While running the engine today, it developed a noticeable knock at high idle.
I isolated the knock to #3 by shorting the plug.
At low idle it is quiet, but above idle it gets noisy. Adjusting the spark helps, but it is a definite knock.
So far I have:
Isolated it to #3
Pulled the cap and checked the clearance - it is right on 0.015" with plastiguage
Rotated the engine by hand and watched the rod movement - it tracks nice and straight
When I had the cap off, I grabbed the rod and it had real easy movement side to side, but I couldn't feel any slop while pushing/pulling up/down
Cylinder wall is clean and has no marks
I checked compression and I got 55 across the board. (Don't think it was necessary, but thought I would check anyways)
I took a video of it the other day, and never really noticed until now, but you can faintly hear it in the video at about 23 seconds in when I idle it up
This engine has just been put back together with new babitt, rods, etc. It has only been around the block once so far.
Next plan of attack would be to pull that one piston and have a better look?
Do you have a 4-dip pan? If not, use a mirror and a light. Bring #3 to BDC and look at the wrist pin clamp bolt. Check to see if it's broken (missing). Some of the repops were having problems.
The head of the bolt is still there and the cotter pin is still in it. This is what is baffling me. Nothing seems loose.
Not knowing the history of the engine, I can only suggest you check the following.
1. Is the crank pin round? (MAX OoR = .002")
2. The rod on the crank pin should NOT move side-to-side with ease. I suspect the clearance and/or #1.
3. Aluminum or CI Pistons? Check for cracks in the skirt and near the piston pin.
4. Check the clearance between the piston pin end of the rod and the piston.
I'm in body shop mode right now so I'll think about it more today and defer any more comments to others.
New Aluminum pistons and pins (0.030 over)
Engine short block was completely done:
Cam and crank checked and polished
The other weird part is that this is the third engine the truck has had in it, and all three have had the same knock.......any way this could be timing/fuel related, or is it just a fluke?
I have tried different timers as well - re-timed the engine using the methods from this forum. I installed the front cover using a centering tool.
Another thing to add:
When I was wiggling the piston pin back and forth, the pin and rod moved together
I would check the centre main also.
Did you check alignment on your rods before use. Twist, Bend, and Off Set?
Rods out will cause a knock every time!
I didn't assemble the engine myself, so I can't say for sure.
Can any good machine shop check them, or do they need to be sent to someone who specializes in T's?
The only thing it takes is some one that has a good machine, and knows how to use it.
The Model T's having a 1.250 shaft makes it hard when most machine shops have a rod aligner that starts at 1.500, and up.
Just remember, you have to check all 3 positions!
Greg, I checked your Profile, man I like your truck.
Could you post some more pictures, I just like Model T pictures, Old, and New.
I am working on a truck Motor right now, and I am sure the owner would like to see them, and anyone else also.
Here are a couple more pictures:
Thanks, you done one great job there!!!
I wish I had that, and you had a better one!
Now if could get it to run as good as it looks, I'll be all set.
You mentioned your rod clearance at .015. Was that a typo ? Should be closer to .0015 I think.
Sorry, I should have added another zero.....when I checked the clearance, it was right on the money.
I would not trust the plastiguage measurement. It only measures one spot. It's meaningful only on a freshly turned bearing journal with a freshly bored rod. Otherwise its not an accurate way to measure.
You should take out a shim from the one that is knocking on each bolt. Be sure the rod bearing is well oiled, then put it back together. If you can move the rod from side to side with your fingers it is still too loose when adjusting clearance. Note - the previous sentence does not apply to rods that are not making noise!!!!
Royce - this is a brand new engine with less than an hour of run time on it......
I would be suspicious of a twisted rod then.
But first I would try to tighten the rod by removing a couple shims (one from each bolt). Worst case, it doesn't fix the problem and you have to remove the head and replace the twisted rod.
Did the same person(s) rebuild all three engines?
I still suspect the clearance. .0015" is like a gnat's eyelash and on an oiled rod/crank will feel dang tight. You say you can move the rod side to side. If that's the case, that's your knock. It's too loose.
Can you post a picture of the rod cap?
When I mentioned that I could move the rod side to side, it was when I had the cap off and the rod was disconnected from the crank - the side to side movement was at the wrist pin. The wrist pin was moving with the rod.
I have the cap off right now, and to me it looks like it has been running tight. I'll see if I can get a picture of it.
Here is a picture. Maybe the issue is not enough contact? The crank is still nice with no marks.
That looks like you have bent rod or the cap wasn't matched to the rod. The wear, even new, should be even. It looks heavier on one side (bottom). The left side is probably the thrust side but should be even top to bottom.
Check the rod side and see if it looks the same.
Ken - the rod side is the same.
Do you think I should pull the rod and check it for straightness?
That would be a start. The clearance looks loose too. Tough to get a good Plastiguage reading if the rod side looks like that too.
It may be a good idea to check the other rods too. A tight clearance can hide a bent rod until it wears in.
That rod is poorly fitted if you have new babbitt on a reground crank. Any machine shop should be to check the rod for twist using a surface plate, v-blocks and dial indicator. If the rod is true, then you need to scrape or timesaver the bearing and set your clearance. Since you have a 50% bearing, you could just pull a shim 0.002 from one side of the rod and see if it fixes the problem.
I have used the method in paragraph 386 in the Ford Manual for setting rod bearing clearance (shown in Royce's posting above).
For me it worked really well. Its a lot simpler and I think better than using plastigage. Lacking a "small brass hammer" I used a tack hammer inheirited from my grandfather. About 4 oz I'm estimating. Worked fine.
Just checked the other three. All of them are nice, with even wear. Nothing like the one pictured.
So that makes me feel better
The twisted rod theory is starting to look like the answer. I am going to pull the rod out and get it checked.
Pulled the cap and checked the clearance - it is right on 0.015" with plastiguage
I suppose you actually meant 0.0015", if not that is your problem. The twisted rod sounds closer to the problem.
On a fresh rebuild, I would be talking to the rebuilder first. After you disassemble and tweak things, only to find they may have made a mistake, they're not likely to want to warranty things.
When you say side to side, do you mean, side to side, such as left side of the engine to right side of the engine? Or do you mean front to back of the engine? When you pull on the rod front to back,there will be some front to back movement of the rod, and when it moves the wrist pin will move with the rod, because it is bolted in. There should not be side to side, movement such as left to right side. The internal measurement of the rod bearing should ideally be a perfect circle. It almost sounds to me as if the rod was fitted to a larger diamater crankshaft and then shims were removed or the cap filed down so that it would fit top to bottom, but the side to side is still loose. Wipe it off and put some prussian blue on the bearing and rotate the crankshaft. Then remove the cap and look at the wear pattern. The areas which are tight will wipe the prussian blue, but the areas which do not have a snug fit the blue will have a shiny surface. It should be wiped almost everywhere on the bearing surface if it fits correctly.
This is a different problem than above if the rod is bent, you will either notice the rod moving front to back and back to front depending on whether the crank is pushing or pulling on the rod. Or the piston to cylinder clearance would be tighter in line with the end of wrist pin either front or back of the piston depending on which way it is bent. With a bent rod,if you were to remove the piston, you would see scoring at the top on one side of the piston and at the bottom on the opposite in line with the ends of the wrist pin.
Good luck of finding and repairing your problem.
When I said side to side, I meant front to back. There was no other directional play that I could feel at all.
I have the piston out of it now. Couple of marks on the side by the pins, but nothing huge.
My local machine shop told me to bring the rod by in the morning, and he will check it for me. He told me he usually does bigger ones, but should be able to check it for bend/twist. He told me the charge would be a ride in the truck when I get it back together
I had the rod in my hand, with the piston removed, and the wrist pin bolted to the end of the rod. I might be seeing things, but it looks bent - like the wrist pin is closer to the big end of the rod on one side compared to the other. I took the cap off and stood the rod on a flat level surface and took my calipers and it is measuring 0.030 less on one side than the other, measuring from the flat surface up to the wrist pin. I am not a machinist by any means, and tomorrow will hopefully point me in the right direction. Can a rod be bent that far that you can actually see it? I am probably just seeing things........
I appreciate all the help guys.
The human eye can detect variations in size down to a few thousandths of an inch. Thirty would be easy.