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 Posted: Apr 25, 2017 11:22AM
Total posts: 268
Last post: Apr 27, 2017
Member since:Jun 18, 2014
Fellow Minoids,  OK, now I figured out what these over-sized pistons are.  They are AE #18463 Triumph Spitfire pistons for a 1296cc engine from 1967-72.  They are low compression, which would work out if I put a turbo on the engine.  Still undecided.  I need to measure the dish but I am guessing maybe 9cc and most likely 11cc.  They are 2.900 inches.  73.67mm.  Now I need to find a good gasket and some standard rings.  Suggestions?

Dogscarf

 Posted: Apr 24, 2017 04:35PM
Total posts: 995
Last post: Apr 24, 2017
Member since:Nov 3, 2011
Of course not!  It's just now, the available head gaskets make it mandatory!

Jemal

Sales & Technical Support at MiniMania

Follow progress on all my projects at CooperRoadMini.com

 

 Posted: Apr 21, 2017 06:59PM
TK
Total posts: 1042
Last post: Apr 21, 2017
Member since:May 13, 2002
We have always offset bored, even in the old days. it's nothing new.

 Posted: Apr 21, 2017 05:55PM
Total posts: 3251
Last post: Apr 24, 2017
Member since:Feb 26, 1999
so are you looking for an A or A+ block?

 Posted: Apr 21, 2017 02:54PM
Total posts: 995
Last post: Apr 24, 2017
Member since:Nov 3, 2011
Oh yes!  Boring to 1380 on bore centers leaves only .097inch wall thickness between 2 & 3!!  In the "old" days, head gaskets were good enough to work!  Now we 'off-set' bore to achieve about .115 inch between cylinders and that works fine up to full race compression.

You will give up an easy 10-15% of your power and torque if you go back to std or + .020....

Jemal

Sales & Technical Support at MiniMania

Follow progress on all my projects at CooperRoadMini.com

 

 Posted: Apr 21, 2017 12:35PM
Total posts: 268
Last post: Apr 27, 2017
Member since:Jun 18, 2014
The number on the casting is 18463 they are AE pistons.  I would only need one as three pistons are ok.  I need rings too obviously.  I was looking at the gap between cylinders 2 and 3 and it is damn small, maybe less than a 1/4 inch.  I don't think a gasket will seal there.  Still leaning toward liners, bored and honed to fit my .020 pistons I already have.  Total machining cost labor and liners $440.  Then I could just sell my new in the box 73.5 pistons.

Dogscarf

 Posted: Apr 21, 2017 11:03AM
Total posts: 995
Last post: Apr 24, 2017
Member since:Nov 3, 2011
Consider using forged pistons... Your machinist may find the looser fit acceptable for forged pistons, which have to be set up, um, looser!  If your numbers are right on, then you have .0063 piston to wall,  acceptable for forged pistons.

Any markings on your "2.9"" pistons?  Someone must have made them!

Jemal

Sales & Technical Support at MiniMania

Follow progress on all my projects at CooperRoadMini.com

 

 Posted: Apr 21, 2017 10:09AM
Total posts: 1177
Last post: Apr 27, 2017
Member since:Oct 8, 2013
Probably the same source as your mechanic but try LA sleeve for the liners they will custom make them if needed and pretty reasonable on the price to.
https://www.lasleeve.com/

Mini's are like buses they come along in a bunch

 Posted: Apr 21, 2017 07:21AM
Total posts: 268
Last post: Apr 27, 2017
Member since:Jun 18, 2014
It is not an S block, but later 1275 block.  My machinist said he could do the liners.  He also has a source for liners but I wonder if a source in the UK that does this thing as routine would be better.
Dogscarf

 Posted: Apr 21, 2017 12:34AM
Total posts: 9283
Last post: Apr 27, 2017
Member since:Mar 24, 1999
GB
If it's an S-block then liners are a good idea to reclaim some profitable scrap metal, something that is becoming increasingly popular over here as the straight-to-1380 brigade are finding out. If it's a normal block, then it would almost certainly be cheaper to find another core.

If our hosts don't carry big liners, then it's worth contacting Keith Calver http://www.calverst.com or Classic & Modern Engine Services http://cmesuk.com/ as they both are known to sleeve 1380s back to normal.

Metric is for people who can't do fractions...

 Posted: Apr 20, 2017 06:42PM
Total posts: 97
Last post: Apr 20, 2017
Member since:Apr 6, 1999
At 2.9" bore you are past the size for factory type liners (O.D. 2.875", 73mm) which would work with std or +.020" bores.  Oversize non-mini specific liners can be found to sleeve your block and will have suitable wall thickness to use your +.020" pistons.  If this is an S block, sleeves may also stiffen it up, a good thing. 

 Posted: Apr 20, 2017 04:16PM
Total posts: 268
Last post: Apr 27, 2017
Member since:Jun 18, 2014
Fellow Minioids,  I am back at it with this problem.  I have an over-bored 1275 block that currently has 2.900 pistons in it.  They are not in good enough shape to reuse.  I also have a set of brand new 73.5mm pistons which comes out to 2.8937 inches.  My machinist says they are too small.  Now I am thinking of sleaving the entire block and going to .020, which I also have new pistons for.  Thoughts?

Dogscarf
67 Aussie Cooper S
68 Cooper S