[DeTomaso] WARNING: .050 may be the wrong kind of Bomb

[Dave Londry]

Dan,
If your secondaries don't open, you'll be running more air through the 
primaries than was ever intended.
I think that could well go lean.
I'll be interested in what the guys-who-know-carbs have to say.
dave

Dan Courtney wrote:
> I haven't picked up a borescope yet but I ran a compression test tonight and 
> all 8 cylinders were consistent around 150 psi. Haven't done a leak-down 
> test yet.
> There were no rings on these AP 25 plugs and I noticed #8 is gapped at .045, 
> pretty sure it was put in at .050. The other plugs are at .050.
> Could impact from the domed piston to the plug tip crack the electrode 
> without breaking the tip? Although #5 is missing 1/2 the tip, #6 has an 
> intact tip but not much electrode. The other 6 plugs all look brand new.
> I may convert to AP 32's, to lessen any potential detonation, and hopefully 
> they come with rings.
> I may check the intake gasket, to see if it shows sign of an intake leak. 
> The intake bolts at the end by #5 & #6 are studs with nuts (to hold the 
> throttle linkage I fabbed for the AirGap) and may have loosened.
> Otherwise I can't think what could be potentially causing detonation.
> I'm assuming the backfire I'm getting about 6 seconds after any significant 
> deceleration is being caused by the collector donuts, as those locknuts keep 
> getting loose, but maybe from an intake leak?
> The secondary butterflies do not appear to be opening, but it seems like 
> that would lead to a rich condition, rather than lean for detonation.
> I'll try and find a borescope tommorrow, to see if anything is damaged.
> If it looks good I'll try for a dyno tune appointment.
>
> Dan
>
> Dan F. Courtney
>
> La Jolla, CA
>
> (858) 551-5455 Phone
> (858) 551-5456 Fax
> ----- Original Message ----- 
> From: "P. Rimov" <rimov at charter.net>
> To: "Dan Courtney" <dfcex at excaliburre.com>
> Sent: Sunday, May 24, 2009 7:45 M
> Subject: Re: [DeTomaso] WARNING: .050 may be the wrong kind of Bomb
>
>
>   
>> Dan are you running domed pistons or have you had the heads milled to 
>> increase the CR? If so you may need to add an extra ring or two on the 
>> plugs of the offending cylinders. It is possible the extra gap on the plug 
>> was just enough to result in contact with the piston. Plugs are great for 
>> heat but not so good when they are dropped or bumped by a piston.  It is 
>> possible the spark plug wire was loose or popped off at some time to cause 
>> the #? to foul. I would not start worrying about pulling the heads just 
>> yet. What ever pieces broke off in the cylinder are long gone through the 
>> exhaust. I would be more concerned about any valve damage from the plug 
>> remnants before or while they exited the exhaust valve. Valve damage can 
>> easily be ruled out through a compression check and lead down check, but 
>> again I don't think you have to start worrying just yet. One last thing I 
>> would change your oil and make sure to filter it and check for any foreign 
>> material.
>>
>> Cheers my friend
>>
>> Paul
>> ----- Original Message ----- 
>> From: "Dan Courtney" <dfcex at pacbell.net>
>> To: <JDeRyke at aol.com>
>> Cc: <detomaso at realbig.com>
>> Sent: Sunday, May 24, 2009 7:12 AM
>> Subject: Re: [DeTomaso] WARNING: .050 may be the wrong kind of Bomb
>>
>>
>>     
>>> Jack,
>>>
>>> I timed it at 12 deg @ idle, 32 deg total in around 2,800 rpms.
>>> Fuel pressure is from an electric pump internally regulated at 6.5 psi.
>>> The plugs in the same cylinders looked OK before switiching out after 600 
>>> miles of highway and desert driving.
>>> It's not just the ceramic part missing, also the electrode and, on #5, 
>>> 1/2 the top of the tip.
>>> It's seems strange that the other 5 plugs (except #2 / fouled) look new.
>>> Where would I find this scope? I really don't want to pull the head.
>>>
>>> Thank You,
>>> Dan
>>> Dan F. Courtney
>>>
>>> La Jolla, CA
>>>
>>> (858) 551-5455 Phone
>>> (858) 551-5456 Fax
>>>  ----- Original Message ----- 
>>>  From: JDeRyke at aol.com
>>>  To: dfcex at pacbell.net ; detomaso at realbig.com
>>>  Sent: Sunday, May 24, 2009 12:27 AM
>>>  Subject: Re: [DeTomaso] WARNING: .050 may be the wrong kind of Bomb
>>>
>>>
>>>  In a message dated 5/24/09 12:10:59 AM, dfcex at pacbell.net writes:
>>>
>>>
>>>    What worries me more is, where are the tips of the plugs? Are they 
>>> sitting in the cylinders, about to punch through my brand new pistons? Or 
>>> has that already happened?
>>>    I'm also wondering if detonation could have played a role.
>>>
>>>
>>>  Thats a sign of detonation. Check your total ignition advance and your 
>>> fuel pressures. Normally, a plug gap will either fire, or not, so thats 
>>> not the cause of your detonation. The piston crowns likely look 
>>> shot-blasted but unless they made really deep pits, the pistons will be 
>>> OK. Any extra pieces of ceramic are long gone out the tailpipe. A fiber 
>>> optic borescope can look thru the plug hole and inspect the piston tops 
>>> without pulling the heads. My best guess- J Deryke
>>>
>>>
>>>  **************
>>>