If you're using stock pushrods I'd consider something a little less
flexible. Larger diameter thinwall chrome moly or even titanium. I'm sure
Kas is right about the cause, and most over-rev damage happens on
downshifts. Especially now when most races cars have rev limiters. I
stretched the rods in my Radical shifting to the wrong gear. No way I
could do that with the throttle pedal.
By the way, I saw some composite cam followers the other day--Kenny Dreer
is using them in the new Nortons he's building. Very cool. He said that
after a very long dyno session the tore down and found the cam faces
looking brand new and the followers lightly polished. I understand they
are some powdered metal and resin. Half the weight of high-perf followers
(something like 58 grams for the Chevvy ones that Kenny's using VS. 90+
for the metal ones).
-----Original Message-----
From: kas kastner [mailto:kaskas@cox.net]
Sent: Sunday, August 24, 2003 3:05 PM
To: Richard Taylor; fot@autox.team.net
Subject: Re: The old barking carburator syndrome
Sounds like an over-rev downshift to me. The valve springs cannot contain
the weight of the valve train and thus everything is free to go it's own
merry way.....and the pushrods did. (had it happen long long long ago to
my first MG (circa long ago)
----- Original Message -----
From: "Richard Taylor" <tarch@bellsouth.net>
To: <fot@autox.team.net>
Sent: Sunday, August 24, 2003 2:49 PM
Subject: The old barking carburator syndrome
> Group,
>
> Three weeks ago I put out an APB for help on my "barking carburetor"
problem.
> Andrew Stark and Russ Moore focused more on ignition and fuel
> anomalies
and
> Kas more on valve or carburetion problems. Naturally I started with
> the ignition system...it's easiest to get to. New points, condenser
> and coil
did
> nothing but make me feel better about giving some attention to these
> items
for
> the first time in several years.
>
> There was little left to do but cave in to Kas' thoughts about valve
problems.
> As soon as I took the valve cover off, there it was. Three of the push
rods
> were displaced from their sockets in the rocker arms! All three were
exhaust
> valves and the valves were wedged in the closed position. How can a
> motor
run
> like this? Remember, I drove the car from the racetrack in
> Birmingham,
AL, to
> Atlanta, 150 miles at 2500 rpms and it did okay.
>
> I put the pushrods back into place, adjusted the valves, checked the
> compression and the motor runs like a ball-bearing sewing machine.
>
> It's terrific to have everything working again but what's the deal?
> I've never seen anything like this before; especially three offset
> push rods.
How
> sensitive are these things? I twirled them around and they looked
> fine to
my
> uninitiated eye. Do I need to replace them just for good measure or do
> I
just
> train myself to shift sooner. My normal shift point is 5500 rpms, but
> when everything went wrong I was trying my damdest to keep up with
> Allan
Pinel's
> much faster TR-4 and I may have been enjoying just a little whiff of
> the red-mist. It can happen.
>
> The only time I may cheat on my 5500 limit is on downshifts, and this
> only
on
> a new track. Does the valvetrain know the difference between the load
> of pulling for an up-shift and the blip for a downshift? The innards
> of my
motor
> are absolutely box-stock. The little bit of extra horsepower I have
> (125 [total] on a dyno) is derived from a mild cam and a little higher
compression
> ratio.
>
> Obviously, my MO is dependability and lots of seat time - not blazing
speed.
> Birmingham was my first dnf in 18 races with this car. Maybe I lost a
little
> bit of my discipline and just wanted to be a race car driver for a few
laps.
>
> Andrew, Russ and Kas, thanks for your help
>
> Richard
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