[DeTomaso] Asa Jay's 1985 built 351C Forensics part II

[Asa Jay Laughton]

Good grief Jack... catch up.  Here is the Cliff Notes version

- Rebuilt .030 over with stock 2V heads and new .030 over cast pistons 
in 1985
- 4V heads swapped onto engine a few years later
- Valves stems are sealed with a positive lock seal -not- the stock 
umbrella seals
- Engine was pulled in 2001 due to rattle/knock in engine at certain 
rpm. (Was in the Mach I)
- New engine installed in 2001 (again we're talking about the Mach I)
- Engine has sat on stand in garage since 2001
- The excess carbon flakes in #2 are what we're bench theorizing on in 
this thread
- I would not consider the carbon ash in the intake port to be excessive 
(the photo is misleading)
- The head drains are clear
- No photo of the backside of a bearing so I'm uh... not sure where you 
got that one.
- I anticipate -all- bearings will look the same -- Bad
- As I recall, the crank was turned .010 under during the rebuild in 
1985 (I'll mic it later to know for sure)
- Didn't do a leak down test at any time, symptoms didn't lend 
themselves to needing one.  I was dealing with a rattle/knock at certain 
rpms and no mis-firing or backfiring via carb or exhaust.  It sounded 
metal, leading me to think bearings or broken piston skirt or some such 
nasty metal breakage.  At the present level of dis-assembly, it may have 
been detonation in cylinder 2.  That may be the most suspect at the 
-moment-.  I'll still pull the rest of the pistons and finish a complete 
inspection, but the excessive amount of carbon flaking in #2 was curious.


Oh, and I figure this engine has about 80,000 miles or more since I 
rebuilt it in 1985, and it was my very first engine rebuild.  I hope all 
my others last as long.  ;)

Asa Jay

Asa Jay Laughton, MSgt, USAFR, Retired
&  Shelley Marie
Spokane, WA
******************************
http://www.racingagainstautism.com
http://www.teampanteraracing.com


On 11/27/2010 23:18, JDeRyke at aol.com wrote:
> The rings may be locked in the piston grooves and thus not sealing, so oil
> migrates up from the bottom, into the combustion chamber. I see way-too-much
> carbon ash around the plug area, and more carbon in the ports. Since the
> intake only inducts fuel and air, any carbon in the intake means the valve
> guide seal or the valve itself is leaking. Stock Ford valve guide "seals"
> really aren't. They are umbrellas that ride up&  down with the valve. If one of
> the head drains is partially or fully plugged, the rocker cover will fill up
> with oil at higher rpms, and oil will run under the unbrella&  down the
> valve stem. I like all-teflon positive valve guide seals that fasten to the
> guide.
> You can check the straight head oil drain by pushing a drill thru it. The
> other drain has two dog-leg bends in it. A long doorspring of appropriate
> size can be slowly twisted thru that drain like a roto-rooter, clearing the
> debris down into the pan.
> That rod bearing has no babblt left either top or bottom. All I see is the
> thin copper flash; below that is steel. I would pull ALL the bearings and
> check them, too as its really rare to only wear ONE rod bearing. 351-C cranks
> are arguably the toughest part of the engine but this one may be a candidate
> for a crank-grinder. Your micrometer will tell the tale. And 40-year-old
> cast pistons are running on borrowed time, too so I wouldn't waste much time
> trying to clean out the ring grooves. Did you ever do a leak-down test on
> this engine? I think you caught it just in time. Good luck- J DeRyke
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