Engine Knocking

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Model T Ford Forum: Forum 2012: Engine Knocking
Top of pagePrevious messageNext messageBottom of page Link to this message  By Joe on Sunday, July 01, 2012 - 01:05 am:

I dont know the history of My 22 T other than it sat for almost twenty years before I got it. Engine runs fine fully retarded on start up, once it starts and and I advance it I get a very slight knock not bad..As I drive and decelerate it starts knocking loud...what the heck is it? other posts blame a poor rebuild, wrist pins etc..Is it me not doing something right or is something in need of repair?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Sunday, July 01, 2012 - 01:18 am:

likely to be a rod knock, prolly shouldnt drive it like that. if you run the engine up till you can kinda hear the knock, then ground out each plug, when you ground out the cyl. thats knocking the sound will change.

in the Model T Ford manual it describes how you can take up the bearings.

its also possible that it could be a main knock, its hard to diagnose over the computer, acctually as i remember in the manual it describes the different sounds that problems will cause.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Sunday, July 01, 2012 - 02:14 am:

With the engine running at a speed the knock is evident short each spark plug using an insulated screwdriver.
If the knock quits you have found the problem....... :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Garrison on Sunday, July 01, 2012 - 02:29 am:

Joe, Curious that I'm going to pull the inspection pan off the bottom of my oil pan in the morning and start pulling rod caps to pull some shims out. I bought some plastigage tonight to help me get the right clearances. My engine started knocking just as you described toward the end of the last tour I was on. I doubt if you just started hearing the knock that you'll have too much damage. Actually I doubt you've damaged anything. I'll let you know how my project goes by tomorrow afternoon. I want to get it done because we're going to have a tour around Central MN on Wednesday and I want my running good. If you get into your engine and find out all the shims are out from between the rods and the rod caps go ahead and put the cap in a vice and file the caps down nice and flat and work on it till you get about .002 clearance and your knock should disappear. Normally if the motor knocks when there's no load on it you'll find it's a piston rod. A main bearing will knock too but it'll usually knock with a lot deeper thud and it'll knock with or without the load. A good way to check it is with a sawed off broom handle used like a stethoscope. Just put one end against the block in the area of the mains and put the other end up to your ear and listen. The culprit will knock louder when you get near it. Or if your wife's a nurse, steel her stethoscope and use it the same way. Good luck Joe and have a safe and happy 4th of Jurly.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan B on Sunday, July 01, 2012 - 06:39 am:

I'm very interested in how both you and Joe make out and your procedure. I too have a knock under light or no load. I've been driving it like that for about two years, and before I got it, it had sat for over 50 years. I wouldn't be suprised if it was knocking then too.

Anyways, would like to fix this so it doesn't sound like my engine is about to fly apart!

Thanks,
Dan


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joe on Sunday, July 01, 2012 - 09:25 am:

Thanks for everyone's help, like I said it's starts fine fully retarded and even on acceleration to find the best mixture no knock only on the road on deceleration and if If I advance the spark on warm up it knocks. I could run the car fully retarded and no knock but I chance overheating. I typically leave the spark lever halfway on the quadrant after warm up..My driving is all around town so lots of stop and go. would a combination of wrong fuel mixture and wrong spark advance cause this ? I'm going to short out each plug later on and see what happens.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joe on Sunday, July 01, 2012 - 09:29 am:

Dumb question, If I do find that I need a shim how do I know how thick ? do I put a plastigauge in and retighten it? or file the cap sides down? when would I do one over the other?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Sunday, July 01, 2012 - 11:54 am:

If it knocks on deceleration, it's a loose rod.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, July 01, 2012 - 12:05 pm:

Regarding Plastigage it can give you misleading information on a used engine because you are measuring clearance only in one small spot. The nature of rod wear is not typically even wear around the circumference and width of the rod. Rather, the wear will be egg shaped. Also, the crankshaft does not wear evenly. So measuring with plastigage is in my view just a waste of time. I don't think it is useful except on new rods with a freshly ground crankshaft.

To diagnose which rod is bad simply adjust the timing with the engine running to make the knocking noise constant. Then short out each plug to determine which cylinder is at fault 9or cylinders). I take the coil box lid off and hold the points open, it is easier than using a screwdriver to short the plug wires to a head bolt.

Once you have determined which cylinder is at fault, remove the pan access cover and then remove shims from the offending rod(s) until the rod cannot be moved side to side by hand. When properly adjusted the bad rod can be moved side to side with a tap from a small ball peen hammer. The engine will be able to turn with the hand crank.

Warning, the above applies only to rods being adjusted. Rods that are in service but not knocking will move side to side with finger pressure.

When you start the engine it will immediately wear in the babbitt to achieve the proper clearance. There is no reason to take it apart and measure with plastigage, just go driving and enjoy your T.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joe on Sunday, July 01, 2012 - 01:44 pm:

well I ran the T at a medium idle the the spark advance in the middle quadrant and got the knock. I grounded each plug and heard the knock go away when I grounded the 2,3,4 plugs some more than others. Does this mean the caps on the rods are worn and need shims? or filing down the caps ? how should I proceed?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, July 01, 2012 - 05:03 pm:

You remove shims to tighten the rods. Proceed to remove the lower pan cover and then adjust 2,3and 4 if they have shims that can be removed. You want to remove one shim at a time, then reinstall the rod cap nuts to see what progress you have made.

Where do you live Joe? Perhaps there is someone local to you that can help. It's not rocket surgery but it can be easier if someone who has done it before shows you how easy it is.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Sunday, July 01, 2012 - 05:33 pm:

I would proceed by adjusting the shims in the connecting rods. Tighten until it becomes hard to turn with the crank, then add one layer of shim. It should turn easily. Loosen the nuts after adjustment. Do same with each rod. After you get them all adjusted, torque the nuts and install the cotters. Now put the inspection plate on and add enough oil to bring it up to the top petcock. Try it out. Don't over rev the engine until it has a few hundred miles on it.

The mains are harder to adjust, because you can't get to cap off the front one without pulling the engine and the rear is very hard to remove on a 4 dip crankcase and impossible on a 5 dip crankcase. The center is easy to adjust, but run the chance of bending the crankshaft. It is better to leave the center one loose unless you can adjust all 3 at the same time and use a straight edge to be sure they are all in alignment. The center main tends to wear at the top instead of the bottom, because of the weight of the transmission. When you adjust the mains, turn the block upside down and use prussian blue with the caps off. All 3 mains should show good contact with the block. It is important to get the 4th main in alignment at the rear of the transmission to support that weight properly. This can be done by turning the engine nose down with the crankcase and hogs head in place. Put in the two bottom bolts into the crankcase loosely. The 4th main should slide back and forth easily. If it doesn't, the crankcase could be bent and needs to be straightened on a jig. All this is done with the engine out of the car. Likely someone in the local club has the jig, and a stand to support the engine in the various positions. Or they can suggest someone who can do it.

Anyway, first things first. Start with adjusting the rods. With luck, you won't need to adjust the mains.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug Money - Braidwood, IL on Sunday, July 01, 2012 - 06:00 pm:

The shims are laminated, that means a bunch in a stack that looks like one. You can peel off one leaf of the stack. That equals one shim.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Garrison on Sunday, July 01, 2012 - 07:57 pm:

Joe. Plastigage has always worked for me whether a new crankshaft or used crankshaft. I'll be using it on my T and I'll bet it works very well. A word of warning. If you're only interested in working on the lower end of your engine and don't care to end up pulling the head do not I repeat do not push the piston up to the top of it's travel in the cylinder. The piston is able to go up high enough in the combustion chamber for the top ring to go out of the block and become a locking ring that can only be put back into the block by taking the head off and using a ring compressor. Although it does give a person a chance to clean the carbon out of his engine and do some cleaning and flushing of the water chambers in the block.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan B on Sunday, July 01, 2012 - 09:16 pm:

What torque value is used on the connecting rod cap nuts?


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Monday, July 02, 2012 - 12:45 am:

Mike, good point. Also, don't pull the rod too far down in the bore, the bottom ring will do the same thing. Don't ask how I know this! Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joe on Monday, July 02, 2012 - 01:33 am:

Thanks for everyones advice, Im going to open her up this week.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, July 02, 2012 - 06:27 am:

Ford didn't specify a torque value for any fastener on the Model T, and did not use torque wrenches in the factory or dealerships during the T era.

Torque on the rod nuts needs to be snug with a standard 3/8" drive ratchet handle, then advance to the next castellation where a cotter pin can be inserted. Do not use all the strength you have, the rods can easily be twisted by undue amounts of force.

If I was going to recommend using a torque wrench I would say no more than 25 ft - lbs, then advance to the next castellation with a cotter pin hole that aligns.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren (Australia) on Monday, July 02, 2012 - 06:33 am:

How in gods name could you twist a rod Royce by doing up a con rod bolt on a shaft???


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, July 02, 2012 - 06:41 am:

You can twist them by over torqueing the wrist pin bolt with the rod held in a vice Kerry. Another place you don't need a torque wrench, just good technique! Sorry to confuse the issue.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Monday, July 02, 2012 - 12:07 pm:

Royce, if you want good technique, you should never put a rod in a vice. You should put the crank end over a piece of shaft about .010 or so smaller then the hole. The shaft should be polished, so it won't mark the babbitt.

Model T rod bolts should be torqued to 30 foot pounds, and then pull to the next key hole if they don't line up.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, July 02, 2012 - 03:09 pm:

This is how I tighten the wrist pin bolt in the rod. I use a long phillips screwdriver through the wrist pin to keep the piston and rod from spinning then use a wrench to tighten the bolt. Not too tight. Then put in the cotter pin. That way, the rod will not be bent. If you attempt to tighten it by clamping the rod in a vise, you are very likely to twist the rod. I don't think you can twist the rod by tightening the two bolts on the large end, however, you can strip the threads or stretch the bolts if you over tighten them. 25-30 ft lbs is enough.

Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Monday, July 02, 2012 - 07:47 pm:

I don't think you can twist the rod by tightening the two bolts on the large end.(end Quote)

Norman, if you ever get a chance to check alignment on a 100,0000 rods, you won't agree with your own statement!

Some rods you can throw out of alignment, with only a hand on each end, and twist, and or bend.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Garrison on Monday, July 02, 2012 - 09:35 pm:

Wow, everybody's got there own way of adjusting the clearances on the rods. And torquing them or at any rate tightening the rod bolts. But here's something to think about. In the late 1920's and through the thirties guys use to pull their model t's into camps at night on their way between jobs and adjust the rod clearances with a Ford wrench and a jack knife to scrape the babbitt with. They'd shim with whatever they could find. These are model t's not Swiss watches. That's why everyone's technique works. That being said, I will say that tightening rods by feel is an ok way of doing it as long as you know your babbitt isn't high on one side and not the other. And that's why plastigage works when you lay it across the cap. So today while I was tightening my rods, I used the plastigage and then checked it by moving it side to side. When the plastigage was right and The feel was good I'd grab the crank and give it a twist. Though it's a little tighter now I did find some before tightening that checked up to .007" with the plastigage. No wonder the thing was knocking. So now I've got one more rod to do and then I've got an ice cold michelob in the ice box. God bless all you guys. Bye -Mike


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, July 02, 2012 - 10:16 pm:

Right Kohnke, I use a long drift punch in the vice stuck in the wrist pin. I don't clamp the rod in the vice either.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer on Tuesday, July 03, 2012 - 02:36 am:

I use this one :
152R
153R
Toon


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Tuesday, July 03, 2012 - 06:55 am:

That is a nice way to do it Anthonie Boer! I may hve to make some pins like that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Richard Bennett on Tuesday, July 03, 2012 - 07:02 am:

Royce, I do mine the same way as Anthonie. If you are not ready to make your own pins, you can use two sockets which have clearance in the piston pin bore.

Just quick hint.

Allan from down under


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Tuesday, July 03, 2012 - 10:12 am:

I suppose that if you were to remove too many shims which would leave a gap between the rod and the cap and then torque down on the bolts it could distort the rod, but the normal way is to just remove the number of shims needed to snug the rod bearing while still being able to turn the crankshaft. So maybe Kohnke is right if you were to do it wrong you could distort the rod!
Norm


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