Question re Turbo Crank Machining
Turbo Mini Forums

Hi, quick question please...

I purchased a turbo crank of ebay and had it sent to the workshop for some work.

Came back and has only had a regring and wedged.
It was not hardened or crossdrilled.

Supposedy a turbo crank is too hard to cross drill and since it was hardened at the factory it doesnt need to be re hardened after the machine work.

I have my opinion about this but I would like to hear it from others.. What do you think?

Cheers
Tareq

When you harden a steel component its only the outer surface and its only hardened down a few thousanths of an inch this allows the component to be strong and hard ratheer than hard and brittle! How much was taken off when it was ground and how big are the journals now?

If its the first re-grind yous hould be ok if its on its second then the surface treatment may need redressing.

Check your journal sizes against those in the workshop manual to be sure.

Own the day

Thanks for the info..

The thing is that this was an ebay crank which although is a turbo crank I dont think it was the rarer hardened type.

At the moment it is very easy to scratch the surface. Even on the journals.

I was told that because it was hardened he couldnt cross drill it. Obviously it can be drilled because I can scratch it.
If I hadnt been charged a load of money I would let it go but I was charged for a fully worked crank and looks like he wedged it and reground.. and then just sent it.

I want to be a high revving engine and now I am not very confident of the work done.

is the crank a cam6581 or a cam6232?

Team Racing

He machined the casting number off

Only the early metro turbo crank is different the other ones are just a standard crank IIRC

The later 6581 cranks are definately 'harder wearing' than all the earlier 6232 cranks. I think it's BS that the earlier cranks were hardedned...

Anyone who has worked the two different cranks would know, as surely if the 6581 been toughned in anyway the machinist would know?

I say they have been toughned, just because i have one in mine

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

Is there anyway to tell the difference between the two without the numbers.
I.E. color or any other differences?

Oh and is it possible to cross drill one of the hardened cranks?

Take a look at these two threads

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=5698

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=5117

The search button works wonders even though I had to go through google to get there!

Own the day

if its been hardened a the file test is a good starting point, run one over it and see what happens, if its un treated the file will remove material if its hardened it wont mark it as such, also look inside the threads at either end , are they dull in colour or not,is the damper end dull or shiney,

you need to look for traces or a dark dull srrfce, areas that dont have anything running on it , , thats why i siggest the threads, also the counter sink lead on the front pully end, nothing really touches that so should still be either dull or shiney ish,.

carl

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

Thanks Joshua... I've read those threads already.

As far as understand. Both cranks are the same shape. Only difference might be the material and one is hardend.
Both are not through drilled.

Here is a picture of my cranks timing chain spigot. In one of the threads you linked to it was stated that the harder crankshaft had a grey finish and not a shiny reflective spigot.



So do you think that this could be the harder crankshaft.

Sorry for asking so many questions. I am not in an area where I can take a look at different parts for comparison.

Carl.. I just read your post after my reply. Yes looking to the countersink it is not shiney like the picture of the spigot.

Can this crankshaft be crossdrilled or is it too hard to drill?

it'll be too hard to do anything to other than by grinding.


carl

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

Its had a regrind. The journals dont seem very hard anymore as they can be marked quite easily. Should it be rehardened after a regrind?

What sort of rpm would this crank hold with a set of arrow or sc rods?

Cheers
Tareq

If you take an early crank and a later one, assuming the journals are the same and they are unwedged and "ding" them. Are the dings the same?

EN40 and an EN16 have different dings.

Bugger off, I'm getting there.

WWW.FORCE-RACING.CO.UK PLEASE CLICK HERE

The guy said he balanced it. Closest place for balancing in is Dubai. Maybe next time I am over there I will take the crank with me.

There are a few chunks machined out of the B/E ends of the webs.

I think I will probably do as you recommended and use the crank.
Will probably order a set of SC rods and some omega pistons.

Think I will stick to a N/A engine and in future build a turbo once I have some more experience with the a-series.