pistons

[stuupnorth]

Hi technical gurus
looking for a set of pistons for my 1098 cc midget engine(10 cc engine code) for rebuild
best place to get them ??
cheers
Stu

[bmcecosse]

Frankly - if I had a 10CC engine, I would see what it's worth to a formula Junior racer! In a Minor - it's no better than any other much less valuable 1098 engine. Depends what you plan for the engine - just a rebuild, or upgrading it? Std bore - or a rebore ?

[stuupnorth]

Hi mate
I'm just looking to rebuild it up standard not too fussed about power
it might need a overbore only to clean up bores
as its a mg version are the pistons any different I think they are flat top pistons in the 10cc engine
am I right??

[ACDodd]

Try www.calverst.com

Ac

[bmcecosse]

I doubt they are flat tops - the engine power spec etc is no different to the normal 1098. What's in it right now?

[liammonty]

I doubt they are flat tops - the engine power spec etc is no different to the normal 1098. What's in it right now?

Eh?! They were 55 bhp from memory - the standard 1098 in the Minor was 48 bhp. It will (or would) likely have a 12G295 head, possibly raised crown pistons and a set of Roy's favourite twin carbs to give it that. Of course it may have been robbed of those bits now.

[bmcecosse]

Yes - no different to the normal SPRIDGET engine I should have said......with the 295 head and tiny twin SUs........ Thanks for pulling me up on that one Liam - I had thought it was a bit obvious...... The BLOCK assembly has no power advantage over any other 1098.. they were only made to give them a strong 'production' block and crank for FJ racing - and as a pre-cursor to the Cooper S engine range.

[liammonty]

Well, that's put me back in my place

Bizarrely (or so I thought) the one I had had the 295 head but with dished Pistons. I wonder if the dish was less than on the ones used with the 202 head. I'd have thought with the 295, the compression would have been low otherwise.

[bmcecosse]

Not at all Liam - it was my mistake.

[liammonty]

Not at all Liam - it was my mistake.

It's all tongue-in-cheek Roy! That's not conveyed terribly well in writing sometimes, unfortunately.

[bmcecosse]

I know -but we have to have a little bit of fun....

[stuupnorth]

hi all
thanks for all the feedback
with regards to the engine
as far as I know it complete as it left the factory ie twin carbs and 295 head
haven't checked the pistons yet raised or flat top
just going to rebuild to use for road use

[bmcecosse]

See the edd barker engine build and ask him where he got his pistons.... But please don't start putting the stupid pockets in the block - if you decide to go for a 940 head!

[philthehill]

bmc
Pocketing the block is not stupid but a different way of fitting a 940 head to a small bore block.
Thank goodness we all have different ways of doing things otherwise it would be a boring world.
Phil

[bmcecosse]

It's all gone wrong in Edd's case - and if you pocket the valves it's only the head at risk (and can be rescued in future by fitting unleaded seats if needs be, the block remains standard, it's much easier to do (10 min job), it lowers the CR nicely by creating a full valve diameter dip in the head, and Calver ( ) even claims it improves gas flow down the exhaust throat, I can see where he's coming from with that - although I am slightly skeptical there. Having done pockets 50 years ago (full S head on a 998 with 649 cam ) , and sunk valves several times much more recently - I know where my vote lies...... Have you ever done the job Phil?

[edd_barker]

I'd struggle to disagree my pockets are pretty stupid! Stupidly deep.

Pistons are standard 'County' brand supplied by engineers. They have a lower dish than the standard Morris ones, 3cc rather than 7cc. Not flat top. If you happen to need +.040 give me a call!

Edd

[philthehill]

bmc
In reply to your question above I have never had to (or would want to) recess the valves into a 940 head or physically fit pockets into a small bore block but that does not mean I have no experience of pocketed blocks or of pocketing the block.
As an aside - My 998cc Minor engine had a 12G295 head with larger valves and was gas flowed to suit, a 649 cam was fitted but that is another story.
It has not all gone wrong in Edds case as once you deviate from standard things have to worked through. He will get there but comments like "it's all gone wrong in Edd's case" are not helpful to Edd.
Lets think positive!
Phil

[bmcecosse]

The pockets have gone wrong - and the top rings are now in danger.....and I bet it has cost a small fortune at the supposed 'engineers'. The job is always a bodge - fitting another head not intended for that engine - the far preferred way these days is to keep the mods in the head. Costs much less, no risk to the block or pistons, and easily reversible if the result is not as expected. The 940 head on 1098 is a terrific modification, very well worth doing - and is not expensive. Just don't over-engineer it unnecessarily.

[stuupnorth]

just removed the head
its defo a 295 head and the pistons have a dish in them
Stu

[bmcecosse]

That too is a good head - although the ex valves are really too small. A 940 is much much better. Hopefully the 295 has been skimmed at some point - measure the thickness - they all start at 2.750" - otherwise the CR will be horribly low. New inlet valves for that head are also stupidly expensive these days for some reason, so take good care of them!