135 hp less 20% drivetrain loss = 108 hp at the wheels.
150 hp less 20% drivetrain loss = 120 hp at the wheels.
I've never heard any authoritative (i.e. factory) claims for rear-wheel hp.
A couple of weeks ago we dynoed Guy Selle's U20 at 135 hp, but that's got
10:1 compression, Solexes, B cam, header, big exhaust and a hot ignition
system (it's a vintage race car, not really streetable because of the
exhaust). Doing the reverse calculation, that made almost 170 hp at the
engine. The interesting thing was that making changes to jetting, advance
and spark plug gap gained him 10 hp on the dyno (started out at 125 hp), but
when he ran the next race, it was running too hot, so he backed out the
changes.
A few years ago I dynoed mine when it was still jetted WAY too rich. It went
basically flat at 5000 rpm but still peaked at 112.0 hp and 117.2 lb/ft of
torque. That's with Solexes with 34mm chokes, header, ignition, 2" exhaust
and a cam that I think is probably not a good grind.
I think the bottom line is that there are far more variables than most
people usually deal with.
> -----Original Message-----
> From: owner-datsun-roadsters@Autox.Team.Net
> [mailto:owner-datsun-roadsters@Autox.Team.Net]On Behalf Of Dan Neff
> Sent: Monday, October 11, 2004 5:37 PM
> To: Roadster Listgroup
> Subject: dyno time!
>
>
> We had 8 WyCROCers show up for a dyno day in Colorado Saturday,
> thought y'all might be interested in the results..
>
> All U20's, all have EI distributor's (I think all but one were
> Gary Boone distributor's). I tried Keith Williams SU Brit needles
> for comparison. The MC's came out better than N17's by 5 hp, and
> waayyyyyy smoother air/fuel mix thru the rpm's (3200-6500). I
> didn't list the guy's names below that aren't on the roadster list:
>
> hp torque
> 1 81.7 97.5 SU's, B-cam
> 2 90.9 103.9 Solexes, aftermarket 'hot' cam of
> unknown origin
> 3 91.8 100.6 45mm Webers, ported, L20B cam grind
> 4 Dan Neff 95.0 104.8 SU's, N17 needles, B-cam
> 5 97.3 103.3 Solexes, B-cam
> 4 Dan Neff 100.1 107.8 SU's, MC needles, B-cam
> 6 106.2 111.1 Solexes, A-cam
> 7 John Over 108.4 115.1 Solexes, B-cam
> 8 Gary Boone 117.1 117.7 TWM carbs, B-cam
>
> Conclusion: Um.. carbs and cams ain't all there is to it? Sheesh,
> you got me!!
>
> I'm still trying to figure out how I could end up with 18 more hp than
> the other SU/B-cam guy with a fresher engine! (he also only gained 1 hp
> with the MC needles)
>
> Clearly being a member of the roadster list gets you more hp :) ..
>
> #6 (Solex/A-cam) gained *14* hp by removing his Supertrapp plates (he
> only had 4 on there)
>
> While these nbrs are adjusted for sea-level (figure 23% less O2 up
> here in the Rockies), I still wonder if the tweaks needed to lean the
> fuel don't limit the potential vs a comparible sea level tune (at
> sea level)...
>
> John Over's just-completed overhaul looks like a topnotch job, yet
> he only got 2 more hp than #6 A-cam/solex on an older motor! The
> implication that a B-cam only gets you 2 more hp seems kinda
> dubious...
>
> So, what kind of nbrs do you flatlanders get? Do (shouldn't?) these
> compare? If they do, then mine's losing 35 hp between the crank and
> the wheel?? Or is the 135 hp rating in 1969 a different scale or
> something? What's the 100% stock U20/SU/A-cam hp supposed to be at the
> wheel?
>
> The 5 hp gained on mine IS noticeable on the road (you betcha I left
> those needles in!) in acceleration, hill climbing, and to a smaller
> degree (I'm not sure anyone else would notice), smoother acceleration.
>
> Any thoughts to educate me would be appreciated, altho I'm not laying
> awake nights worrying about it, 'cause I'm here to ENJOY THE RIDE.
>
> thanks,
>
> dan neff '69 2000
> colorado springs, co
> http://www.wycroc.org
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