28hp Speeditwin busted rod / swap options?

[kdiddle]

Unfortunately my 1964 Speeditwin lost a piece of the lower connecting rod over the July 4th holiday and I have the engine torn down to discern the damage. Its amazing how much damage such a small piece of metal can cause. It seems there is no damage to the bore, but the piston skirt and crankcase bottom took a pretty good beating.

I have an entire spare powerhead that was supposedly running well when it was removed, though it has a few issues that prevent me from wanting to use it as is (several broken bolts that need extracting from the block being a large part of that reason). Plus I also don't know how good the compression is, while my block is newly honed with new pistons and rings - so I'd like to be able to reuse my good block/pistons if at all possible, which brings me to my question.

Question - is there any reason I can't pull my pistons out, swap the connecting rods, crankshaft and crankcase bottom from the 'old' engine to my powerhead (ensuring the connecting rods go back into the same orientation as before)?

 

[racerone]

When you put this engine together describe how you installed / torqued /lined up the rod caps.-----Just need to know.----These 28 HP blocks use the same crank / rods as the 40 HP engines.

 

[racerone]

Describe how you installed / lined up / torqued the rod caps.----4o Hp models used same crank and rods.

 

[kdiddle]

When I reassembled last time, I ensured the dimples that were on the rod/caps were lined up and on the same side. I understood that they are directional and have to be put back on in the same orientation. Was that the correct method?

 

[kdiddle]

For what its worth, I had about 8hrs (or so) on this engine after 'rebuilding' it...The pistons/rings were new, everything else on the bottom end was re-used. It was running great until it wasn't...:-/

 

[racerone]

Well those caps are fractured and you have to adjust / fiddle with them so that they fit EXACTLY the way they broke during the process at the factory.----Just making sure the dimples are there is not good enuff.----If you just torque them up the motor will go " BOOM " in short order !!

 

[kdiddle]

Ugh now I wish I would've marked the old/new caps before removing from the crankshaft that I was gonna install. That way I would've known for sure...

How do you know for absolute certain they're oriented the way they were fractured? I'm assuming there should be no gap, but is that the only way to tell?

 

[racerone]

Well it is very , very obvious when you have the correct cap on the correct rod.--------There will be no gap and parts go together perfectly matched.-----It takes some time to learn how simple this really is !

 

[jimmbo]

Ugh now I wish I would've marked the old/new caps before removing from the crankshaft that I was gonna install. That way I would've known for sure...

How do you know for absolute certain they're oriented the way they were fractured? I'm assuming there should be no gap, but is that the only way to tell?

The joint between the Rod and the Cap will be almost invisible when the fit is correct. And there will be absolutely no hint of a edge when running a fingernail across it

 

[kdiddle]

Thank you both for your responses... Hopefully I can keep the engine together on this round...