Glenn Sez:
>
> Along with the carbs I also installed that 1 7/8" stainless exhaust. I
> needed a new system; the old one was dented in about half and rusted
> through. It fit the primrose better than the maroon - bolted right up, and
> no fitting involved. All this, of course with new filters, vacuum check,
> valve adjustment, plugs, oil, timing, everything.
>
> So when I finally get around to starting the car up I finally found a nice
> smooth even idle at about 1k rpm and took it out for a drive. As soon as I
> get out the drive I got nothing. Sputter. No power. Yeah, it'll run, but it
> limped up to the corner. Limped back to the drive and started playing with
> it again. More test drives and still the same thing.
> The question that comes to mind is; What is the effect of opening up the
> exhaust pipe diameter on an otherwise standard high compression 18G engine?
> That is the only non-stock item in the mix. 1 7/8" pipe with a single rear
> free-flow silencer. I can't imagine that one item trashing the entire
> system, but that's the only thing different from before. Is it back-pressure
> I'm staring at?
No, it's not the headers. I have the same size and the car ran fine with
a massive leak in the exhaust. (I now have it all welded, a "free flow"
Ansa exhaust). You might see a small torque reduction below 1500-200 RPM
but the power should be noticeably >better< at 2500 and above. Sounds
like it doesn't get there.
Gooberheaded things I have done which caused this problem (good idle, no
power when moving):
1) Crossed two spark wires. Idle was tolerable but it doesn't well rev at
all. Even with no load. Now my firing sequence is written on the heater
housing.
2) One spark wire disconnected. Yes, it runs pretty well on 3 cylinders,
but it won't accelerate. Now this is the first thing I check, especially
if I have been checking plug color.
3) Loose Carb metering needle. The needle stays in the jet while the
dashpot piston goes up. Lean mixture to two cylinders, somewhat
compensated for by the crossover tube.
4) Massive air leak. All the hoses and whatnot (especially the whatnot)
are reconnected, right?
5) Vacuum advance disconnected/hole in advance diaphragm. This will cause
loss of low-end power. (small air leak, but the advance you expect at
part throttle isn't there).
6) Loose distributor cap. Duh.
As others have suggested, check the dashpot oil. This should only be a
problem with throttle movement, and you should be able to baby the pedal
up to highway speeds. As far as the colortune goes, I think "blue" has
always been way too lean in my car, and I go for blue with a hint of
orange. But I find timed tests and plug cuts to be more reliable (my
Red-Green Daltonism doesn't help!).
For those who are interested in Weber DCOE-style carbs, I have posted an
article on my web site:
http://www.tsquare.com/tscc/webertune.html
--
John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP | '69 Spitfire H Stock | '88 RX-7 C Stock
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