Miata Mailing List: October 1997, Message #86
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From: 	"Brian K. Dore'" <bkd@usl.edu>

Subject: Re: Crankshaft Repair

Date: 	Wed, 1 Oct 1997 10:38:53 +0000



You said:



> I have seen quoted the price of $3,000 for repair of the short nose

>crankshaft problem on early Miatas. I assume some of this money goes

>to repairing the top end (valves, OHC, etc.).

> This seems like an awful  lot of money for the repair. Does anyone

>have some information on exactly what is involved for 3k?



For $3,000 US, you should be able to get a brand new Mazda 1.6L long block

installed.  I think Tommy at PBC told me that he could sell them for under

$2,000 and I'm pretty sure you can have it installed and cover all of the

gaskets and fluids for the other $1000.





> I had a timing belt go on a Ford 2.4L OHC and i think it cost about

>$300-400 to repair the top end and replace the belt.

> Any insight greatly appreciated



In this case, the timing belt broke, and since the 2.4L is an interference

engine, the valvetrain was damaged, and the repairs were probably limited to

the head.  The Miata 1.6 (and 1.8) are non-interference engines so the

valvetrain is usually not damaged if the timing belt breaks.



  The 1.6L crankshaft problem has nothing to do with the timing belt

breaking, it has to do with the crankshaft itself breaking.   To repair a

1.6L engine with a broken crank, you of course need to buy a new crankshaft.

I don't think any mechanic would replace the crankshaft without at least

replacing the connecting rod bearings too.  That assumes that the rest of

the engine is in good shape and it's worth repairing just the bottom end.

If I remember correctly, there are three different crankshafts for the 1.6L,

the original used in 1990/early 1991 Miatas, a similar, but stronger drop-in

replacement part for these Miatas, and the late 1991-1993 crankshaft that

was completely redesigned and uses a different oil pump, timing belt gear

and accessory pulley.  Read the stuff in the Garage section of Miata.Net by

Lance Schall who did a lot of work to find out all the details.



Brian Dore'

Lafayette, LA