The Triumph Dolomite Club - Discussion Forum

Rimmers list max oversize on 1850's as 0.020". Is this for piston availability reasons of is the core thinner around the bores? Thinking of using a brand new 1850 block and boring it to suit 2.0

Also is the 1850 crank the same as sprint or shorter at the front for the duplex gear?

Cheers

Tony

The cranks have different part numbers: RKC278 = 1850, RKC514 = Sprint.

Not sure what the difference is, but I think historically folk have put the duplex gear onto an 1850 engine. You'd need the deeper timing cover though.

I understand the 1850 block would need Sprint liners fitting, but I'm prepared to be corrected on that...

The 514 part number appears on rimmers as 1850 and sprint crossdrilled (but with different suffix) that made me think they may be the same. If folk put the duplex sprocket on and deeper cover it may be the same? Block is more important really, I wouldnt want liners fitted if poss. The factory maybe started with different castings but that seems expensive although boring a further 3.5mm approx would be time consuming too. Maybe Jeroen has done it (or Hans)

Tony

I was under the impression that the blocks were the same, bored out the same but the sprint bore was then honed to size and the 1850 had liners fitted to reduce the bore size and then honed.

Malcolm

That would be good if so. I could cut the liner out and then final bore /hone to 90.3mm . Maybe thats why max oversize is 020 thou?

Tony

just looking at the Rimmers web site, it would appear that the 1850 and sprint blocks both use liners but of different wall thickness, so i was partly right, both blocks machined the same but different liners fitted to achieve bore size,

so you could cut out the 1850 liners and fit sprint liners which are still available.

M

Yes maybe, but sprint blocks are not linered from the factory (unless they were saving a block). Rimmers used to sell std bore sprint blocks that were generally lined to get back to std bore. Out of the 5 I have (sprint blocks) none have liners. Be interested in finding out the O/D of the 1850 liners.

Tony

Are you certain Tony? I thought they were all linered, part number 158700; I took Quicksprint back to standard from +20 by replacing the liners

Took years ago the heads off all my 1850 blocks. The few lined ones I weighted in and almost all were unlined and I did keep for reboring to sprint size in the future.

All the "project" engines through the years started as solid 1850 blocks and ended up as std bore sprint blocks. One out of ten was lined.

Jeroen

Ok Jeroen that makes sense. If the 1850 is linered do you know the size of the liner on the O/D? Would a removed liner leave enough room for boring to sprint size?

Alun, Im pretty sure the liners in sprint blocks are for repairing and proper blocks would be no liners. The ones I have here are non linered

Cheers

Tony

I always thought Sprint blocks had liners...I was wrong:-

viewtopic.php?f=3&t=26137&p=250006

Pretty much as I thought then although I Knew mine didnt have any nor do any iron blocks Ive seen unless its for reclaiming.
Still it would be nice to know what the liner O/D is on an 1850 so if I buy a new block from Rimmers and it has liners fitted I can safely bore to sprint size ie the liner O/D is not bigger than 90mm.

Cheers

Tony

I see no reason why you cannot bore an 1850 block but I do remember some saying the castings were not that good quality so actually you may be better lining it. Of course there's nothing wrong with using liners, though perhaps at the extremes of performance you may not want to. Of course linering means you could use standard sized pistons which can be easier to obtain.

I thought mine was linered but it's not so I was able to easily go to 1st oversize. Some engines are linered as standard like Jaguar XK so you can have many rebuilds!

I dont like the idea of removing parent metal when its not needed, especially with the weak area around the main bearing saddles. Not pushing any limits power wise so maybe Im being over cautious. The engine in question will be my spare with the VW pistons fitted and at 90.5mm just right for a standard bore with a clean up. If it works I'll produce a few sets

Tony

I'll be interested to see how you get on with the VW pistons. Be good to see how they compare in terms of design as well as compression ratio etc.