

I hope that the old guy is right about those ribs. I might have been able to save some time and expense, but instead I ended up with a large collection of rods, trying to find six that were close enough to begin with that I didn't have to remove much metal, especially from the bottom end, to bring the heaviest down to the lightest.

Here's a comparison of the original and balanced rods:

[NAM VET]

my machine shop balanced my engine, rods, and I think flywheel too, and while I have never driven or even ridden in any other M37's, my motor does seem to be really smooth. I also keep my speed down to 40mph, with the OEM gearing and NDT's. Read about the tendency of these long stroke rods to break at "high" rpm.

I don't know where our "rods" are most likely to break, but I am guessing it is the bottom of the big end. Here, a pic of one of my rods, keeping the "ribs" intact.

Dodge did not originally balance these engines, for a number of reasons, perhaps one being that when sent back to depot for rebuild, it was too difficult to keep the internals together, and then it would have been necessary to balance them every time they were re-assembled. And better to have unbalanced but stronger rods too.

All I know is in the about 7K miles since it my engine went together, all is well. Perhaps peening yours now might be a good idea. This one must have been the really heavy rod. hal

[sturmtyger380]

It's a small world. I took my engine for machine work to a guy in a little town just south of me. This was months ago. Then took the rods for him to size the pin bushings and he saw my address on the box I brought. Turns out we both live in the sticks north of town about 4 miles away from each other.

I was talking with him about A guy I know about 2 miles away from both of us that builds flathead engines. He didn't know about him.

Each day I work in an office with a guy that builds drag racing engines on the side, and I mentioned to him that it was suggested to shot peen my rods. He said he knew a guy that he helps from time to time that builds racing engines and does shot peening. So, I call that guy up and it turns out he lives a mile from the first guy who was the machinist. So, tonight I plan on hauling the rods over there for him to look at and shot preen.

[NAM VET]

other than rebuilding a few TR and MG engines long ago, and my M37 experience, I know nothing about rebuilding engines. But thinking about the stresses on a con rod, I would suspect the maximal stress is when the combustion slams the piston down, ie, stress on the upper part of the big end bearing, where there seems to be an abundance of metal. Then when the piston/rod swings thru its arc and then hurls the piston/rod upwards in the bore. So great stress is on the lower part of the rod/bearing. Polishing the rod's surface I think can reduce stress cracks too.

No doubt engine builders have a lot of experience on con rod bending and breaking.

When Charles Talbert pulled my pistons out in his correction of my own assembly, he did not shot peen my balanced rods. I was out to our Heritage Associans's Motor Pool, ie in the hanger yesterday, was so nice to be be under cover in a hard rain. Found that my small coolant leak was under the outlet on the top of the water pump, and a little snugging down of those two bolts seemed to have resolved that. Setting up my shop site in my corner spot, bought some new shelving, and I have taken almost all of my truck tools and supplies out there. All I need for our home cars is perhaps someday a screwdriver.

All this for about a hundred a year, plus the comradeship of the others there. hal

[sturmtyger380]

All I need for our home cars is perhaps someday a screwdriver.

I know what you mean. The new cars we have at home, I don't even change the oil like I used to. That would void the warranty!

[T. Highway]

Nice job.

Regards,

Bert

[sturmtyger380]

Not a lot of pictures from the last two months. I have been running the wiring and connecting up items.

Redid the Voltage Regulator:



Sandblasted and painted the Glove Box



I got those dreaded draft pads on by using the boiling water technique:



Also worked on getting the Dash squared away:

[John Mc]

Looking good!

Is that a tach just to the right of your steering column? If so, where did you pick up the signal for it?

[sturmtyger380]

Yeah that Tach is for a 6cly boat engine. It barely fits there. It's not connected yet but I plan on maybe drilling a small wire sized hole in the test cap of the distributor cap, feeding it through and connecting it to one of the terminals.

[T. Highway]

That Is coming together nicely.

Regards,
Bert