Have all the parts for my 1275 rebuild ... Or so I thought.

Went to clean the pistons up tonight and discovered 3 of them are 040 and one is standard (wtf?)

So here is my question.

I have a standard A series block (needs reboring) and a good A+ series crank and cooper s small journal pistons and a 104 cam, stock 12g940 head. I want a solid, reliable and good speedy road engine. What should I do?

Option 1
Offset grind the A+ crank, use my cooper s small journal conrods and buy new pistons, thus giving me a stroked engine, with greater cc.

Option 2
Buy large journal conrods and new pistons and maintain the standard stroke.

Option 3
Something you know that I don't and please give me other options if they are better.

Note. This is for a club reg car, that I would like to keep up with traffic but don't expect to re-rebuild for many many more years.

I appreciate your input

Jonvan1

_________________
68 Ute (current project)
71 GT (storage 4 after ute project)
74 S (current project with kids)
65 mark 3 AH Sprite (weekend driver)

Sozz, I said small journal pistons but meant conrods.

_________________
68 Ute (current project)
71 GT (storage 4 after ute project)
74 S (current project with kids)
65 mark 3 AH Sprite (weekend driver)

I'll swap you the little ended rods for some big ended rods

I'd go with option 1. Rebore + stroked crank = more cc = more mumbo.

72.5mm or 73.0mm bore is a good size, as you still have a couple of rebores possible in the future.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

extend the life of your block as much as possible, they are getting hard to find these days. The gain you will make from overboring a lot is nothing compared to the gains you can make with a proper combination. Remember its not just the biggest of everything that will make it work but how you combine the right mix. Keep it simple. If you arent trying to compete for every ounce of HP then spend your money wisely.
Just do a 20th over bore (hepolites are good enough). Flick the S rods for 1100S rods (stroking can get very expensive from a machining point) Rather spend your money on a quality head. Cleanliness is the key, and check all tollerances. Then re-check them. get the bottom end balanced (crank, flywheel assembly and balancer). A little weight off the flywheel will help pickup and dont get too carried away with a big cam. Throw on a set of 1.5rollers if the budget allows. .....Just my 2c worth. Keep it very simple. You wont go wrong.

_________________
1970 Cooper S ex-Bathurst & ATCC
1964 Austin Cooper S ex-Group C race car
1967 Morris Cooper S ex-Group B
1962 Mini Speed sports sedan
1968-71 ex-Peter Manton Shell car

If you must use big journal 1100S crank and rods for cost reasons, mill 8-9mm off the big lumps on the rod caps, which served no purpose except to add weight.
Also, lighten their little ends by linishing the lumps off, so the rod eye is a round shape.

Here's some I prepared recently for 1970minik's 1360-

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Unless the journals are perfectly round and the same size, you will need to grind anyway to ensure reliability.
Spiro at St George Crankshafts will offset grind for around the same price as a resize grind and it is only going to be a couple of hundred bucks at most (last time i got it done was 2006 -$150). And he does a stirling job.
If you already have the small journal rods, this is the way to go because they are often more expensive than the offset grind itself!

cheers
michael

_________________
the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

Spiro now charges $150 for a straight regrind, add another $100 for a stroker. There's another 1/8" of metal to come off, and time is $$.

Then for a stroker add $150-$200 for some S rods, some more $$ for narrowing them, and $$$ for a new set of ARP bolts. It does add up...

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

He said he had the rods already

_________________
the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

Yeah alright point taken, I'm just saying there are more costs, even if you DO have a set laying about.
(If anybody else here needs a set to do the same, this is what things cost).

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Throw in piston machining as well......If you are on a budget and not looking for every ounce of power, stroking may not be the answer......Sure it gives you bragging rights to say you have a stroked motor but does that really matter? Just keep in mind real HP isnt made below the top of the block.

If you have all the money in the world to blow on it, chances are you wouldnt be asking this question. Do yourself a favour get Vizards big book on how to modify the A series. Will answer many of your questions and get you thinking along the right lines.

Oh, if you do modify the small end on a set of 1100S rods make sure your grinding lines and linish lines follow the length of the rod, not across it.

Good luck with it. G.

_________________
1970 Cooper S ex-Bathurst & ATCC
1964 Austin Cooper S ex-Group C race car
1967 Morris Cooper S ex-Group B
1962 Mini Speed sports sedan
1968-71 ex-Peter Manton Shell car

massive +1