Carb spacers and the Performer RPM intake

beanhead

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Just wanted to share some personal experience, as I have seen this question come up many times. Take with as many grains of salt as you wish....
I've been running a 1" 4-hole phenolic spacer on my 440. It's 9.5ish/10 to 1 compression, auto trans, RPM heads, 850 speed demon mech. carb, XE274 cam(230° @.050 and .488 lift on the intake) with 1-7/8 headers and 3" pipes. 2500 stall converter and 3.73s to 28" rear tires. I originally installed the 4-hole spacer to alleviate fuel bowl heat problems and it worked very well. So this morning I decided to swap in a phenolic open spacer that I had stashed....and it works well, contrary to some people's fears that it would not function well with the dual-plane intake. The first thing I noticed, is that the car would not idle at the present settings so I needed to adjust the four corner mixture screws(no big deal).. I also noticed that I lost one inch of vacuum at idle in gear(no big deal). Once readjusted, as I've driven it throughout the day I have noticed a very slight loss of some torque down in the 1500 to 2000 range. That is pretty much my cruising RPM though, so there isn't much throttle movement at that point anyway. Coming off the line with some throttle, it moves right past that point and as it approaches 3000 rpm(which happens very quickly) I feel a definite increase in power, no question. Before, this damn car would begin to spin the tires if I throttled it too quickly at even 25 or 30 miles an hour so I decided that I could afford to lose a couple lbs/ft way down low, and it seems the trade-off was a good one. One caveat: I don't have track times to back this up, it's strictly seat-of-the-pants feel...but I can definitely feel the difference in the rpm range where the car can use the extra power. Another caveat: the Performer RPM, as you're well aware, it's not a full dual-plane intake, as it has the divider cut down some. So this may not be an apples to apples comparison on a regular dual-plane. The point of my rambling is, using the open spacer didn't "kill" the throttle response, it didn't "ruin" the vacuum signal or "flatten" the bottom end, or any of the other maladies I'd read about. With no changes other than about 1/8 of a turn out on the mixture screws (ha that's a lot for a Demon LOL) it's feeling stronger than before.. Next step will be to hook the A/F meter back up and go through and fine-tune it, I have a feeling there's a little more to be wrung out of this baby!
 

rumblefish360

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What most people write about (if they actually know or not) the loss was f low end torque is exactly what you reported. Often over exaggerated, it seems you nailed the real feel description.

The reports of killing the low end to a poor driving point are due to several reasons. Most importantly, the actual combo & state of carb tune. Or simply, they don’t know what there doing.
 

MOPOWER871

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thank for the info, running same heads/ intake on my 493 I always wanted to try spacers but unless I cut my hood it's no spacers for me. put a set of Mickey Thompson drag radials on they will fix that tire spin issue. I can testify too that
 

beanhead

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What most people write about (if they actually know or not) the loss was f low end torque is exactly what you reported. Often over exaggerated, it seems you nailed the real feel description.

The reports of killing the low end to a poor driving point are due to several reasons. Most importantly, the actual combo & state of carb tune. Or simply, they don’t know what there doing.
True, and again this is on a big block which makes plenty of torque down low anyways... It may be a little different story on a small block I suppose
 

beanhead

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thank for the info, running same heads/ intake on my 493 I always wanted to try spacers but unless I cut my hood it's no spacers for me. put a set of Mickey Thompson drag radials on they will fix that tire spin issue. I can testify too that
Ooh stickier tires have been on my list for awhile now... I like the Mickey Thompsons, because I currently run Coopers with the raised white letters and that's the look I prefer. But, my tire guy can get me a really good deal on those Nitto 555s that people like.. just haven't pulled the trigger yet!
 

steve340

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I saw some dyno work done by Ford Racing and Richard Holdener and they tried many different spacers on the Performer RPM. Cannot remember the exact details but main story was they got some slight gains in horsepower but they were outweighed by the losses of torque.
There summary was no spacers worked that well on the RPM manifold so fit the carb straight to the manifold.
Since then I have never been keen on using a spacer on either the Performer or the Performer RPM.
 

rumblefish360

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I disagree with that statement and findings because it is solely dependent to n application and the venue it is used in. Each engine will ether like it or not. Just as much as each driver will or will not.
 

BSB67

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thank for the info, running same heads/ intake on my 493 I always wanted to try spacers but unless I cut my hood it's no spacers for me. put a set of Mickey Thompson drag radials on they will fix that tire spin issue. I can testify too that

Simply mill the divider down. If you get creative with your air cleaner, you will be able to add about 1/2" spacer too. Like the OP states, you'll loose nothing meaningful down low, and it will put measurable power above 3000 rpm, especially on a 500 inch motor.
 

beanhead

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I saw some dyno work done by Ford Racing and Richard Holdener and they tried many different spacers on the Performer RPM. Cannot remember the exact details but main story was they got some slight gains in horsepower but they were outweighed by the losses of torque.
There summary was no spacers worked that well on the RPM manifold so fit the carb straight to the manifold.
Since then I have never been keen on using a spacer on either the Performer or the Performer RPM.
Mopar Muscle once did the same, and they did show gains in torque and that the power band simply shifted some. This was kinda the point of my post...dyno stories and conditions vs. a real world driving report. It's also why I tried to put up as much info about my combo as possible. Different setups, different results. A couple of things I didn't mention, it was a fairly dry and sunny 60° day and I run pump 91 (premium for us in ca). I didn't mess with my timing (20/36)
 

MOPOWER871

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Simply mill the divider down. If you get creative with your air cleaner, you will be able to add about 1/2" spacer too. Like the OP states, you'll loose nothing meaningful down low, and it will put measurable power above 3000 rpm, especially on a 500 inch motor.[/QUOT/]


Has anyone done any real dyno work on that center divider? remember the old direct connection engine book they use to do some real research back then, would be interesting to see some numbers.
I'm at the limit as far as clearance goes running a 14" 3 1/2" drop base air cleaner base with a K/N 3" filter and K/N filter top. I have a 3/8" clearance between the filter and hood. and a real good torque strap.
anymore drop in the base interferes big time with the throttle and kickdown Geometry.so only other op I see is going to a $$fiberglass $hood and scoop $$ or 2" filter and being at near 500" choking off the air intake by going to a 2" element is kinda like taking a step backwards. The gains if any are no worth the hassle in my situation. my motor 9:7.1 at 535 HP @5,200 and 586 TQ @4,000. auto, 3:23"s 67 GTX at 3,750 lbs less driver.
I'll take all the torque I can get. 10 more HP on the street is not gonna make a difference light to light so to speak.I use to blow the tires off from a dig, from a roll away's brake loose middle of second gear, at that speed I almost lost control once or twice scared me, drag radials took care of that. whats the sense of building Horsepower if you cant get it to the ground, now I can punch it from a stand still and they stick like glue.
where I'm from we lost our drag strip so I purposely built this motor to be a stump puller to play in the streets. running a car an 1/8 or 1/4 mile in the street is crazy and dangerous suburbia could turn catastrophic in the blink of an eye imagine hurting someone else, your self your car, prison..game over. sorry for the ramble "the coffee she good " Merry Christmas everyone
 

Mike67

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Here is a comparison of a 4hole and open on a 10.5 / Eddy headed motor

Screenshot_20181222-191346.png
 

mopar 3 B

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Run the open spacer with a modified 67 factory dual plane intake and thermoquad on the BB. Only ill affect was going to a manual chock and winter driving.
 

BubbaMope

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Ooh stickier tires have been on my list for awhile now... I like the Mickey Thompsons, because I currently run Coopers with the raised white letters and that's the look I prefer. But, my tire guy can get me a really good deal on those Nitto 555s that people like.. just haven't pulled the trigger yet!
Mickey Thompsons are the way to go. My 275 60 15 BFG T/A Radials went up in smoke on any full throttle run. I replaced them with same size MT SS Radials. I'll still spin out if I don't have the steering wheel straight but with the wheel straight she just goes. They are so sticky they pick up loose gravel and even dead grass. Good news is it all falls off once you get back on the road.
 

69a100

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Hey Beaner, you really need a vacuum gauge on that when you tune it to get it right. Tune for the most vacuum between timing & carb adjustments for best results. Good Luck
 
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