[DeTomaso] Update - cause of death - blown engine

Mon Jan 11 09:02:05 EST 2010

The crank is a stock 351C stroker from Dennis Q.  It is offset ground to
3.7" and uses SBC rods.

The rods are SCAT H-beam, 6".  They have ARP cap-screw bolts.  The rod
torque is listed on the side of the box the rods came in.

I didn't look for the original paperwork this weekend, but I seem to recall
the instructions were to torque to spec and then to replace the bolts when
either

a) the untorqued length stretched more than 0.001" or 0.002" from the
original length (don't remember 0.001 or 0.002) or

b) the torqued-to-spec length stretched more than 0.007" than the original
untorqued length.

I bought the stretch gauge intending to torque to stretch.  However, once I
read the docs, I ended up torquing to 67 and then measuring the stretch.

And, like I said I must have set the torque wrench incorrectly.  It's either
that or the rod bolts lost 15-20 lb/ft - which I find hard to believe.

Another possibility is I torqued them to 40 and forgot to go back and do the
final torque to 67.  If that's the case, it's the dumbest (engine related)
thing I've ever done.  And that's saying a lot.

I don't think I forgot to torque to 67, though.  I distinctly remember
setting the torque wrench on the "7".

-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of Tomas Gunnarsson
Sent: Monday, January 11, 2010 7:19 AM
To: 'De Tomaso List'
Subject: Re: [DeTomaso] Update - cause of death - blown engine

I understand that Göran. Will mentions a torque that is 50% higher than
stock and assuming that the bolt size is unchanged this alarms me. If the
bolt quality was upgraded from 8.8 to 12.9 it would make sense but I hope
that the stock bolts are not made from "coathanger steel". Let's await
Will's response.

Tomas

----- Original Message ----- 
From: <hemipanter at hemipanter.se>
To: "Tomas Gunnarsson" <guson at home.se>
Cc: "'De Tomaso List'" <detomaso at realbig.com>
Sent: Monday, January 11, 2010 1:28 PM
Subject: Re: [DeTomaso] Update - cause of death - blown engine

> There are rodbolt Tq that are quite high, my own is 80 fp for example.
> Many aluminium rods has higher Tq recomendations, but also rod bolts
> designed for it.
> Goran
> 
>> 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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