I have just joined the list so I did not catch the beginning of this
discussion butI will share my experiences with triple Strombergs on TR6
engines.
I first made a manifold and installed a third Stromberg on my '71 TR6
back in the mid '80's. At the time I had a '72 head that was shaved to
9.8:1 compression and had some grinding done in the ports. I was using
the stock '72 long manifold with some smoothing done inside. The cam was
stock '72 with stock rockers. I did not have a dyno at the time but by
seat-of-the-pants I could tell that the triples definitely increased the
power. Later I reground the cam for another big boost in power. Then I
made and installed a set of 1.65:1 roller rockers and got about as much
increase as I got from the cam change. You know how it is. You get
addicted!
I have made alot of triple manifold kits since then. Some went on
totally stock engines with customers reporting a nice improvement in
performance. Most have gone on modified engines with more gain in
performance. I agree with Tim Holbrook and always recommend starting on
the inside first, but triple Strombergs won't be wasted on your stock
engine if you are not ready to pull it apart yet.
I have never done a back to back 2 vs. 3 carb dyno test. I would have
had the chance last spring when I was testing my own engine but did not
think of it. Probably didn't have the time either. Takes alot of that to
play on the dyno. Most of the engines I have built and dynoed have had
triple Strombergs because the customer wanted the full package and the
triples are a vital part of the performance equasion. I did one for a
customer with stock duals with the long manifold instead of triples and
stock late exhaust manifold instead of a Monza header but otherwise the
same a others I tested. It produced about 140 hp at 6000 rpm where I
would normally see about 150 with triples.
One thing I do know is that the triple Strombergs do not "over carb" a
modified TR6 engine. The three CD175's have their air valves wide open
when the engine is producing 150+ hp at 5000+ rpm. I agree with Don that
there is no "correct" position for the air valve. The air valve "rides
on" the air stream keeping the velocity up across the needle and jet
even when the flow is low. If we have three carbs instead of two and a
direct line of sight from the carb to the intake port there will be less
restriction and we will get more air in. The more the engine is
modified, the greater its need for air. The more air it needs, the more
the triples with help. If you have a TR6 engine producing 150 hp with
duals, it will produce more with triples.
Richard Good
Good Parts
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