[DeTomaso] Update - cause of death - blown engine

Tomas Gunnarsson guson at home.se
Mon Jan 11 09:23:28 EST 2010


Thanks Will. As the rods are not Ford the torque figures I had are not directly relevant.

Tomas

----- Original Message ----- 
From: "Will Kooiman" <wkooiman at earthlink.net>
To: "'De Tomaso List'" <detomaso at realbig.com>
Sent: Monday, January 11, 2010 3:02 PM
Subject: Re: [DeTomaso] Update - cause of death - blown engine


> 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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