I cant wait to find out what caused this. Engine is coming out this afternoon
Too much end play in crankshaft? The rear main can be fixed by adding babbitt or just needs to be re-gaped.
Be sure to check all the clips and brass screws because the scraping could cause them to break off. Looks like either the clearance of the thrust at rear main bearing wore down or that the original setting of the magneto coils was too close to the flywheel. Usually the wear will cause the flywheel to move farther away from the magneto, but I suppose, if you always drive downhill?
No drive up hill so it slides back!
I got the engine ready to come out. Its been a long day. I will hook the lift in and pull it out in the morning.
I took the oil pan off and the gap seemed to come back to where it should be. Why?
I can think of three possibilities. 1. end play in the crankshaft. Try to pry it forward and see if the gap disappears. 2. Bolts holding the flywheel to the crankshaft are loose. 3.The crankcase is bent at the back lifting the rear of the transmission putting a strain on the crankshaft pushing the top of the flywheel closer to the coils. Here too it is opposite of what usually happens. Usually the rear of the transmission will drop.
Let us know what you find. This is interesting.
On my 26 I replaced the non functional magneto and after setting the required gap and putting it together, had scraping sound on turning it over. Fortunately I didn't have it back in the car. Removal of the pan again gave correct clearance It seems the prior owner must have hit something or somehow shoved the wishbone back and bent the pan to put pressure on the lower mag ring when the pan was put in place. This is very possible if it is a 4 dip pan.
I got on the end of the transmission with a bar and could not move at all. Heres my conclusion, Last spring I noted that the front crossmember was broke causing the engine to sag in the front.. After reading Noels post I have to wonder that maybe the oil pan is bent just a little causing the problem as I can't see any other reason for this to happen. There's no crankshaft movement at all. So for right now, I have to get this car back on the road again for a special occasion next month for a family member. Im going to remove the mag for now and run it without the mag. I will find another oil pan for it and reinstall the mag in the future.
The magneto gap should always be set with the engine setting verticle with the transmission on top. This pushes the crankshaft flange against the backside of the 3rd main bearing and eliminates any end play. The magneto gap is then set to 0.025 at the top and 0.030 at the bottom using the magnet with the least clearance to make the adjustment. This insures that the magneto will have the proper clearance and provide for some change in clearance as the rear 4th main wears and the tail shaft drops reducing the magneto clearance at the bottom. Just discovered that neither the MTFCA Motor manual or Transmission manual have any instructions for mounting the transmission or adjusting the magneto. It't too late to blame Bruce so I guess we will have to fix this oversite.
Glen, George King was the last to build my engine, He did a great job and I'm very impressed at his craftsmanship as I look inside the engine at his work.. That was about 1500 to 2000 miles ago. Do you feel the wear in 4th main bearing is at fault? Maybe I should just readjust the mag? The thing that I wondered about is that as soon as I removed the oil pan everything went back into place. I will readjust the mag and reinstall the oil pan just to see what happens. Now the big question, The magnets rubbing on the coil ring scrapped off the coating off the face of the coil ring contacts, But just the contacts. The wrapping is just fine., Will this interfere with its operation?
Will, If your magneto gap is ok with the engine disassembled then your pan is bent. I have never put a pan on my pan straightening table that wasn't bent. Florida is a little too far for me to check your pan but that is a very important part of rebuilding an engine. Ask your rebuilder if he checked the pan. You can't just look at it and say that it looks ok it has to be checked.
There is no coating on the faces of the coil plate or magnets. Would be hard to set gap if there was.
Its most likely the third main. The thrust surface has worn.
Glenn spot on
Mark is spot on too. When a magneto plate is baked after re-winding, the boss around which each coil fits has to be cleaned off back to bare metal. Otherwise it is impossible to set the correct gap.
Hope this helps.
Allan from down under.
Yes there should be no coating on the pole piece, but if there were that would give you more clearance not less.
2000 miles will not wear a rear main thrust, not even 10,000, and more.
It was set wrong, or the thrust surface was uneven, and wore off the small high spots that were the longest. Seen it many times. Wore .008, to .010 thousandths play, and the part line still had .004 to .005 thousandths to go, to touch the complete cap thrust.
I'm sending the oil pan to Gator in Alabama to make sure it's not the pan, If the pan turns out to straight then I'll send the engine out to be re babbitted and aligned. What I don't want to happen is a broken crankshaft because something was out of alignment causing the shaft to run uneven..
Will, What happened to Gator? I can help but Gators closer!
Glen, I had a long talk with Gator today. He made some suggestions that I had not considered. Gator seems like a very nice person, I would love to meet him in person.
I did want to ask Herm a question, If the surface was uneven, Did it true itself and if it's not the oil pan then can I reinstall and reset the mag and run the car?
Yes it would true its self, in time, but it would still be to much end play.
To reset the gap would be fine if you build up the thrust if that was part of it.
The clearance should be not under an honest .003.
Thank you everyone for your help.
One thing to add to this that was told to me by the guy that does my babbitt (really two) the face of the flange that rides on the rear babbitt needs to be as smooth as the journal and over time the flange can get a groove worn in it from the babbitt and give a false reading when checking end thrust. If the surface is ruff, over time it will act like a file.