The Stovebolt Site Forums The Shop Area The HiPo Shop Hey machinists- - - -thrust bearing question

Can anyone think of a good reason it wouldn't be possible to control the fore/aft thrust on a stovebolt crankshaft with a brass or bronze washer permanently installed on both sides of the #3 main bearing cap instead of the conventional flanged main bearing that's usually used in that position? I've worked on various other engines that use separate thrust washers from the main bearings that fit into machined grooves in the engine block and/or bearing cap. That system is pretty common on British sports car engines from the 1950's and 60's, and also some pretty heavy duty industrial and farm equipment engines. I've acquired some 4" outside diameter brass washers that could be cut in half and fitted to both sides of the #3 main bearing cap with flat headed brass machine screws, and then ground or machined for the correct width to keep the crankshaft in its normal fore/aft position in relation to the engine block and timing gears. If necessary, an upper thrust washer could also be attached to the block the same way, after some machining with a line bore tool, but I believe a wide enough thrust face on the main bearing cap alone should be sufficient. This modification will be part of my project to retrofit a stovebolt engine to big block Chevy V8 main bearings. Comments/suggestions,/ laughs/gripes, etc.??????
Jerry

I see absolutely no reason why your plan wouldn't work. You'd need to be sure that enough screws were used to handle the shear that might occur. I think I'd also use some bearing mount loctite when screwing the washers in place, just as a belt-and-suspenders kind of thing.

I'm thinking of using 3 or 4 8-32 flat head machine screws, countersunk a few thousandths below the surface to assure that the washer is the primary carrier of the thrust. The only time a noticeable increase in fore/aft pressure will be there is during shifting, or idling at a stoplight with the clutch pedal depressed. A good psychiatrist might be able to help that clutch pedal!
LOL!
Jerry

I would prefer to use bronze before brass as I think it would hold up better.

John

Maybe add a couple of oil grooves starting at the journal and dead-ending before the outside diameter of the washers. That would leave a small oil reservoir or two in the thrust washers.

Good idea- - - -I'm also planning to taper the ends of the washer at the parting line where the cap meets the block, to give the washer some hydrodynamic lubrication from the crankshaft rotation. The countersunk Allen screw heads will also trap a little oil, as they will be recessed a few thousandths below the contact surfaces. That's also why it's important to chamfer the crankshaft oil galleries a bit where they intersect the boundary layer at the rod and main bearings.
Jerry

I agree with John. Oil impregnated bronze would be a better choice. Any kind of small oil grooves would also be a plus.
Machined a bunch of bronze punch press bearings over the years.

Don

Since the usual material on a thrust bearing flange is some variation of Babbit metal, either brass or bronze will probably be more durable. I've got a good source on big military surplus brass washers at a reasonable price. I'll also investigate bronze as a possibility if the prototype engine shows any noticeable wear during dyno testing. It's not uncommon to overstress an engine or three on the test stand, working out the research and development gremlins. One of our favorite sayings was "The turns are a long way apart on a dyno, and the hills never end!"
Jerry

Gmc all ready did that back in the Ducts in ww2 there was a heavy duty version of main bearing for the 270 that came in them. It was 2 pins that held . the thrust bearing in place

If you are designing a method to replace hard to find bearings with a common bearing, don't use a hard to find thrust bearing or the whole operation won't matter. Try and find a common bearing with the proper thrust size that could be removed and be used, most machine shops don't have the man power or time to custom machine one off parts. If the thrust bearing could be made relatively quick using an already made piece, they will be more likely to try it, but if they have to source a piece of 4" diameter brass or bronze, forget it.

A piece of 1/4" brass flat stock and a band saw would serve the same purpose to rough out the part, and any so-called "machinist" who can't make a simple thrust washer with a reasonable amount of effort probably doesn't have any business working on an antique engine. Everyone wants a quick, simple, no-brainer fix these days. That's why they demand a "kit" for everything associated with things like IFS front ends, disc brake conversions, etc. I'm firmly convinced that creative thinking and "making things fit" will probably die out entirely once my generation starts looking at the brown side of the grass! Pretty soon, all the stovebolt sixes will be relegated to the scrap heap, and any of the old trucks that survive will be running "belly button" ("Everybody's got one!") LS engines!
Jerry

I can agree the flat stock and saw will work, but the trusted shops in my area are so backed up with work, they are not going to take the time for one off projects. The others are not busy for a reason. Its a four to six week back up at the cylinder head shop and they work 3 shifts and still can't keep up. Block work is a little faster, but not much. Custom crank work, good luck with that!


10 years from now, I doubt anyone will care about gas engines, it just seems to be the way the world is headed

I'm glad I've been accumulating machine tools for the past 30-something years, and acquiring the knowledge of how to use them. My machinist looks back at me from every mirror I pass. The quality control department of the foundry where my son works sends me custom machining projects to do on a regular basis, and never gripes about what I charge.
Jerry

Custom machining is getting scarce these days. My go to shop has tarps over the crank and cam grinding machines and turned me down on replacing the center of a camshaft distributor drive gear replacement some time ago. Crankshaft forgings are cheaper from China that the U.S. electric bill so all type stroker kits are available.

Evan, ask them if they want to sell their cam grinder. I lost out on a nearly brand new one a while back, and I'm still window shopping.
Jerry