Raymond :
But, consider this, of each pair of cylinders fed by a single throat on
the TR, only one intake valve is open at a time, no matter how wild your
camshaft. And since the volume under each throttle plate is fairly
small compared to the displacement, there is little or no 'smoothing'
effect from the intake manifold.
IMO, if you're looking for a better carburetion setup, get the HS6 carbs
and curved intake manifold from a later TR4A. They will work better
than Webers (on a near-stock engine), at 1/10 the cost. Don't forget
the K&N's, and stub velocity stacks.
Note that, for the reason mentioned above, the Webers suffer a great
deal of reversion, some of the intake air goes backwards through the
carb when each intake valve closes, and then forward through the carb
again when the valve opens. On some engines, this problem is so bad
that the air cleaner becomes wet with fuel. And IMO, the reversion is
part of the reason it's so hard to get Webers tuned to match an engine
throughout the throttle and rpm ranges. Race engines are easier to tune
in that regard, they only care about full throttle and a relatively
narrow band of (high) rpms.
The biggest advantage of the Webers is their easy adjustability, a
secondary advantage is having a smooth shot from the carb to the intake
valve, without the 'corners' of the early intake manifolds.
As far as restriction, the TR3A-early 4A heads already have very large
intake passages (relative to engine displacement), larger than many
American V8s ! Large passages are not conducive to mid-range power
(which is usually more important on the street), which is why the late
TR4A heads actually have smaller head passages and manifold runners.
V8 engines with downdraft carbs suffer from a whole different set of
intake problems than our sidedraft L4's, it's dangerous to generalize
from one to the other ...
Randall
Raymond Hatfield wrote:
>
> I was having an interesting discussion with a hot-rodder friend of mine last
> night concerning carburetors. He was talking about the improvement in his car
> after going to a dual 4bbl setup, and made the comment to me that my TR4A
>would
> perform better with 4 1bbl carbs than with the two ZS I currently have. The
> point he was trying to make was that 4 suitably sized carbs would more
> precisely meter the air/fuel mixture, and also relieve the restriction on
> 'breathing' most factory engineered intake setups have.
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