I just got my car back from an overhaul, which included replacing the
A-cam with a B-cam (ALL head parts were replaced). I thought somebody
might be interested in what I thought of it. My assessment is
subjective; no dyno's or timed 1/4 miles, or even a side-by-side test
against a U20/SU/A-cam. Based upon about a 1000 miles of driving.
The first couple of days I was pretty concerned about the extent of
loss of power at the low end, lumpy idle, and only a noticeable (but
not significant) power increase on the high end. But I hadn't driven
it in 3.5 months, so maybe I was re-adjusting to roadstering again...
because after several days, the low-end loss didn't seem as apparent
and even the idle seemed smoother.
I think it boiled down to adjusting to a different rpm power
range. It takes a little more gas on launch, 3200-3400 rpm seem about
the same power as an A-cam, then the B-cam takes off. Previously I
would up-shift around 5,500 rpm on a highway-onramp type acceleration,
now it's 6,500 (and then some ;) ).
The B-cam is cold blooded! It takes noticeably longer to warm up the
engine to where it will idle without cracking the choke. But it starts
right up, just as easily as the A-cam.
Highway cruizin', mostly around 3000-3400 rpm (60-75mph est, 70-85 by
my speedo), does fine, altho on a good hill (6-12% grade), it doesn't
hold as well as the A-cam; if I'm in a hurry, I need to downshift or
go faster (3500rpm+) ;) .
I'm getting 30-32 mpg gas mileage (mostly highway), which is slightly
better than before, altho that could be attributed to the many other
fixes that occurred with the overhaul.
I am having vaporlock problems. It did before too. It appears to
come on at about the same time/temp, altho the B-cam seems to hold the
idle better without spluttering. But it does really cough and splutter
on takeoff when it's hot. Current theory by my mechanic/buddy (Tom
Hoagland) is that because I have a header, the carbs are getting hotter
than with a stock exh manifold (plus my theory: we're at 7,000' altitude,
gas boils at a lower temp).
Tom has a U20 Solexed A-cam in his roadster. He put about 250 miles on
my car, and he concluded that our cars were comparible performance.
I went autoXing last Sunday. OH THAT'S WHY I GOT THE B-CAM! :) Holy
smoke. I was surprised to find I got a better launch than with the
A-cam; or at least with less effort. Once up over 4000 rpm, it felt
like there was so much more power than before that I didn't have to
downshift as much! The acceleration was wonderful! But alas, my
times didn't reflect it; I stunk. 6 months since last autoX (and
having only started autoXing last August), a 5th heat run (8:00AM walk,
2:30PM run) I forgot the course - DNF'd twice, and got mentally
sidetracked after blowing a heater hose on the first run (easy fix,
fortunately!). It didn't vaporlock though!
Conclusion: if you have more money than sense and want more power,
get it. 'Course if you had more money than sense, you'd get solexes
too.
At this point I would say that if I had it to do over, I'd do it
again, GIVEN that my cam and rockers are trashed and I'm facing cam
replacement anyway. Frankly, I don't think I'd spend the money if the
A-cam is good. I would say it's definitely worth consideration for
autoXing, but again, if you have money to invest in autoX improvements,
you'd probably be looking at Solexes too.
Ask me again in another couple of months :) !
dan neff '69 2000
colorado springs, co
http://www.wycroc.org
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