Short stroke cranks

minorv8 · Post by **minorv8** » Mon Jun 13, 2011 3:59 pm

Does anyone know if there are any short strokes cranks around ? I am interested in locating one for a oddball project, just about any stroke less than 71 mm would do. There is one flat plane crank for sale in fleabay but price is astronomic

Ian Anderson · Post by **Ian Anderson** » Mon Jun 13, 2011 4:10 pm

I believe the fleabay one make it a 2l screamer

Ian

Wotland · Post by **Wotland** » Mon Jun 13, 2011 4:49 pm

Why not start from a stock 4.0 crank (2.8" stroke) and destroke it by machining rod journal

spend · Post by **spend** » Mon Jun 13, 2011 4:58 pm

You can even offset crank more if you use rods with even smaller journals (and you would need longer rods or different pistons either way)

kiwicar · Post by **kiwicar** » Mon Jun 13, 2011 6:13 pm

Hi
How short stroke do you want to go? you can probably go down about .2" with a change to small journal rods, about the same again as suggested with the 4 litre crank off set ground, more than that then if you can get an unmachined crank you can probably knock off another .1" to .2" but more than that it will have to be a custom forging. If you went as short as 2" stroke you might be able to get one turned out of a billet of 5" diamater steel stock, it would be simplest to go single plain but would be do-able but whoever turned it would have to be prepared to do it in stages over several weeks. Again you could go for a motorcycle style crank, made of several disce and pins all pressed together, can be made very light.
Best regards
Mike

CastleMGBV8 · Post by **CastleMGBV8** » Mon Jun 13, 2011 8:26 pm

minorv8 wrote:Does anyone know if there are any short strokes cranks around ? I am interested in locating one for a oddball project, just about any stroke less than 71 mm would do. There is one flat plane crank for sale in fleabay but price is astronomic

JE does a 63mm. race crank for a short stroke 3.5L with the larger 94mm. bore, not cheap as you can imagine.

http://www.rover-v8.com/jeales/web.nsf/ ... endocument

What are you looking to achieve?

Kevin.

minorv8 · Post by **minorv8** » Tue Jun 14, 2011 5:57 am

What are you looking to achieve?

To satisfy our silly legislation...

If one wants to swap engine into any vehicle the maximum increase in capacity is 25 % over the biggest engine within the model range. E.g. for SD1 (3,5 litre + 25 %) maximum capacity would be roughly 4,4 litres. In addition, maximum increase in power is + 20 % over the most powerful engine within the range. It is possible that these engines are not the same, e.g. diesel variant could be bigger and petrol engine more powerful.

But if you want to do interesting swaps like small car with V8 things get difficult. E.g. my Morris would be impossible to get legal according the current legislation. It was done and registered over 10 years ago and then it was possible to get a vehicle specific approval. In theory it is still possible but the few approval have mostly been street rods.

So, if one wants a V8 it needs to be small. Downsizing bores is not practical, there is a limit given the stroke/rod length. Biggest gain or just the opposite is achieved with shorter stroke.

I do know all the above suggestions and thank you all for them. I was curious to see if anyone would have some old race "junk" around. I have asked some local shops if they would be interested in offset grinding a crank for longer stroke but found very little interest. I doubt that they would show more interest in destroking

inspector · Post by **inspector** » Tue Jun 14, 2011 5:25 pm

Ian Anderson wrote:I believe the fleabay one make it a 2l screamer

Ian

Does anyone know that is this the same crank that is used in Supercharged TVR V8S for Italian markets only ??

With 40,25mm stroke it would make 2,235 litres with 94mm bore.

Nice

mgrv8 · Post by **mgrv8** » Tue Jun 14, 2011 5:54 pm

Sorry to butt in on this , but i would like to know more about this legislation...Is this just for kit cars etc? that have to pass a sva type test?or does this affect anyone putting a v8 etc into say a classic car? when did this rule apply from??,.... thanks Steve

ged · Post by **ged** » Tue Jun 14, 2011 6:03 pm

minorv8 lives in Finland.

Regards Ged

minorv8 · Post by **minorv8** » Wed Jun 15, 2011 4:33 am

Yes sorry about that, I was explaining the situation in Finland. Similar rules apply in different countries also but I really hope that system in UK stays the same. Kit cars are practically impossible to get legal here, let alone Locost type home built chassis. Big engines in a small car is a real NO NO NO. So, I am a buit envious about your "freedom" to swap engines.

paul c · Post by **paul c** » Wed Jun 15, 2011 7:18 am

Could a 2.5l Daimler v8 be used then?

Wotland · Post by **Wotland** » Wed Jun 15, 2011 8:28 am

Supercharger TVR kit sold by DJE come from Italian 2.0 superchargerd TVR V8S/SC. Also 1.586" billet flat plane crank.

Found on wikipedia : " The engine was a modified 3.5 litre Rover V8 fitted with a smaller-throw crank to reduce the engine capacity, retaining the 88.9 mm bore but with an extremely short stroke of 40.25 mm. This meant a displacement of 1,998 cc (2.0 L), with a compression rate of 8.0:1. Lucas electronic fuel injection was fitted, along with an intercooled Eaton supercharger. All of this produced 233 PS (171 kW; 230 bhp) at 6,200 rpm and 266 N·m (196 lb·ft) at 3,700 rpm. "

kiwicar · Post by **kiwicar** » Wed Jun 15, 2011 9:08 am

Hi
there are quite a few people doing V8s made from 2 X l litre motorcycle engines, may get you a v8 of the capacity you need, not cheep but the sound should be impressive!
Best regards
Mike

topcatcustom · Post by **topcatcustom** » Wed Jun 15, 2011 9:45 am

Bit of cutting and welding on the cranks and you're sorted! Bike originated V8's rev silly

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