Con rod pin bushing

[flatjack9]

I have a question about the installation of the pin bushing. What is involved in the burnishing process and why is it the preferred process? Is there a problem with installing them with a press fit?

[Karl Wolf]

Burnishing pushes the bushing out to fit the surface of the inside of the hole- in the rod... I had the mandrel to do it, as an addendum to a Sunnen hone... I think that it helps hold the bushing in place, and helps the bushing hold its size...
You still have to press the bushing in, first
I don't think that I ever used it...
Karl

[Russ/40]

I don't know what tooling was used on them, but I would think with a little ingenuity it can be done by the home mechanic. I'd experiment with a few junk rods first. My first thought would be to use a lathe live or dead center in a press. Just enough to flare the bushing slightly. With that, it's not going anywhere.

[Ol' Ron]

This is why I never change them unless they're really bad, usually find another rod. If ya can't do it right , don't do it.

[quickchange34]

The best thing to do is take your rods to a good auto machine shop. Have them install new pin bushings and wet hone them to the correct clearence for the piston pins. While they are at it get them check the rods to see if they are straight.

[Ol' Ron]

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Most shops don't have the right tooling, this is not something that is done to modern engines. Some after marken rods have them, but of a differant size. Yes find a shop that doz this.

[Kurt in NJ]

Most modern rods have a smooth machined bore for the bushing --a pressed in bushing has good contact with the rod ---the Ford rods have a much more coarse machined surface ---to have the bushings stay in and fit properly they need to be "burnished" to swell the bushing into the valleys --if you take them to a machine shop make sure they understand this, another way to do it is with a ball bearing pressed through ther pin hole to force the bushing to conform to the machined surface ---as Ol Ron says sometimes it is best left as is ---trying to replace them can come out worse, for all the work many times a NOS rod is cheaper, and a set in the box can be very close in weight --I just bought a set at Hershey, all the rods are within 1 gram end for end, and total weight varied by less than 1 gram and it would have cost well over the 100$ I spent to make old rods that close

[Karl Wolf]

The (one that I know of) tool that does this job is a Sunnen hone... The mandrell that this is for has a relatively small rounded button that is pressurerized by the machine. As this is rotated inside the installed bushing, pressure can be increased... The point loading is relatively high, stretching the bushing outwards into the rough rod bore... Not anything that I could do at home...
Karl

[GOSFAST]

Originally Posted by Karl Wolf

The (one that I know of) tool that does this job is a Sunnen hone... The mandrell that this is for has a relatively small rounded button that is pressurerized by the machine. As this is rotated inside the installed bushing, pressure can be increased... The point loading is relatively high, stretching the bushing outwards into the rough rod bore... Not anything that I could do at home...
Karl

Correct, Karl has it exactly right, and this is the ONLY recommended way to do the Flathead bushings. I had mentioned this in another post here earlier!

This part of the procedure is done on the Sunnen rod reconditioner!

You could hone the bores smoother also (just changing the finish) then press the bushing in, this becomes an alternative method, but if you have the "burnisher", it really isn't necessary! And you do not want to compromise the press fit with this method! It can all be measured beforehand.

Also, it helps to pre-heat the pin ends in the rod heater to help ease the bushing into place! We use this method in conjunction with the "burnisher"!

One VERY important step BEFORE pressing the bushings in is to "chamfer" the pin holes, at least on the one starting side where the bushing will go in! It helps to do bushing also, at least on the starting side!

(Add) This "burnishing" procedure is the very same method we use today to finish the valve guides (on the Flatheads also) when "lining" them with the .030" bronze inserts. The only difference being when you run the "burnisher" through it leaves the desired finished size without any add'l honing! They come in increments of .0005" (half-thou) for sizing!

Thanks, Gary in N.Y.

P.S. There was some mention also earlier about "shortening" the rods (C/C) slightly by the resizing procedure. It really isn't an issue BUT, this can be corrected also, by resizing the rod first, then do the bushings, but before finish-honing to the desired pin clearance you would "bore" the bushing in another fixture correcting the C/C by slightly off-setting the hole in the bushing! You only have minimal material to make the correction! Normally you only need about .002"/.004" offset to correct the distance. It will make the bushing slightly thinner on one side, but again, this a non-issue!

[Walt Dupont--Me.]

I've bunished 100's of rod bushings with the Sunnen machine. WE also had a Tobin Arp machine to resize the pin pushings for C-C . You clamped the rod in the machine on the big end with an expandable clamp, set the micromerter scale for the correct C-C and then bore the bushing. We used this machine mostly for big engines, Mack, Cummin, Detroit, Ect. Walt

[flatjack9]

Does the flathead pin bushing come in just one OD or are there oversise bushings available? If there were, it would seem that the bore could be sized for a proper pressfit.

[GOSFAST]

Originally Posted by Walt Dupont--Me.

I've bunished 100's of rod bushings with the Sunnen machine. WE also had a Tobin Arp machine to resize the pin pushings for C-C . You clamped the rod in the machine on the big end with an expandable clamp, set the micromerter scale for the correct C-C and then bore the bushing. We used this machine mostly for big engines, Mack, Cummin, Detroit, Ect. Walt

Hi Walt, I still have access to the T/A machine, but don't really use it anymore. It is an excellent tool specifically for this procedure!

As you would know, it has "super-accurate" bearings and "air-operated" centering mandrels for both ends of the rods!

We have now have conn rod fixtures for the CNC equpiment!

(Add) If I could just bring out an important fact here, when "totally" reconditioning these Flathead rods today, you really need to consider whether it is cost effective or not! The price on aftermarket rods, although seeming somewhat expensive, becomes very relevant. Basically speaking, with "new" rods you have a lot to gain! And above to "FlatJack", yes you can accomplish that task, but again, you need to weigh the costs! We can actually make our own bushings, in fact, we often have. One more note, you have a limited amount of material to work with around the "eye" of OEM Flathead rods!

Thanks, Gary in N.Y.

P.S. The Tobin-Arp mentioned here was accurate and you had 100% control over the C/C. If it needed to be changed it was easy. You couldn't always get the desired C/C, depending on the overall condition of the individual rods. Didn't make a huge difference though, if you needed to alter it you could at least make them all identical (equal)!

[Karl Wolf]

I have redone a few rods... If one measures the amount of distorsion in the big end, on a torqued rod- say it's .004- a real common wear on a flathead rod- You can cut the cap say .005 or .006... This can leave you with a minimal amout of material to remove to get to size, and you lose almost no length in the rod....
Also, note that I have found that the rods wear to an egg shape- up and down being the long way... And if you have a Tobin Arp rod boring machine center to center can come out perfect... If you just do the small end on a Sunnen... I wouldn't worry about the rod length...
Come on-it's a flathead...
Karl

[Russ/40]

Clearly, I had no concept of the complexity of the task.

[Randy/In]

On rebuilding Lycoming aircraft engines, the con. rods and rockerarm bushings get burnished by using a broche, and the rods get cut on a Tobin Arp machine, The rockers are burnished to size. Randy

[jake197000]

i swegh them in then hone

[Ken/Alabama]

This is the mandrel I have to expand the bushing into the eye of the rod before honing to size.

[tubman]

Twelve years! I wonder if that's a record?

[Ronnie]

I think it is tub "lol"



Ronnie

[Bored&Stroked]

Time to award a prize for resurrecting the dead . . . Dr. Frankenstein has nothing on us Barners! LOL