Last summer we drove one of our Tigers over 3500 miles in ten days to & from
SUNI.
It was equipped with a H-Po 289 & a Holley 600 cfm Vac secondary carb with a
T-5.
To the seat of the pants, the felt great even at nearly 11,000' elevation
over the Bear Tooth Highway in Montana. Door to door we averaged almost 24
MPG. We never changed jets but twice adjusted the idle screws on the
primaries (about 1/12th a turn each time.)
However we also borrowed a neat device from our racecar - an Innovate LM-1.
The LM-1 reads fuel ratios and is accurate to a tenth. We took notes of
manifold vacuum, fuel ratio, speed and elevation the entire trip.
Since I was a teenager, I've "known" that a properly adjusted 1850 runs fine
with a 289. However I live on the edge of the Pacific Ocean, literally at
sea level. What I discovered last summer is that there is not enough signal
for this carburetor once the vehicle has climbed above 4 to 5,000'
elevation. The carb works but the precision disappears. At the higher
elevations the carb was always too rich or too lean. It was never "just
right". Then on the way home, as we decended from Park City to Provo, the
precision came back to life. Last summer I learned that the Holley engineers
knew much more than I'd given them credit for. (I owe them an apology.)
One caveat. Many of the smaller (Holley) carbs do not have a port for a PCV.
You can run a plate under the carb but some Tigers then have air cleaner
issues. Many years ago Steve Laithman combined the top of his 450 with the
base plate of a 600 which had the PCV port. I like to run the PCV valve
because it keeps the engine compartment cleaner.
Right now we're experimenting/dialing in a 390 CFM Holley as a replacement
for the 600CFM. It's looking encouraging.
Buck Trippel
----- Original Message -----
From: " Ron Fraser" <rfraser@bluefrog.com>
To: "'Tom Parker'" <tkparker1941@gmail.com>; "'wsamouce'"
<wsamouce@kc.rr.com>
Cc: "'Tigers Den'" <tigers@autox.team.net>
Sent: Monday, June 21, 2010 12:58 PM
Subject: Re: [Tigers] Best Carburetor(s) for the Tiger
> BTW, when the Tiger ran I'd have been proud to get 18 - 20 MPG at highway
> speeds. I think 28 MPG is a tad high with a 4 speed, improbable even with
> a
> carbureted engine and a 5 speed, but probable with a 5 speed, fuel
> injection
> and an engine management system.
>
>
>
>
>
> I easily get 25 MPG and my friends MK II with 600 cfm, 4 bbl gets about 22
> MPG. I once saw 29 MPG but only once. I'm pushing the ignition and
> carb
> tune on my 260 to the max and I hope to cross the 30 MPG mark. If I do
> cross 30 MPG constantly I will report back on that.
>
> Ron Fraser
>
> 260, 2 bbl, 4sp
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