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Author Topic: Engine Autopsy Results
Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
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I pulled apart what was left of the bottom end after Rose Cup and the damage was impressive. The whole #4 piston and connecting rod literally exploded. It's not like 3 or 4 pieces. It's shards of metal with some recognizable chunks left.

At first I didn't think I'd be able to figure out what broke first considering how mangled everything is but I found a clue. I found one of the bolts that hold the connecting rod to the crankshaft in the debris. Bent but not broken and all the threads are intact. Then I found the nut that goes with it. The first two threads are stripped. It looks like the bolt loosened up, then ripped out the last two threads, then the piston exploded.

What could be the really bad news is that it looks like the piston hit the combustion chamber, denting the aluminum all around the edges, there's shiny spots on the valves of #4 so they probably got hit, and there are shards of metal in 1-3 also so the big bang may have destroyed my shiny new head too. [Frown]

Steve...if you want to sell that motor I borrowed, give some thought to how much. Right now I don't have a number in my head myself.

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Keith Novak
(Will work for tires)

W. Bonsell
Member

Region: NWR/Oregon
Car #: #26
Year : 1991
Posts: 334
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Sorry to hear about your motor Keith. Just out of curiosity, how many miles on the motor and were there any tell tale signs of impending doom?
As the owner of a 122k motor, I am wondering as to the likely hood of its' similar demise...or is it just simply a crap shoot? And is there anything you might have been able to do more in the way of a preventative nature having seen the internals?


Bill

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William Bonsell
SCCA/ICSCC #26
SM/ITA

Shop Teacher
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Region: SF Nor Cal
Car #: #39
Year : 1990
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Keith if it helps i lost my engine at Infineon this week. I dont know what happen just yet but sounds like i lost the lower end also. I have a Sunbelt going in. I was going to save it for the next Rose Cup but i need to finish the season. I have been showing the new motor my Rose Cup videos and it feels it will have no problems taking you guys. I have about 4 other friends that want to race the Rose Cup next year so far but expect more. I was surprised to hear that you had that much damage when you were only going a blistering 30mph.
A

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Al Angulo
Auto Instructor
Ford Senior Master Tech
ASE Master Tech

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
Posts: 2000
Status: Offline
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It'll be good to have you up again Al. Good times. Sorry to hear about your motor too. I know how it goes. [Smile] I need to find a time to head down there and try out some of your tracks too.

Bill- your motor is probably fine. I think mine was built late on a Friday afternoon. I found several parts that didn't seem to have been torqued down so I'm thinking the connecting rod was another one that was missed. There were less than 20 hrs on the bottom end. At 120+ miles, if something was loose in the engine you'd know it by now.

No warning signs really. Ask anyone who talked to me that weekend and I was really happy with the bunny stomping, baby seal clubbing power (for a Miata at least). The only sign was when we went full yellow I dropped the RPMs, it coughed a couple times then popped. Temp was fine, oil pressure fine, then flat line.

I changed the oil, filter and plugs after every race, changed the oil cooler after my replacement head died (spendy part), broke the engine in properly. What I probably should have done while I had the engine out was tear down the bottom end, inspect and reassemble everything. When you have the motor already out and mostly disassembled it's really pretty easy and much cheaper than a new engine.

I wouldn't worry about yours doing something similar. You could do a leak down test and try talking you son into refreshing the bottom end but otherwise drive it like you stole it. I think Pat's motor had many more miles than that on it when he bought it and the thing just goes faster.

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Keith Novak
(Will work for tires)

NV Racer Verified Driver
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Region: SFR
Car #: 70
Year : 1990
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quote:
Originally posted by Keith in WA:
The only sign was when we went full yellow I dropped the RPMs, it coughed a couple times then popped.

That sounds about right most rod caps pop on deceleration. Load is against caps on deceleration against rod on acceleration.

AL,
If not for bad luck Well you know the rest. I lost a motor at Infineon 3 years ago The track seems to be hard on motors.

Dennis

Shop Teacher
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Region: SF Nor Cal
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Seems to me when i built one of these engines i had to look twice at the rod torque spec. i think it was around 18-20 lbs seem low to me. But i went with it. Any time you guys want to come down just drop me a line, you can stay with us. We are 1.5hrs from Thunder Hill and Infineon but 4hrs to Laguna.

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Al Angulo
Auto Instructor
Ford Senior Master Tech
ASE Master Tech

NV Racer Verified Driver
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Region: SFR
Car #: 70
Year : 1990
Posts: 768
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quote:
Originally posted by Shop Teacher:
i think it was around 18-20 lbs seem low to me. But i went with it.

Al,
I hope your remebering wrong. Per FSM it is 37-40 Ft Lbs.

Dennis

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
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Well that explains Al's motor at Infineon. [duck]

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Keith Novak
(Will work for tires)

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
Posts: 2000
Status: Offline
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#4...minus the parts embedded in Al's nice paint job

 -

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Keith Novak
(Will work for tires)

Kyle Keenan Verified Driver
Pass right

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I don't see anything wrong?


[duck]

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Driver, #44 Spec Miata
ColdTrackDays.com

J. Douglas
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Region: San Francisco
Car #: 72
Year : 90
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After one of my buddys blew up his air race motor he said you could check the oil with your fist now.
There are parts in there that should be in the dark. Windowed the block. Big dollars in the game.
Jerry

TillerTech
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Region: SoPac
Car #: na
Year : 89
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Didn't you notice a loss of power after a lap or two?

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Miata Race glass and CF from Legacy Molds. 4 1/2# CF Hood
http://www.jnent.net

Kyle Freiheit
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Region: NWR
Car #: #78 sorry Terrell
Year : 1992
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That will buff out.

Chris Klein
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Region: North West
Car #: 386
Year : 1994, 1991
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Keith... Don't toss the head!!! It may never be a Spec Miata head, but Jeff can do wonders... It my be a good endurance motor head...

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Chris Klein

Drago Verified Driver Made Donation to Website Series Champ
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quote:
Originally posted by Keith in WA:
#4...minus the parts embedded in Al's nice paint job

 -

Wow!
From the looks of that, I suspected worse in the head [Smile]

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Jim Drago
East Street Auto Salvage
jdrago1@aol.com
2006-2007 Mid-West Division
07,09 June Sprints Champion

EAST STREET RACING

Chris Klein
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Region: North West
Car #: 386
Year : 1994, 1991
Posts: 257
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Yeah... weil... Go easy on the chump motor... ok Keith! [Smile]

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Chris Klein

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
Posts: 2000
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Chris- I'll make you a deal. I'll make sure to not blow the motor if you make sure your welds hold so the front of the car doesn't fall off. [Smile]

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Keith Novak
(Will work for tires)

Chris Klein
Member

Region: North West
Car #: 386
Year : 1994, 1991
Posts: 257
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Fall off??? This is the first articulating Shark Miata! So when the whole nose point left and right you're ok

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Chris Klein

Chris Klein
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Region: North West
Car #: 386
Year : 1994, 1991
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Check out the pictures on Facebook... There is a sleve welded inside the frame, and then it's boxed in all the way around... Not Will nor Bruce could brake the car there!

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Chris Klein

Shop Teacher
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Year : 1990
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just got back from having my new engine dynoed and big numbers heading up to Portland to do battle. http://www.facebook.com/profile.php?id=1000002272...437592&id=100000227299392

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Al Angulo
Auto Instructor
Ford Senior Master Tech
ASE Master Tech

Shop Teacher
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Region: SF Nor Cal
Car #: #39
Year : 1990
Posts: 457
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Oh the old engine spun a rod bearing and broke a skirt.

--------------------
Al Angulo
Auto Instructor
Ford Senior Master Tech
ASE Master Tech

B Wilson Verified Driver Series Champ
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With that new motor, you just might hit 95mph in T10 [Smile]

-bw

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Bruce Wilson
2010 Oregon Region Champ
2010 Monte Shelton Driver of the Year
2010 25 Hours of Thunderhill E3 and Under 2 liter Overall Champion
Oregon Region SM Class Advisor

Shop Teacher
Member

Region: SF Nor Cal
Car #: #39
Year : 1990
Posts: 457
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quote:
Originally posted by B Wilson:
With that new motor, you just might hit 95mph in T10 [Smile]

-bw

Coasting down to 95!

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Al Angulo
Auto Instructor
Ford Senior Master Tech
ASE Master Tech

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
Posts: 2000
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Just for the record...I never said you were wearing a skirt. You brought that on yourself. [Razz]

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Keith Novak
(Will work for tires)

Thomas Micich
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Region: Oregon Region
Car #: 92
Year : 1990
Posts: 9
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My dif that blew up at the rose cup isnt that bad but theres a hole in it.

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2010 Howard Allen Novice Driver of the Year
7 Time Karting Champion
Amsoil/Mayor Apparel/KKR Products/Spy Optics/Fluid Muscle Recovery

Kyle Freiheit
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Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
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Hey,
I still have pieces of it in my windshield.. and my whole car got a nice hot oil bath [Smile]


Kyle

Keith in WA Verified Driver Made Donation to Website
Pack Fodder

Region: NWR / Oregon
Car #: 88
Year : 95
Posts: 2000
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I sort of wondered what happened when I saw the smoke coming out.

Amusing conversation in the paddock but I don't remember between whom... (Driver 1) "Anyone know what happened?" (Driver 2) "He blew his diff." (Driver 1) "No. I don't think it was the diff." (Driver 2) "Well when I looked it had a big hole in it so I'm pretty sure it was."

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Keith Novak
(Will work for tires)

Kyle Freiheit
Member

Region: NWR
Car #: #78 sorry Terrell
Year : 1992
Posts: 270
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Yeah.. I pulled behind Thomas in the draft and as I was pulling out to pass was sprayed with diff oil and parts. Remarkably, Thomas' car then sped up. Apparently there is some windage in the diff [Smile]

Kyle

Kyle Keenan Verified Driver
Pass right

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I've never seen a diff blow like Thomas's did, so he's doing something right....

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Driver, #44 Spec Miata
ColdTrackDays.com

   

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