Rich,
I have been doing further research on this matter, which is why I am
so long responding. To address your question, the male fuel line nut
that fits a Longbridge tank female outlet measures 9/16", or .5625",
for thread diameter, and has 18 threads per inch with a 5/8" hex. This
does not match any BSP, BSW, or BSF thread or diameter. The only thread and
size match is to 9/16" UNF, which is a very rare size for pipe
fittings or any other hardware, for that matter. So a 1/4" BSPP female
boss would not work with the factory line nut. The issue is somewhat
moot anyway, since no supplier offers a fuel tank for the Longbridge
BN4.
The problems I have seen on this list with Cervera tanks are due to the
wrong MALE outlet threads on later-model tanks. If they are in fact
1/4" NPT then they are not compatible with the 3/8" BSPP fuel line
nut. A 1/4" NPT tapered male thread starts at a diameter of about .514"
and the taper adds approximately .005" per 3/8" of thread length. With
18 tapered tpi on the outlet a 19 tpi BSP fuel line nut, with a diameter of
.503", will only screw on a little more than one turn before galling. Going
beyond this seizing point, as is necessary to get a sealed fit, only
destroys
the thread on the nut, the outlet, or both, and can result in the nut
splitting
if it is forced far enough.
As I said in an earlier post, I don't know if chasing the 1/4 NPT threads
with a 3/8 BSPP die will solve the problem or not. It might work fine,
or it might remove too much of the already-cut material to leave enough
thread for the nut to be able to grip. According to Ron Fine it would still
be necessary to machine a mating surface for the compression nipple on
the outlet, too. Fact is, no buyer of a Healey gas tank should be faced
with this kind of problem. The tank should come with an outlet that mates
correctly with the fuel line fitting; anything less is sub-standard.
"Close"
DOES NOT equal "correct."
Doug Reid, 18G Motorworks
----- Original Message -----
From: "Rich C" <richchrysler@quickclic.net>
To: <jobu1950@yahoo.com>; "Mr. Finespanner" <mrfinespanner@earthlink.net>
Cc: "JORGE CERVERA" <jorgecervera218@hotmail.com>; <healeys@autox.team.net>
Sent: Friday, August 18, 2006 8:14 PM
Subject: Re: Cervera Gas Tank (was gas tank)
> While at Conclave in Akron Ohio, Craig Rice (email:
craigsuerice@iquest.net)
> showed me a brass female tank boss drain fitting he has all made up ready
to
> solder into the bottom of the gas tank on Hundreds to replace stripped or
> damaged ones. This would also serve for the early 100-Six tank. Craig has
> these available for anybody who needs them. he specifies the thread is the
> correct 1/4 BSPP (British Standard Pipe Parallel). I believe this would
> serve for the inlet fitting too, would it not? Craig??
>
> Maybe Jorge could purchase a bunch of these fittings and install them in
the
> tanks. Problem solved.
> Rich Chrysler
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