I have an engine that I opened up for repairs and it has the Dunn weights welded to the crank shaft. The engine would shake your fillings out running it down the road. Who ever did it looks like they did a nice job, looks to be balanced out well, has the heavy rods? do not know why they would of used them on a later engine, has aluminum pistons that have been balanced also. Has any one had this experiance with the weights?
Untill you check balance,how can you tell?
I have Dunn weights on my '27 which I installed in 1978. NO welding involved but a heck of a lot of careful hand fitting. It is a SMOOTH sweet running car. One of the problems I have noted on some engines I have fixed for others is it is easy to distort the crank (bend it) when putting the weights on.
So first I would check the crank for straight.
Then I would have it checked for cracks (especially around the welds). Or perhaps do this first.
If that all checks out then it needs to be balanced.
If the babbitt is good in the rods and they have shims, then I would just run them.
I sent the crank and flywheel out for spin balancing it and the crank was right there, the fly wheel was out a few grams. I do not know if I want to install another crank with out the Dunn's or not? I sure as heck not going to reassemble it this way with out knowing where the vibration is coming from.
I guess this a case for methodical analysis. To shake as you describe there has to be a cause. I assume the engine shook when reved up but not being driven?
Les you are correct, I have always wondered about trying the Dunn's but now this has changed my mind.
I have Dunn weights in one of my cars. It is really smooth! As Les mentioned it takes a lot of time to fit them to a crank properly.
Joe have you checked compression and ignition? I don't think the Dunn weights would cause vibration, unless perhaps one came loose somehow.
If the car is starter equipped maybe remove the bendix and starter and then carefully inspect the flywheel / magneto to see if anything is loose there?
Joe,A few years ago Trent i think did a study and i think the shape of the crank webs has much to do with the Dunn weights?? Still smooth-Bud.
Joe, From what you have said, I would have a suspicion that there is a possibility that the crankshaft was not ground properly and that the rear flange is not concentric with the third main bearing journal. I worked on a car several years ago that had a similar issue. At certain road speeds, the radiator cap was blurry! The engine had been rebuilt somewhere else a few years prior and had always acted that way. I found the rear crank shaft flange had .012" indicator runout when supported on V blocks at the first & third main.
Many times, the "local engine machine shop people" who grind T cranks, don't do them right. Sometimes they don't know, or don't care that everything has to be set up based on the front gear area, and the outside of the rear flange. I've seen many T cranks come out of shops around the Midwest with up to .005" runout at the front and .015" runout at the rear.
Especially on 1926-1927 EE crankshafts... Now, this may just be "the luck of the draw" for me, but I have noticed that I hardly ever find any cracked 26-27 EE cranks, but they generally seem to have more wear issues. The big wear issue I typically find on the average EE crank is that they are worn more on the third main than anywhere else and the really bad part about that wear area is the wear seems to be quite a bit off center, probably due to imbalance in the flywheel and transmission that it was connected to all its life. It is not uncommon for me to find an EE crank with a rear main journal that is around .010" undersize when measured with a micrometer, but when put on centers, most all the wear is on one side of the journal, not even all the way around. Sometimes, a crank that measures like it would grind fine at -.010" won't clean up all the way round at -.020". I have kind of developed a theory that the EE cranks were more resistant to forming cracks and maybe less prone to breakage, but that they are less resistant to wear.
An original crankshaft that had uneven wear on the third main and that was set up improperly by the person that re-ground the crank can cause the flange to be off center, and cause a pretty severe vibration that is really hard to diagnose unless you know what you are looking for... It's one of the things most people won't suspect because its one of the things the average T hobbyist doesn't check for. Heck, most crank grinding shops don't check 'em before they go out the door... And this is actual experience with 8 different crank grinders I tried before finding one that would do them correctly! I actually almost got kicked out of a place where they machined "race car engines" because they didn't machine a crank per my instructions and I complained about it!
We grind the rods, set the weights, and then grind the mains.
Everything is then straight.
Joe, was the rods balanced? You never said.
We have never had balance problems after done.
Also you can't grind the rods after the weights are on.
So if they ground the crank, and then welded the weights on, I don't think that can be done with out warping the crank.
You said you had it checked for balance.
Is it straight?? I have seen them where the centre main is being pulled .010-.015 off centre. If they were installed after the crank was ground (which is likely), and they didn't worry about making sure they weren't pulling the crank crocked , and then they had it balanced (which it would have been done by supporting it on the front and rear mains). When you bolt it into the block now nothing is right anymore.
Which brings me back to my statement that installing them was a LOT of careful hand fitting. Others may have different experiences
I did not check the rear flange yet to see if it was still in line, As Adam said about grinding the crank true with the flange is how my crank grinder does them but I have not check that yet, Thanks that is where I am looking tonight. Herm the rods and pistons have drill marks from balancing and I put them on a scale that was my first thought, The flywheel has been stripped, just slingers. Thanks for the imput guy's!
Dunn counter weight are bolted on. Even if they were taken off to grind the crank they could be marked to return to the same place.
I see I missed the part about this set being welded on, sorry.
If the problem is not the flange, then here is one more thing that is pretty much a "long shot"
When I CC the heads, I have occasionally found some heads that are way out of being equal. Occasionally the combustion chambers are progressively larger from one end of the head to the other and it can make a noticeable difference in the smoothness of the engine. However, I can't imagine a head being so far out that it would cause an "unusual" vibration.
Also, some really bad engine noises can be frame or body noises too... I know of at least one engine that was pulled & inspected and the bad vibration ended up being a resonating body noise from loose fasteners. The engine in my TT sounds like it is going to come apart at certain speeds. When someone makes a comment about it, I reach over and put my finger on the handle for the cowl vent and the noise disappears...
Bent transmission shaft or bent output assembly?
Well the indicator on the flange did not move .001 so I guess I am heading towards the transmission area, Adam it has a Z head on it. It also has a ball bearing fourth main that was glued in place, I have heard some people complain that it would put to much pressure on the rear main when heated up? I can't answer that one.
I have seen a few failed ball bearing fourth mains... The bearing locks up, the driving plate shaft doesn't seem to have any trouble breaking the locktite bond, and the output shaft spins in the seized up inner bearing race from that point on. The real kicker is that when you find one failed in that manner, you have no idea how long its been that way because there is generally no "symptom" present. I've got a suspicion that there are probably quite a few T hobbyists out there that are happy with their ball bearing fourth mains and they may have failed many many miles ago and there is no symptom and no indication that it has happened... The only way you can tell sometimes is by removing & inspecting the fourth main.
However, unless the inner or outer race broke and fell in along the u-joint, I don't think it could cause a vibration unless the balls ground themselves down, or a couple popped out and it was allowed to off-center itself. Either way, I think you would have had a more catostrophic issue by now if that was the case.
Unless it bent the drive plate shaft off center when it seized up...
Next step would be to look at the run out of the main shaft.
Mount the flywheel/main shaft to the crank, you should have zero run out as low as you can measure on the shaft and at the top. If not the run out will just get worse at the four main.
Next would be to set the brake drum and drive plate over the main shaft and see what you have for run out at the bearing surface of the drive plate (fourth main). Zero run out would be ideal but the fact is you wouldn't see it. There are three bearing that ride on the main shaft, more than likely worn some.
Spin the flywheel and note the run out, now rotate the brake drum 45 degrees and spin the flywheel again noting the run out. Do the same until the brake drum has rotated 360 degrees from the starting point.
I always check run out with the engine nose down. Should have some run out but not more that .004" to .006"
You state a fourth main that was glue on, if this bearing required the drive plate shaft to be turn down in ID, maybe it was not cut on C/L,
Something else that is "way out there" because it is pretty rare: A broken driven gear sleeve (the shaft riveted onto the brake drum). Depending on how it broke could cause a real vibration. And you might have no indication of it being broke until you pull the disc drum...
A driven gear shaft that is in the process of failing (or has failed) sometimes presents its "symptom" as a lack of power, or bogging but only in low and/or reverse, but no apparent issue in high gear, neutral, braking, etc. And might not even make any unusual noise!
Well after tearing everything down and rebalancing and checking tolerances and run outs on all of above,I did not find anything that I thought would of caused this much shake in the engine. I reassembled it except for the glued fourth main which I changed out to babbitt, I fired it back up yesterday and the shake was gone? It had a little gear noise from original lower gear and new aluminum upper gear, I changed that out today with the good old westinghouse fiber one, not liking that thought but it was here and something cheap to try first before taking it back apart for new sets of gears.