Rod Knock - seeking advice

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration
Model T Ford Forum: Forum 2016: Rod Knock - seeking advice
Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Adey on Wednesday, October 05, 2016 - 06:04 pm:

Well…. I am getting ready to do my first engine work on my 14. It has developed a knock when running fast and quickly decelerating there is a clear knock. Reading the forum and ford service manual this sounds like a rod knock. The service manual is pretty clear on steps to take – file down the connecting rod caps. It also says to check roundness of shaft (easy enough) and to look for babbitt damage. I am not sure how to check that – or what to really look for. I have not cracked her open yet. Any advice on what to look for or things that may go wrong!? I admit I am a bit nervous – but this “sounds” easy enough.. Advice from experts would be greatly appreciated!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Saggese on Wednesday, October 05, 2016 - 06:19 pm:

Apparently "file" is a dirty four-letter F word on this forum regarding caps. Someone with more knowledge should chime in, but I'm under the impression that it shouldn't be done that way nowadays.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Wednesday, October 05, 2016 - 06:41 pm:

There may or may not be shims. The Babbitt should not be cracked , chipped or broken. There is nothing wrong with filing down a cap. It needs to go back on just like it was, don't mix caps up or turn them 180 degrees. When you file a rod cap you shouldn't just grab any old file and get after it. You will need a 12 or 14 inch mill bastard file. It will be best if you can draw file it, use two hands, one on each end of the file and pull it across the cap. You want to remove a little material on each stroke and keep the surface flat. You should check it go flatness on the machined cast iron surface of your drill press or table saw. It should not rock. Of it does lay some emery paper on your flat surface and take enough off so it doesn't rock. If you take too much off then you will need to add a shim.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, October 05, 2016 - 07:04 pm:

Please check the centre main. Your symptoms lead me there


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Eviston on Wednesday, October 05, 2016 - 07:10 pm:

I don't disagree with checking the center main. But, is it a metalic knock or a 'thud'sound?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Wednesday, October 05, 2016 - 07:30 pm:

You can test if the knock comes from a specific rod by shorting the spark plugs one at the time with a screwdriver while revving the engine trying to recreate the knock. When it disappears, you know what cylinder the offending sound comes from.

If you get a slightly reduced knock both when shorting #2 and #3, then you may have a loose center main. It can also be adjusted with the engine in car, but there are risks involved if adjusting more than once - if it's worn upwards into the block, the crank may be adjusted into a bend, shortening the life of the crank. But adjusting it once is probably OK. When the engine is fully torn down you can check with a ruler so all the mains are in line.

Those who have unlimited funds or have rod babbitting equipment in the shop may avoid adjusting the rods and switch them as soon as the first knock appears, but us other poor folks may use the method described in the Service manual.

On a '14 you probably have a three dip pan, and adjusting rod #4 may be a tough job - especially if you have dippers made of soft steel that tends to get into the rod bolt threads and make removal of the #4 cap very hard.. But without dippers it shouldn't be too hard with the right tools and the crank shaft turned for easiest access. Be very very careful not to drop anything into the flywheel area of the pan..

Driving with a knocking babbittt bearing for too long tends to give metal fatigue to first the babbitt, cracking it, and later to the rod itself or maybe the crank shaft - that's what causes a rod going through the crank case in some total engine failures..

So inspecting for babbitt damage is just that - look for cracks or signs that the babbitt isn't closely bonded with the steel part anymore - that's a cause for replacement / rebabbitting.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham on Wednesday, October 05, 2016 - 09:43 pm:

If it turns out to be a knocking con-rod, and it's #1 or #2, make sure your oil return tube is not obstructed.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Peter Adey on Thursday, October 06, 2016 - 12:24 pm:

Thanks for the input. The engine is actually a '20 or there about. It has a 1914 serial number original to the car - but the block is 19-21- has generator port and 2 valve covers ... I really cant check the cylinders for which is knocking because it does not knock without a load. It only knocks at about 30 mph when I decelerate. It runs like a watch idle or revved - warm or cold - when stationary. I think it is more of a "thud" sound than metallic. I'll crack her open soon and post what I see. Hope to get at it by the weekend...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Eviston on Thursday, October 06, 2016 - 02:37 pm:

Peter, I like your T, and I am the same color as it with envy.Interesting it may have a dealer replaced engine. If it were mine, I would drop the bottom cover and shake rods and do some gentle prying up and down on the crank. Hopefully, there are shims under the mains. If so, I would remove a pair from the center main. If no shims, I would probably pull the engine and take engine apart and adjust all the bearings so you are not just guessing how tight the are.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Thursday, October 06, 2016 - 08:53 pm:

When you take off the cap take a good look at the upper side of the bearing, the part in the rod itself. It should not be cracked, chipped or worn through. It is that part of the babbit which takes the most wear when the bearings get loose. If it still has babbit on both the rod and cap, you can remove shims or file the cap to tighten. If you do file, it works best if you can lay some emery cloth on a flat surface and slide the cap back and forth trying to keep the amount removed even on both sides.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Friday, October 07, 2016 - 02:20 am:

"Dull thud" and only on a load - sounds like a main bearing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Friday, October 07, 2016 - 01:40 pm:

From your description it sounds like a rod. This would knock loudest when you are running at a constant speed or very slight deceleration. It sounds like a very fast hammering something like a woodpecker. It would not knock under heavy pull or very strong deceleration.

A main knocks when pulling. Also a piston slap happens during pulling hard. Main or piston slap will be loudest with spark fully advanced and retarding part way will make it quieter. A main will usually knock under high idle and when you short the plug nearest the main will lessen the knock. If it is a center main shorting plugs 2 and 3 at the same time, the knock will stop. The problem with tightening a center main knock is that if it is caused by the rear of the transmission sagging, the wear will be at the top of the bearing and tightening the bearing will pull the crankshaft up in the center. unfortunately that will increase the chances of a broken crankshaft. It is easy to adjust the rods in the car and that is what I would suggest. The books tell exactly how to do that and other posts will also give you advice for rod adjustment. Aim for .0015 thousandths. Do one rod at a time leave enough clearance that you can turn the crank. Then loosen that cap and do another each time loosening the cap until you have adjusted all 4. Then tighten all caps and cotter pin. You might have to pull start the first time and drive slowly until it loosens up a bit.

If you still have the knock, the rods were not the cause. The best way to adjust the mains is to pull out the engine and remove the crankshaft. Use a straight edge to be sure all the mains in the block are in alignment. If so, you can adjust the mains the same way as you did the rods. When you put things together again, check the alignment of the magneto to get between 25 and 40 thousandths all the way around rotating the crankshaft so that you can check every magnet against every pole. Then check the condition and alignment of the 4th main at the back of the transmission. With the engine hanging nose down and the crankcase in position, start the two lower bolts at the 4th main to the crankcase. The 4th main should move in and out freely if the crankcase is in alignment. If you can't get the crankcase into a position where this is possible, it is time to align the crankcase on a jig. You can find posts on how to do this and check with local club members to find out who in your area has the jig. This crankcase alignment is very important for the life of the 4th main and also for the life of the crankshaft as well as the center main in the engine


Add a Message


This is a private posting area. Only registered users and moderators may post messages here.
Username:  
Password:

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration