friend with lbc having engine troubles

[RickB]

My friend Pete went down the dark path and got a little MK1 Spitfire a couple years ago.
Well he was out on a run with his club last weekend and says he spun some bearings.
He pulled some things apart today and says one of his rods is "blue". He spoke to someone at BPNW who said he needs to have it rebuilt. I said "rebuild the rod??" and he said 'Yup'.

So - what can you tell me about this? Sounds strange to me.
Maybe his motor is rare and hard to get parts for, sounds like it's a little 1100 or 1197 or some such thing.

 

[dklawson]

You can re-size the big end of rods but I'm not sure I'd bother if the part has turned "blue". The common early Spitfire was the 1147. Some people do rebuild them but there are probably hundreds waiting in sheds as parts donors. I would look for someone divesting their collection of Spitfire parts and get a set of good, used rods for the rebuild.

 

[spritenut]

Triumphs! That's why I got rid of mine way back when.
Mine spun a main bearing, it was still new, 11,000 miles on it.
So I have been into Sprites ever since.
I have had rods "rebuilt" a machine shop can make them round again.
I always have mine checked and re-sized if needed on every rebuild.

 

[RickB]

I asked, it turns out his is the small crank 1296.
I don't know much about them, hopefully he can find replacements somewhere.

 

[dklawson]

If your friend is going to rebuild the 1300, you may want to post in the Triumph section of this board to get recommendations on how to squeeze more out of the engine. A lot of people swear by (not at) a properly rebuilt 1300.

 

[Billm]

Rick
Does he just want to put a 1500 in there?
BillM

 

[Bob Claffie]

Not quite as simple as it sounds. To true up the rod you have to cut the mating faces of the rod and cap slightly to make the ID undersize and THEN rebore the rod to the correct dia. This will throw off the balance a smidgen, usually not enough to bother a street engine. However spinning the rod bearing usually does a job on the crankshaft requiring it to be turned undersize necessitating new oversize rod bearings. Many shops automatically also cut the main journals too so you end up with all new bearings. Once you get to this point why not replace the rings and oil pump -- and so it goes into a couple thousand $$$. (And NO a 1500 is not a good substitute) Bob

 

[Hap Waldrop]

Rick, I wrote up an article here about resizing connecting rods when I was rebuilding Ray MaCaleb's 1275 engine, it's in the archive here or can be found on Ray's website in the "Spridget Project" section, in engine section www.raysmg.com

 

[RickB]

Thanks Hap - I'll send that to Pete.