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Old 02-12-2014, 09:27 PM   #1
Toyanvil OP
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Mazda Miata 1.6L question

In the search for a EFI motor for my 1961 Sunbeam Alpine I have started looking at Mazda Miatas with 1.6L motors and 5 speed trans. I currently have a Nissan A14 with a 4 speed in the car now. I have heard that the 1991 and older 1.6L have a problem with the crank and to look for a 1992 or newer, is this true? There is a 1991 local for a good price, just not sure if I should be looking for a 1992 and newer. P.S a 1.8L motor is just to big.
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Old 02-12-2014, 09:32 PM   #2
rocker59
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FWIW, I put 120,000 on a 1991 Miata with no problems.
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Old 02-12-2014, 10:15 PM   #3
rbjenterprises
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Early 1.6 motors had the short nose crank problem. Check out one of the miata sites to find out when it was changed. I have a 1991 and it does not have the short nose.
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Old 02-12-2014, 10:32 PM   #4
Mike.Gail
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Short nose crank issue isn't an issue as long as you pay attention. It's related to insufficient thread engagement of the crank pulley bolt when servicing the timing belt. There are workarounds and solutions to the issue.

But it's about as common as a KLR doohickey or a BMW final drive failure. Doesn't happen enough to be an issue, but everybody's brothers sisters cousins former room mate had it happen so it must be serious.

The 89/90 body style is the lightest. Start from there, and have fun.
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Old 02-13-2014, 07:48 AM   #5
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After having and building a few Miatas I feel reasonably qualified to answer.

The change-over for cranks was mid-year 1991. There is a simple and clear cutoff for the VIN. All the VINs after a certain number are long nose cranks. You can also identify them by the crank pulley. I believe the long nose crank pulleys have 8 elongated holes in the front of the pulley and the short nose has 4. Like the VIN though, you will want to look it up to be sure.

The short nose issue is pretty much just like it sounds. The nose end of the crank is too short and doesn't provide great thread engagement for the crank pulley bolt. Over time the bolt can looses, causing the crank to wobble and the keyway to wear. At this point it really isn't worth trying to fix. If this hasn't happened yet you *should* be safe. Occasionally they are damaged when removing the crank bolt to fix the issue (happened to a friend of mine), but generally speaking if it hasn't loosened noticeably yet it is entirely serviceable. The common fix is simply to remove the crank bolt, clean everything well, and reinstall to good revised torque specs with loc-tite on the bolt.

On the plus side, short nose engines can be had for a song since people are so worried about them, but even long nose 1.6 engines are cheap since most people want the 1.8.

If you need any little install parts for your conversion PM me. I have all kinds of odds and ends sitting around from a 95 I parted out. Many parts are interchangeable.
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Old 02-13-2014, 11:21 AM   #6
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Lots of spares, engines too, on www.miata.net
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Old 02-13-2014, 04:18 PM   #7
fireflyr
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Quote:
Originally Posted by Toyanvil View Post
In the search for a EFI motor for my 1961 Sunbeam Alpine I have started looking at Mazda Miatas with 1.6L motors and 5 speed trans. I currently have a Nissan A14 with a 4 speed in the car now. I have heard that the 1991 and older 1.6L have a problem with the crank and to look for a 1992 or newer, is this true? There is a 1991 local for a good price, just not sure if I should be looking for a 1992 and newer. P.S a 1.8L motor is just to big.
Hey John. My original Miata (I think a 1990) had a short nosed crank. These were susceptible to cracking and the balancer coming off. I never had any problems and drove the living dog $hit out of it. Great motor!
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Old 02-13-2014, 05:12 PM   #8
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Originally Posted by fireflyr View Post
Hey John. My original Miata (I think a 1990) had a short nosed crank. These were susceptible to cracking and the balancer coming off.
True, but nearly always because of improper instillation following timing belt replacement. Because of the short nose on the crank, and the short keyway, it is exceedingy easy to get the woodruf key in cockeyed and either crack the crank, or round off the edges of the keyway.

I've had a '90 since '92 (the vehicle went into service in '89) and through careful (RTFM) reassembly have had 179,000+ trouble free miles on the original crank while replacing the timing belt on schedule. I would not hesitate to buy another short-nose engine, but I would ABSOLUTELY insist on being allowed to pull the crank pullly and balancer for inspection as a condition of the sale.

One more thing of note on the NA Miatas. When Mazda moved the engine around to adapt it to the RWD Miata platform (it's the same engine as in the 323), they chose to retain all of the coolant piping for the FWD platform. What this means is there is an unused coolant fitting at the rear of the Miata engine (under the coil pack) that is capped by a rubber cap. That little cap that Mazda used cost me a top-end rebuild after it blew out on the freeway.

Inspect that little fucker as often as you can. I'd go so far as to just add it to your annual maintianance schedule as a replacement item, or do as I did, and replace it with a short peice of coolant hose that has been capped at the other end by a brass bolt and worm clamps (I actually left mine fairly long and use it to burp the coolant system. Makes for a very handy high-point in the system and it zip-ties out of the way nicely).

k-moe screwed with this post 02-13-2014 at 05:49 PM
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Old 02-13-2014, 07:42 PM   #9
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Thank you guys, for all the great info. This is the info I am looking for. I think it would be a good motor for the Sunbeam, the cars are about the same size and weight. The Miata 1.6 has about 50 more HP and a 5 speed, the cars am looking at are in the $600 to $1000 range for a running car. My plan is to buy a running car, take out everything I need and then part out the rest.
Here's my Sunbeam

The A14 motor
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Life is like riding a bicycle, to keep your balance you must keep moving.
Some people try to turn back their odometers. Not me, I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved. Hell, some of the places I’ve been there weren’t even roads!
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Old 02-14-2014, 09:14 AM   #10
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John,
I was thinking about installing that same combo in that Cortina GT up the hill before I got involved in this Karmann Ghia. I seem to remember that the Miata has a different driveline layout (torque tube?) and wasn't sure how that would swap in. Maybe someone with more info can chime in. That 1.6L is one of the sweetest engines out there and should be a blast in your Alpine.

Pat
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Old 02-14-2014, 10:16 AM   #11
Mike.Gail
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Quote:
Originally Posted by fireflyr View Post
John,
I was thinking about installing that same combo in that Cortina GT up the hill before I got involved in this Karmann Ghia. I seem to remember that the Miata has a different driveline layout (torque tube?) and wasn't sure how that would swap in. Maybe someone with more info can chime in. That 1.6L is one of the sweetest engines out there and should be a blast in your Alpine.

Pat
Not a tube, but an arm. There's no transmission mount in the Miata. There's a long arm that goes from the transmission to the differential and that's what holds the back of the engine up.

But given how the arm attaches to the tailshaft housing on the transmission I figure a mount could be devised without too much trouble.
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Old 02-14-2014, 10:21 AM   #12
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Quote:
Originally Posted by k-moe View Post
One more thing of note on the NA Miatas. When Mazda moved the engine around to adapt it to the RWD Miata platform (it's the same engine as in the 323), they chose to retain all of the coolant piping for the FWD platform. What this means is there is an unused coolant fitting at the rear of the Miata engine (under the coil pack) that is capped by a rubber cap. That little cap that Mazda used cost me a top-end rebuild after it blew out on the freeway.

Inspect that little fucker as often as you can. I'd go so far as to just add it to your annual maintianance schedule as a replacement item, or do as I did, and replace it with a short peice of coolant hose that has been capped at the other end by a brass bolt and worm clamps (I actually left mine fairly long and use it to burp the coolant system. Makes for a very handy high-point in the system and it zip-ties out of the way nicely).
Ahh, the cursed water plug.


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Old 02-14-2014, 04:47 PM   #13
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The first large nose crank was mid year 1991 with the vin# ending with 209447.
I actually own a red 91 with the infamous vin# 209447. And can verify after doing a timing belt replacement that it has a large nose crank.
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Old 02-14-2014, 05:07 PM   #14
BillsR100
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Originally Posted by Tj007m View Post
The first large nose crank was mid year 1991 with the vin# ending with 209447.
I actually own a red 91 with the infamous vin# 209447. And can verify after doing a timing belt replacement that it has a large nose crank.
Wow, thats kinda cool when you think about it.
------------
If I were thinking of putting a Miata engine in that Sunbeam, I would be lean towards a 1.8 Miata engine since they are plentiful and will fit just like a 1.6 one will.

(We are a two Miata family, 97 and 99 models)
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Old 02-14-2014, 05:17 PM   #15
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Honda s2000?
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