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Large journal crank, S rods
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Author:  howey [ Mon Mar 04, 2013 1:18 pm ]
Post subject:  Large journal crank, S rods
Hi,

I bought a 1275 and box, in a subframe, from a member here. I haven't pulled it apart, and don't know enough to know exactly what I have. The intention for this motor is to be a mild combination that is capable of cruising, while still being lively enough to enjoy every now and then. It's first home will be my clubman, but it will eventually end up in a moke I have put away.

I don't want to spend fistfuls of cash on a forged stroker crank, but I believe the large journal cranks can be offset ground to S journal size for a modest stroke gain? I presume there are also pistons available with the correct pin height to suit?

My question is, how readily available are these cranks and/or rods? I may need one or the other, or both if I have a crank with cracks in it.

Is there a ball park price I can expect to pay if not wanting to wait for a bargain to turn up somewhere?
Author:  Lillee [ Mon Mar 04, 2013 1:25 pm ]
Post subject: 
To stroke the large journal crank it will cost you a packet ($750? to do it properly) so I suggest if you are on a budget to just checking the journals on the crank and reground if necessary and put new bearings, new conrod bolts and put it back together without too much work.

Plus if you go the Cooper S rods stroker route, you'll need to find a set of S rods ($$$ or $699 for H beam rods) whereas you can just use your large journal rods.

When regrinding you can ask for the crank to be crack tested first before proceeding which I would do. Never put a crank back in without checking for cracking...

As for how rare they are, they aren't as rare as Small Journal 1100S or EN40B S cranks, but they aren't dime a dozen either. I have one that is 000,000 on mains and big ends with a perfect taper and crack tested, and that cost me $250 years and years ago, but now I wouldn't part with it for twice that (just not worth getting rid of without twisting my arm if you know what I mean).

I'd take it one step at a time. Dismantle it and check the parts one by one and replace only if necessary. Otherwise we are talking big $$$$
Author:  drmini in aust [ Mon Mar 04, 2013 3:23 pm ]
Post subject: 
I have both a 1412 stroker and a 1360 (std stroke).
The stroker crank was a big journal- is offset ground, wedged and balanced.
The 1360 is a stock S crank, balanced. Both motors run S rods.
Big journal cranks really need wedging, because they have poor counterweight design.

The stroker motor has a bit more low end torque (partly due to the smaller cam), however it cost around $100 extra to offset grind 1/8" off, and would have cost $300-400 more to get wedged (if I'd not milled it myself). Then as Lillee says, you need to find some S rods (unless your motor has em in already) and modify their width to fit.

Bottom line- apart from pub points I don't think it's all worth the extra $$$.
My 1360 has more HP and is generally smoother. And now it's jetted right it pulls good from 2500 rpm up, even with the 282 cam and 1.5 rockers in it.
Author:  Bubbacluby [ Mon Mar 04, 2013 4:16 pm ]
Post subject: 
Lillee wrote:
To stroke the large journal crank it will cost you a packet ($750? to do it properly)



drmini in aust wrote:
it cost around $100 extra to offset grind 1/8" off, and would have cost $300-400 more to get wedged


So i assume grind it + 100 (for offset)

That what only be about $400 or so....


So in general what would a general machine shop charge to offset grind a crank??
Author:  willy [ Mon Mar 04, 2013 5:18 pm ]
Post subject: 
Lillee wrote:
To stroke the large journal crank it will cost you a packet ($750? to do it properly)


Where the hell do you pull these bizarre figures from?! :?
Author:  drmini in aust [ Mon Mar 04, 2013 6:17 pm ]
Post subject: 
Bubbacluby wrote:
Lillee wrote:
To stroke the large journal crank it will cost you a packet ($750? to do it properly)



drmini in aust wrote:
it cost around $100 extra to offset grind 1/8" off, and would have cost $300-400 more to get wedged


So i assume grind it + 100 (for offset)

That what only be about $400 or so....


So in general what would a general machine shop charge to offset grind a crank??

Bubba,
St George Cranks charged me $300 late last year to grind the mains and offset grind the big ends to 1.625" dia (ie stroke it).
A std regrind was $200. Could be more for Joe Blow off the street.
YMMV of course.

My $300-400 estimate for wedging was a guess but I think is close to the mark if you paid to have it done
.
I wedged mine at home, on a much smaller mill than GR's, it took me 6 hours and the bloody hot sharp steel chips went everywhere. And on this particular crank ^^ that I got stroked, the owner wedged it at work on a Bridgeport and it took him nearly 6 hours too.
But when I then balanced it, the crank was already spot on. Precision machining (by a toolmaker) has its benefits.

[edit] typo
Author:  surtees [ Mon Mar 04, 2013 7:04 pm ]
Post subject: 
I found a set of cooper S rods on ebay http://www.ebay.com.au/itm/mini-1275-co ... 500wt_1414
Not mine but might be worth a look if you want to go that way.
Author:  drmini in aust [ Mon Mar 04, 2013 8:10 pm ]
Post subject: 
If you buy s/h S rods, remember you don't know where they've been or what used for.
They need crack testing, new bolts (ARP), check/hone big end sizing, straightening, and then mods to width if building a stroker.
[edit] check the little end bore size too..
Author:  Kennomini [ Mon Mar 04, 2013 9:00 pm ]
Post subject: 
So what would be a normal price to pay for those rods on Ebay or just in general for S rods?
Author:  drmini in aust [ Mon Mar 04, 2013 9:05 pm ]
Post subject: 
I'd say 4 good looking ones with matching caps and no visible damage are worth $200 a set now. Scruffy rusty ones cheaper, but not worth the extra hassle.
Don't use the old bolts or nuts in either case.
Author:  Bubbacluby [ Mon Mar 04, 2013 9:19 pm ]
Post subject: 
Thankyou for explaining that Doc.

Going from no crank to obtaing a crank and stroking/wedging/balancing ends up being an expensive exercise.
Author:  howey [ Tue Mar 05, 2013 1:43 am ]
Post subject: 
Thanks for the replies, glad this has generated some talk.

Just looking around today, trawling the web, I didn't see anyone offering anything but standard length pushrods. Are they readily available in different lengths?
My background is that I am/was a mechanic. I now do some work off the floor, but in a diesel environment. My spare time is spent usually playing with V8s of the Ford variety. I've had 3 or 4 minis, but all a long time ago. Being a family man with a limited budget for toys always made it hard to have anything other than a family car. Even the V8s aren't my own. Anyway, I now have the clubman, and it's being used to teach my daughter to drive a manual. When she gets her license, and her own car, the clubman will be the recipient of an R1 engine, hence the reluctance to over capitalise on a 1275. It might be that a simple freshen up is the way to go with this one.
Author:  drmini in aust [ Tue Mar 05, 2013 7:21 am ]
Post subject: 
There are only 2 pushrod lengths.
Smallbore (these also used in 970S and 1071S), and 1275, which are ~3/8" longer.

[edit] If you need a new set of 1275 ones (as I did recently) I found Karcraft cheapest for these among local suppliers.
Author:  howey [ Tue Mar 05, 2013 7:32 pm ]
Post subject: 
surtees wrote:
I found a set of cooper S rods on ebay http://www.ebay.com.au/itm/mini-1275-co ... 500wt_1414
Not mine but might be worth a look if you want to go that way.


Thanks for the link. I ended up winning them. Waiting for the owner to reply to a message so I can go and pick them up.
Author:  surtees [ Tue Mar 05, 2013 7:48 pm ]
Post subject: 
awesome I hope they work out for what you want to use them for. Can't wait to watch an engine build thread.
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