Knock at high speed only?

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Model T Ford Forum: Forum 2016: Knock at high speed only?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas - Centerville, Iowa on Saturday, March 12, 2016 - 07:51 pm:

Developed a knock in my engine. Dropped the pan, and adjusted each rod. #1 removed one shim each side, #2 one shim on one side, two shims on the other, #3 2 shims on side, and 3 shims on the other, #4 2 shims each side. Started it up and it sounded quiet both low speed and at high speed.

Took it out for a drive. No knock, until I got up to about 40mph. Now I don't generally run that fast, 30 to 35 mph is good for me, but I wanted to be sure the knock was gone.

Slow back down to 30 to 35 and the knock is gone. I have a Z head and aluminum pistons, rebuilt the engine and transmission in 2006. Probably got about 12 to 15,000 miles on the engine.

Could I have something in the transmission? No knock, unless I am going down the road. Changing spark advance makes no difference in noise.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Saturday, March 12, 2016 - 08:26 pm:

I've always blamed such a knock on the center main.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Saturday, March 12, 2016 - 08:46 pm:

I'm with Jerry, probably centre main


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed Baudoux Grayling Michigan on Saturday, March 12, 2016 - 08:50 pm:

I had a similar knock a few years ago on a '27 Tudor. The previous owner was an experience T guy and mechanic. He had gone to great lengths to solve it, including a custom rear main cap to limit crank end play. It turned out to be a loose set screw on the inner clutch drum, allowing the drum to slop back and forth on the transmission shaft. Tightened and safety wired, it went many happy miles. I ran it back and forth between Grayling and Traverse City Michigan a few times, with both levers all the way down. An hour and a half each way. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas - Centerville, Iowa on Sunday, March 13, 2016 - 09:21 am:

Thanks for all your suggestions. Sounds like I will have to pull the engine to check the main bearings.

I have never attempted any transmission work, other than to adjust the bands. I looked in my books and it looks like I would have to disassemble the transmission to check that set screw on the inner clutch drum.

Do you think that if I pulled the floor boards out and drove the car, that a mechanics stethoscope would isolate the problem? Where would a center bearing noise be the loudest?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Wrenn-Monroeville OH on Sunday, March 13, 2016 - 09:47 am:

I'm no expert by any means, but I would think to check for the center bearing noise it would be best to put your stethoscope right between #2-#3 where the bearing is located. I would doubt removing the floor boards and driving would help much, what with all the other noises, rattles etc. going on at 35 mph. JMHO. Others may disagree.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Duey_C on Sunday, March 13, 2016 - 07:26 pm:

Are there any (nowadays) "cheat tricks" to check main bearings with the engine in the car? Especially the third main.
How'd they do it in the shops back then? I need to check my bearings too....
Michael, IF it turns out you NEED to check that setscrew on the inner drum, it CAN be done with the engine in the car. I tightened mine up this past summer (it was loose) and put in the missing cotter key when I installed a clutch pack of turbo 400 disks I had modded years ago. I should have safety wired the screw.
Wow do I like that new main clutch.
Keep us updated would you? :-)
WAIT! Guys, what is the difference on Michael's engine between running the engine fast in the driveway verses running it fast on the road?
I've been pondering this all day and does it really have to do with the engagment/disengagement of the high speed clutch?
Does Michael have a "whip" going on at the front of the drive shaft?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas - Centerville, Iowa on Sunday, March 13, 2016 - 09:40 pm:

Duey, my thoughts exactly. I know different forces come in to play, when the vehicle is moving and the transmission is in gear. But, would a worn center main not make noise without a load, but would with a load? How to check the set screw on the clutch drum in the car would be nice to know if someone can describe the procedure for me. Thanks! Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joseph A. Stearns on Sunday, March 13, 2016 - 10:46 pm:

I had to check a center main for play a while back. This is what I did after first recording the clearance between the bearing cap and the crankshaft journal using Plastigage

After removing the inspection cover and removing the center main cap I set up a dial indicator on the center journal with the magnetic base mounted to the block. I then pushed upward on the crankshaft using a bottle jack and observed the movement of the indicator gage. This movement was the clearance between the journal and the upper bearing in the block. I think much over .003 TOTAL clearance including the cap clearance could possibly produce a knock under certain conditions.

Hope this helps to identify your problem. Joe


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, March 13, 2016 - 10:49 pm:

Could be piston slap.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les VonNordheim on Sunday, March 13, 2016 - 10:56 pm:

Michael,
An old school method for checking a loose center main is loading the engine against a curb. If it knocks under load.....chances are the center main is too loose. A loose rod will be quitter when under load.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Duey_C on Sunday, March 13, 2016 - 11:07 pm:

Oh. The load verses no load......... I never thunk that out. Good notion. All I thought was mass rotating and the clutch spring....
That setscrew. Leave that as your last resort, hopefully you'll find the trouble in the bearings. I KNOW mine need to be re-set.
IF you need to in the end, I'll help.
The abridged version.
This is SOOO wrong here! Sorry guys. Last resort! Or a couple afternoons.
Pull the fan off (don't ask how I know-no fins/round tubes wrecked in my research), pull a bunch of block to pan bolts, leave some front ones in but loose, pull the rear axle back after pulling the hogshead off, remove the wire and bolts for the "clutch cover", slide it back until it hits the pan, Thread a coated (in my case a dog) cable around the transmission shaft in between the clutch cover and the rest of the transmission, lift and separate the "cover" from the transmission and set it aside. Set the engine and trans back down and then you can get at that setscrew. Sooo wrong but it works. You can also check your clutch disks at this time.
I sit here and laugh out loud about what I just typed but it did work for me and right now, my life with my T is carrying on like when I started in the 90's. I had nothing but will, few parts and some steel. For me, the next time that engine is away from that frame, several thousand dollars will be thrown at it for my life's enjoyment/endurance. :-) As long as I can crank it! :-) True.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Duey_C on Sunday, March 13, 2016 - 11:13 pm:

What Les says is right about an engine's rod bearings.
Railroad steam engines: They seemed to be quiet under load but when the throttle is closed, then the clunking/clanging loose rods happens, mentioned in songs!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Duey_C on Sunday, March 13, 2016 - 11:17 pm:

Joe is correct also. I'd say.
Royce, do tell more would you?
3 posts in a row? Go to bed Du.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Monday, March 14, 2016 - 02:26 am:

Duey,
Ah yes, the clanking of the rods, part of the mystique of the steam locomotive. Of course, the sound should be just so, or it indicates other problems!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Thomas - Centerville, Iowa on Monday, March 14, 2016 - 09:15 pm:

I will pull the engine in the next couple of days and let you folks know what I found. Thanks for all your suggestions and knowledge. Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, March 14, 2016 - 10:18 pm:

The cylinders wear and the then the Pistons no longer run true, creating a noise that can sound like a bearing. You can measure the Pistons and the bore to see if that is the problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Coiro on Tuesday, March 15, 2016 - 01:38 am:

Mine does that too, but only if the timing is sufficiently advanced. _I'm told that high-compression heads (such as mine) require less advanced timing. _So maybe retard the timing a bit. _If it works, great; if not, at least it didn't cost anything.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd, ............Red Deer, Alberta on Tuesday, March 15, 2016 - 10:32 am:

He already tried that: "Changing spark advance makes no difference in noise."


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, March 15, 2016 - 10:56 am:

I've experienced the rattle of a loose centre main, and it behaved just as Michael describes - only noticeable at higher speeds. It can be fixed with the engine in the car - but there's always a risk doing that since the centre main has a tendency to wear upwards, and by pulling shims and tighten the cap you may introduce a slight bend in the crank that shortens the time until you get that dreaded fatigue break.. :-(

But for just a few more miles more this season - go for it and make a proper check of the babbitt straightness during off season :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Tuesday, March 15, 2016 - 11:39 am:

Roger,

For the reasons you stated, I never take up the center main till snug, but just enough to reduce the clearance. And, I only do it once.


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