Scoop question

[afret]

At what horsepower level does a scoop with an opening about the same size as a shaker become a restriction?  I think a shaker opening is somewhere around 16.5 square inches.

[Posi67]

I'd like to know just how much air actually goes into a shaker, or any scoop for that matter. At one time I was going to tape a small ribbon on my hood in front of the scoop just to see if the air was going in or over. My scoop is considerably bigger than a Shaker and sealing the carbs to the hood gives zero gain in performance which is telling me something, I just don't know what. 

[jayb]

When I was on the dyno with my 706 HP 511" FE back in 2005, I ran the engine with and without the shaker.  The shaker cost about 11 HP at that power level.

[FElony]

Most Phord factory scoops are sitting down in the boundary layer, where the slow or turbulent air from impacting the hood is. Mopar had it right with the design of the '70 T/A Challenger hood, getting it off the "floor".

[afret]

When I did back to back runs with my street car which had the regular Mach 1 scoop, sealing the carb to the hood helped quite a bit.  I think it was due to the colder outside air instead of the hot underhood air.  It seems like the results of doing this varies a lot.

Jay, even though you lost some power on the dyno, didn't your car actually run a bit quicker with the scoop at the track?  Could it be the the effects of the cooler air made up for the effects of the air intake restriction of the scoop?

Just looking for another way to get a little bit of ET improvement.   

You can get a shaker above the hoodline a bit.  This one can go up another 1/4" or so with a different base but it's close to bottoming out at that point.  Don't know if raising the scoop just this much makes a difference though.

[Joe-JDC]

On my '69 Mach I, I installed a fiberglass hood with stock scoop.  I installed a tunnel wedge with 2" open spacers, and had to cut an oval for the hood to close.  I marked where the two studs touched the underside of the hood, and then used a cobra dual carb air cleaner base and marked the outline on the underside of the hood, and cut that out and smoothed the fiberglass edges.  I primed and painted it the matte black, and installed the scoop.  That helped some, but when I made an aluminum pan to fit over the carbs and sealed it to the bottom of the hood with foam strips, the engine ran cooler, and quicker.  I tried velocity stacks, but they were too tall, and I finally used K & N stub stacks which added a few hp when we dyno tested them.  Joe-JDC

[FElony]

You can get a shaker above the hoodline a bit.  This one can go up another 1/4" or so with a different base but it's close to bottoming out at that point.  Don't know if raising the scoop just this much makes a difference though.

All the boundary articles I've seen over the years seem to define one inch as the spec.

[jayb]

Earl, I do recall testing that car in 2005 without the shaker, and I think I lost part of a tenth without it, but I don't remember for sure.  Could have easily been cool air.  Also, my shaker scoop was up even higher than yours, because I was running the Victor intake with a Dominator carb.

[afret]

Thanks for all the info everyone.

Jay, did you make a custom mid plate for the dominator shaker?  I think my mid plate just about hits somewhere on the hood when I use the air cleaner base which raises the scoop a little bit more than the one in the photo and the hood just starts to distort a bit when closed.

[jayb]

I set the factory shaker assembly aside and bought one of those fiberglass reproductions when I went to the Victor/Dominator combo.  I cut the center out of the bottom and riveted on the base of a Dominator air cleaner.  I hacked up the mid plate too, to make the opening bigger and use a filter top on the air cleaner.  I recall seeing the shaker assembly bobble around a little bit when I closed the hood, and I'm sure the hood deflected somewhat, but not a lot.  Bottom line - my shaker assembly was far from stock, so I'm not sure I can really answer your question...

[Falcon67]

Not specifically "shaker" but on my mild 351C (3250 lbs running 7.80s @ 88 1/8 mile) back to back testing between a tear drop scoop open to the engine compartment vs a carb pan sealing the scoop to the carb/air cleaner area was .3 and 3 MPH in the 1/8 mile (open slower).