Don Terrill’s Speed-Talk

I've got some BB Mopar rods here that I'd like to size down to the 0.927 SBC pin. I know I could bush them down to that size with a bronze bush, in fact Diamond Pistons used to offer them in their catalog for Hemi rods.
Anyway I was also thinking if it was possible to just put in a steel bush, hone it to size and then shrink in the piston pin like you would with a stock OEM setup...
This is not for racing..
Question is...Has anybody done this with any success? I think I saw MadBill elude to this once in a post..

Either way would work just fine.
Even cast iron would work for the "steel" route. May be better due to ease of achieving the final finish?
Regardless of the material chosen I would (and have done) use your rod heater and shrink fit in the bushing.

Thanks Dave,
Using the steel bush allows me the option to use a budget piston that does not have retainer clip grooves. What size interference fit do you think I should use between the bush and the rod? The same as you would normally use between the pin and a rod, 0.0015 inch ?

Are you going to use a press fit bush, then a press fit pin into the bush? If so, I don't think that is a good idea.

I think it would be fine, I'd use free machining steel so it bores nicely.

Super_Stock wrote: ↑Sun May 09, 2021 6:49 pm Thanks Dave,
Using the steel bush allows me the option to use a budget piston that does not have retainer clip grooves. What size interference fit do you think I should use between the bush and the rod? The same as you would normally use between the pin and a rod, 0.0015 inch ?

.0012 - .0015 would be ok with heat installation for the bushing.
.001 for the press fit pin.

You are going to have to give some thought to the heated rod/bushing installation. Chamfered edges, etc.
You will only have one chance to get it in there.
I suggest a sacrificial rod and bush as a test piece to get the heat setting right on the sunnen induction heater along with your installation tooling.

Ok thanks Dave,
I've already got some old rods and pins, as I was planning to do what you have said. I want to test a few things first.

Geoff2 wrote: ↑Mon May 10, 2021 4:32 am Are you going to use a press fit bush, then a press fit pin into the bush? If so, I don't think that is a good idea.

Yes , that's what I'm doing, and I've got to tell you, I think it's a fabulous idea.

Super_Stock wrote: ↑Mon May 10, 2021 8:22 am

Geoff2 wrote: ↑Mon May 10, 2021 4:32 am Are you going to use a press fit bush, then a press fit pin into the bush? If so, I don't think that is a good idea.

Yes , that's what I'm doing, and I've got to tell you, I think it's a fabulous idea.

You've done this before?

I've seen it attempted and it was not pretty.

Momus wrote: ↑Mon May 10, 2021 9:40 am

You've done this before?

I've seen it attempted and it was not pretty.

Well if you can give me a sound reason why this won't work, then I'm all ears..

SS,
I have actually seen two engines in the last 30 years that were like that. They were both from a big rebuilder and I figured they did it to save some rods that were messed up. Both times they just had a "normal" rod bushing pressed in. They had apparently been running that way for many years so I guess it should work. Both times a couple of the bushings came out when I pressed the pistons off the rods.
I personally replaced both sets of rods and I don't know if I would do it on anything other than a completely stock engine. My luck does not work well with those types of things

Unless you get all your diameters, fits and alignment, fixturing, and temperature spot on you will shift bushes and lock up.

I've done it once, and it's not a commercial proposition, but if you can do the work yourself ......

Dave Koehler wrote:You are going to have to give some thought to the heated rod/bushing installation. Chamfered edges, etc.

You will only have one chance to get it in there.

This is the crux of it

Hone the rod end to a nominal oversize, OD/ID the bush for interference, I think I used one & one plus a pinch for good luck

Chamfer the rod ends, sweat the bush in, swage the (overlength) bush into the chamfer, dress to width, hone to size

Slowly and evenly heat the bushed small end (I used a torch, carefully, but the heater makes more sense) ...... I usually only ever let the end go straw, but this had a touch more ..... get in their quick with a stop, don't gauge it

Never again .......

Just curious. What will be the wall thickness of the bushing?

Super_Stock wrote: ↑Sun May 09, 2021 8:20 am...
Question is...Has anybody done this with any success? I think I saw MadBill elude to this once in a post..

Good memory SS! I think I must have posted re the dangers of using a bronze bush to downsize the bore for a smaller press-fit pin. A friend of mine's aftermarket-turboed BMW started pouring out smoke. It turned out the builder had used bronze bushes to reduce the rod small end diameters to accept the smaller press-fit pins of the Ford Falcon pistons he used and the bush's lubricating properties allowed two pins to shift, furrowing the block. [Smokey Yunick is quoted as saying: "Bleeped if I know where those (pin) forces come from!"]