Rod adjustment question

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Model T Ford Forum: Classifieds: Rod adjustment question
Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed Fuller on Monday, September 04, 2017 - 08:33 pm:

I have never adjusted the rods on my T that was my grandfather's. Every once in a while when I am driving I will hear a slight noise that makes me wonder if it's a rod knock.

The engine is a lower mileage engine and still has cast iron pistons. I always drive the car very conservatively and try my best to go easy on it since it is mostly original.

Today I dropped the inspection plate and all of the rods slide fore and aft on the crank but there was no noticeable play in any of them. All four felt the same. I didn't take the rod caps off so I don't know if any of them have any shims.

I know that from reading up on adjusting the rods that rods in service are supposed to move forward and aft on the crank. Should I try to tighten them?


Top of pagePrevious messageNext messageBottom of page Link to this message  By James J. Lyons III - West Virginia on Monday, September 04, 2017 - 08:47 pm:

Ed. You should confirm that you have a rod knock first. To do this, take the lid off the coil box, and with the car idling, depress the points on one coil at a time to kill that cylinder for a second or two and then let off the points to allow the cylinder to come back to life. At the moment the cylinder fires back to life, you will hear a single distinct knock in that cylinder if there is a knock developing. repeat that test for each cylinder a couple of times each. If you don't hear any knocks, then don't pull the caps. The noise is coming from something else.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed Fuller on Monday, September 04, 2017 - 08:55 pm:

James,

Thanks for the answer even though I accidentally posted in the classifieds!

I have shorted out each cylinder one at a time but have never heard a knock.

I am probably being overly paranoid when I drive and listening to close to an engine that's over 100 years old since I try to go easy on it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Monday, September 04, 2017 - 09:07 pm:

I agree with James and will make 1 addition...

I have several "T"s; two with original cast iron pistons. I have a very mild knock on both of them that is unrelated to the rods/crank (I have checked numerous times and rod clearance is fine). After years of driving them without any increase in loudness or severity I am concluding that they are either worn wrist pins or a little piston slap or both. My noise is worst when going down hill with the throttle closed or at a very low idle. Neither wrist pin wear nor piston slap is grounds for concern (assuming that is the true source). They both are sweet running engines and I am not inclined to dig deeper to remedy the knock (you can get into real trouble replacing bushings in old pistons as a minute change in the cant of the piston relative to the rod from reaming operation can create wear and/or oil consumption among other things).

There are a myriad of reasons a T may knock, but telling us that you have cast iron pistons makes me think this is possibly going on if you find that adjusting the rods doesn't clear it up.

Tell us what you ultimately find...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Monday, September 04, 2017 - 09:13 pm:

And to your specific question: "should I tighten them?"

Do some research as to how to CHECK them, and check them. They may need no adjusting and tightening them for the sake of tightening them may not yield the results you seek.

If you do check them, start with #1 and work back. By the time you get to #4 you will have a good idea if they are truly loose. Number 4 is a real pisser on a 3 dip pan and you really don't want to pull that rod cap if you do not have to. It can be done and I've done it, but it isn't the sort of job I'd advise a neophyte to jump into as there are all sorts of bad results if you drop any parts into the transmission, and that is really easy to do if not careful. If you have a 4 dip pan...no sweat.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dallas landers on Monday, September 04, 2017 - 09:26 pm:

Ed, Im glad for your question. I pulled my pan cover to check mine. Scott's description of the noise when going down hill is mine to a T. Pun intended. After my adjustments I had no change. I was a bit puzzled. Thanks Scott.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ed Fuller on Monday, September 04, 2017 - 10:35 pm:

Isn't there a method of putting a piece of newspaper under the rod cap and if it's to tight that's a good indication that the rods don't need to be adjusted?


Top of pagePrevious messageNext messageBottom of page Link to this message  By James J. Lyons III - West Virginia on Tuesday, September 05, 2017 - 08:53 am:

Ed... YES. Here you go: I cut and pasted my comment below from an older thread:

The way to adjust model T Connecting rods is to cut a piece of newspaper that is the width of the connecting rod journal surface, minus the radius, and long enough to stretch 2/3rd's along the surface of the rod bearing cap. You don't want it to run the full hemisphere length of the rod cap surface otherwise, you get a pinching effect.

Soak the piece of newspaper in oil so that it is very wet and saturated. Pull the rod cap off and place the newspaper piece on the cap surface and re-install the rod cap and tighten. Grab the hand crank and try cranking the engine. If you can spin the crank, pull the cap back off and sand a little bit off the cap surface and repeat the process. A correctly adjusted rod will spin freely when the cap is installed without the newspaper, but be locked up when tight with the newspaper shim in place.

Go slow. The newspaper when wet is no more than .001". You can blow through .001" real quick if you aren't careful.

This is a tried and true method that has been used since the model T was being manufactured and will give perfect results. Good Luck!

Here is the entire thread if you want to read it. There is some good information in there, and good advice - to stay AWAY from plastigauge!!

http://www.mtfca.com/discus/messages/708324/718739.html?1485960703


Top of pagePrevious messageNext messageBottom of page Link to this message  By John V. Dow on Tuesday, September 05, 2017 - 02:18 pm:

I pulled my hair out for months trying to find the source of my knock/rattle. It had all the symptoms of a loose rod. I performed all the trouble shooting tests as those mentioned above. Removed the inspection plate twice, used the piece of newspaper technique (which works great). The noise was still there until recently. I replaced the brushes in my generator and when reinstalling I replaced the mounting gasket. Noise GONE!! The gen. gear and the aluminum timing gear had enough slop to cause the rattle. Adding the thicker gen. mounting gasket moved the meshing point to fresh surfaces and that was it!! I know in time the noise will return but when it does I'll know it's just a harmless "Model T" noise. BEST OF LUCK!!


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