I've been helping a friend with his Model T engine, Turns out it is a 1921 engine in a 1925 car. The engine is tired and he doesn't want to spent a lot of money on it. The engine ran fine prior to problem that recently appeared. The field coil failed in such a way that the coils came loose on the ring and the magnets tore them to ribbons. Today I found that the Crankshaft end play is nearly 0.040". I thought the end play was to be no greater than about 0.007". Since money is an issue, re-Babbitt is not an option. I seem to remember a thread on the forum where a guy would build up the thrust surface on the rear cap, so that the clearance was improved, without having to re-Babbitt. But I can not remember who could do this. Can anyone help? Thanks Mike
i have built up the thrust flanges using an oxy./actylene torch and babbitt stick ( i made a thin babbitt rod by pouring babbitt onto a plate then shearing it into strips )...with a small torch tip melt filler into the base metal , being careful not to heat too much and have bearing melt away ... then i machined the thrust faces to allow .003/.004" thrust clearance ...not difficult to do , just takes time ...always an optimist gene french
Mike, Ted Aschman published a tip of mine on this subject in one of his "Tinkerin' Tips" compendia.
Briefly, I used a heavy electric soldering iron and a strip of melted babbit to solder additional material to the rear face of the rear main bearing cap. I would caution against using a torch because it is much harder to control the heat.
Then the additional material was hand filed at a slight angle so the cap was wedged between the crankshaft flanges. Once I had a start between the flanges, the cap was held perpendicular to some fine sanding sheet on a glass plate and the cap worked until it fitted.
Hope this helps.
We (Martynn Vowell and I) when working on Derrick Pang's Runabout had the same issue. Replacement caps were out of the question for us at the time. So we got one of these. The vendors were out at the time but one of our member posters said he had a few in his stash and sold us one. Thanks Royce !. worked like a charm and got our clearance to maintain at 25thou. https://www.modeltford.com/item/3030SHIM.aspx
It is possible to buy just the rear main cap that has been repoured from the vendors. The price was about $60. last time I checked.
I added material to the rear of my main cap as stated above using a torch with a small flame went slow then used a file to fit. You are going from .040 to a lot less and anything you do short of melting the babbitt out will improve the workings of the engine even if it's not 100% square to the crank. It was a first time for me and did not want to screw up the babbitt in the cap. Make sure the babbitt is clean before you start. When you are done you will need to reset the magnet to coil gap.
your statement regarding " SMALL" torch tip is important ...i used a jewelers torch not a rosebud tip ...also used a short piece of 1 1/4" diameter steel stock as a core to act as a heat sink and hold the babbitt inplace in case i got too hot ...the oxy./actylene torch allows a quick , local heating so that you can puddle the babbitt filler ...clean the surface with sandpaper and fill in excess to allow re-fitting ...been done before with success...always an optimist...gene french
Mike---if this is above and I missed it I apologize. If you are not running a Mag ring in it you don't need to worry about the excessive end play. Run the tired old gal the way she is.. 040 won't hurt anything.
"If you are not running a Mag ring in it you don't need to worry about the excessive end play."
I agree with the above statement but will add this. Given that the timing gears are helical, .040 fore & aft movement of the crank will result in some fairly "variable" camshaft/valve timing. Not saying it won't run that way, just pointing out the effects of excessive end play. If he's running a distributor, it will also effect spark timing, since that's a function of camshaft timing as well.
Jerry-I agree with you. But chances are there are that engine is so out of spec. that will be the least of its problems. And I will wager a (very) small sum of money that it will run amazingly well.
Gene, Mark, the small torch is great but even though I have one I just use one of my old copper irons and it does a great job. For some one who might not have a torch these (irons) can be picked up at a flea markets lots of times for a couple bucks, also good for soldering gas tank pin holes. KGB
I used one of those bronze shims behind the crank pulley for two years before I tore the engine down and rebuilt it. It enabled me to run on mag but that does not matter for you because the mag ring is toast anyway but it might help if the timing issue is a problem.
Even if you built up the main cap, or even bought a rebabbitted one and sized it, at least half of the trouble is still in the crankshaft itself. The thrust faces of the crankshaft also wear. The wear forms grooves adjacent to either end of the main journal. Unless you remove those grooves, even a perfectly sized main cap will do you no good, as the high, unworn edges of the groove will not allow the main cap to pass in order to install it. Chances are, after lots of work, it will only be marginally better.
I would leave it as-is until his finances allow for a proper rebuild.
Mark G. - Hmmm,....I guess I don't see why merely replacing worn away thrust surface by adding material to the thrust face of the rear main would necessitate "resetting the magnet-to-coil gap." Seems like that gap would just be restored to what it was before the thrust surface wore away,.....???
I'd be willing to bet that Val Soupios did not need to "reset the magnet-to-coil gap" when he successfully used the bronze shim behind the crank pulley to decrease crankshaft end play!
Yeah, but! A new bearing cap will have Babbitt on both the front and back, PERHAPS moving the c/s flange to the rear.
Also, who makes those bronze thrust bearings that Bolt to the timing Gear bolts? A number of years ago, I sold one of those to someone that said they were going to reproduce them. I forget if it was eBay, but could have been.
Gee.... quite a bit of discussion. Yes the magneto will be used. I think what we have decided is to have the main cap re babbitted, size it to the crank and hope for the best. Let you know how this turns out. Mike
Harold you are right about that but I was a bit concerned that the shim might bring it too far forward and cause the magnets to hit the coil ring. that did not happen fortunately and thinking it through it would seem to be unlikely to occur since the wear should be in the opposite direction increasing the gap not decreasing it.
I got one from Langs and bought a couple of them because I didn't know how long they would last. Turns out they hold up pretty well and can be adjusted forward a bit more as they wear.
Check out this articel.
Excessive Crankshaft Endplay repair