Pistons

[pigeon56]

Hi

My 1850 engine is being rebored but i need to find at set of pistons which are standard +20 thou.

Unfortunately the machine shop have told me that they are unable to rebore further to take a bigger size pistons due to the size of the liners.

[Mad Mart]

Do you want new or used?

[pigeon56]

Hi

Prefer new but if i cannot get new would consider used.

[cleverusername]

Are you sure they can't bore it any larger? I have had an 1850 block bored up to Sprint size. That is 87mm to 90.3mm, which is 3.3mm.

Now to be honest I don't really understand imperial measurements but I am pretty sure that is way over 20 thou.

[Mad Mart]

I had the same thought. 0.020" is only just over 0.5mm.. They should easily be able to bore it to +0.040".

[xvivalve]

The OP says it is a linered block, so it would be the residual wall thickness of the liners which dictates what they can and cannot do.

[Mad Mart]

Liners are fitted from the factory. They have a certain OD and ID. The ID is bored & honed to standard size and are able to be bored out to at least +.040" if not +0.060". Even if replacement liners have been fitted, the OD would still be the same as the originals.

[xvivalve]

I too thought that until recently Mart, particularly as liners are shown in the factory parts book, but those who know better contested this not too long ago…

https://forum.triumphdolomite.co.uk/vie ... rs#p327975

[Mad Mart]

So is that just the 1850s? as I've never come across a Sprint block without liners. I had assumed the 1850s were the same.

[2Toledos]

Hi

My 1850 engine is being rebored but i need to find at set of pistons which are standard +20 thou.

Alas, I only have new Hepolite sets either side of that: Standard and +0.040".