Fuel Selection, How Good is Too Good?

[Dave Krugler <dkrugler@xxxxxxx>]

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Never say you can't teach an old dog new tricks.  When I first got the 
blue 1963 Dodge 330 Max Wedge car from Wayne Smothers I thought it was 
the best running street car I ever drove.  It had Hoosier radial slicks 
on the back with narrow mags on the front.  With the 4800 Dynamic 
converter and 3.91 gears when you stood on it it would hook up pretty 
quickly and pull cleanly to 6,200rpm and was as smooth as butter.  I 
asked Wayne what kind of fuel he used and he said he was getting fuel 
from an airstrip near his home.  He said he could pull it right up to 
the pump and no one ever bothered him.  He told me he stepped it up to 
VP racing fuel at the strip and definitely left me with the impression 
that with 12.5-1 compression I needed to run the highest octane fuel I 
could find.  

In the Detroit area there are a few places where you can buy 110 octane 
Torco leaded racing fuel right at the pump.  The price at the nearest 
station on Gratiot never changes, it's only $3.59/gal.  When I filled 
the Dodge on a busy day people's jaws would drop when they saw the total 
hit $75.00 on that Torco pump while they were pumping their buck-75 
unleaded.  Suddenly they didn't feel so bad about the outrageous price 
of gas they were pumping into the family sedan.  As time went by the 
Dodge started mis-firing.  First it was popping out the 3" tailpipes as 
it got up to 5,000 RPM.  I thought it was getting to the end of the 
useful life of the plugs and changed them.  As time went by it just got 
worse.  At it's worst it broke up as soon as you stood on it and by 
4,000 RPM it was cackling to the point you got out of it to keep from 
hurting it.  

I systematically tried everything I could think of.  I suspected the MSD 
rev limiter and took the box off.  Eventually I replaced the Mopar 
electronic distributor and orange box setup with a new Mallory 
mechanical advance dual point distributor and the matching coil.  I 
changed the wires.  When I got the car Smothers had it set to run 
40degrees advance all the time.  After talking to Don and several others 
I set the timing back to 34degrees all the time.  I tested the car after 
each change to no effect.  

Satisfied it couldn't be spark related I turned to the fuel system.  I 
worked with Don Dulmage to get Max Wedge carb settings for the 3447SA 
AFB's and bought a precision pin gauge set so I could see if someone had 
drilled the jets.  They all checked out.  I put a fuel pressure gauge on 
the car and discovered when I stood on it the fuel pressure dropped from 
7psi to about 3psi.  The car had a Hemi mechanical Carter pump on the 
engine and a cheap Carter electric pump at the tank.  I discovered it 
had some pretty small right angle fittings at the electric pump and 
while correcting that I opened the pump and found it was packed with 
debris.  I wound up putting a Carter black series 15PSI competition pump 
on it and solved it's plumbing prblems.  Now I had 15PSI at idle which 
is probably a fire hazard.  I bought a good Mallory fuel regulator and 
put that in place of the Max Wedge fuel line tee and got the fuel system 
set up to run steady 7PSI all the time.  

I re-adjusted the valves looser, Smothers had them set at 0.020" intake 
and 0.022" exhaust.  The old Ramchargers handbook said they should have 
been considerably looser at 0.028" intake and 0.032" exhaust.  That's 
where they are set today.  After all that it still ran crappy.  I was so 
frustrated with it when I put it in it's storage bag for the winter I 
thought of selling it.  

Over the winter I thought about the car often wondering what simple 
thing was I missing?  One idea I had was maybe it was the fuel I was 
using.  Could it be the 110 octane fuel burned so slowly that it 
couldn't complete the combustion cycle before the exhaust valve opened?  
Hmm, that's an idea I guess.  Finally in early April the weather started 
getting nice and I decided to take the car out of it's cocoon.  It sat 
there for a week because I was busy with other stuff including getting a 
68 GTO I'm working on ready to go back to Milt Schornack to have it's 
freshly rebuilt engine and trans installed.  Meantime and interesting 
article on fuels appeared on Dan Dvorak's website 
(www.dvorakmachine.com).  He built the engine in the Dodge so I tend to 
watch his tech tips.  The crux of his article was that "the right fuel 
is the lowest octane fuel the engine will run correctly on". His 
qualifying statments were that the fuel has to be of high enough octane 
to eliminate detonation when you stand on the throttle (no detonation 
allowed under any load) and it must shut off immediately from an idle 
with the key switch.  Reading that article gave me some hope I was on 
the right track.  

I always like to pull the distributor and crank some oil to the engine 
before I start it to make sure I don't crank or run it on dry bearings.  
It started right up like always and had about a 1/2 tank of fuel.  I 
drove it down to the Mobil station and put 5 gallons of 93 octane 
unleaded premium in it.  This was the first time I had put anything 
except Torco in the car since I had it.  On a cool 65degree day the car 
responded almost immediately.  I drove it a few miles and tried just 
shifting it manually under moderate throttle and it ran up to about 
5800rpm with only a hint of cackling out the tail pipes.  When I tried 
standing on it from a stop it lit the tires and revved to 6,000 and 
shifted, not perfect, but significantly better and did not ping. It also 
shut off fine with the key.  I went back and put another 5 gallons of 
Mobil premium in it and now it has virtually no sign of cackling.  I'm 
gonna guess I'm at about a 70percent unleaded premium to 30percent Torco 
mix now.  

The only loose end is after the car is warm it spark knocks when you 
first hit the starter and pull that first cylinder through.  Once that 
occurs it starts immediately.  Not being interested in a broken starter 
and having talked to Don Dulmage I made an adjustment to put some very 
low rpm retard in the distributor again to facillitate startup with out 
the spark knock. 

I'm a very happy camper now.  I got intimately more familiar with the 
tuning aspects of the Max Wedge and believe I have finally solved it's 
problem.  Per Dvorak's reccomendation I will keep experimenting with 
lower octane until it pings or gives some sign it needs more octane then 
raise the octane just enough to make it happy.  I'm getting back to my 
roots here as I once won a debate with a college professor on the 
effects of octane on flashpoint and flame propagation rates.  I learned 
through all of this that when it comes to fuel there is such a thing as 
too good.    

Dave Krugler
Harper Woods, MI 
63 Dodge Polara 440
63 Dodge 330 Post 426 Max Wedge
To see these cars please visit my website at
www.geocities.com/dkrugler2001/davesuperstockgarage.html

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