[DeTomaso] Pantera fall down go boom :<(

[MikeLDrew at aol.com]

Hi guys,

Those of you who were at the POCA Fun Rally last weekend perhaps noted that 
every single Pantera that drove to the event, safely drove home at the end 
of the weekend, save one.

Unfortunately, that one was mine. :<(

I've been loving my new 408 stroker Cleveland, which has utterly 
transformed the car.   I had a wonderful drive up and over the Sierras, tempering my 
enthusiam a bit in deference to the handful of Panteras that were running 
with me (also a reflection of a recent run-in with Johnny Law that I managed to 
escape from for about $300, but my next ticket will result in points on my 
license).

At the track event, the first thing I did was to bleed my brakes, as my 
pedal was soft and squishy.   I got a bit of trapped air out, which improved 
things, but they are far from where they should be.   I think this is a result 
of some uncharacteristically horrible engineering that took place when my 
friend who restored the car years ago, fabricated new brake lines.   For 
reasons unknown, he deliberately placed a big loop in each line, which is 
seemingly guaranteed to trap air and result in a spongy pedal--exactly what I have 
had all these years.   I think I am going to trash all the hard lines and 
start over.

But anyway.   Once the brakes felt up to the task (although far from 
perfect), I started driving on the track Thursday afternoon, and the car was much, 
MUCH faster than two years ago.   I'm still very handicapped by my 
super-crusty tires (my intent was to burn them off at this event and then replace 
them when I got home) which kept cornering velocities laughably low, but also 
provided lots of opportunity for sideways antics at relatively low speeds.

Two years ago, I would enter the front straight in 3rd gear, upshift to 4th 
at about 5500 rpm, and just be nudging 110 mph when I felt it was prudent 
to lift for the first of the three S-curves leading to the hairpin at the 
end.   This year, with all the extra power, I was topping 130 mph.

Whee!

The thing is, I would reach the 6000 rpm rev limiter well before the 
turn-in point.   My choices were to either upshft to 5th gear for just a moment, 
then back down to 4th, or to just coast for a bit.   Since nobody was paying 
me for this and there were no trophies on the line, I elected to do the 
latter.   My car has an MSD system with the 'soft touch' rev limiter; the bumpf 
that comes with the MSD box indicates that there is no harm in just riding 
the limiter, as it randomly cuts spark from various cylinders to keep the RPM 
at a predetermined maximum point.   So often times, I'd keep my foot to the 
mat and just ride the limiter for 100-200 feet or more, then lift off and 
turn in.

At the end of the first day, the car was running just a little bit weird.   
I was having trouble with the idle speed, and in fact the next morning I 
had to turn the idle up quite a bit.

I then went out for a second day of more fun and games on the track, and 
the motor seemed 'off' ever so slightly.   I was driving with a raised 
eyebrow, and then I came down the front straight and noted that it was well down on 
power; with my foot to the mat it was 20 mph off at the turn-in point.   I 
determined that I would pull in at the end of the lap for a look-see.

Didn't happen. :<(

When I got to the steep uphill, the engine started stuttering, and I had my 
foot on the floor trying to keep it going to at least the top so I could 
pull off.   But just before the top, it went POP and quit, leaving me stranded 
on the side of the track, and causing a yellow flag in that area for the 
rest of the session.

I figured the distributor shear pin had sheared.   There were no other 
indications, I had fuel, no clanking noises from the engine, so it was pretty 
apparently an ignition issue.

They threw the checkered flag and I coasted down the hill to a safe spot 
and abandoned the car until lunchtime.   Rich Boschert was kind enough to tow 
it in to the paddock on his flatbed trailer, and then any number of 
volunteers stepped in to help sort it out.

Steve Liebenow offered up some shear pins, and I figured I'd be rolling a 
short time later.   But then the distributor cam out.   Bad news.   
Distributor gear totally mangled. :<(

Then we started thinking about getting a replacement gear from Summit, just 
down the road.   But Chuck Melton took a look-see down into the engine, and 
what he saw was far from good--the drive gear on the end of the camshaft 
was destroyed as well. 

Trailer time. :<(

Fortunately for me, Rich has to drive within a mile of my house on his way 
home.   He was kind enough to trailer my Pantera back to the hotel, and then 
back home Sunday afternoon, and allow me to follow behind at the wheel of 
his lovely green Pantera, so all things considered, this went about as well 
as could be expected under the circumstances.   Sunday morning we had an 
uneventful drive home, and since we had two other truck/trailers and another 
Pantera in convoy with us, it was easy to unload the car and push it into the 
garage, where it now sits, sad and forlorn.

Here's some photos of the gear on the distributor.   All of the teeth were 
filed razor-sharp, creating much slop in the timing (the cause for my idle 
problems no doubt).   But then, a number of teeth simply sheared off 
completely, which caused the car to stop dead.

http://www.poca.com/index.php/gallery/?g2_itemId=32311

When you click on each photo, it opens up in a normal-sized view, but you 
can select the max size, which shows really excellent detail; you can clearly 
see where the teeth were literally sheared off.

I've since been in touch with Dan Jones, John Christian and others, 
attempting to determine the cause of the problem.   I was using a steel hydraulic 
roller cam core, and a Crane steel gear advertised to work well with such 
things.   However, I did have a couple of things going against me:

1)   Excessive oil pressure.   I purposely re-used the oil pump from my 
previous engine because it delivered 50 psi there (verified with a mechanical 
gauge) and I did not want high volume or high pressure, both of which are bad 
for Clevelands.   However, my new engine (perhaps due to tighter 
tolorences) sees the oil pressure gauge pegged.   Probably 80 psi at operating RPM.   
The literature that comes with the cam gear says that it will live with a 
steel cam, EXCEPT if excessive pressure or volume oil pump is used.   They say 
that rapid wear will then result--which I got.   So, since oil pumps are 
cheap, I'm going to start over from scratch with a new Melling M-84A.   (The 
Summit website is incorrect and doesn't list this for the 351C, only showing 
it as applicable for the 351M and 400M.   But in fact this is a 351C pump, 
as shown on Melling's website.)

2)   Driving on the rev limiter.   Although MSD says this about their 
system:

There are two ways to limit your rpms. The rough way simply cuts off 
ignition spark, which can cause backfiring, extreme engine roughness, and possible 
engine damage. The gentle way is with these MSD Soft Touch rev controllers. 
They use sophisticated computer circuitry to drop spark one cylinder at a 
time, until your engine is at or below its maximum rpm. Those cylinders are 
then fired on the next cycle, to prevent them from loading up with fuel. The 
result is smooth rev limiting action without all the rough stuff.

The truth appears to be that even this 'gentle' process is rather hard on 
the system, perhaps aggravated by the fact that I'm running a gear drive 
instead of a timing chain.   It didn't occur to me that running on the limiter 
for a few seconds at a time would stress the system, but in hindsight (and 
after consultations with Dan, who hadn't heard of such a thing but 
subsequently did research and found other stories of people suffering similar damage to 
mine after running on the rev limiter, regardless of whether they were 
using a timing chain, gears or whatever) I'm sure that my driving habits on the 
track created this problem.   I'm going to address this by fitting a higher 
RPM pill in the MSD (the motor is built to go to 6500 all day long but I was 
being 'conservative' and had a 6000 rpm chip in the MSD) and by avoiding 
touching the rev limit, if at all possible, and certainly avoid deliberately 
doing so and just keeping it on the limit.

I think the gears were perfect when I drove over the hill to Reno, and I 
just busted them all to hell at the track.

Tomorrow I'm ordering a new cam, same as the old one (did I mention how 
wonderfully this engine ran?).   Dan also turned me on to a new distributor 
gear.   Tri-Tec Motorsports now makes a carbon-reinforced polymer distributor 
gear for the 351C/460.

http://www.tritecmotorsports.com/Carbon_Ultra-Poly
-Ford_Distributor_Gears.htm

I am going to phone them and see what they have to say.   I don't want to 
run a bronze gear, because of all the maintenance hassles, but a steel gear 
might not be as good a bet as one of these glorified plastic ones.   At this 
point I think I've got nothing to lose by trying.

The motor will come out of the car early next month (no time before then), 
by which point I should have my new components in hand.   With the help of 
friends more knowledgable than I am (which is most of them, when it comes to 
engines anyway!), I hope to have it repaired and ready to go in a day, then 
installed another day later.

I will have to pull the oil pan and clean all the metal shavings out (and 
also from the front of the engine), and the oil pump pickup is likely filled 
with debris.   It goes without saying that the oil filter will be changed as 
well.   While we'll take a look at the bearings while we're in the 
neighborhood, I'm fairly confident that the rest of the motor was unaffected by this 
little glitch.

We'll see!?

Once it's up and running, I'll pull the distributor every few thousand 
miles to inspect for any signs of untoward wear or failure.   I'm hoping this is 
a one-time situation to be quickly and relatively painlessly resolved.

Fingers crossed!

Mike