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Old 10-06-2006, 03:51 PM   #1
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Default Hurt engine, which direction to take?

OK, so here is the story. I have been running my 227K mile '90 Greddy 1.6 at 8 psi for a while. About 2 months ago I had an injector fail and got some pretty serious detonation. I limped the car home and installed the 460cc injectors I had waiting and the car was back to running pretty good. I got it tuned, but it has had a miss with no load on the engine every since. I finaly decided that the night the injector failed, I probably burnt a valve. I did a compression and leakdown test and it shows:

#1 - 160 psi, 10%
#2 - 155 psi, 16%
#3 - 155 psi, 14%
#4 - 165 psi, 8%

So, the conclusion is she is pretty well done. Options to get her back on the road are:

-Buy a cheap junkyard head for $125 and run the **** out of her knowing I'm not making great power.
-Rebuild the engine I have and the car be down for several weeks and know it is strong when I'm done. Anyone have a guess what this would run? I'm guessing $700-800 for the machine work and freshing up the head?
-buy a known good 1.6 w/ 0-3% leakdown for $600
-buy a 1.8 for $500 and swap over to a HKS manifold (additional $250)

I need a larger downpipe and would by one of turbotony's if I go 1.6 and fabricate one if I go 1.8 w/ the HKS.

What else would I need for the 1.8 swap?

Opinions, other options?
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Old 10-06-2006, 05:02 PM   #2
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For the 1.8 swap, it's probably best to get the FM kit... since it includes the adapter for the TB, and all the other 1.6 accessories.....

I already had a 1.8, but did the swap to another 1.8 in spring. The swap while took time, since I had to swap accessories, and install a different head on the block, it really wasn't that bad....

You should make the choice if you want the extra coin into the swap or not. Just remember, you can prep all your parts a head of time, then just "do it" unlike a rebuild, when the car is down while everything is in pieces....

Dave,
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Old 10-06-2006, 05:14 PM   #3
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Quote:
Originally Posted by sbrian2 View Post
compression test:

#1 - 160 psi, 10%
#2 - 155 psi, 16%
#3 - 155 psi, 14%
#4 - 165 psi, 8%

So, the conclusion is she is pretty well done.
First thought, those are not horribly terrible (?)

The largest variance is about, what, 7-8%? Now if I could just remember the factory limit numbers....

In theory, what should the leakdown look like? (I have no idea)

As far as the numbers being low, you could just turn up the boost to compensate.


Out of your options, I'd love to see you rebuild it, the 1.8 swap is the coolest, but replacing the 1.6 with another is probably the best option. (Ugh, the boring one too. Nevermind that do the rebuild!!)
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Old 10-06-2006, 05:19 PM   #4
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I'd buy a jumk yard motor (1.6) and rebuild the entire thing. Decide if you want the extra expense of building the bottom end. Then when you are ready it's just the labour of swapping it. Buy a long nose while you are at it as well.

I'd hate to go through the hassle of sourcing and swapping a motor with out at least rebuilding it using OE parts. My luck I'd put in the "good" motor and have it **** itself a month after I do it.

I honestly don't think the 1.8 swap is worth while. The only reason I would consider it is if I had my heart set on running a supercharger. The M45 on a 1.6 is just too limited.

Jay
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Old 10-06-2006, 05:23 PM   #5
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On leakdown, anything over 10% is bad. I would actually love to rebuild it, but I just hate to invest the time (something I don't have right now). The car runs right now, it just has a bad miss with no load on the engine (idle and cruising) It actually runs OK under WOT, although I can tell it is not as strong as it once was.
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Old 10-06-2006, 05:31 PM   #6
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That's why I suggest getting a junk yard motor and rebuild it over time. Drive the car as it is for now.
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Old 10-06-2006, 05:56 PM   #7
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i agree. i did this method with a head. i bought an extra head, diassembled it, sent it out for p&p, gasket matching, shave, hot tanked. bought all the gaskets and studs, etc, sent out the extra IM and VC out for powdercoating, polished the valves.

when the head came back, i reassembled it.

swapping out the heads was pretty easy. one day of down time.
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Old 10-06-2006, 06:15 PM   #8
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Numbers aren't that bad, what's bad is your weakest cylinders are on the same stroke. Spec is something silly like 138. That engine as is would probably last you way longer than you think. The only thing it's hurting right now is power. If you're sure it's the head, then I go cheap and do the salvage head swap. Otherwise I'd be in for the 1.8 swap so there was some kind of reward and improvement over the old setup after all the hard work. - rob
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Old 10-06-2006, 07:09 PM   #9
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Here's a guy selling a parts car... mapquest says it's 800miles from you. It might be worth it to you to take a weekend and go get it with a flatbed.
You'd have about $500 in the trip including rental, gas, and motel. Then another $700 for the car. That gets you the 1.8 motor, full driveline, brakes, and half a car left to re-sell to make back the money. Those tires are probably worth $300 to someone... complete top and interior... etc...
The only thing you'd need would be like you said, the 1.8 conversion kit and new manifold.
http://www.miata.net/cgi-bin/isc/cla...revaction=show

It probably doesn't have a Torsen, but the open 1.8 is just as strong.

It's an idea.

What about this one in Jersey... don't know about shipping:
http://www.miata.net/cgi-bin/isc/cla...revaction=show
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Old 10-07-2006, 08:53 PM   #10
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There is a guy in Cookeville has a bunch of wrecked miata's that he either makes parts cars or fixes and sells them. Not sure what he wants for a motor but hes pretty close. Just an option. I bought a viscous lsd diff from him about a month ago for $350 (housing and all). His name is Buddy Gaw their used car lot where you can find him is Big Bud's Auto Sales, 40 N Cedar Ave Cookeville, TN 38501-2415 (931) 526-5506
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Old 10-08-2006, 09:45 PM   #11
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if you have a spare car, but a 1.8 and just freshed in up. Do new ductile iron mazda rings (oem rings are typically easier on piston walls from my experience), get the cylinder walls hones, ARP fasteners and ARP bearings.

It shouldn't run you more than $400 in labor and parts, and it will be perfect for reasonable boost and tracking.
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Old 10-09-2006, 10:51 AM   #12
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Good news. My guage was wrong and after checking with a new guage apparently I was 10 psi off across the board. The numbers now look like:

#1 - 170 psi, 3%
#2 - 165 psi, 6%
#3 - 165 psi, 4%
#4 - 175 psi, 1%

So, you ask, why was the car running so crappy? Well, I started undoing mods untill it ran well again and it seems the injectors are the culprit. I will send them off and have them cleaned and balanced and see if I can get it running as well on the 460cc injectors as it does on the stocker pushing 100% duty cycle.
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