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crank re-grinds


ferny

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I've been think about the engines and what to do and I'm semi-decided on getting the crankshaft in the 13/60 reground. It's small bearing and in the long term I want a revvy engine so that makes sense to me. Having never got it done before I'm doing some research first. What sort of costs are involved? £10ish per journal? How do I spec. what I want done and how (may seem a silly question but not as silly as having the engineer throw a term at me I don't understand)? Anything specifically I need doing/asking for?

Whilst I'm at it, is it worth going to the effort of getting the rods and pistons balanced etc? If so, what are the costs there? At some point it'll have a TR5 profile cam. in it and megasquirt.

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Hello Ferny,

if you can find someone that can tuffride the crank for you, that's worth doing as you seem to be looking to drive it.
I balanced the pistons on my engine but didn't bother with the rods (I used an accurate set of scales at work). I also had the crank\flywheel and clutch balanced.
There's nothing very complicated about grinding the crank and the machinist will tell you what size it will go to. I can't think of any odd questions he may ask?

Alec

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On the balancing front, I built an engine out of 2 that went in my Herald estate.
I had 8 std sized pistons and 8 rods. I weighed then all on Gill's kitchen scales, which is to 1g.
I then got the 4 closest matched pistons, and the 4 closest rods. heaviest piston with lightest rod. In the end they where all within 1g of ech other as pairs, so I think that helped. The worst scenario was prabaly about 25g out, but there was 1 odd piston  :-/

Get the crank ground, new set of bearings and thrusts, hone the bores and a new set of rings.
I reckon do the TR5 cam and skim the head while you are at it, then its all sorted :) about another £100 odd?  

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ferny wrote:

Whilst I'm at it, is it worth going to the effort of getting the rods and pistons balanced etc? If so, what are the costs there? At some point it'll have a TR5 profile cam. in it and megasquirt.


Mine cost around £100ish for a dimensional check and regrind (it was bent a smidgen that was taken out by the regrind). before you get any work on it then a crack test will ensure you are starting with a good crank, no point grinding a cracked crank.

Balancing of the crank rods and pistons will only do good things especially if you are thinking of upping the power/revs a bit. Smoother running is the obvious advantage and this also leads to reduced wear on your bearings. Is a good bit od future proofing

Tiftriding is another good upgrade at around £100, but possibly not totally needed if not holding high revs a lot.

Andy

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Good point about the crack testing - these cranks do break occasionally, usually across the webs between the front main and no.1 BE or between the the rear main and no.4 BE.  Often caused by a dodgy regrind which doesn't leave the correct fillet radius on the edge of the journals.  They could do with a torsional damper too although Triumph didn't see fit to provide one......

Nick

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