[DeTomaso] Update - cause of death - blown engine

Tomas Gunnarsson guson at home.se
Mon Jan 11 03:05:00 EST 2010 

Will,

Did you torque the bolts until you had whatever strech you wanted or did you torque to your decided figure, then measure the strech just for verification (without adjusting torque)? I'm also wondering if you simply over-torqued the bolts so that they went into plastic deformation. I just checked my Tom Monroe rebuild book and it says 40-45 ftlbs for std engines and 45-50 for Boss and HO. Where does the 67 ftlbs come from?

Tomas

----- Original Message ----- 
From: "Will Kooiman" <wkooiman at earthlink.net>
To: "'De Tomaso List'" <detomaso at realbig.com>
Sent: Monday, January 11, 2010 5:40 AM
Subject: Re: [DeTomaso] Update - cause of death - blown engine


> The bummer is I know I torqued the rods.  I even used a rod stretch gauge to
> measure the stretch - just for grins.  I can't explain, however, why it only
> took 40-50 lb/ft to loosen the bolts.
> 
> Also - I'm definitely not a professional, but I've put together several
> engines - maybe 10 or 15.  This is the first time anything like this has
> happened.
> 
> I'm going to put the next one together too, but this time I'm going to make
> damn sure the torque is correct on all of the critical bolts.
> 
> I'm also going to buy a better torque wrench - probably snap-on.
> 
> -----Original Message-----
> From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
> Behalf Of Asa Jay Laughton
> Sent: Sunday, January 10, 2010 9:23 PM
> To: 'De Tomaso List'
> Subject: Re: [DeTomaso] Update - cause of death - blown engine
> 
> wow
> 
> 
> 
> 
> Asa Jay
> 
> Asa Jay Laughton, MSgt, USAFR, Retired
> 
> & Shelley Marie
> Spokane, WA
> 
> 1971 Mach I Mustang  [ASA JAY]
> 1973 Pantera L 5533  [ASASCAT]
>    
> ******************************     
> http://www.asajay.com
> http://www.teampanteraracing.com
>  
> 
> 
> 
> Will Kooiman wrote:
>> I pulled my engine today.  I haven't taken it completely apart, but I
> pulled
>> the pan.
>>
>>  
>>
>> The official cause of death is:      The #4 rod cap came off.  It appears
>> that the rod bolts were not properly torqued.
>>
>>  
>>
>> Here's what I found inside the pan:
>>
>>  
>>
>> The #4 rod cap was not attached to the crank.  A rod bolt was in the pan.
>> I'm sure the other rod bolt is in the pan somewhere, but I haven't found
> it
>> (haven't looked through the sludge).
>>
>>  
>>
>> The #4 rod cap was in one piece in the pan.  It was flattened out.
>>
>>  
>>
>> I found the #4 rod bearing.  It is still in a half circle.  I haven't
>> examined it very much.  It was getting dark, and I had to do chores.
>>
>>  
>>
>> The #8 rod is broken in half.  The cap is still on the crank.  I
> previously
>> thought it was the #4 rod that was broken.  I couldn't tell for sure
> because
>> I was looking down the #4 bore -- which had the #4 piston lodged sideways
> in
>> it.
>>
>>  
>>
>> The #8 piston has the pin broken out of the piston.  At first I thought
> the
>> piston came apart to cause the destruction, but it looks like the crank
>> counterweights cut it off after the rod broke and the piston dropped into
>> the crank.  The counterweights have some debris on the leading edge to
>> support this theory.
>>
>>  
>>
>> The #4 main cap (between #3/7 and #4/8) is cracked at the base.
>>
>>  
>>
>> The #4 cylinder is cracked.  I think this happened when the #4 piston went
>> sideways.  I don't know about #8.  I haven't removed the driver's cylinder
>> head.
>>
>>  
>>
>> The #4 rod journal is gouged slightly on one side.  It looks like it got
> hit
>> after the rod came off.  If the bearing had spun, it would have cut
> grooves
>> along the entire circumference.  I think the crank is going to be
> reusable.
>>
>>  
>>
>> I just bought a new torque wrench -- in case my old wrench was inaccurate.
> I
>> checked the #8 rod.  It was only torqued to 40 lb/ft.  It is supposed to
> be
>> torqued to 67.  I checked a few of the other rods, and they were in the
>> 40-50 range too.
>>
>>  
>>
>> I checked a couple of the inner mains (ARP studs).  They were around 120
>> lb/ft.
>>
>>  
>>
>> I don't think the torque wrench is bad, otherwise the mains would be off
>> too.  The inner head bolts were correct too.  The outer head bolts have
>> always lost torque due to the excessive heat compressing the aluminum.
>>
>>  
>>
>> I'm guessing that either
>>
>>  
>>
>> a)       I set the torque wrench incorrectly when I did the rods or
>>
>> b)       I didn't use the proper procedure to torque the rods or
>>
>> c)       Both.
>>
>>  
>>
>> I did not torque it, loosen it, torque it, loosen it, torque it.  I used
> the
>> grey moly grease that came with the rods on the threads and under the bolt
>> heads.  I snugged them up with a ratchet, and then I torqued them to about
>> 35 (don't remember -- I usually go about ½ of the final torque), and then
> I
>> torqued them to 67.  I measured the bolt length before and after they were
>> torqued.  I didn't write it down, but I'm pretty sure they stretched
> 0.004".
>>
>>  
>>
>> The block is probably reusable with a sleeve, a new #4 main, and a line
>> bore.  It will probably cost more than it's worth, though. The crank might
>> be reusable.  The #4 and #8 pistons are obviously trash as are the #4 and
> #8
>> rods.  Everything else looks like it's in good shape.
>>
>>  
>>
>> I'll do pictures eventually.  It's going to be at least 2 weeks, though.
> I
>> have a lot of non-car-stuff going on -- going out of town next weekend.
>>
>>  
>>
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