I'm gettin close to being able to firing up and going for a test ride. On pretty much a stock 351C I used a 1" spacer on a Performer intake and got 350HP 2 @ 5200 RPM on the dyno. The 1" spacer is pretty much necessary for clearance on the Holley 700 linkage. My question is would it be beneficial to use more spacing like a 2" spacer?
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I just installed a new QF carb and also needed a 1" spacer to clear the fuel line inlet fittings. That said, I am happy with the performance as is.
The spacers will affect the position of the air cleaner in context to the deck lid and the engine screen (if you use it). You might want to test fit your air cleaner before making changes to the spacers. I ended up going with minimal spacers to keep the air cleaner from contacting the deck lid.
My 1" spacer and new K&N air filter are way above the 71 mess engine cover but it had already been cut by the PO so I am good.
...here are the Physics of a Spacer. On a Carbureted, 'Naturally Aspirated' Intake.
When you increase the Length of the Fuel/Air 'Column', with-in a Port, the 'Charge' MUST Flow Faster, per Time. This 'May' add to the 'Volumetric Efficiency', That Will Increase Horsepower. BUT, The FARTHER the Carb 'Butterflies' Are FROM the Intake VALVE, the More 'Lazy' the 'Throttle Response'! Because the Vacuum 'Signal', Sensing, is 'Delayed' by that Increased Distance.
...The Very Reason, Smaller Ports (2V) create a More 'Crisp' Throttle Response than Larger Ports...such as found on the Cleveland 4V Head. The Difference in Response time may not be felt/detectable...only the Dyno and a Timer will know for sure.
...'Fuel Injection' over-comes this Phenomenon, because the Fuel is Delivered 'Separate' from, Independent of, the Air Flow...Almost Instantaneously! When the 'Shot/Charge' is Injected to the Back of the Intake Valve Or Directly into the Combustion Chamber, Making the Throttle Response nothing Short of Amazing! Plus, Much Higher RPM is Obtainable.
MJ
Putting an open spacer on a dual plane Intake like the Edelbrock Performer changes the way the engine behaves more into the way it would with a single plane Intake. Putting a larger Spacer on it will increase that behavior.
Common knowledge is, that a dual plane Intake increases low end torque and lacks top end power while a single plane does it the other way around. The reasons why can be read above. Basically it all depends on where you have the best air flow.
What also has to be considered: The vacuum signal gets worse, as you increase the volume of the plenum. The same happens to the booster signal in your Carb. So less fuel gets pulled through and your air/fuel mixture gets leaner.
You could consider a 4-Hole-Spacer for example, but what definitely should be avoided are sharp edges or any sort of disturbances of the air flow.
If you want to read more about this:
https://www.motortrend.com/how...-carburetor-spacers/
And as always: Sorry for my bad english
I used the 1" open spacer when the engina was on the dyno. I'll run that and see how it acts on the street.
