The dashpot oil issue resurfaces from time to time and there are a variety
of answer of what people use. The dashpot oil ONLY performs a function
during acceleration and does nothing during idle, cruising and decelerating.
It dampens the rise of the piston causing an enriched mixture during
acceleration. The heavier the weight of the oil, the slower the rise of the
piston will be and the richer the mixture during acceleration.
I use ATF which is rather thin. I use ATF because there is a lil rubber
o-ring at the bottom of the tube sealing the needle holder against the tube
preventing the oil from running out. ATF will not attack the o-ring
requiring replacement less often.
The bottom line is: use whatever makes you feel good.
Jim Altman jaltman@altlaw.com Illigitimi non Carborundum
http://www.altlaw.com/metro/jaltman.html 69-TR6 76-TR7 80-TR8 W4UCK
-----Original Message-----
From: owner-tr8@mercury.lcs.mit.edu
[mailto:owner-tr8@mercury.lcs.mit.edu]On Behalf Of Eganb@aol.com
Sent: Sunday, February 18, 2001 11:22 AM
To: Triumphs@autox.team.net; british-cars@autox.team.net;
tr8@mercury.lcs.mit.edu
Subject: TR7 BFH#56B -- Dashpot oil
Well, patience pays off again. After filling up the dashpots with PB
Blaster
and letting them soak overnight, the mixture adjusting allen screws now turn
in both carbs. Lots of crud inside the tube after 20 years.
I'll try to lean the carbs out today, maybe using the old "lift up the
piston" trick, or maybe the "propane into the throat of the carb" trick
which
I've never done before. Hey, don't start yelling at me yet! I just want to
see if the carbs are at least in the ballpark in terms of mixture!... But
you probably still have some comments anyway...
By the way, if you lift the piston, and the RPM's go down, is that too rich
or too lean?...
And one other question -- what's the thinking on dashpot oil these days?
I've always used Marvel Mystery Oil, but heaven knows what the weight is of
that stuff. And I've seen posts where people use everything from ATF fluid
to regular motor oil.
Also, I assume a lighter oil will lean out the carbs when you accelerate,
but
what about at a constant RPM, like idle, when they do the emission check?
On a historical note, I remember driving my dad's '63 MGB in 1972, cross
country back to college in California. I stopped in the desert, some where
in the middle of nowhere, at a Fina gas station, and asked for some
20-weight
oil for the dashpots. The guys at the station had never seen an MGB, so we
had quite a conversation as they checked out the dual carbs and the wire
wheels.
Bruce
1980 Inca Yellow TR7 5-speed convertible
Chapel Hill, NC
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