Jomar Power cone

I run a factory DOVE manifold with a 4 square Holley pattern. When I go to the Jomar power cone, I wondered if I should open up the plenum to resemble older two plane manifolds (keep the divider between left and right), open it up like a single plane, or leave it as is. We run < 6000rpm 472ci and are resticted to a 650 carb.
Perry

TTT

which spacer are you trying? which configuration?

The typical power cone is intended for a open single plane manifold and might not be the right choice for a factory dual plane.

Dave when you use a second open spacer, it goes under the power cone right, I asked this question in the stickey, but got no answer, thanks Harold

Open spacer on the manifold first, then the power cone on top of it.

or you can also, put the power cone on first and use an appropriate 4 hole on top of it.

jomar does make spacers intended for dual plane intakes.

They have 2 holes on one side and are open on the other side.

dfree383 wrote:Open spacer on the manifold first, then the power cone on top of it.

or you can also, put the power cone on first and use an appropriate 4 hole on top of it.

Thanks Dave, the sticky said the two inch open, and the power cone flowed the best, so that is the way I was going to try it.

You got it.

I tried several configurations back when I was running a stealth intake. Found the 1" power cone right under the carb with a 1" open below that worked the best. Might have just been in my head, but I swear I could feel it want to pull harder that way.

kjett wrote:I tried several configurations back when I was running a stealth intake. Found the 1" power cone right under the carb with a 1" open below that worked the best. Might have just been in my head, but I swear I could feel it want to pull harder that way.

kjett,
Were you running the 8021 stealth, what cubic inch motor, which heads, I'm into this spacer 'deal' and would sure like to know
Thanks.

hpwdboss1 wrote:I run a factory DOVE manifold with a 4 square Holley pattern. When I go to the Jomar power cone, I wondered if I should open up the plenum to resemble older two plane manifolds (keep the divider between left and right), open it up like a single plane, or leave it as is. We run < 6000rpm 472ci and are resticted to a 650 carb.
Perry

I have tested all kinds of this stuff on a stock class mud engine with a 600 cfm Holley..
You gotta remember that this tested engine was a legal "vacuum" engine and not all "cheated" up to need a whole bunch of manifold area.

The best was to mill the higher side of the two plane to resemble a bathtub and bore the deep side holes to 1.785" hole diameter; (the standard for an 850 Holley). Mostly the front hole needs enlarging as the back hole is almost this size already.
We milled two bathtubs after and had to get another manifold as torque went down with no horsepower increase.
. Use two 1" thick spacers ... a "tapered 4 hole" Jomar spacer, (going from 1.600" to 1.78" hole size), with another straight 4 hole under it and hand cartridge roll the bottom of one side to resemble a "powercone" on the open "bathtub" side of the manifold only.
A "tapered 4 hole" for a 650 carb with have a smaller taper; 1.690" to 1.78".

rmcomprandy wrote:

hpwdboss1 wrote:I run a factory DOVE manifold with a 4 square Holley pattern. When I go to the Jomar power cone, I wondered if I should open up the plenum to resemble older two plane manifolds (keep the divider between left and right), open it up like a single plane, or leave it as is. We run < 6000rpm 472ci and are resticted to a 650 carb.
Perry

I have tested all kinds of this stuff on a stock class mud engine with a 600 cfm Holley..
You gotta remember that this tested engine was a legal "vacuum" engine and not all "cheated" up to need a whole bunch of manifold area.

The best was to mill the higher side of the two plane to resemble a bathtub and bore the deep side holes to 1.785" hole diameter; (the standard for an 850 Holley). Mostly the front hole needs enlarging as the back hole is almost this size already.
We milled two bathtubs after and had to get another manifold as torque went down with no horsepower increase.
. Use two 1" thick spacers ... a "tapered 4 hole" Jomar spacer, (going from 1.600" to 1.78" hole size), with another straight 4 hole under it and hand cartridge roll the bottom of one side to resemble a "powercone" on the open "bathtub" side of the manifold only.
A "tapered 4 hole" for a 650 carb with have a smaller taper; 1.690" to 1.78".

All the 'outright' cheaters run in the back and nobody cares if they cheat. When you run "up front" there can be some creative rule interpretations within those rules but, not blatant cheating.