60 thou' u/s crank

[JOWETTJAVELIN]

The 803 rebuild is progressing slowly, but the crank is nearly out. My question is, with it being 060 undersize and badly scored on one of the journals, should I weigh it in?

[crossword]

JJ ,
I would ask the advice of whatever engine machinist is local to you . I recently sent a MGB crank with obvious scores on pins and journals , already 20''' under to one of ours
It came back still 20''' and polished . It may look worse than it is . It may also be on the top limit of 60''' and have enough 'meat ' on for polishing to be effective .
Having asked for opinions and a price , you can take it away if you are unsure , or indeed elsewhere .
Good luck with it .

Andrew

[chickenjohn]

I was just going to suggest the same as Andrew, before writing it off, speak to your local engine reconditioners!

They may be able to save it.

[JOWETTJAVELIN]

Thanks, I'll see what the pros think then. Just assumed with it being in such poor condition it would only be fit for scrap!

[les]

60thou and badly scored, I'd agree, scrap ---------wish I was as optimistic as the rest!

[bmcecosse]

I can only say - DO NOT be persuaded to have the crank 'metal sprayed' - it's a complete waste of time. However in extremis it could be welded up and then reground. But frankly - for an 803 engine....is it worth it? Use a 948 crank instead with 948/1098 conrods... no one will know!

[JOWETTJAVELIN]

That's the thing, I am no expert on parts interchangability - never knew the 948 crank would fit. This would also I suppose kill two birds with one stone in that it would solve the 803 problem of running bearings.

I'll get an expert opinion on the old crank but as you say there is no point lavishing money on it. I do have a std 803 crank which will also need a regrind but that is in the other engine still... more work to get that out... sigh.

At least I'll have practically a brand new engine at the end of all this.

[bmcecosse]

Exactly - the big ends are larger, which is why you need to use the 948 rods.....

[mike.perry]

No point in me offering a 50 thou polished 803 crank then.

[bmcecosse]

Well yes - there could be ! Can you get shells at +50???

[JOWETTJAVELIN]

No point in me offering a 50 thou polished 803 crank then.

That would be nice Mike, if the shells are available!

[mike.perry]

Will have to check that it is an 803 crank as I was told.
Are the mains a different size on the 803 and 948 cranks?
If it was as easy as swapping the cranks and rods then surely it would be common practice

[bmcecosse]

Mains are same size - the big-ends on the 803 are smaller than the 948/1098 cranks. And.the 803/948 have same stroke - so it's perfectly possible swap, provided the 803 pistons will fit 948 rods? Maybe possible to bore out an 803 to take 948 pistons...? I don't know if anyone has tried that?

[JOWETTJAVELIN]

OK, my man in the engine remanufacturing business has checked and unfortunately nothing can be done with this crank.

A shame but everything wears out eventually.

[mike.perry]

Mains on my 803 crank measured 1.712 and ends 1.400. Is it still usable?

[bmcecosse]

The mains started at 1.750 - so probably 40 thou under? I'm not sure what size the big-ends started at.... 948 etc are 1.500 when new.

[liammonty]

I'm pretty certain you won't be able to bore out the 803 to take 948 pistons- I'm alomost certain that I've read that the 803 has additional water channels between cylinders 2 and 3 (I think) that were deleted with the increase in capacity to 948, to allow for a strong enough block to cope with the almighty 37 bhp.

If you really want to rebulid the 803, I'd use the best parts you can get hold of- it might prevent it from breaking for a little bit longer that way... Personally, I think rebuilding an 803 is futile if you want to actually 'use' the car, but I'm sure there are plenty of those out there who will disagree with me!!!

[JOWETTJAVELIN]

Yes, I would be uprating it but have decided to rebuild the original, matching numbers engine because there can't be many about now with the engine they left the factory with.

It is a second car now so will be OK for pottering about and those longer journeys on the A roads.