Differance in crankshafts

Nearly too late · Post by **Nearly too late** » Tue Nov 03, 2009 10:10 pm

Can anyone tell me the differance between the B6 and the B6T cranshafts.
This is the early 1600 motor (NA6CE ).
Thanks

Habanero666 · Post by **Habanero666** » Tue Nov 03, 2009 10:15 pm

Hi there,

I have built a new B6 turbo block using a B6T crank from a 1989 familia BFMR. No difference.

WideOpenThrottle · Post by **WideOpenThrottle** » Wed Nov 04, 2009 1:03 pm

While on this type of subject can you interchange 1600 GTI engine parts into a 1600 NA motor & is any of it worth doing?

Habanero666 · Post by **Habanero666** » Wed Nov 04, 2009 2:05 pm

A B6 block is a B6 block. The variation is in the external manifolding and distributor as opposed to a CAS. Piston types vary as do camshaft lift,overlap and duration for different model car and spec.

Nearly too late · Post by **Nearly too late** » Wed Nov 04, 2009 5:28 pm

Thanks all for your replies.
I would like to keep the car standard as much as possable but get away from the short nose crankshaft problem.
Thanks for your help

mazline · Post by **mazline** » Wed Nov 04, 2009 5:32 pm

Just look for a 91> motor with 7 slots around the front lower pulley,Early motors have 4 slots.Thats the difference between short nose crank and long nose crank.

Habanero666 · Post by **Habanero666** » Wed Nov 04, 2009 5:47 pm

Yes that is the only difference.....

If you are concerned about the small nose (22mm) crankshaft failing don't be. I reviewed this matter and according to Keith Tanner from Flyin Miata he has seen more failures from the big nose crank (27mm). I found a low kms crankshaft from a 1989 bfmr familia turbo here in NZ.

dynofiend · Post by **dynofiend** » Wed Nov 04, 2009 6:32 pm

Agreed, short nose crank failure is blown out of all proportion. It is as likely as any other major engine failure attributable to poor maintenance practices.

In other words, if someone has taken off or played with a fairly major part of the cars engine, and not done it right, there is a chance it will break in the future. This applies to the crank pulley bolt as much as any other moving part of the engine. Granted the crank pulley bolt and key is not a terribly brilliant design on early NAs, but it works fine as long as it is dealt with correctly when re assembling it.

Habanero666 · Post by **Habanero666** » Sat Nov 07, 2009 9:47 pm

UPDATE*****

I just weighed my B6ZE crankshaft (MX5), Then weighed a B6T crankshaft....... I found a difference! The mx5 one is a lot lighter.

Oh yeah, both these crankys are small nosed.

Nearly too late · Post by **Nearly too late** » Sun Nov 08, 2009 12:18 am

Hi,
Thanks to all for the infomation you have posted.
The way I understand it there are three crankshafts, Small short nose (22mm),small long nose (22mm), and the big nose (27mm).
The short nose is a light weight crankshaft for the MX5 ( I think thats how it goes from what I have read lately )
I think I have found a good long nose crankshaft which I think I will use.
The weight differance may effect the performance, if it does may have look at lightening it.

Habanero666 · Post by **Habanero666** » Sun Nov 08, 2009 4:28 pm

Just 2 types of crankshaft for the B6:
long nose or short nose,
big nose or small nose,
27mm or 22mm,

The problem lies with the person tightening the pulley bolt.

For boosted 1.6s I use the B6t crankshaft (small nose).
For NA 1.6s use the b6ze (big nose or small nose, both will do).

If you want to spin a crankshaft at high RPM you will need to lighten and balance it along with the harmonic balancer, conrods, pistons, flywheel and clutch assembly.
If you are doing the job properly, there are a lot of other critical things to do aswell.

Oh yeah, The lightest crankshaft will be easier to spin, but will it break??????? Find your self a good engineer???

J Hartley

Fletch · Post by **Fletch** » Thu Nov 12, 2009 11:56 am

The problem lies with the person tightening the pulley bolt.

Then how do you explain the failures where the pulley bolt was never touched?

Habanero666 · Post by **Habanero666** » Thu Nov 12, 2009 12:53 pm

Simple, the bolt isn't cast on the end of the crank is it?
Someone had to put it there originally.

Fletch · Post by **Fletch** » Fri Nov 13, 2009 3:17 pm

Simple, the bolt isn't cast on the end of the crank is it?
Someone had to put it there originally.

Ha ha ha....

So let me get this straight..... Mazda designs a crankshaft and bolt, and trains and supplies the workers (or robots?) on the assembly line, and some of them come loose after 80 or 100 or 150,000km..... but its not a Mazda design fault, it's the line worker who got it wrong?

Sure.

So why did they change the design again?

Habanero666 · Post by **Habanero666** » Fri Nov 13, 2009 4:18 pm

The same reason they still keep coming off the long nose crankshafts?

WideOpenThrottle · Post by **WideOpenThrottle** » Fri Nov 13, 2009 9:05 pm

Like most nuts & bolts they can do one of two things-stay put or work loose!Eh?

brownie · Post by **brownie** » Fri Nov 13, 2009 11:40 pm

Thats why you use loc tie or a thread locker when you do them

Habanero666 · Post by **Habanero666** » Tue Dec 08, 2009 10:11 am

Fletch wrote:
Simple, the bolt isn't cast on the end of the crank is it?
Someone had to put it there originally.
Ha ha ha....

So let me get this straight..... Mazda designs a crankshaft and bolt, and trains and supplies the workers (or robots?) on the assembly line, and some of them come loose after 80 or 100 or 150,000km..... but its not a Mazda design fault, it's the line worker who got it wrong?

Sure.

So why did they change the design again?

The engines are hand built by Mazda engine techs on engine assembly lines, machines and humans make mistakes otherwise us mechanics would'nt have to contend with WARRANTY CLAIMS.

Anyway here is some more damning evidence from the link below

*****Warning contains graphic crankshaft and keyway violence******

http://www.miataclub.org/orlando/94crank/

Differance in crankshafts

Differance in crankshafts

THREE???

Just when you thought it was safe.

Who is online