I have been having problems with my engine stumbling all over itself and
an idle that refuses to stay put since it has been rebuilt and could use
some advice.
The engine: TR3, nitrated crank, harmonic dampener, 87mm pistons, 280
degree cam, 10:1 compression with TR4A head, reworked valve pockets,
matched ports & oversize valves. 4 into one header, 45 DCOEs plus
numerous odds & ends. I've tried to set it up for a redline of 6000 RPM.
The Symptoms: The engine only idles around 5-600 RPM. If you try to set
the idle higher, when the engine RPM runs up it may or may not eventually
come back down to idle after the linkage is returned to idle.
The engine stumbles over itself in the idle progression stages but goes
like a bat out of h**l above 3200 RPM. or from idle when the accelerator
pump comes into play. In other words the idle & progression circuits are
not acting like they should but everything else seems fine (50F9 idle
jets)
At idle the rear carb occasionally spits. Having the car professionally
tuned did not help other than a smoother idle at 500 RPM. I was told it
was a matter of the carbs not being designed for the engine & I would
have to live with it.
Breakthrough:
Thanks to some detective work recently completed by Bill Babcock I have
discovered that my professionally rebuilt and recurved distributor starts
advancing at 500 RPM (It did not occur to me to double check the work of
the company. I assumed the problem was with the mysterious DCOEs since
the company that tuned my engine and rebuilt the distributor said the
carbs were were the problem)
(from here on I'm going by hearsay so please correct me if I'm wrong)
I'm assuming the mechanical advance should start coming on at about 1200
RPM (street driver).
I have been reading about setting timing with DCOEs. My latest book says
advance the timing 2 degrees, momentarily run up the engine and watch the
tach to see if the the initial return idle RPM is higher. If it is,
advance it another 2 degrees and try it again. The initial timing should
be where advancing the timing another 2 degrees does not increase idle
RPM after running the engine up. The book also mentioned that a common
cause of DCOE spitting is timing not advanced enough for the carbs & cam
(Yes I've checked & rechecked for air leaks & ran compression).
Does this sound like a reasonable process for determining initial advance
for my engine?
Also any input as to what the total advance should be and at what RPM?
The book suggests about 34-36 degrees total advance at about 3,300 RPM.
How hard is it to set the distributor mechanical advance up to start at a
given RPM, then advance a given number of degrees by a certain RPM?? I
assume one needs access to a distributor machine and a tech that knows
what they are about.
Would I be better off going to a Mallory system (only 6000 RPM redline)
Mallory advertises that their distributor are easy to set the advance
curve on.
I'm thinking about the Mallory brakerless distributor with the mechanical
tach drive (4632001). But I'm not sure. Maybe I would be as well off
with a Pertonix unit in a properly recurved stock distributor. It would
be a lot cheaper, depending upon the cost of getting the curves right on
the stock distributor. Opinions???
I have noticed that a new Mallory distributor is a bit pricey. Anyone
have a good condition Mallory distributor gathering dust they are willing
to part with?
Once I get the timing taken care of I can address fine tuning the carbs
and enlarging my collection of like new expensive jets and tubes
gathering dust on a shelf.
SO please take a few moments out and educate me. Thanks!
I'll be offline through through Sunday evening & camping at Lugna Secca
8*)
Take care
TeriAnn
Http:www.shadow-catcher.net
Original photographs to view and purchase.
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