Welding connecting rods

[Dave123]

Looking for someone out there that has experience with shortening and welding connecting rods. I understand this has been done for years, with varying success.

On this project I am installing a 28 chev crankshaft into a model T.
The modifications to the crankshaft front end and rear flange are completed. Next step is too make new main bearing caps to accomodate the larger journals on the chevy crank.

Before I grind the crank I need to decide whether to reduce the chevy rod throw journals down to accept the T connecting rods ( which will mean grinding from 1.5" down to 1.375" ).

Another option is to cut and shorten the chevy rod and attach the T rod upper end, therefore I can use the larger diameter (Chevy) big end while running the stock T pistons.

Dave

 

[Milland]

No idea if this would work, but I'd rather find short Chevy rods and bush the small end to the T piston bore. What are the actual sizes for the C and T piston pins of this vintage?

 

[john.k]

Used to do something like this years ago...........Had a long term job reconditioning V4 Wisconsin motors for the army (they had thousands of them).......the makers pistons were like $400 each (in 1970), GM Holden car pistons were $5 each ,but the compression height was too great by 1/4"....so I made a jig to hold the rods while they were heated red hot,then the rod was compressed by 1/4" in a press ......A lot quicker than welding......All the old time rods were soft steel and could be bent cold for alignment.

 

[Dave123]

No idea if this would work, but I'd rather find short Chevy rods and bush the small end to the T piston bore. What are the actual sizes for the C and T piston pins of this vintage?

Milland, I know the chev rods are 7.440” in length which is .437” longer than the T rod,
pin dia on the Chevy is .85” the T is .75” dia.
Sorry but I do not have a Chevy piston on hand to measure the distance from the pin to the piston top

 

[Milland]

There's probably a connecting rod size and interchange database somewhere out there, might be worth looking to see if anything else is close to what you need to use for your hybrid. I just feel a little nervous about welding a rod, but if that's the way you have to go good luck.

 

[BOB-OO]

I would do anything other then cutting & welding. In order:
1. have a custom rod made by a reputable company that does this everyday-Carrillo or others. Custom Aluminum rods are cheap and would likely have a long life in your application (low rpm).
2. Would try Johnk's suggestion.
3. Would make myself from quality steel billet- if no other options.

 

[Milland]

I would do anything other then cutting & welding. In order:
1. have a custom rod made by a reputable company that does this everyday-Carrillo or others. Custom Aluminum rods are cheap and would likely have a long life in your application (low rpm).
2. Would try Johnk's suggestion.
3. Would make myself from quality steel billet- if no other options.

This sounds like a one-shot program, I could see John's method working after some fixturing (including a guided press for compression) and process tuning, but for four rods I bet it would be a disaster to try.

If this is a low use hours venture, then Al or steel rods shop-made could be an option. But again, I'd hope there's existing rods out there that could be repurposed.

 

[john.k]

I dunno about aluminium rods being cheap......a set of new Square 4 rods are $2000 from the AOMCC......made in the US....from billet,so they say.

 

[Mud]

I'm familiar with T engines. Ford used very good steel by the standards of the 20s, but nothing exotic or particularly hard to weld by today's standards. A machining and hot rodding mentor once did boxed rods for flathead Fords long ago, a rather common practice at the time, they had plates welded to the sides to give them more beam strength, many were done with stick welding with any old stick rod like 6013 or 7018 and mild steel sheet, and they held up under significant loads of fuel at high RPMs. I'd guess (without researching) that T rods are made from simiilar material. An XRF gun at a junkyard might be illuminating about the Chevy rod alloy. Tig welding with ER70-S or ER80-S rod would likely work quite well, sacrificing a few junk rods would tell you how ductile the finished rods are. I'd be tempted to make a small end from new known material than to reuse the small end of the Ford rods in order to create a better mechanical joint to prepare for welding, in order to have more finished weld bead length than what a butt weld would provide.

 

[ratbldr427]

You never know but some times speed equipment manufacturers can and will be helpful. I'd call one of the rod makers and ask if they know of a rod that is close to what you need, cc length and bore diameters ect. They will have a data base of every rod combo they have ever made. Just be honest with them and offer to pay for their time. Maybe even get a quote. Also any crank grinding auto machine shop would be a good place to check as they probably have seen just about every rod made for auto use. They will know all the journal sizes used and then what rods might be closer to your length.

Also custom pistons might be cheaper than rods.

 

[gbent]

If grinding the crank 1/8" so you can use the ford rods is an acceptable solution, I'd go that way rather than change rods. If that doesn't work, depending on how your rods look, I'd not be afraid of tig welding the rods in a Model T engine.

 

[Cole2534]

I'm familiar with T engines. Ford used very good steel by the standards of the 20s, but nothing exotic or particularly hard to weld by today's standards. A machining and hot rodding mentor once did boxed rods for flathead Fords long ago, a rather common practice at the time, they had plates welded to the sides to give them more beam strength, many were done with stick welding with any old stick rod like 6013 or 7018 and mild steel sheet, and they held up under significant loads of fuel at high RPMs. I'd guess (without researching) that T rods are made from simiilar material. An XRF gun at a junkyard might be illuminating about the Chevy rod alloy. Tig welding with ER70-S or ER80-S rod would likely work quite well, sacrificing a few junk rods would tell you how ductile the finished rods are. I'd be tempted to make a small end from new known material than to reuse the small end of the Ford rods in order to create a better mechanical joint to prepare for welding, in order to have more finished weld bead length than what a butt weld would provide.

I'm with you on this, I think with good joint prep and adequate layout you'll acheive sufficient strength. Balancing and honing should tackle the rest.

 

[cyanidekid]

welding a con rod is a screaming NO! a complete jackass move, BUT If your RPMs are low enough you can prob get away with it.
so.. chopping and channelling, and now "boxing" are a thing?? who knew...

 

[EmGo]

so.. chopping and channelling, and now "boxing" are a thing?? who knew...

Ja, boxed rods were a thing in ... the fifties ? The pinnacle of hot rodding innovation years ? In fact, there's a chapter in one of Phil Irving's books, maybe Motorcycle Engineering about the potential to make conrods as weldments. I'd consider that for this project, in fact. Get exactly what you want, probably no more work than finding then bashing around a bunch of parts that have been used for seventy years. Or paying two grand or more for Carillos.

Mr Irving was the engineer behind the Brabham engines that won F1 championship in ... 1968 or so ? He's no slouch.

Use 4130 plate ? Heat treat afterwards ? Should work nicely.

Or .... okay, this is overkill ... make them from bar, hollow, like Offy rods. As a lathe guy I find that appealling

 

[David_M]

Don's Boxed Rods from the fifties.

Read this.

A guy was making tubular cast rods back in the seventies. He used 17-4ph stainless steel. After casting, an opening was left under the top rod bearing's position, and for that, he made separate inserts that he welded in before machining and heat-treating. I think it may have been Dale Vogel from Vogel Engineering in Indianapolis.

 

[Limy Sami]

By the time you've finished effing about cutting and shutting a set of rods (with shall we say ''dubious results'') you're well on your way to making a set from scratch

 

[triumph406]

 

[Dan from Oakland]

"Don's Boxed Rods from the fifties."

Small world- I worked with Don Alpenfeld's son for many years early in my career. One day Bill came to me and said he was moving and had a bunch of his dads old tools in his garage and wanted to get rid of them and did I have any interest. I said sure and collected them up. Found out later who his dad was and what he did. I still have the egg scale that his dad used to balance his rods on in my shop.

 

[john.k]

I wouldnt worry too much about weld........modern rods are made from powder.

 

[cg285]

welding a con rod is a screaming NO! a complete jackass move, BUT If your RPMs are low enough you can prob get away with it.
so..

that's what my cuban employee said. they routinely cut and weld to mate russian pistons for their cars. he said they never drove fast so it didn't matter