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large journal cranks
https://www.ausmini.com/forums/viewtopic.php?f=5&t=50246		 Page 1 of 2
Author:  Bubbacluby [ Fri Feb 13, 2009 10:05 pm ]
Post subject:  large journal cranks
can somebody please explain to me how to determine a large journal crank from a standard cooper s/GT journal crank??

Also are all 1100S cranks large journal??

Also can any large journal crank be stroked or they have to be a non-touched crank

AS i want to start colecting bits and peiced to build a go hard stroker motor

Thanks for you help

Brenton
Author:  850man [ Fri Feb 13, 2009 10:19 pm ]
Post subject: 
Large journal cranks are just that, the big end journals are much bigger than a std 1100 S or Cooper S crank. 1.625 for the little one & 1.750 for the big one.
The main bearing journals remain the same size between the two.

1100S cranks were both small and large journal

Only large journal std size cranks can be stroked, there offset to the desired stroke & macnined down to the smaller journal size, requiring S rods.

Also, if you want to use a 1100S small or large journal crank in a S block you will need oversize thrusts that are no longer made. I have a few sets if you need them.

Regards
David
Author:  mini7boy [ Fri Feb 13, 2009 10:39 pm ]
Post subject: 
850man,

are you sure that only a standard crank can be offset ground to increase the stroke? I don't see why a reground crank cannot also be stroked using the same process. Of course, the amount that the stroke is reduced will be less, but not much so.
Author:  TheMiniMan [ Fri Feb 13, 2009 11:13 pm ]
Post subject: 
It really is best" to use a std/std large journal for increasing the stroke,,, (if you can find them) .... it is, after all, the whole point of doing it... altho you can go further past std small journal size when doing it to gain some back if you use an already undersized large journal, but it starts to get weaker the smaller you go & you also end up with less to carve off (if need be) at any later stage for repairs.

I`ve made .080 undersized cranks for 2 of my road engines , takes them to about 86mm stroke (makes them 1510cc-ish) with 74.7mm bores


:-) I have a big one :-)
Author:  drmini in aust [ Sat Feb 14, 2009 6:38 am ]
Post subject: 
850man wrote:
Also, if you want to use a 1100S small or large journal crank in a S block you will need oversize thrusts that are no longer made. I have a few sets if you need them.

Regards
David

They ARE still made in Oz, by ACL.
p/no is 2T2204+.030. I'm looking at the packet... :wink:
I got them from www.minis.com.au
Author:  Bubbacluby [ Sat Feb 14, 2009 12:05 pm ]
Post subject: 
I was at a mates and he is getting rid of some of his stuff and he has two cranks there (that i saw amongst others) that are 12G1505A in raised lettering. By veiwing with the naked eye one has larger journals than the other.

* Is the one with the larger journals a large journal 1100S crank??
(or i really have to measure it ?)


* How likely is it that it would be cracked (ie was it a common fault?)


* Also i have been told that 1100S blocks are better for performance than S blocks because they are stronger without the removable chest covers.
(plus my mate doesnt want me to use an s block because it is an S block)

* Do i have to use S conrods to stroke it?

* So what would an appropriate price be to pay for the 1100S block and journal with and without rods??

Thanks everyone for your help because this is a learning curve for me, and something i have little knowledge about, but am keen to learn


Thanks Brenton
Author:  drmini in aust [ Sat Feb 14, 2009 3:33 pm ]
Post subject: 
Bubbacluby wrote:
I was at a mates and he is getting rid of some of his stuff and he has two cranks there (that i saw amongst others) that are 12G1505A in raised lettering. By veiwing with the naked eye one has larger journals than the other.

* Is the one with the larger journals a large journal 1100S crank??
(or i really have to measure it ?)
12G1505 is large journal.



* How likely is it that it would be cracked (ie was it a common fault?)
50/50, get it crack tested before shelling out $$$.

* Also i have been told that 1100S blocks are better for performance than S blocks because they are stronger without the removable chest covers.
(plus my mate doesnt want me to use an s block because it is an S block)
Yes they are a stiffer block (and heavier).
* Do i have to use S conrods to stroke it?
Yes.

* So what would an appropriate price be to pay for the 1100S block and journal with and without rods??
Block I wouldn't pay more than $250,
Crank it depends- whether it needs a grind, what size it's worn down to. $50-$300 depending on how lucky you are.
If worn work on paying $150 approx for a regrind, add another $100 if you want it stroked.
If stroking it I would get it wedged too, then balanced.
If it's cracked, walk away. :lol:
1100S rods- $50/set, S ones- $100/set and up.

Thanks everyone for your help because this is a learning curve for me, and something i have little knowledge about, but am keen to learn


Thanks Brenton
Author:  Bubbacluby [ Sat Feb 14, 2009 4:21 pm ]
Post subject: 
Thanks Kevin, Very much appreciated.

Just what i wanted to know
Author:  TheMiniMan [ Sat Feb 14, 2009 4:25 pm ]
Post subject: 
Bubba,,,, If/when you decide to go the stroker cranky route,,, you will need those "S" con rods yes,,, but you also need to skim about 15thou of each side of them...K?
Author:  Bubbacluby [ Sat Feb 14, 2009 4:27 pm ]
Post subject: 
ok why do i need to do that???
are the journals smaller in width?


Do you have the tools do that?
Author:  mini7boy [ Sat Feb 14, 2009 4:35 pm ]
Post subject: 
Mini man,
so the answer to my question is that you CAN offset grind a non-standard crank. Maybe it's not the best, but given how hard it is to find a standard crank, most people would find it much easier to use a 10-under crank. Since you are grinding from a 1.75 inch diameter to a 1.625, the amount of .010 is insignificant in terms of weakening the crank or reducing the amount of stroke change. Once you have your 1.625 journal, you can grind it undersize as needed to rebuild the engine after crank wear. I really don't see any problems with offset grinding an undersized crank unless you consider losing .005 in stroke length to be a problem.
Author:  TheMiniMan [ Sat Feb 14, 2009 4:45 pm ]
Post subject: 
mini7boy,,, you`re perfectly correct, yes.

the strength part i was getting at was more to do with grinding it down further than std small journal size like i have with my .080 undersize cranks,,,, very "iffy" indeed,,,

edit--> but you could grind it down to .010 or .020 to gain back the extra stroke without tooo much compromise of integrity.

& Bubba,,, just about any machine shop or engine reco shop can mod the rods for you, easy-peasy... & yes it`s cause they`re narrower in the journals than the small journal cranks.
Author:  drmini in aust [ Sat Feb 14, 2009 7:42 pm ]
Post subject: 
Unless you are making a stroker, I reckon the small journal 1100S ones are a better crank. Most were tufftrided (surface hardened), unlike the 12G1505 ones which were all soft over here.
:wink:
BTW I've been told nobody is doing tufftriding any more in Oz (even in Melbourne), you would need to send the crank to UnZud to get it (or similar process) done.
Author:  TheMiniMan [ Sat Feb 14, 2009 8:27 pm ]
Post subject: 
cryogenic treatment is the go these days i hear,,, havn`t tried it yet, i`m still old skool & nitride them
Author:  850man [ Sat Feb 14, 2009 8:52 pm ]
Post subject: 
ACL thrusts are NOT made anymore. The last production of +30 thrusts ACL made were a special order through a mate i have that works there and was a once off. I had them produced as i was sick of hunting around trying to find old stock and when they did turn up they cost a fortune. The sets that Linsey sells he got from me.
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