The book tells you to put the cap in a vise and file the surface down. You should only be taking a couple of thousands from the face. Couldn't you use emory cloth on a surface plate and lap a couple thousands off? Seems like you will be sure the surface is flat doing it this way.
Yes, that's the way I do it.
Absolutely agree, I've seen a lot of rods with unparallel mating surfaces from using a file.
Absolutely agree, I've seen a lot of rods with unparallel mating surfaces from using a file. "END QUOTE"
I have seen thousands of them.
I have half of a grinding wheel off a crankshaft grinder that does a good job. Dan
Jonathan, I use emery cloth too. Works just fine.
Couldn't you use emory cloth on a surface plate. I use my cast iron table saw deck.
Do it this way, go 3 or 4 swipes then turn 180, do 3 or 4 swipes then check fit. Sneak up on it.
The reason you do X numbers of swipes then turn and repeat is you put more pressure on the one end as you press down. Turning evens out the sanding down of the cap or what ever you are fitting.
What works the best is glued 80 grit air board strips, press lightly, and full strokes.
Pull the paper on the glued back, lay on very flat surface, press down. Used for many things.
Mains, or rods, always have the bolt holes in the cap pointing forward, or backward.
We run two strips together.
Now do you guys use Plastigage to check clearance?
You may use plastigage, but I learned to just use a 1" strip of paper from a newspaper as a go/no go gauge here at the forum - works fine
When testing the play I place the 1" wide strip along the crank journal and mount the cap tightened down. If correct play, the crank shouldn't be able to turn with the paper in place, but free to turn without it (and the cap tightened down)
80 grit seems a little coarse.
Just make sure your con rods don't have shim stock on them
Cheapest flattest easiest to find surface? Believe it or not it's modern plate glass.
I used a bench mounted belt sander believe it or not. A little more refined approach than the methods used in the old days, which I hear included dragging it across concrete or other paved surfaces in a pinch.
With respect to clearance, the right amount is achieved when the rod moves side to side with the slightest tap from a hammer.
And all of the above explains why it is so hard to find good rod caps!!! Once the shims have all been pulled it's time to rebabbit!!
Les, there were no shims in rods that were installed in Ford engines from the factory, only at the main bearings. Replacement rods had shims so they could easily be fitted to a slightly worn crank.
(Message edited by Roger K on August 11, 2016)
I had to find a large file that would accommodate both surfaces of each rod cap simultaneously.
And I'm sure that all these people are adjusting the rods of engines that have never been overhauled!!
Have you ever tried to find a good set of caps to rebabbit?
Once they have been "filed" too much it gets really difficult to refit them to a nice full size crank. I've ended up having to use two shim packs per rod so you still can get a decent amount of Babbit in the cap. Just saying
I would never file or remove any material from a rod or main cap. If you got no shims, its time for new babbit. Sorry, but filing, sanding or grinding on a machined main or rod surface kind of goes against my grain. I've had some "fixed" rods where the caps would not seat correctly, which are now residing in the "junk" pile.
Also a quick note about using glass- Yes it is a flat surface. but it is only as flat as what you have it sitting on. If your base is slightly warped, your glass will flex and conform. Just my 2 cents...
Thank you for the "corroboration ".
One other thing. Often by the time you need to file the caps, the crank is "out of round " on the crank pins. So this filing isn't going to buy you much useable life. I suggest that before you file the caps, measure the crank for round. Even .002" is not going to last well, as the crank wears the most in the " high load" places.
So if you want a car that you can drive all day at 35-40 mph or better, then think about it. If you are content with 20-25 mph for 5 mile trips, then you may be on the right track
Here's the problem. Most of our cars have had the crankshaft turned down which leaves more room on the caps between the babbit and the steel. And most of the wear is on the top surface which is on the rod, not the cap. Therefore after the shims are removed, there is still steel which can be removed from the flat surfaces of the cap without a problem with the babbit. However, when you replace with a new crankshaft which is standard grind, it is hard to find a cap where the babbit is thick enough and so it is necessary to install many shims to bring it back to standard. The caps will last longer if the babbit is repoured when the last of the shims are removed and there is still too much clearance.
Filing the caps was a routine job at Ford repair shops and it was described in the Service Manual, pages 97-101.
Is there a shortage of rods?
Lots of rods. Probably not a excess of late style light weight rods. Shortage of good caps
I'm going to come full circle. How do I diagnose a rod knock. Could the knock be a main?
Jonathan - loose rods tends to knock more when you let off the throttle and be quiteter when pulling / accelerating while loose mains knocks more when pulling - and tends to increase with increasing speed. Make sure to fix knocks as soon as possible since knocking never fixes itself - and it chrystallizes the babbitt so suddenly you can't take up the play, the babbitt is cracked so you must get a new rod or rebabbitt. There's also a risk to damage the crank.
There is a risk with taking up play in the mains more than once - you can get the crank in a bend, since number one and three tends to wear in the caps, while number two also wears in the block. With the crank shaft out, you can check if the mains are in line in the block with a straight edge for better control.
You can diagnose rod (and main) knocks by running the engine while shorting out various spark plugs with a screw driver to see if the knock goes away when a certain plug doesn't fire.
I find the same problem with main caps. Most have been filed, sanded or ground on. So I jig up my TA 14 and take a little cut in the cap to give it more room for the Babbitt. Same with rods. Dan
We are often warned about using shims behind the crown wheel and excess shims on the back axles/hubs. But shims on rods and mains never draw the same reaction. Can someone please explain the rationale behind this?
Our old time bearing man never used shims when pouring new main and rod bearings. He did insist that the rod caps be measured to make sure that they had not been filed too much. From my not-to-be-trusted memory, I think he insisted on at least .625" thickness at the bolt holes. His protege' has adopted the same practise.
Allan from down under.
The problem with shims at the crown wheel is that it reduces friction in a place where the crown wheel is designed to transmit all the power through friction - with less friction the power goes through the bolts that eventually fails.
The problem with stacked shims on the rear axle taper is that they have more of a tendency to wear and get cold forged in use than only one thicker shim and you loose the torque on the nut - the hub starts to move and wears the shims faster, destroying the key slot in the hub. It's easy to check the torque on the rear axle nuts often - much easier than the other locations discussed, so if checked often it shouldn't be too much of a problem. The proper fix is a better hub that doesn't need any shim - it's been worn due to unchecked torque on the nut in the first place.
The connection surface between the rod and its cap doesn't rotate - it should be torqued so it can't move under the strains it's used in. The purpose of the shim pack is to bring back a filed cap to it's original position so it can have the original babbitt thickness when repoured - and so it can easily be adjusted to a slightly (not oval) worn crank. And be easily adjusted as the babbitt wears. It doesn't have to be repoured until it's really necessary, like when it's very dirty from impureties in the oil that gets imbedded in old babbitt - or if the rod has been knocking for so long that the babbitt has chrystallized and it's cracked.
You can't compare the different uses of shims - it's different mechanically and its been proven through 100 years of use what works fine, what works for a while and what usually doesn't work
(Message edited by Roger K on August 12, 2016)
I have a TA 14. Can you tell me about your process please?
Note the warning in the repair manual. "The repair man must exercise considerable care to hold the file squarely on the cap." Very easy to exert uneven force on one side or another. I've tried it. The number of caps and rods with unparallel mating surfaces is good indication the practice should be avoided.
I always just pull out the engine for bearing adjustments and do it on the bench. Wear in the block babbit at the centre main is invariably caused be a bent pan. The easy test is as follows.
1 pull centre main cap.
2. Install a dial indicator resting on the "crown" of the bearing
3. Press on the shaft towards the block.
Anymore than .001-2 is too much. Ideally no motion
Personally I have never had wear on the front or rear main and never in the centre on the block side. I have definitely encountered wear in the centre cap. Consider that the centre main has double the loading of the front and yet is the same size.
The "tell" I go by is a mild knock at 30 mph road speed at mid throttle. Don't ignore it. It will get rapidly worse.
If the bearing is worn in the block then you are faced with a lot more work. I know guys who have successfully scraped the front and rear mains down if it isn't too bad. Ignoring it will break your crank!!!
Les: Check your email. Dan
I decided to pull the hogs head to change the bands. The tool I bought to hold the bands together does not go on. It is hanging up on the boss diameter of the center band.Not enough room to fit between the boss and the band?!
Jonathan, I had the same problem with the band clamps. It's best to take the hogshead off anyway to avoid bending the bands out of round. Make sure to take the bendix off before the starter.
I use heavy string. Not wire just in case a piece breaks loose I don't want it going to the magneto parts
I used sandpaper on a window pane. Switching cap around every ten passes.
Looking at the caps now, I can move them slightly front to rear but does not move side to side or up and down. I know there is only supposed to be only .0015-.002 clearance, should I still remove the cap and check with plastigage? Looks like a straightforward job. By the way, there is shims on the caps.
Jonathan, take the caps off and check them with plastiguage. If they are too loose sand the caps just enough that you cannot slide the rod from side to side. It should take a light tap with a hammer to move them. The Ford book has pretty clear instructions how it should be done. Make sure to clearly mark the caps before taking them off.
Please consider new eye glasses. He says he has shims!!!
Les, I see that now.
The three in the rods in front of the engine were easy, the one toward the rear should be done but if I drop one of those nuts or cotter pins inside, i'm screwed!
Any tips on how to do that one without dropping anything! Thanks
I have not tried it, but I seem to recall a "tinkerin tips" article where someone recommended taking the rear inspection cover reinforcement bracket, moving it back a few holes, then attaching it with a couple of bolts. This provided support for a home-made tray that sat under the #4 rod and extended back to the flywheel.
Does anyone recall the article?
Jonathan, It can be done, but no matter how nimble and careful you think you are, you will drop small parts. Be sure to stuff rags in that big yawning hole up front to catch them. And be sure to count those rags in and out!