Rebuild time on the 230 flat head engine

[outpostm37]

Everyone with input, please chime in.
I purchased a 1963 Dodge Power wagon M37 nearly a year ago. It has the 230 flat head 6 (military) which was marginal at best. This weeks compression test yields very low compression on several cylinders. 70 psi on cylinders 1 and 3. I have several of the military manuals that state 90 psi as a rebuild point. My plan is to pull the engine, put it on the stand and disassemble before purchasing any parts. There is a lot of unknowns about this vehicle. My goal is: to have a solid engine that is reliable with decent (?) power and compression for what it is designed for.
Please give me your input on:
Who to purchase parts from, and NOT to purchase parts from.
Head milling? Would like to bump up the compression A SMALL amount ( friend has a machine shop that can grind the mating surface of the head flat and a tiny bit more .020?)
Tips and tricks on reassembly
Thanks in advance
OutpostM37

[Elwood]

Take lots of photos during disassembly, but don't assume that the last guy assembled everything correctly.

And don't assume that new and NOS parts are good to go. Measure and inspect everything you buy, regardless of the source. I was amazed at how many parts I purchased - many from the "reputable" vendors - that did not meet spec.

You mentioned "grinding" the cylinder head. I hope that your machine shop will be milling the head using a purpose-specific mill such as a Rottler. A Bridgeport is not a cylinder head mill. I just had to have a used Dodge flathead resurfaced because the prior owner had tried to mill it with a Bridgeport, and left a noticeable ridge down the middle of the gasket face. The gasket is thin enough between the paired cylinders without giving it any additional weakness.

Your machine shop should also balance the rotating/reciprocating parts: crankshaft, flywheel, pressure plate assembly, pulley, rods, pistons, pins, and rings. The crankshaft and everything connected to it. Not because these are race engines, but because balancing will make it run smoother, and therefore run longer.

Milling the stock T-245 head (if that is what's on your engine) will give you a very small bump in compression. Or you could find a 218cid head (as ashyers here did in a topic he posted) and get some meaningful compression. Remember, these engines were designed when octane ratings were significantly lower, and compression was limited. Gasoline is much better now (excepting the ethanol), and your engine can take advantage of that change.

There's really no way to post an all-inclusive how-to here, but please post what you find as you go. There are a number of experienced engine builders here, and I'm sure they'll help out. Several good threads here about others who have rebuilt their flatheads - they're good reading and the search function will find them for you.

[jim lee]

Or you can do what myself and 52 M-42 did. Call Midwest Military. They will have a new motor sitting at your place within 2 weeks. (For me it was 2 weeks 'cause I'm on the far North west coast away from them) Swap in te new motor, get it running, then tie your old motor to the pallet and call them. Old motor is picked up, problem solved!

I did the old way with local machine shops, and engine builders. Took MONTHS! Motor lasted 6k miles and spun a bearing. Did it through Midwest the second time and was done and running in about 3 weeks. In the end, cost about $1k less than the first motor. Motor runs great and we're driving the truck all over.

Next time I need a 230, that's how I'll do it again.

-jim lee

[outpostm37]

Or you can do what myself and 52 M-42 did. Call Midwest Military. They will have a new motor sitting at your place within 2 weeks. (For me it was 2 weeks 'cause I'm on the far North west coast away from them) Swap in te new motor, get it running, then tie your old motor to the pallet and call them. Old motor is picked up, problem solved!

I did the old way with local machine shops, and engine builders. Took MONTHS! Motor lasted 6k miles and spun a bearing. Did it through Midwest the second time and was done and running in about 3 weeks. In the end, cost about $1k less than the first motor. Motor runs great and we're driving the truck all over.

Next time I need a 230, that's how I'll do it again.

-jim lee

This sounds like a great option! Do you recall the approximate amount for engine/shipping? I am in the southwest desert.

[jim lee]

Mine was a few years ago so I don't even remember. I only remember being surprised that it was so much less than the one that died. Just give 'em a call and see what their current deal is.

-jim lee

[outpostm37]

On a standard rebuilt 230 flat head engine, what would a cranking compression reading be? The standard military pistons have two oil rings. Are there other pistons that house two compression rings and one oil ring?

[Elwood]

Spec for compression at cranking speed is 120 to 130 psi (per TM 9-1840A) in each cylinder. TM 9-8030 specifies compression of between 90 and 130 psi at a cranking speed of 150 rpm, with variance between cylinders not to exceed 10 psi, but that 90 psi is a low number.

I think that all Plymouth/Dodge small block flathead pistons use four rings: two top compression, and two lower oil control. I've not seen pistons for these engines (NOS or new) that use three rings. Any particular reason(s) why you'd want a three ring piston?

If you don't have copies of the four basic manuals - TM 9-1840A Engine and Clutch; TM 9-8030 Operation and Organizational Maintenance; TM 9-8031-2 Power Train, Body and Frame; and ORD 9 SNL G-741 List of All Service Parts - they're invaluable to working on these trucks. There are other supplemental manuals, but those are the four essentials.

[T. Highway]

Excellent information John.

Bert

[outpostm37]

My last compression test gave 70 psi in two cylinders. After I pulled the spark plugs, two showed signs of a head gasket leak. There were dots of water (coolant) on the ground strap of the spark plug.
Head pulled, gasket showed carbon burning between several cylinders. Going with a new head gasket, and a cylinder head resurfacing, and block clean up. The valves looked good. Will do an adjustment while the head is off. Cold adjustment measurements.
New head bolts should be in from VPW by the week-end. Most people say to use the copper gasket spray on the head gasket, torque to spec, run for 20-25 minutes then re-torque. Hoping this helps, more fun.

[Cal_Gary]

Hi Outpost,
I blew my head gasket a couple of years ago-found a number of the head bolts were loose upon disassembly that probably contributed to the problem-your low compression could be related to the same. Anyway, I wanted to chime in on the head shaving. My local machine shop took .005 off mine, leaving it clean and strraight-edge flat. I also had it magna-fluxed to be sure it wasn't cracked. I gained a bit more power but not extreme upon reassembly and have had no issues, putting roughly 1000 miles on it since changing the head gasket.
Gary

[Kaegi]

I have shaved as much as .075. and run larger cam. but if not rebuilding then I would not shave it unless it needed it.

[outpostm37]

Finally got the tranny and engine out of the old girl. Flywheel has me scratching my head. It has 6 bolts/bolt holes to connect to the crank. The crank flange has 8 holes. Wondering what this flywheel is originally out of.

[Cal_Gary]

Hi Outpost,
You have a civvy Chrysler flywheel. I run the same thing on mine because the military flywheel wouldn't work with my civilian starter. The military flywheel is much thicker than the civilian one, too.
Gary

[Elwood]

I think Gary identified it.

See here: http://www.g741.org/PHPBB/viewtopic.php ... eel#p50535

[outpostm37]

Thanks for the flywheel info. My M37 is a 1963. When the engine did run, it seemed very smooth. Never had any issue with the starter disengaging from the flywheel. Anyone know if these engines were balanced with the crank and flywheel bolted together? I plan on using this flywheel again, I have had it resurfaced, and plan to have it balanced. Any benefit of having the flywheel/clutch assembly bolted together when balancing? The odometer read 64,000 miles. The engine had .030" over size pistons in it. Mysteries abound with this creature.