4-hole or open carb spacer?

[RodgerH]

I have a Blue Thunder dual plane intake with a notched divider under a Holley 4150 with mechanical secondaries. Runs great, flat torque curve, pulls strong from idle to 6000.

I want to add a phenolic carb spacer for heat insulation. I have room for up to 1" thick.

Question: With this notched divider dual plane manifold, should I get a 4-hole or an open spacer?

Rodger

[blykins]

It's hard to really say and no one will be able to tell you for sure unless it's on a dyno where you can see the results. Sometimes the 4 holes give more torque, sometimes the open spacers give horsepower. Sometimes you can turn a tapered Super Sucker upside down and make more horsepower. It just depends....

However, if it's the engine that is in your info, my gut tells me to go for an open spacer.

[mreid]

I agree with Brent, but they're cheap enough that you can always try them both and see which works better. Also, if it's heat insulation you are really looking for, go with the 1". Hood clearance may be your only issue.

[RodgerH]

It's the engine in my info. Just looking for heat insulation, although more power is never a bad thing! The engine is very streetable with a flat torque curve. I just don't want to create a problem or loss in a specific RPM range. Trying both is a thought; I have room for a 1" spacer.

Rodger

[blykins]

You won't notice a difference in it. We generally see about 10-15 hp difference on most street engines, unless the intake really needs a lot more plenum volume. You'll never notice it with that much horsepower and that light of a car.

[charles roybal]

Recommend this:
JEGS Wood Carb Spacers - JEGS

In our S.W. sun/temp 100-107 has worked great.

[vector1]

i asked close to the same question, makes for some good reading.

dual plane phenolic carb spacer question • Speed Talk

[BDR879]

I just installed a 1/2" open phenolic spacer (hood clearance issues) and my tq curve is still flat as a pancake.

[DSM351]

Get the 4 hole (I did) then if you don't like it you can open it up with a scroll saw. Its Wood!!!

[Jeff Frigo]

General (again, I say general) rule of thumb is a 4 hole with a dual plane.