Dan,
Are you sure it's vapor lock? You may be fouling the plugs, are you running
N-17 needles in your SU, these run very rich at low rpm, worse at high
altitude. I too have never experienced vapor lock on my roadster, had a
friends roadster lock up at Tahoe (6200 ft) one time, but it flat wouldn't
run, no sputtering and such. Didn't find the cause, just waited and refired
fine. Mine runs very rough if I have to idle in traffic for more than 10
min., I' running N-17's and probably have the float level too high. Haven't
tuned the SU in in a while since I want to put the Solexes on. You might try
some low speed runs to recreate the problem, then stop immediately and pull
the plugs. If the plugs are black then it's too rich and fouling, if the
plugs are gray or gray white, then it's too lean and it may be vapor lock.
If it's vapor lock I would check the return valve as already pointed out, I
find this valve very funky and I think Tom Walter said you can replace it
with a simple restrictor (~1/4" rod with small hole drilled through it). The
very small but continuous fuel flow should prevent vapor lock. Good luck.
Todd Osborn
San Jose, CA
'68 2L DATSFUN
----- Original Message -----
From: "Dan Neff" <neffster189@adelphia.net>
To: "Roadster Listgroup" <datsun-roadsters@autox.team.net>
Sent: Saturday, April 06, 2002 10:29 PM
Subject: Vaporlocking
> Greetings y'all,
>
> Well, I've been driving and tweaking my car all winter, and figured
> FOR SURE I've got this thing tuned so sweet it couldn't possibly have
> vaporlock problems come summer time. NOT!
>
> Pretty much a normal (non-race) setup: non-smogged, 1.5 yr old
> Ztherapy SU's, header, Boone's EI dizzy, fuel line goes around front of
> engine, bracketed away from it (another WyCROCer ran his fuel line around
> the front of the rad, made no difference). Heat shield's there and in
> good shape. Fuel pump's only a year or 2 old. Valve job a year ago. Runs
> like a top. Gets about: 30mpg highway, 27mpg town, 3,000 mpq oil. NEVER
> overheats - we thought the temp gauge might've read low, but the head was
> STRAIGHT and stock thickness last year. I've put about 60,000 miles on it
> in 4.5 years :) - and it's ALWAYS had vaporlocking problems in the
> summer (80-95 degsF) (until now, there's usually been several possible
> influences/mech'l problems).
>
> Even today where we hit around 70, I get in stop'n go traffic/lights,
> and it puts up with it for a little while, then starts sputtin' and
> farting (so do I, but that's another story...). Maybe it's altitude?
> I'm at 7,000 ft.. Everything boils at a cooler temp up here. 'Course
> once I get on open road, it clears up after a minute or 2. I WOULD say
> it recovers quicker than ever before...
>
> I could've sworn one of you Arizonian roadster folks mentioned never
> having had a vaporlock problem, even in 100+ weather! If so, HOW SO???
>
> Wish I could test the altitude theory by bringing it down to Solvang.
> sigh. Maybe next year.
>
> thanks,
> dan neff '69 2000
> colorado springs, co
> http://www.wycroc.org
>
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