Frank Enstein
Best. Day. EVER!
There isn't a "Best setup for Everything". There are many other factors that flavor the outcome.
As an example, I made a stepped, equal length, 4-2-1 header for my Yamaha 1100. It worked really well but at high rpm it over-scavenged, lost power and went rich. If I reduced the overlap by retarding the intake cam it would have worked even better. As a quick fix (no time or money) I put a more restrictive muffler on that dampened the over-scavenging at high rpm.
If you have more exhaust duration on your cam than the engine wants and/or really good exhaust ports in the head(s) true duals will not show much gain from a balance/merge pipe in the exhaust.
This it commonly overlooked by enthusiasts and racers alike. An X pipe on my Firebird gained 40 horsepower over true duals with the same mufflers and tailpipes. Pontiac heads have pretty weak exhaust ports compared with an SBC, BBC, or LSX.
On a comparable BBC the gains would likely be half that due to the engine pumping out the heads more easily in the first place.
Where people get misguided is what works on one combo may not work on one that is a bit different.
The common denominator is you need to tune the entire package to see the most gains.
Car magazines would put an open carb spacer on an engine and gain 23 horsepower but there was no mention of tuning!
Did the engine run better from the increased plenum volume/larger radius for the fuel to make the turn into the runner or did it gain because the engine was too rich and the spacer leaned it out.
The bottom line is choose what you want for exhaust and tune it until you're happy with how it runs.
BTW the Firebird gained 80 HP tuning the carburetor. The carb ran fine out of the box but careful, methodical tuning brought out it's true potential.
As an example, I made a stepped, equal length, 4-2-1 header for my Yamaha 1100. It worked really well but at high rpm it over-scavenged, lost power and went rich. If I reduced the overlap by retarding the intake cam it would have worked even better. As a quick fix (no time or money) I put a more restrictive muffler on that dampened the over-scavenging at high rpm.
If you have more exhaust duration on your cam than the engine wants and/or really good exhaust ports in the head(s) true duals will not show much gain from a balance/merge pipe in the exhaust.
This it commonly overlooked by enthusiasts and racers alike. An X pipe on my Firebird gained 40 horsepower over true duals with the same mufflers and tailpipes. Pontiac heads have pretty weak exhaust ports compared with an SBC, BBC, or LSX.
On a comparable BBC the gains would likely be half that due to the engine pumping out the heads more easily in the first place.
Where people get misguided is what works on one combo may not work on one that is a bit different.
The common denominator is you need to tune the entire package to see the most gains.
Car magazines would put an open carb spacer on an engine and gain 23 horsepower but there was no mention of tuning!
Did the engine run better from the increased plenum volume/larger radius for the fuel to make the turn into the runner or did it gain because the engine was too rich and the spacer leaned it out.
The bottom line is choose what you want for exhaust and tune it until you're happy with how it runs.
BTW the Firebird gained 80 HP tuning the carburetor. The carb ran fine out of the box but careful, methodical tuning brought out it's true potential.