Morris Minor Owners Club

Hi folks,
I need to pick brains again on the van engine rebuild. My nice new pistons dont have front stamped on them as the manual says they should but they do have an arrow on the top as in the pic below, is this front? They do have a slot machined in the side which matches the old piston so I could work it out from that but it would be nice to get it right!
The other pic is of the bearing caps I just need to know that they go the right way as in the pic.
Thanks, next is the camshaft and timing chain, that looks fun![frame][/frame][frame][/frame]

These look to be very deep dish pistons - hope they are not 'low compression'! I imagine the arrow should point to the front of the engine. The bearing caps (and that's a 'big end' not a 'main') must go on the rods they came off - and they must go on with the little tags against each other. So in other words - just flip that cap over onto the rod and bolt it up.

van engines are meant to have low compression pistons....

My guess would also be that the arrow indicates front, but personally I'd align them based on the features to the old pistons.

shells - the tabs go opposite (i.e one by each bolt) and there should be a number marked on the rod cap to ensure it goes on the correct rod. It's best to use the number on the cap/rod to match the right bore in case the engine comes apart again - otherwise it'll get confusing at the next rebuild.

Low compression pistons were originally fitted to van engines - to allow them to run on the very lowest/cheapest octane fuel (2 Star) - which we no longer have ! Engines with 'high' (!) compression pistons run very much more efficiently.......
Absolutely important as you assemble each bearing (with lashings of clean oil) to check that the crankshaft turns easily by hand before moving on to the next bearing.

Is there a way to check the pistons to see if they are low compression as there not what I asked for from the suplier? The engine that is being rebuilt for the van is from a traveller (1098-- my fault for saying van engine) The parts Im buying are for a traveller engine so hopefully the engine workshop has got the pistons right. if they are low compression does that = low power?

As far as I can see they are Mini 1100 pistons (20397 +30) from your picture) - so no suggestion of low comp there - they just looked to have a biggish dish in your picture - but I guess just the camera angle. Yes - if they had been low comp that would have lost a bit of power - but they seem to be the right pistons - sorry I mentioned it now!

20397s are 7cc dish, if that helps, Roy.

Well found - but what dish are original Minor 1098 pistons ? I ask because thinking about it - I'm wondering if the Mini 1100 engines actually had the standard small valve head and not the 202 head - some have suggested that in the past on the Mini forums. The small valve head is only 24.8cc chamber against the 26.1 chamber of the 202 head.

Thanks for the info, Im glad the low compression was mentioned as im a complete novice on engine rebuilds so the more info the better, just keep it simple!
Is it worth me tracing the number stamped on the piston to be on the safe side, cus i dont want to swap the engine again.

Well you can have a look through these to see what is available.
http://www.minispares.com/Search.aspx

Your link not showing anything Kevin. But searching through their site - they only list the one 1098 piston - the 20397 at +40 and no clue to dish size. At least the price is not too bad - I found them in Aus - but v expensive!

The plot thickens, Ive got the piston box in front of me and it says; AE federal mogul 20397v1 .020 Austin/morris.
Ive had a look at some websites and they seem to be Mini 1100 pistons, anyone out there know if im ok to proceed with these for the Minor, its the same basic engine.
thanks

It is the same basic engine - same stroke/bore etc - I thought your piston said +30 - but it may be + 20 (my eyesight not what it was!) . Just check what size bore you have - and are the pistons the same. My only sliver of doubt is if the Mini 1100 engine still used the standard small valve head with 24.8 cc chamber and had larger dish pistons to keep the CR the same. Our Minor 1100 engines all used the 202 head - with the 26.1 cc chamber - so a smaller dish would be best. I would assemble and then run a compression test. If it seems a bit low - just skim the head to bring it up! Not the end of the world.

No warranty on this info, but I've a strong 97% feeling that those 1100 pistons came in 7cc, 3cc and flat-top. If so, I'd have my money on those being Morris Van pistons



Found it.
20397 7cc listed as 8.5:1 on a 12g202 head
16179 3cc
18520KR 0cc

Where did you find that Bill - i've been looking around and found v little info. 8.5CR while not the greatest - is I think the original standard - so should be ok.

shells - the tabs go opposite (i.e one by each bolt)

I disagree w/this, typically the indexing tabs go beside each other, then I checked the BMC manual, and lo and behold the Morris is typical, see the manual, page AA.5

I agree - the tabs DO NOT 'go opposite' - I've edited my original post to make it even clearer - that the tabs go TOGETHER - ALWAYS.

bmcecosse wrote:Your link not showing anything Kevin.

Just tried and it seems fine.

Well - it goes to Minispares website - but not to anything specific - like pistons!!

Wow! Now Im confused!