1991 na shortnose vs long nose

1991 na shortnose vs long nose

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Discussion

carspath

Original Poster:

832 posts

176 months

Friday 7th February 2014
quotequote all
I am considering a 1991 mx5 na

I have heard that early cars had a short nose ?engine bolt? (please forgive my ignorance) which could lead to significant engine problems


-would a 1991 car have this short nose engine bolt , or the more reliable long nose bolt?
can you tell by the chassis number?

-is it possible to convert the older , less reliable type to the newer more reliable type?
if so, what would need to be done , and how much do you think this would cost?

- how common is it for the short bolt type of engine to actually manifest a problem?

-what problem does the shearing of this bolt cause ?

thank-you

carspath

Original Poster:

832 posts

176 months

Saturday 8th February 2014
quotequote all
bump

info please

pewe

648 posts

218 months

Saturday 8th February 2014
quotequote all
Lots of info on here if you do a bit of digging.
http://forum.miata.net/vb/showthread.php?t=357133
HTH.
Cheers, Pewe.

MX-5 Lazza

7,952 posts

218 months

Saturday 8th February 2014
quotequote all
Nothing wrong with a short-nose crank (it's the end of the crankshaft that is different, nothing to do with the bolt). A few have failed but that's usually down to mistakes in servicing rather than a fault with the design.
For your info, if the crank pulley is correctly refitted and torqued up then it can rattle around a bit which chews up the woodruff key & keyway and that can be terminal for the engine depending on how bad it is.
Personally it wouldn't put me off. Engines are cheap. Condition of the body, particularly around the sills & rear arches is much more important.

MG CHRIS

9,077 posts

166 months

Saturday 8th February 2014
quotequote all
Engines are the least of you problems body condition and rust is far more important factor on these. An engine can be picked up for less than £100 to do rust repair on sills/rear arches will be 3-4 times more expensive to do if you can't do it yourself.

carspath

Original Poster:

832 posts

176 months

Sunday 9th February 2014
quotequote all
thank-you all, much appreciated

carspath

Original Poster:

832 posts

176 months

Wednesday 12th February 2014
quotequote all
please could you tell me if there is a simple reliable way to differentiate a short nose engine from a long nose engine just by looking at the engine

thank you

snotrag

14,446 posts

210 months

Thursday 13th February 2014
quotequote all
www.miata/net/garage/crankshaft.html

The pulley gives it away, dead obvious at front of engine.

VladD

7,853 posts

264 months

Friday 14th February 2014
quotequote all
snotrag said:
www.miata.net/garage/crankshaft.html

The pulley gives it away, dead obvious at front of engine.
Fixed the link.

chasdad

276 posts

143 months

Saturday 15th February 2014
quotequote all
Short nose has 4 holes in bottom pulley . Ive had 3 dhorg nose and the only one im having problems with is my last but im hoping its due to an overtightened cambelt