M-5 Engine

When I got the truck, the flathead 6 engine had not been run in years - and I don't know how many years! I bought a new battery, poured in some fresh gas, and tried to start it. It turned over sluggishly, so I pulled out the starter. The Bendix gear and the bell housing were full of a mouse nest built from the upholstery stuffing. Once I pulled all of that stuff out, the engine finally caught and ran. There was hope! Of course, the exhaust smoked plenty of oil. There was evidence that the head had been off for some kind of work. One of my clues was that a bolt head was missing, but the shank of the bolt was still in the block. I stripped off the accessories, trying to mark and photograph as much as possible. The head came off to reveal clean cylinder bores, not too big a ridge, and all of the valves whole. At least there appeared to be no major damage. I built a cradle on an old wooden pallet and put the engine in the back of the Wagonaire for a trip to the shop.

Sixteen months later, I got the engine back. I thought I picked the right guy. He was very local, had a shop with all the right stuff in it, spoke the right words, even said he had done Champ engines before. Unfortunately, he isn't well organized, is behind on all of his work, and responds first to the to commercial guys who bring him engines every week. I was low on the totem pole. I also made the mistake of telling him that I wasn't in a hurry. I guess I can't complain too much, because I didn't really have the chassis ready to drop the engine in. Anyway, while I have yet to actually start the engine, I did follow its progress through the shop and was pleased with the quality of the work. That's what counts!

The block went into the tank to be boiled, and boiled, and BOILED! Some previous owner must have poured lots of "Barrs Leaks" or other radiator sealer into it. That stuff congealed with the remains of original foundry sand to make concrete in the bottom of the block and many of the water passages. No wonder the engine probably overheated! The crankshaft was pretty good, so it got turned .010 undersize. The bores were taken out to .030 over. Bill Cathcart supplied most of the engine parts. The engine shop struggled with the remains of the broken head bolt, but finally got it out. We put in new pistons, cam, valves, valve springs, oil pump gears, timing gear, etc. I had Bill Cathcart modify the timing gear cover to include a new, modern seal to replace the old felt-style seal. In the picture above, you can see the remains of a lot of leaking oil from the front of the engine. I hope there are few leaks in the rebuilt engine.

The engine was almost together, when I had a "brilliant" idea! Why not add a little horsepower while I'm at it? Yeah, I should have thought of this earlier! So, I read the books, chatted with my buddies, and figured out a plan. I want the truck to be original - or, almost original. I succumbed to the thought of another 10 or more horsepower and bought a head for a 1960 Lark 6 engine, the last of the Champ flatheads. It took the compression ratio up from 6.5:1 to something near 8.2:1. I have seen different numbers published for the compression ratio on the 1549218, but it is at least 8.0:1. It was new, on the shelf at SASCO in South Bend, and cheap. They have more at $71. The only significant difference between the old and new heads is that the original mechanical temperature sensor doesn't fit in the hole in the newer head. I checked out the dimensions as well as I could, stuck feelers in the hole, and eventually ran a larger drill and pipe tap into the head. Now the temperature sensor fits. I just hope I haven't thinned out the head too much. Although the casting had never been used, 40 years on the shelf left the head not-quite-flat, so we had to plane it by .005 to .010 ( a little more compression!). Had I done my thinking earlier, I would have put one of Bill Cathcart's cams in there, too. I had considered taking out my little Dremel grinder and removing the first digit of the cast-in number o the head. Then it would read "549218" and not alert some purist to my non-original 7-digit part number. But, here, I've gone and confessed in public. I might lose a point at a show someday. Too bad!

So, what should I expect now? I bought DYNO 2000 software (http://www.motionsoftware.com/). I plugged in the bore, stoke, valve lift and dwell angles, and a bunch of other factors. I'm not sure of the cfm rating on the little 1-barrel carb with 1.25 in. bore, but I figured about 150 cfm. With all that, I get about 81 horsepower in the 3500-4000 rpm range with 130 ft.lb of torque at 3500-3000 rpm. The rating in the manual is 80 hp, so Dyno 2000 is pretty close. With the compression changed to 8.2:1, the horsepower goes up to 95 and torque to 150 ft-lb. If I ever add one of those neat-looking dual carb set-ups, Dyno 2000 estimates it at 108 hp and 159 ft-lb of torque. Bill Cathcart might be on to something here (see his page at http://www.cathcartsstudebaker.com/).

The horsepower and torque curves are shown on the right. The hp is in red, torque in green. The stock engines curves are the lower of the pairs.

CHAMP ENGINE SPECS

Bore: 3.00

Stroke: 4.00

Cylinders: 6

Displacement: 169.4 cu.in.

Cam: Lift = .312

TIMING (seat to seat)

IVO - 15° BTDC

IVC - 49° ABDC

EVO - 54° BBDC

EVC - 10° ATDC

Valve diam.:

Intake - 1.344

Exhaust - 1.281

Champ engine with stock 6.5:1 compression (lower) and 8.2:1 compression (upper).

Eventually, the engine was done. I hauled it home again and painted it in Studebaker Green. The distributor was rebuilt by Dave Thibeault. I bought an accessory oil filter from Tom Karkiewicz of Mulberry Pride Farm, South Bend, IN. Tom is the guy who drives the big white school bus full of Stude parts to swap meets. At last the engine was ready to go in. And I wasn't! There was still lots of chassis work to do, so I stored the engine in the sun room off the deck for a couple of months. Then one day in the summer, I dragged out the engine on its pallet. Moving 400 lbs of engine by yourself isn't easy. I used some 2 ft. lengths of iron pipe as rollers, laying plywood and planks in front of me. I'm sure the Egyptians built the pyramids the same way. I picked up the engine with a hoist, and rolled it out to the garage. Unfortunately, I had arranged for the paving of the driveway not many weeks before and it was a hot day. I left the hoist sitting on the driveway for just a few minutes while I got the chassis ready. In that short time, the hoist wheels sank about an inch into the fresh asphalt. I almost couldn't move it at all.

Once I got the hoist loose from the driveway, I pushed it into the garage, and lowered the engine into the chassis.It sits on new engine mounts.

REBUILDING THE M-5 TRUCK ENGINE