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Discussion Starter · #1 ·
Hi all

I have owned a 1990 Eunos for the past 4 - 5 years love the car, and been meaning to turbo it from the day I bought it. Other projects have been getting in the way. I've kept on top of all the mechanicals upgrading and renewing lots of parts. I occasionally noticed a couple of drips of oil on the road where its parked, thought I had solved it by replacing the cam cover gasket, removed under tray, degreased everything but shortly afterwards it returned, and been getting progressively worse.

The other day I decided to sort it so ordered crank and cam seals and an OME cam cover gasket. I have heard of the short nose crank woodruff key issues so also ordered a new crank bolt and woodruff key. Crank bolt and sprocket came off easily and no visible damage or wear to the crank nose. whilst reassembling today I noted that the wood ruff key slides in flush to the end of the crank but the nose of the sprocket overhangs the end of the crank by about 10mm. The crank nut then bolts up to the nose of the sprocket holding it onto the end of the crank. There is then a 10mm gap between the shoulder of the bolt and the end of the crank and can't see what is stopping the woodruff key, if there was any play possibly working its way out into the void. I would have thought there should have at least been a bush inside to prevent this.

Maybe this is one reason why they sometimes fail? It seems from what I have read failure is often associated with it being disturbed or replaced, so I decided to use some thread lock in the key way and on the thread of the bolt.

Whats your thoughts?

Mark
 

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Eunos would be long nose crank not short nose and they do not give much trouble.I must advise you that the woodruff key itself has barely noticeable taper on one corner , on one end only, and this MUST be fitted in to keyway in correct position as the keyway itself tapers away on the inside nearest the seal. I can explain more if needed
 

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Discussion Starter · #4 ·
Eunos would be long nose crank not short nose and they do not give much trouble.I must advise you that the woodruff key itself has barely noticeable taper on one corner , on one end only, and this MUST be fitted in to keyway in correct position as the keyway itself tapers away on the inside nearest the seal. I can explain more if needed
Hi all

Thanks for the replies.

Definitely an early short nose crank engine fitted to my car. I thought they were fitted to all 89 and early 90's Mx5 Eunos and Miatas, maybe an early engine has been fitted to my car but being a 1990 Eunos think its original to the car,but could be wrong. I had to order the early seal from MX5parts as the seal in the long nose crank is a different size.

Thanks, I am aware of the chamferd end to the woodruff key, and reassembly went fine, just having the niggling concerns as I outlined in my first post.

Mark
 

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Ah Ok.Definitely should be LNC not SNC especially in Eunos as SNC was for Euro spec early cars.Makes no odds really I suppose as long as you get correct parts etc
 

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Ah Ok.Definitely should be LNC not SNC especially in Eunos as SNC was for Euro spec early cars.Makes no odds really I suppose as long as you get correct parts etc
Just to correct this post - ALL early Eunos's (1989 and 1990) has the "Short Nose" otherwise known as the "Light Weight Racing" crank shaft. Would assume that this also applies to UK spec and Miata's of the same age.

Rod
 

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It is my understanding that ALL 1989 & 90 cars will have the SNC as will some 91 cars regardless of region.

There is a good article on Miata.net : https://www.miata.net/garage/crankshaft.html

Unfortunately i have first hand experience of this as my original engine suffered the crankshaft key way failure, there is a picture somewhere in my build thread.
 

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It is my understanding that ALL 1989 & 90 cars will have the SNC as will some 91 cars regardless of region.

There is a good article on Miata.net : https://www.miata.net/garage/crankshaft.html

Unfortunately i have first hand experience of this as my original engine suffered the crankshaft key way failure, there is a picture somewhere in my build thread.
Mine's cover 95K Miles and has had two Cam Belt changes and one front oil seal. So far no issues at all keyway in fact when last checked, last year, was showing no sign of wear at all.

I may be just lucky but would be interested to hear how many of the early power units are still going strong.

Rod
 

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Just been checking out the “short nose” crankshaft situation prior to having a new cam/timing belt fitted (second time around) at 105k miles. “G” Reg Eunos 1990 daily runner – showing its age, but still great fun! I’ve read the Crankshaft article (I have the “short nose” 4 slots pulley) & if no serious oil leak, will ask my mechanic to leave the pulley well alone!
 

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@iainstargazer the issue is wildly mis-reported and mis-understood and I think for the most part, people worry far too much about it becoming an issue, when really it's just something to worry about if it becomes an issue.

The biggest issue is that people don't correctly torque the hardware back down properly using the specs from the handbook. The new 'larger' nosed crank(s) (yes there are actually 3 versions, more on that in a sec) from what I've understood are more tolerant to general "mechanics" just gunning them back on with an impact and not using proper specs - couple that with setting the belt tension properly and it's a recipe for disaster - or just follow the handbook.


When the issue was identified early on by Mazda, they tried to quickly remedy this by offering affected customers a swap to the "Long nose" crank fix, this is where things get confusing because the band-aid approach was only applied to handful of cars, after all most customers weren't going to identify a wobbly crank pully within 2 years of a new car unless they had somehow managed to do 60k miles in 2 years, or have the timing belt incorrectly assembled at the factory..so they moved to a "Big nose" crank from the factory (which is what most people refer to as a long nose crank..not that it matters I just like matter of fact)

Drive it and don't worry about it. If you are really worried about it becoming an issue, use a really trusted mechanic that you know will follow the correct torque specs.
 

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the issue is wildly mis-reported and mis-understood and I think for the most part
^^This(y)
they're 30+ year old engines now, my '90 Eunos's crank is perfect (I fitted a new cambelt / pump etc ~2 years ago) and I have a perfect condition spare crank in the workshop (somewhere) so not a worry😎

Drive it and don't worry about it
^^THIS:cool:

if it does fail then replacement engines are cheap & easily available, can use a mk2.5 1.6L engine or crank & oilpump if you need(y)

Rich.
 

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@iainstargazer the issue is wildly mis-reported and mis-understood and I think for the most part, people worry far too much about it becoming an issue, when really it's just something to worry about if it becomes an issue.

The biggest issue is that people don't correctly torque the hardware back down properly using the specs from the handbook. The new 'larger' nosed crank(s) (yes there are actually 3 versions, more on that in a sec) from what I've understood are more tolerant to general "mechanics" just gunning them back on with an impact and not using proper specs - couple that with setting the belt tension properly and it's a recipe for disaster - or just follow the handbook.


When the issue was identified early on by Mazda, they tried to quickly remedy this by offering affected customers a swap to the "Long nose" crank fix, this is where things get confusing because the band-aid approach was only applied to handful of cars, after all most customers weren't going to identify a wobbly crank pully within 2 years of a new car unless they had somehow managed to do 60k miles in 2 years, or have the timing belt incorrectly assembled at the factory..so they moved to a "Big nose" crank from the factory (which is what most people refer to as a long nose crank..not that it matters I just like matter of fact)

Drive it and don't worry about it. If you are really worried about it becoming an issue, use a really trusted mechanic that you know will follow the correct torque specs.
@guitaristanime & Zed Thanks for the swift replies, guys. My son and I (I’m an Old Timer now!) have jointly owned three NAs (all at the same time, at one time) since 1998 and obviously loved them to bits – literally! All matching silver, and now finally down to the 1989/90 Eunos import which we’ve always known as “The Shed” as we considered it the least attractive of the three.

All three have been imports, and the really attractive one (now gone) had front & rear skirts and spoiler and looked stupendous without looking silly or boy-racer. It was an absolute magnet if you stopped! We once attended a “local” MX-5 rally at MX-5 Heaven, Dorchester, where all the petrolheads were showing off their turbos, track day fitments and spotlessly clean engine bays, and at the end of the day (almost) everyone was asking why we didn’t display the car in the concours!

All three drove slightly differently (I’m talking “normal” driving here, not track day) and here in Devon (a hilly county) we have several winding uphill dual carriageways where we would wind up the Porsches, Beemers, AMGs etc. that just could not catch us up through the bends! Our last daily runner “The Shed” can still do it – 32/33 years old! We love it to bits.

Anyways – the short nose problem. The “Shed” is/was the only one with the short nose, of which we’ve always been aware, and my concern was would the fitting of its second cambelt lead to the demise of our cherished Shed. I read the Yank “Short Nose” article (dated 2001), which pretty well lays out the historical problem. Pity – as the NA version, for us, has been pretty indestructible. If only other cars were so well made, instead of the over-computerised junk that abounds today, and mainly due to the punter demanding iPhone connectivity, infotainment, GPS (who cares where they are going in an MX-5? – they’re out for a fun drive!) etc.
What I took away from the Yank’s article is exactly (down here in Devon we say “presackly”, which is an amalgam of “precisely” and “exactly”) as you explain, guitaristanime – the main problem being boy-racer tinkering, or under-par mechanics. Luckily, I do have a trusted mechanic, so maybe the “Shed” will prevail! Cheers, Guys.

Incidentally, I am a stargazer (astronomer) - hence the avatar - and have spent many a night with the hood down in the local Dartmoor National Park, with the sky lit up! Nothing like it!
Car Sky Vehicle Plant Vehicle registration plate
 

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TL/DR: Don't bother doing it unless it's clearly leaking. :D

I've done the front crank seal replacement on my 1989 shortnose. It had started leaking.

It was a pig to do and I ended up using a motion pro seal puller to get it out, You need a lot of area/leverage, but it's hard to do without scratching the bore of the oil pump or the OD of the crank nose.

At the same time I put in a new cog, new crank pulley damper, new woodruff key, etc.

Put it back together and it's been good.
 
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