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PostPosted: Mon May 19, 2008 9:43 pm 
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998cc
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Joined: Mon Aug 06, 2007 12:16 pm
Posts: 523
Location: Canberra
Thanks for that. That gives me a good idea of the money involved thanks.


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PostPosted: Tue May 20, 2008 7:21 am 
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religious status
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Joined: Fri Mar 19, 2004 6:19 pm
Posts: 39754
Location: near Baulkham Hills, NSW
I did a 1412 stroker for our van recently-
Offset grind crank (St George Crankshafts)- $240
Bore and hone block to 73.0mm (GR) $150
Balance crank (GR) $50.
Wedge crank $0- I did it here :P
Machine sides of S rods to fit crank $0- I did em too
Balance rods- $0- same deal. I then got GR to straighten them- Mini rods are nearly always bent a bit.

So, it's not much dearer to do a stroker than a stock rebore and crank grind, you do need a set of S or early 1100S rods though (which my motor had already). :wink:

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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. :mrgreen:


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PostPosted: Tue May 20, 2008 10:11 am 
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Joined: Mon Sep 06, 2004 4:36 pm
Posts: 8606
Location: Brisbane
Kev that`s a very good price for all that & as you`re well & truely "in the know", not everyone can do so much for themselves tho.

However, when we offset grind our cranks for strokers, we spend a fair bit more time on them & put them through extra processes than just a grind, harden & a linish

we grind them down to just a tad (2 thou) above the size we want, then we balance them, then we harden them & then we grind them again so they`re dead true & then we balance them again
Doing them this way gives a far better & safer end result

as you know, they grow a little in the hardening process, but they also bend , some cranks bend quite a fair bit in fact, so that`s why we allow that little extra on our first grind because they bend we have enough meat left on the other side of the bend to grind them true to size. The extra balance job in the middle is so that whatever metal is needed to be taken off during the balance its done early in the process so that we don`t have to break into the hardening crust any where near as much on the final balance & we very rarely have to take much off at all on the 2nd balance when they`re done this way.

It`s probably going to sound a bit lame to some people that we are so anal about doing cranks this way, but i can assure you all that it`s a far far safer way & the end result is a far stronger & dead true crank

If there`s any wedging &/or blade-ing to be done then we do all that well before any machining or balancing or hardening is done, that way we end up with the thickest hardening crust & the most even hardening crust thoughout the entire length of the crank

Also with the con rods, yes Cooper "S" or early 1100"S" small journal rods are needed so there`s the initial cost to buy them, then there`s all the work we spend on those to make sure they`re straight & strong & then there is the cost of the ARP rod bolts & then the fitting & re-sizing etc etc etc,,, so there is way more money needed to be spent on the rods than just a quick grind to narrow them & bung some bolts in.

To anyone reading this, i appologise for the long winded typing , but i don`t really want people to get the wrong idea here,,, Kev knows what he`s doing, GR knows what he`s doing, & there`s quite a few others out there who i`m sure know what they`re doing also,,, & i`m not rubbishing any of them at all here, in fact i`m agreeing with them whole heartedly, just that we choose to extend the process a little more, spend a bit more time on them & it is difficult to type the right words for the "Average" Joe/Jane to understand it all , but if you don`t know what you`re doing & havn`t allready done a few stroker donks before, then please don`t take them casually/lightly,,, if you treat them like they only cost a few extra dollars to do, then that`s what you will end up with, an engine that`s only worth a few extra dollars... Unless you`re someone like Doc & GR, they know what they`re doing & obviously do a lot of their own work & can get machine work done at reasonable prices compared to Joe & Jane Average

we are very anal about our stroker donks , sorry "Butt" it`s just the way we do things
I`ve seen the results of many many other stroker cranks done by people who didn`t take our recomendations/suggestions & didn`t do things the way we do, & it`s not a pretty sight.

When a crank fails inside an engine it usually takes out a whole pile of other stuff in the process, so it`s not just the cost of the crank at stake here,,, the entire engine will need to be re-built & another pile of your hard earned is down the tube,

again sorry for the rant, but i really needed to make people aware of the amount of time & money we spend doing a stroker ,,, it`s not cheap

ok,,, i`m done

& thanks for being patient with me :-)

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.


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