Just to put my $0.02 into the discussion re. DCOE's vs SU's per Jon & Jerry's
posts.
I use my vintage racer as my daily transportation. (And, yes, I drove it in
yesterday's snow & today's slush. Will do a thorough hose-down tonight.) I
had 1-1/2" SU's on the B when I bought it in 1997. In 1999 I installed a
Sasco Sports modified head that generated more power from 3,000. Switched to
1-3/4" SU's a few years later. After a year like that, I installed them on a
cross-flow head. Two years ago I installed a new engine with 5-port head & the
1-3/4's. This engine includes a highly modified head & high compression ratio.
Last year I switched to a single Weber 45 DCOE.
Here's what I have experienced:
A - 1-1/2" SU's - Original smooth power band changed with switch to Sasco
head. From 3,000 up it was improved. Still as easy to drive on the street as
stock.
B - Larger SU's really didn't make much difference on the street other
than a little more power on top end & less mpg.
C - Switch to cross-flow head made a LOT of difference in low end power
with the 1-3/4 SU's. Absolutely great for ease of driving and really usable
power.
D - Installation of Fab-Tek engine with 1-3/4" SU's requires 100+ octane
to run well, 110 to race. But with 93 the best available on a regular basis, I
have to retard the spark quite a bit to avoid detonation. Result is far less
power below 3,000. But, still relatively drivable despite even lower mpg.
E - With single 45DCOE, it's really tough getting going on any kind of
hill. On flat ground not very easy. But, remember, this is with the spark
retarded a lot. The worst part of the current setup is the lousy gas
consumption - 15 around town, 22 on the highway. And, driving when the engine
is cold is a real bear. It sputters & stumbles & I need to keep it "on" choke
a long time. If I were to do it over, I would have gone back to the 1-3/4"
SU's for the winter. But, the power of the DCOE on my engine is proven by the
second I cut off my lap time at Lime Rock. And, besides, the sound made by the
roar of the carb air coupled with the exhaust note is music to my ears. Takes
me back to the Chrysler Sonoramic sounds of the '60's.
Next step is to install the cross-flow head with twin 45DCOE's & try to get
under 1:10 at Lime Rock. I'll report on street drivability after I do that.
But, for now, you have my driving impressions of the various carbs. While they
are varied due to the heads & engines I've had, you can draw some basic
conclusions re. drivability.
I hope this helps.
Norm Sippel
'66 MGB
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