Short nose crank...telltale signs? *HELP NEEDED*

Engines, Transmissions & Final Drive questions and answers

Moderators: timk, Stu, -alex, miata, StanTheMan, greenMachine, ManiacLachy, Daffy, zombie, Andrew, The American, Lokiel

User avatar
sabretooth
Speed Racer
Posts: 2119
Joined: Wed Apr 23, 2003 11:00 am
Vehicle: NA8 - Turbo

Re:

Postby sabretooth » Mon Mar 19, 2007 7:17 pm

Sean wrote:YEs it assumes the key will always fall into the worn part of the keyway.

The first rotation will not be different, I just rotated a few times to be sure. Also give you a chance to stuff teh skewer back down through teh peg to retest 8)

Yes I am king dodgy.

My soluion if I had a brone crank would eb to leave it , put a newmark on the pulley where TDC is NOW, and move teh cams a tootch to compensate.

I'll say again - Yes I am king dodgy.


Really though,m with an import 1.6 available for $500ish, I'd say agrand would get you out of it to buy and fit the new engine...

Why bother with shonky fixes.


First, congrats on a sentence with 3 "the"s and not one "teh". :p

So with your way, I guess you'd want to start with a short rotation backwards (without moving the crank/pistons), shove the skewer in while mounted on a glued peg... sounds like it would work.. but surely the piston will still reach TDC regardless of crank timing?

Boags'MX5 wrote:WARNING - DO NOT ATTACH A SOCKET TO THE PULLEY BOLT AND TURN THE ENGINE MANUALLY.

This *might* alter the torque on the crank bolt, and if it wasn't f*&ked before, it will be now.

The reading I did when I thought mine was kaput suggested that rotating the crank using that bolt was asking for trouble. I'm not sure how else you could do it though. :?:

Boags

Yank the spark plugs first and you won't need to worry about putting too much force on the bolt - no compression = less resistance = easy to turn.

User avatar
Sean
Racing Driver
Posts: 1755
Joined: Thu Apr 24, 2003 11:00 am
Vehicle: NB8A
Location: NSW
Contact:

Re:

Postby Sean » Mon Mar 19, 2007 7:42 pm

sabretooth wrote:
Sean wrote:YEs it assumes the key will always fall into the worn part of the keyway.

The first rotation will not be different, I just rotated a few times to be sure. Also give you a chance to stuff teh skewer back down through teh peg to retest 8)

Yes I am king dodgy.

My soluion if I had a brone crank would eb to leave it , put a newmark on the pulley where TDC is NOW, and move teh cams a tootch to compensate.

I'll say again - Yes I am king dodgy.


Really though,m with an import 1.6 available for $500ish, I'd say agrand would get you out of it to buy and fit the new engine...

Why bother with shonky fixes.


First, congrats on a sentence with 3 "the"s and not one "teh". :p

So with your way, I guess you'd want to start with a short rotation backwards (without moving the crank/pistons), shove the skewer in while mounted on a glued peg... sounds like it would work.. but surely the piston will still reach TDC regardless of crank timing?



Yes as cranking the engine you watch the ingenious glued peg/skewer combo to see where it stops coming up. If it stops and you looks down to see teh marks aligning correctly. BINGO one good keyway:D

I'm a tad worried on Boag's comments - I often crank by hand using the front nut and a large socket...

BUT, Mine's all good :D
When results speak for themselves - don't interrupt.

User avatar
Boags
Speed Racer
Posts: 3533
Joined: Thu Nov 10, 2005 6:25 pm
Vehicle: NB SP
Location: Brisvegas
Contact:

Postby Boags » Mon Mar 19, 2007 7:56 pm

Just passing on what I read Sean. Most people will never have the short nose problem, those that do will tell you that it was most likely caused by over torquing or under torguing that bolt...

Boags
Spartan Motor Sport : http://www.SpartanMS.com.au

User avatar
deez
Fast Driver
Posts: 341
Joined: Thu Nov 02, 2006 9:20 pm
Vehicle: ND - 2 GT
Location: Sydney
Contact:

Postby deez » Mon Mar 19, 2007 8:04 pm

Good suggestions guys.

However without going through all that...if the crank is seen to be wobbling, even to the most casual observer, can that already confirm a short nose crank problem?
89 Eunos Roadster
Image

User avatar
Sean
Racing Driver
Posts: 1755
Joined: Thu Apr 24, 2003 11:00 am
Vehicle: NB8A
Location: NSW
Contact:

Re:

Postby Sean » Mon Mar 19, 2007 8:11 pm

deez wrote:Good suggestions guys.

However without going through all that...if the crank is seen to be wobbling, even to the most casual observer, can that already confirm a short nose crank problem?


I can't comment as I've never suffered the crank woble myself.

If you ever drive in teh Newcastle area, let me know and I'll be happy to inspect it, only takes 5-10 minutes.
When results speak for themselves - don't interrupt.

User avatar
sabretooth
Speed Racer
Posts: 2119
Joined: Wed Apr 23, 2003 11:00 am
Vehicle: NA8 - Turbo

Postby sabretooth » Mon Mar 19, 2007 9:51 pm

I've not had it happen with my short nose BP either (the Familia engine).

I think a lot of the failures can also be attributed to getting the woodruff key either upside-down, or back to front.

User avatar
Boags
Speed Racer
Posts: 3533
Joined: Thu Nov 10, 2005 6:25 pm
Vehicle: NB SP
Location: Brisvegas
Contact:

Re:

Postby Boags » Mon Mar 19, 2007 10:32 pm

sabretooth wrote:I think a lot of the failures can also be attributed to getting the woodruff key either upside-down, or back to front.


According to m.net, very few of the short nose problems are caused by this (about 1%, how they'd know baffles me, but that's what they say), the major cuase is under/over torquing.

Boags
Spartan Motor Sport : http://www.SpartanMS.com.au

User avatar
Sean
Racing Driver
Posts: 1755
Joined: Thu Apr 24, 2003 11:00 am
Vehicle: NB8A
Location: NSW
Contact:

Re:

Postby Sean » Mon Mar 19, 2007 10:38 pm

Boags'MX5 wrote:
sabretooth wrote:I think a lot of the failures can also be attributed to getting the woodruff key either upside-down, or back to front.


According to m.net, very few of the short nose problems are caused by this (about 1%, how they'd know baffles me, but that's what they say), the major cuase is under/over torquing.

Boags


Isn't the key slightly shaped? Perhaps they examined the keys from a sample of broken ones.
When results speak for themselves - don't interrupt.

User avatar
Boags
Speed Racer
Posts: 3533
Joined: Thu Nov 10, 2005 6:25 pm
Vehicle: NB SP
Location: Brisvegas
Contact:

Postby Boags » Mon Mar 19, 2007 10:45 pm

Yes, but to get a figure of 1% they must have examined at least 100 cranks... Perhaps rooting 1.6 engines is a sport in the US? :?: :lol:
Spartan Motor Sport : http://www.SpartanMS.com.au

User avatar
JBT
Speed Racer
Posts: 7946
Joined: Tue Jun 03, 2003 11:00 am
Vehicle: NC
Location: Brisbane

Re:

Postby JBT » Mon Mar 19, 2007 10:54 pm

deez wrote:...if the crank is seen to be wobbling, even to the most casual observer, can that already confirm a short nose crank problem?

Probably, but there should be some power loss associated with it too. The owner of the engine with that chewed out keyway (photo that OMY005 posted) reckoned pedestrians could accelerate faster.

I believe the problem can be either an incorrectly inserted key and/or re-using the pulley/sprocket bolt. My understanding is that the bolt thread distorts slightly to hold the applied torque and is a one use only item. If re-used, it may not hold the torque to which it has been tightened and thus allow the sprocket to move about and slowly but surely wear the keyway.
Image

User avatar
Sean
Racing Driver
Posts: 1755
Joined: Thu Apr 24, 2003 11:00 am
Vehicle: NB8A
Location: NSW
Contact:

Re:

Postby Sean » Tue Mar 20, 2007 6:39 pm

Boags'MX5 wrote:Yes, but to get a figure of 1% they must have examined at least 100 cranks... Perhaps rooting 1.6 engines is a sport in the US? :?: :lol:


LOL I have a few that you can take next time you're round and start your own testing :lol:

Problem is none of them had crank failure...
When results speak for themselves - don't interrupt.


Return to “MX5 Engines, Transmission & Final Drive”

Who is online

Users browsing this forum: No registered users and 5 guests