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SM newbie motor saga and recent failure w/ questions

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#1
djames22

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So I lost a main bearing in my 1.6, and decided to do a 1.8 swap in my track car a few years ago.

Shortly thereafter, I decide to go all in and build my track car into a full spec miata.

 

Well, I quickly learned my 1.8 swap wasnt legal and I needed to go back to 1.6 ugh.

Got a freshly rebuilt long block from a racer on craigslist, that turned out have mismatch cam caps from other heads and cams wouldnt spin with more than finger tight bolts. Joy. 

 

After having to return another motor bought online, I scored a fresh rebuilt motor from a local wreck yard here in the bay area.

Took it to TFB for dyno tune, and got some decent #s for a junkyard dog, 115+hp/108+tq. I was excited and in the game after over 1year building and swaping motors!

 

I made the last race of the season this year in Oct 10,which was my 1st race. I stayed out of trouble, got to mix it up in the back and finished Sunday in 26th. So I dipped my toe in and got one step closer to getting my license. The motor ran good and car worked really well. Lap times were nothing special, mid to low 159s when clean laps, but I changed everything in the car and hadn't driven in over a year, so I was pleased, enough;) 

 

Had a great day at Sonoma on Friday Nov 27th, clicking solid low 158's with a personal best of 158.09, over a second faster than pervious best. So I was really excited about the season starter coming in March for Nasa Norcal region and getting a full season in and being in the mix and doing this.

 

That next Monday I went to Thunder hill to get some more seat time and try and learn the SM east route to see if I could settle into a competitive mid pack time. First run was a mostly feeling it out, but felt good that by end of day I could be where I wanted to be. Someone dumped oil all over the track in the group before my 2nd session. The entire track go kitty littered to soak it up, but I was linked up with some other SMs and it was almost like we welcomed the days of thunder lack of vision and the lost traction to further test our skills and feel.. Well, they had NBs with stock air boxes, and paper filters, and I had the highest flowing green cone.. The kitty litter was everywhere when I got back to the pit. I wondered about it getting into the motor while out there, but got sucked into stayin with the NBs and let it go. 

 

That next session would prove that was a bad decision after my motor blew a hole in the low end under the #4 piston underneath the header. I was able to pull off the track to a safe spot, thankfully, as the motor caught fire and I had to jump out, grab the extinguisher and get to putting it out before I lost more than a motor. Got the tow of shame back to the trailer and had a good 3h drive to think about what went wrong and where the budget would come from to make it right again. 

 

I yanked the head off, all was well, but the #4 piston valves were white. 

There was some damage to the piston top of piston 1, but that might have been the last failure prior to rebuild.

The motor was tuned lean, like most 1.6 getting #s up high. 

The #4 piston is not connected to the crank, but has the rod connected, so big end failure I guess.

 

 

Questions:

Am I nuts to vilify the kitty litter used to absorb the oil and blame it for my engine failure?

Is it possible to lose a ring and then a rod bearing or rod as a result?

Or did I have a time bomb low end that was bound to blow sooner or later with a bad big end rod bearing?

 

Thanks!

 

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#2
bmarshall1

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Just another newb here (I lost a motor 3 weekends ago also  :( )

 

I don't see in any way how kitty litter would cause this.  Even if some KL got into your airbox and blocked airflow, the computer should compensate A/F ratios.  

 

I am more familiar w/ 1.8s, but due to the cooling routing, #4 can run hotter, if you're already running lean, perhaps combine that with some other variable and there could be your issue (overheat, too much detonation etc...) How does the plug and the top of the piston look?  Is the piston seized in the bore?

 

It's also possible over over-revs, money shift, or, it was just this motor's time to go. 

 

I had a buddy lose a $6k race motor when his alternator died, therefore he had insufficient fuel pressure, ran lean and that was it (per his engine builder).


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#3
Michael Novak

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Kitty Litter didn't kill it unless the filter wasn't even connected!!!  Wear yes if the filter somehow wasn't stopping anything. There were other problems..


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#4
Steve Scheifler

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Definitely not related to the kitty litter.

From the picture you are correct that #4 was lean. It appears 3 is pretty good then 2 & 1 each richer, so if on the dyno it was overall lean (average of all 4) then it was fatally lean on #4. Apparently that same cylinder failed before given the non-oem (and non-compliant) valves, so it’s possible there’s an actual problem with the already limited coolant flow to it but more likely your injectors are not well matched and producing a good pattern. Did you have them cleaned & flow tested? Did you use your old ones or did they come with the reman engine?

General word of caution, generic reman engines for old cars are not a great idea. They are meant as a cheap way to keep your POS alive for basic street use. Don’t count on careful attention to tolerances and definitely don’t expect them to pass any kind of invasive tech.
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#5
djames22

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Thanks a ton for the feedback and insight.. 

 

I got the motor from a wrecker and was surprised to see new freeze plugs in the block and the head was like brand new. 

Even cnc marks were fresh, and the cam area not even stained from oil, totally fresh silvers everywhere. 

 

Steve's keen eye called out the #4 valves being diff, so I guess this was a reman'd head or even long block that I got from the wrecker. 

So maybe the reman co didn't change the rod bearings on #4 that likely compromised. Then it was just one or two hard drives away from failure.

That theory makes enough sense for me to sleep at night ha. I did put cleaned injectors in, and did put new injector seals and intake gasket etc.  

 

Have a line on a good used race motor now from someone I can trust, so the quest is back on ha. 

 

Well, at least I won't have to fear kitty litter next time its out there;)

 

Thanks again!



#6
Bench Racer

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Information on limited coolant flow and thermostat location for the Miata.

 

"The Miata engine was originally designed to sit transversely (sideways) in front-wheel drive cars. But, when engineers fit it into the little two-seat rear-wheel drive car, the engine had to be turned to connect to the driveshaft, which put the thermostat housing against the firewall. To remedy this, engineers moved the outlet to the front, so coolant flows in and out of the front of the engine, instead of in one side and out the other. As a result, cylinder #4 is significantly hotter as the flow is significantly reduced."

 

There is a coolant workaround but it's illegal for SCCA/NASA racing. Mazda changed their head gaskets for the 99 plus engines to force more coolant to flow to cylinder #4 and less coolant to flow to the preceding cylinders. I don't remember or have any 1.6 heads/gaskets around anymore but there is something which may be done to the gasket to improve flow. Can someone who knows share the gasket with djames22


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#7
dickcdawg

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If this is a 1.6 Miata head in the photo, isn't that the #1 cylinder running lean?

 

Dick H.

#39 ITA

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#8
Steve Scheifler

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If this is a 1.6 Miata head in the photo, isn't that the #1 cylinder running lean?

Dick H.
#39 ITA
Knoxville, TN

Ha, ha, ha ha!! Good catch. Stupid of me to not notice. I took his post about #4 being the problem, saw the picture and didn’t question it. Not sure it changes much, but it reduces the odds that a lean condition contributed to the catastrophic failure. Then again, heavy detonation could disguise a lean burn that triggered it. What I can see of valves and plug probably not.
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#9
djames22

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Ugh, sorry for the confusion fellas, I clearly got things crossed up, my bad.

 

I still haven't gotten the low end apart, but did observe the #4(the rear most ha) piston fall to bottom of cylinder and stay down while #s 1/2/3 moved up/down when I cranked it over by hand. So it was clear there was a rod or at least a wrist pin failure. 

 

Is it typical to see progressively leaner burns in cylinders as you go from 4 up to 1?

I was expecting the opposite due to the cooling issues people point to.

That #1 looks scary lean. Seems odd how it richens from 1 to 4, that can't be normal right?

 

Maybe I had an air leak in the intake runner at 1 and 2? 
I don't run that alloy support that runs behind the alternator, maybe I should from now on. Have other's arrived at the same place and running it? 

Admittedly, since I drove Fri and Mon, I didn't have time to do a full once over, so intake bolts could have settled from the build and come loose.

 

I'll just try to be thankful for the lesson I guess.

Pay'n my dues on wreck'n yard motors is getting off light compared to learning hard way lessons on a $6k race motor(knock on wood.)

Still stings though;)



#10
Alberto

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I haven't had my engine apart to see if the color of the deposits on the combustion chamber indicate rich or lean but I have not seen a variance in how my spark plugs look from cylinder to cylinder.  

 

Definitely get your injectors cleaned.  Reliable sources:  RCeng.com, witchhunter.com, https://www.advanced...njector-service

 

Can't hurt to run the brace to insure that the manifold is well supported and is not impacting the sealing of the intake manifold but that is probably not the cause of your failure.


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#11
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Maybe I had an air leak in the intake runner at 1 and 2? 

I don't run that alloy support that runs behind the alternator, maybe I should from now on. Have other's arrived at the same place and running it? 

Admittedly, since I drove Fri and Mon, I didn't have time to do a full once over, so intake bolts could have settled from the build and come loose.

Your admit being new to Spec Miata racing/race cars and you commented when you decided to race a 1990-1993 car you read the rules and were required to install a 1.6 engine. Here's a solid statement referencing a Spec Miata race car and your car lacking the alloy support from block to intake manifold, if a rule specification doesn't say you can do something then you can't do it. Another point on the alloy support, folks running Miata engines in other classes leave the support in place because of the considerable harmonics of the engine. Also I believe you'll find other classes don't install an flex plate flywheel at 2-3 pounds compared to the OEM flywheel 17-19lbs or aluminum flywheel at not legal 7-9lbs because of the engine harmonics. The OEM alloy support is in place for a reason. My harmonics comment should pull a comment or two out of the woodwork. :bigsquaregrin:


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