Technical Con Rod substitution.

Try heavy truck diesel rods.

 

The last pic with all 4 rods is how these went into the engine. I have done other sets where I ground and smoothed the rods after welding, but this set was going in a mostly stock T engine. The rod set in my T speedster looks very similar, and has been spun up to 4k many times over the last dozen years and probably 30k miles. If I had to guess, I would say bout 60-70hp…

Here is a link to the model T forum where I discuss the process

https://www.mtfca.com/phpBB3/viewtopic.php?f=2&t=35219&p=273732#p273732

 

Not sure but somewhere near 3-3500

This engine is a 14/40 Vauxhall engine 2.3L or 140CI rated at 40hp from the factory.

 

Thanks @Kevin Pharis, I'll look into it.

 

Would any of the Vintage racer / hillclimbing/ trialling fraternity here in the UK have any information ? The VSCC for example or perhaps someone like Ivan Dutton ( Shed Racing on you tube) all sorts of interesting vintage stuff on his you tube even though he is a Bugatti Specialist.

 

The flaw is that they are aluminum.
Aluminum has no fatigue limit. Steel, as long as the load stays under the yield strength, will last forever. Aluminum, no matter how gently it is used, WILL fail eventually.
Aluminum rods are common in drag racing, but they need to be replaced on a regular schedule.

 

@Outback with mentions of tractors I was reminded of the Farmall M which has a rod length of a bit over 10 inches. I think 10.3 or 10.4 somewhere around there. I think the rod journal size is a bit bigger than your crank though I'm not certain. The old John Deere 2 cylinders also had quite long rods but again probably larger journals.

 

Those rods did remind me a lot of B or H John Deere rods, but I don't have specs on those.

 

I agree with what you said, but we don't know that fatigue is what is the problem. They use aluminum rods in lots of small engines like lawn mowers and they last a long time. In racing, they get extreme stress on them.
I was wondering if the failures were from wear if no bearing or bushing was used. The titanium rods used from the factory in LS7 engines was known to have galling problems even though they had bearings. I thought if it was wear, that maybe closing the bore by cutting the caps and rehoning might work.....and then use better synthetic oil and possibly a modified oiling system. Don't know if its a splash fed or a pressure fed system.

 

They do have bearings, they are poured Babbit bearings, & the bottom end is fully pressurized.
I suspect that the main reason for replacement is the worry about the fatigue life as @Relic Stew mentioned. .

Part of the reason for such a long con rod is because these engines have a separate block & crankcase arrangement.

 

International Farmall M tractor rods are 10.3", I think.

 

The Teledyne/Wisconsin VH4/VH4D engine has a long connecting rod, and the ID of the big end insert bearing is 1-7/8".

 

My boss is connected in that world & it would seem a suitable alternative (aside from new rod's) is yet to be found, or is not widely known if so.

 

Very good, will do some digging

 

Wisconsin 8.5" long.
Having trouble finding the diameter of the Farmall - one place said 2.5" but not sure yet

 

I would contact an Aircraft engine builder, there are a few in Melbourne and maybe sale and see what they may have. aircraft engines are often rebuilt on hours, not condition. Therefore you may end up with an out of hours set of conrods to your dimensions at a fair price.

 

I happen to know a couple. Parts like con-rods will get re-used subject to crack testing usually.

 

wouldn't the substitution of steel rods require adding weight to the crank counterweights?

 

I still have to wonder about the point of failure, and the cause of failure. You seem kind of vague on what actually is failing and why. I would wonder if maybe the rods failed because of things like poor oil and seizing or if they just came apart during normal operation. Also, if they were hot rodded beyond normal expected rpms, not well balanced.........lots of reasons that they might fail.
If you replace them with new rods, will you hot rod it? Will new rods be any better than the original rods? If you find alternate rods, will they be any stronger...will they be heavier? I wish you well on your endeavour .

 

I am a little vague because I don't have much good info. The Ally rods originally had a 'bob weight' that was on the end of the rod, these bob weights were known to fly off.
My plan is to 'hot rod' the engine, the later cranks were counter-weighted (which I have).
Mostly Restorers who have some money will replace the Aluminum rods with steel ones, the original's are forged, but most people are nervous about keeping a 100yr old aluminum rod in service due to the potential of work hardening & stresses opening the door to failure.
Refer to @Relic Stew's post earlier
The oil system is quite good for an engine built in the 20's.

 

@Six Ball I'll leave this here