Other causes for a knock

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Model T Ford Forum: Forum 2015: Other causes for a knock
Top of pagePrevious messageNext messageBottom of page Link to this message  By Nathan Fahrni on Monday, April 27, 2015 - 08:56 pm:

I have a horrible knock in my engine that I cannot track down. It knocks while under power with the throttle 1/3 open or more in high gear. The more load there is on the engine the greater the knock is. It will also knock if you wind the engine up high enough in low gear as well. So-far I have checked the following:

- The front crank pulley was sloppy and the front of the crank was wore so I installed an aluminum adjustable one from the vendors. I re-bushed the fan pulley while I was at it. Still knocked.

- Although my better judgement told me that it wasn't a rod knock since it would not knock when the engine was "free wheeling" I checked and tightened them to .001-.0015 with plastic gage. Hoping that it wasn't a main knock. Still knocked.

-Realized that I was losing engine oil to the rear end due to an aftermarket 4th main. Had a custom poured 4th main poured shipped in (See other thread "Fourth Main Woes"), pulled the rear end and installed it. Filled it back up with oil. Didn't really expect any change in the knocking situation, but now it holds oil better.

-Finally decided that I needed to check the mains,(SIGH!) Tried to do I from the 4-dip inspection plate until I dropped a shim in the drink and decided it would be much quicker to just pull the engine (even bigger SIGH! GROAN!) Took 1 shim from one side on each main taking them to each to .001-.0015 with plastic gage. Put it all back together expecting everything to be hunky-dory and it still knocks!!! I know that the rods and mains are good and tight as you could practically lift the front of the truck up with the hand crank, but the starter could spin it over.

Sometimes it sounds like it is going to let loose. Not sure where else to check. I was going to pull the generator off and block off the hole tomorrow thinking it is a generator bearing/generator gear-to-timing gear issue. Could it possibly have anything to do with transmission triple gears? If so I wouldn't think it would knock in low AND high as in one instance the gears are meshing and rotating and the other they are locked down. Short of removing the bolts from the engine and replacing them a zipper what else is there to check?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, April 27, 2015 - 09:12 pm:

End play in the camshaft can make a real noise. The trick is it will not always be there. Pull the timer and see how much end play you have


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Monday, April 27, 2015 - 09:13 pm:

Did you check the wrist pins? Piston hitting the head?


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Monday, April 27, 2015 - 09:53 pm:

twisted rod??


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Monday, April 27, 2015 - 10:00 pm:

I guess I'd be a little suspicious of wrist pins.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, April 27, 2015 - 10:02 pm:

How much clearance do you have between the pistons and the cylinders? If you can rock them back and forth when the head is off, they are too loose. You can sometimes help this condition by knurling the pistons to tighten them and help them to hold oil. Usual fix is to re-bore with oversize pistons or sleeve back to standard.

Other causes would be bent rods causing rod to move forward and backward as the piston goes up and down. However this would be more noticeable at slow speeds. The loose piston noise will decrease with retarding the spark and also decrease as the engine gets hot.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Barrett in Auburn Ca. on Monday, April 27, 2015 - 10:10 pm:

Heavy knocks that get worse under load usually mean main bearing or crankshaft problems. I have seen two engines knock due to loose transmission bolts, but I assume you would have caught that when you had the rear main cap off. Check to see if one or more of the rod small ends are touching the piston boss, an indication of a bent or offset rod.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nathan Fahrni on Tuesday, April 28, 2015 - 06:12 am:

I didn't mention that the engine has been "rebuilt." I purchased the engine from an former club member who had the engine "professionally" machined, and all babbit work done. Unfortunately the rebuild took place probably 10 years ago and the rebuilder is no longer in business. I just got my truck completed and can't seem to get rid of this noise. Erik hit the nail on the head with the description of the noise. It is a heavy, thumping knock which is why I thought it was a main. The transmission bolts are tight and wired as I just had the transmission off while the engine was out. How would one check for twisted rods? With the inspection cover off have someone crank it over and see if it slides front to rear? How would you check wrist pins?

Les, There is a noticeable amount of end-play in the camshaft. My father mentioned that may be the culprit also. What kind of noise would that cause and is it only when the engine speeds up/down?

Does anybody think it could be transmission related? Triple gear? triple gear pin in flywheel?
Some more info: aluminum timing gear, solid lifters, aluminum pistons, rebabbited, counterbalanced crank unfortunately, regrind cam.

Thanks to all in advance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis on Tuesday, April 28, 2015 - 06:24 am:

Triple gears are not moving in high gear so it's not them. Camshaft end play is also a source of knocking.
What head are you using on the engine?


Top of pagePrevious messageNext messageBottom of page Link to this message  By James Michael Rogers on Tuesday, April 28, 2015 - 06:52 am:

Nathan, to check for twisted or bent rods, you can remove the inspection pan and have someone turn the engine with the hand crank while you watch the rods one at a time. Bad rods will move front to rear at the wrist pins significantly.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Tuesday, April 28, 2015 - 06:55 am:

Nathan,
Did you check the rod bolts clearing the camshaft??

Andre
Belgium


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed Baudoux Grayling Michigan on Tuesday, April 28, 2015 - 07:16 am:

I had a similar knock in a '27 Tudor. The previous owner was an experienced T mechanic. He had done all sorts of things to solve it. Went all through the engine bearings. It turned out the set screw was loose in the drive hub, near the rear of the transmission.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Marshall V. Daut on Tuesday, April 28, 2015 - 10:32 am:

By "counterbalanced crank", do you mean bolt-on weights? If so, I installed such an animal in a rebuilt engine in 1982 and there was a knock from Day One. Turned out it was the weights that were hitting inside the pan. It was actually the rear weight that was hitting. These were removed and the knock went away. 'Must have been a Taiwanese product that were too big.
Did you see any signs of scraping or hitting inside the oil pan where the add-on weights could have been hitting? Any unexplained shiny spots on the weights or the pan?
Marshall


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Barrett in Auburn Ca. on Tuesday, April 28, 2015 - 11:18 am:

Crankshaft end play will usually not knock in neutral or low because the clutch spring is hauling back on the crank to release the clutch.
Look closely at the horseshoes that the inspection cover bolts screw into. Counterbalanced cranks are known to hit them.
Is it a longer stroke crank? These can cause clearance issues in lots of places. If the block or head has been milled to excess, pistons can strike the head. Look for shiny spots on the pistons.
Just a couple ideas.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Anderson on Tuesday, April 28, 2015 - 05:19 pm:

Check your timing. I had a knock that I couldn't track down. My bearings checked out good and I put a nylon timing gear on. Was running premium with high compression pistons. Switched to regular and saw a definite link between the knock and spark advance position. I was running too far advanced! Backed off and no knock (piston slap). Dosn't overheat anymore either.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Tuesday, April 28, 2015 - 05:39 pm:

Nathan
Camshaft end play can be quite loud, but it usually is just a bit intermittent. You can buy a "repair kit" that can be installed by removing the front cover. I have not actually installed one of these but have read the instructions
How much end play do you have? 1/16" could be enough!
If you hadn't checked the mains I would be thinking centre main, wear in the top(block) from your ball cap problem


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nathan Fahrni on Tuesday, April 28, 2015 - 09:07 pm:

Marshall,
Yes it has the bolt-on weights, but I saw no interference issues when the engine was out and tore down last week. It looked as though someone attached the counter balances and then turned them because there was some high spots that were turned down and holes drilled to get it all in balance.
Les,
I have been suspect of the camshaft end play, so this after noon I removed the generator and blocked the hole, and also pulled the fan belt. I noticed that without the draw of the generator the noise seemed greater and could now be heard near idle in the garage. I did the 'ol screwdriver to the ear trick all over the engine and fund that when touching each of the dips in the 4-dip pan #1 was loudest and got quieter going back to #4. The timing cover was loud as well. It was only then that I noticed the timer was moving! It was kind of oscillating and jiggling around. The finger tension thing that holds the timer on was good and tight. So I pulled the timer and tried to pull the camshaft out by prying between the timer nut and the timing cover. Measuring with one of those small steel rulers I have approximately 3/32" end play! Yikes! That might explain my intermittent high speed miss as well. I think I'll start there and since that will be a easy (hopefully) fix, by just removing the radiator and timing cover and installing one of those kits. If that doesn't help I'll probably drop the inspection cover and/or head and check for the bent rod and piston interference/slap.
Thanks to all for the insight. The combined experience of all the Model T Club members can solve any T trouble.
I'll keep everyone posted
Thanks,
-Nathan


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Wednesday, April 29, 2015 - 10:42 am:

A "rebuilt" engine that does this would make me doubt everything about this motor. However, take one thing at a time and don't worry about the rest now.

What type of timing gear does it have, (brass, aluminum, fiber, etc.)?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, April 29, 2015 - 11:28 am:

Jerry
The engine I observed the cam end play issue on was "fresh"
The problem seems to be between some of the cam bearings available and the camshaft. My observation is that there are MANY ways for things to go wrong, and it is very easy to get caught by one of those


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Thursday, April 30, 2015 - 02:16 am:

I had a similar problem to Les. The new centre cam bearing was a good fit on the camshaft, but was .010" undersize in the block. I had had noisy cam bearings before, usually the front one, so this one was detected before the motor was fully assembled.

The front bearing can be checked in place by removing the timer roller and then levering the cam snout up and down with a block of wood for a fulcrum.

Hope this helps.

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By samuel pine on Thursday, April 30, 2015 - 03:27 am:

I find excessive cam clearance whether used or
new bearings is caused by the assembler failed
to check the bearing lock bolt which can amount
to even .020 plus specified clearance can go
up to 24 thousands. This small little detail seems
to be always overlooked. Correction can be done
pretty simple, remove the first bolt now find
something like a drift punch to find the diameter
of the bearing lock hole, measure that and measure
the lock bolt. I bet you will find the lock
bolt diameter is a lot smaller than the hole. That
causes the bearing to rock back & forth plus the
gear train in a housing, is like a big echo chamber. Then do the same on the center lock bolt.
To correct braze up the bolt or machine a new
one. Any high school can do that (if there any
more school shops???)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Thursday, April 30, 2015 - 04:46 am:

Samuel, I have to disagree with your "fix". The "lock bolt" is simply a retainer. If it was meant as a locker, it would resemble a grub screw. By modifying the retainer so that a load can be applied to the bearing shell is ignoring the fact that pushing aside the shell in the bore in the block will cause the camshaft to be mis-aligned with the rear bush. When the bore of the bearing is worn, pressure on the bearing shell will not fix that wear. If what you suggest stops the noise, then there must be a sideways load applied to the bearings/camshaft which can only mean something is under tension and out of alignment.

I could be wrong, again.

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Thursday, April 30, 2015 - 10:06 am:

Allan
I believe that Samual is suggesting to make it bigger in diameter so it is a close fit diametrically


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Thursday, April 30, 2015 - 10:59 am:

I had the same problem as Samuel and made a shim which I put in the hole in the bearing and tightened the lock bolt. This has lasted for over 10 years so far and is a lot easier than pulling out the camshaft and replacing the bearings. If I ever pull the engine to rebuild, I will replace the bearings and if worn, the camshaft too. For the speeds we drive and the miles we put on our cars, Samual's fix is a good one.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nathan Fahrni on Thursday, April 30, 2015 - 08:46 pm:

The issue that Samuel is referring to would allow the cam bearings to rotate back and forth a little I take it? What kind of noise would that make? Is there anything else on the cam bearings to keep them from rotating other than the lock bolt? I ordered the cam shim kit yesterday at lunch along with gaskets and other things, and it arrived today before 11:00 AM! So this evening I pulled the radiator, timing cover, and installed the shims as the instructions said. By the way Jerry, it has an aluminum timing gear. I now only have .015" of end-play compared to the .094" I had before. I then assembled everything back together except for the radiator and very-very briefly started the engine to listen. I think the noise is still there at least somewhat. I think tomorrow night I'll try and run some coolant thru the block and run it a little longer to listen better, and then check the cam lock bolts. I guess it that doesn't work it's back to checking for a bent rod??
Thank you all for your suggestions and patience with me and this elusive noise.
-Nathan


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Thursday, April 30, 2015 - 08:55 pm:

Nathan
I have to ask, how much backlash in the gears?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adam Doleshal on Friday, May 01, 2015 - 10:27 am:

When a crankshaft breaks between #1 & #2 main, it usually bends the cam a little... And most rebuilders won't catch it...

I worked on a motor a couple months ago that had been built by a "professional re-builder" with decades of experience working on T's & A's. It had a cam with the "long style" front journal, but a "short" front bearing!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nathan Fahrni on Friday, May 01, 2015 - 08:00 pm:

Well, I think I can finally say I know what the real problem is. I have .007" of gear lash between the large and small timing gear and .010" side play in the cam at the gear. Although the side play is excessive I'm fairly certain that a majority of the noise comes from excessive lash. I can rotate the cam gear back and forth and hear the exact aluminum-y ting-ting-ting noise as when it is running. I have learned my lesson the hard way that everyone has a different definition for "rebuilt" When I bought the engine I thought I had a good easy start to building a T. Here's some of the glaring issues I fixed with the engine:
-Installed stock internal magneto (there wasn't any slingers on the flywheel to begin with)
-Installed aftermarket adjustable aluminum front crank pulley because the original was sloppy due to worn front section of crankshaft
-Took up rods
-Took up mains
-Installed a custom poured fourth main due to a turned o.d. on the output shaft.
-Soon will fix the timing gear/cam problem.

Thanks to all, and happy T-ing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Friday, May 01, 2015 - 08:43 pm:

Nathan
Well I'm sorry to hear that you have had so many problems!!
The "good news " is that you know a LOT more about your car!!
Also you know that you can drive it with more confidence


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