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Carb Spacers
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DRR Pro
Picture of nomad
posted
There are some who believe carb spacers work and some who think they serve no purpose. I plead ignorance on the subject.

What are they supposed to do? Are they there to increase plenum size, to allow the mixture to make a smoother turn into the intake runners? Or do they prevent flow from slamming into the plenum floor and disrupting flow?

So, besides taking up under hood space, what do they do?

I’d like a reasoned explanation besides they work or they don’t work.

Thanks.


nomad
Bruce Guertin


Easily distracted by bright shiny objects.

Wife says I'm a new adventure every day.


Call Automotive Performance Engines for all your complete engine building, dyno service needs 863-967-8781
 
Posts: 2544 | Location: Auburndale, Florida | Registered: October 19, 2004Reply With QuoteReport This Post
DRR Trophy
Picture of NC3x58
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To be honest, I put them on because they are aluminum and drilled and tapped for a lean-out valve for when running alcohol. Dragster has no issue with hood clearance and the door car we recently acquired has a 6" cowl hood so no issues there. The hood clearance could become an issue whenever we take off the 6" cowl for something smaller, as that is not completely needed for the little LS we run in the car. Other than that, I don't see a lot of et in spacers honestly.


Nick Craig

1971 Camaro Split Bumper
376ci LS3
 
Posts: 410 | Location: Ohio | Registered: December 28, 2013Reply With QuoteReport This Post
DRR Top Comp
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Reducing the charge temperature improves the volumetric efficiency.
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Sportsman
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I use a phenolic seems to keep carb cooler. Not any difference on slip that I can tell.


BG
 
Posts: 759 | Location: Florence, SC | Registered: August 25, 2019Reply With QuoteReport This Post
DRR Elite
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Bruce, I have tried every configuration of spacer...open, 4 hole, tapered/blended/super sucker, every material...wood, phenolic, aluminum, from most every manufacturer...HVH, Canton, Wilson, Stinnett, on every engine I've owed, with every carb... 4150, 4500 and every manifold over 30 years and I ain't ever seen .01 in ET or .1 mph. None of them are worth anything on the time slip. Now if you want to use it as a heat sink to isolate your carb from engine heat, ok but to buy one looking for an ET/MPH improvement, my advice is don't waste your $. Further, most are running an intake manifold with too much plenum volume for optimum Ets. Adding a spacer only makes it worse.
 
Posts: 13522 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR S/Pro
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If your oversized on your carb. then a 4 hole will likely improve vacuum signal by essentially increasing the length of the throttle bores. Conversely, and open space will move the carb. ****her from the signal and lessen the signal somewhat, an possibly reduce reversion due to physical distance from the signal. As you noted, plenum size is a factor, however I don't think it will impact the physical turn into the manifold runners. Turtles are designed to impact flow slamming into the floor, and subsequent puddling. It's a low cost item and easy to validate a benefit or not. Go for it!

Major engine shops use them on their bracket motors. Don't believe they would run up cost needlessly if their dyno time didn't show it's worth. JMO


Illegitimi non carborundum
 
Posts: 2334 | Location: OKC, OK | Registered: February 15, 2008Reply With QuoteReport This Post
DRR Elite
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Dyno numbers are only good for those that suffer with erectile dysfunction. What’s printed on the time slip is real and 99% of the time on bracket engines, the et/mph doesn’t equate to the inflated dyno numbers.
 
Posts: 13522 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post



DRR Top Comp
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Reher Morrison sheer plate

I had so much timing out of it first time run, it skipped from the time it went to high gear to the stripe, still better mph than 6.30 car.

I've used these since they came out 4150, 4500.

Probably one of the first they sold after the add hit National Dragster early 2000's





 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Top Comp
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Reher Morrison sheer plate in conjunction with a BLP carb, Transmission Specialties spragless converter.

You won't out mph it, sbc n/a 3450 lbs.
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Sportsman
Picture of Bob Deniker
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Back when we ran 4500 carbs with the exposed linkage underneath, we would run a junk plate and a 4 hole spacer to keep the plate secure.
 
Posts: 621 | Location: Latrobe Pa. | Registered: July 30, 2007Reply With QuoteReport This Post
DRR Top Comp
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Reher Morrison sheer plate 1.250" spacer, BLP 4500 carb, PKRE ported 4500 SV2 intake, Transmission Specialties spragless converter.

n/a sbc 23 degree out of box Brodix T1 heads. I've never seen this type of mph n/a sbc at 3200 lbs, in the 6.40's et range.


 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Pro
Picture of nomad
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quote:
Originally posted by 1320racer:
Bruce, I have tried every configuration of spacer...open, 4 hole, tapered/blended/super sucker, every material...wood, phenolic, aluminum, from most every manufacturer...HVH, Canton, Wilson, Stinnett, on every engine I've owed, with every carb... 4150, 4500 and every manifold over 30 years and I ain't ever seen .01 in ET or .1 mph. None of them are worth anything on the time slip. Now if you want to use it as a heat sink to isolate your carb from engine heat, ok but to buy one looking for an ET/MPH improvement, my advice is don't waste your $. Further, most are running an intake manifold with too much plenum volume for optimum Ets. Adding a spacer only makes it worse.


Okay, here's where I'm going with this.

In 2009 when I built my first 540 I used a 1050 with the 2907 intake. A 1/2" spacer hurt it on the dyno to the of 10 HP. This on a manifold that's supposed to work real well with a 1" spacer. I needed a vacuum tap so I used a 1/4" phenolic spacer to provide that.

As familiar and comfortable as I am with carbs I should know the answer to this question. Why does plenum volume matter? What the heck is going on in there anyway? If they seem to hurt or not provide an improvement for myself and Ed, why does everyone else seem to have so much luck with them?


nomad
Bruce Guertin


Easily distracted by bright shiny objects.

Wife says I'm a new adventure every day.


Call Automotive Performance Engines for all your complete engine building, dyno service needs 863-967-8781
 
Posts: 2544 | Location: Auburndale, Florida | Registered: October 19, 2004Reply With QuoteReport This Post
DRR S/Pro
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quote:
Why does plenum volume matter? What the heck is going on in there anyway?

A little visual never hurts.




Illegitimi non carborundum
 
Posts: 2334 | Location: OKC, OK | Registered: February 15, 2008Reply With QuoteReport This Post
DRR S/Pro
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quote:
Originally posted by Canted Valve:
quote:
Why does plenum volume matter? What the heck is going on in there anyway?

A little visual never hurts.


[FLASH_VIDEO]<iframe frameborder="0" height="388" src="https://www.youtube.com/embed/7Iq1B-2paCs" title="YouTube video player" width="690">[/FLASH_VIDEO]



Kasse doing what others wonder about.
Canted, probably one of the most informative videos to see. It’s been out there a while.


Raceless in California!
 
Posts: 4485 | Location: Vacaville  | Registered: January 07, 2004Reply With QuoteReport This Post



DRR Pro
Picture of nomad
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quote:
Originally posted by Canted Valve:
[QUOTE]Why does plenum volume matter? What the heck is going on in there anyway?

A little visual never hurts.

Interesting video. I hadn't seen that before. There sure is a lot of raw fuel slopping around in there. Especially at lower RPM. Now I understand why it was so difficult to get a reasonable AFR when on the stop. A lot of raw gas just draining into the port. And that's a lot of plenum volume on that manifold.

Still, why does plenum volume matter?


nomad
Bruce Guertin


Easily distracted by bright shiny objects.

Wife says I'm a new adventure every day.


Call Automotive Performance Engines for all your complete engine building, dyno service needs 863-967-8781
 
Posts: 2544 | Location: Auburndale, Florida | Registered: October 19, 2004Reply With QuoteReport This Post
DRR S/Pro
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quote:
There sure is a lot of raw fuel slopping around in there. Especially at lower RPM.

If you'll notice, at low rpm, when they start to load the engine it's the accelerator pump shot(s) that starts the extra fuel. If you have four 50cc Rio accelerator pumps that's a lot of unatomized gas!!!


Illegitimi non carborundum
 
Posts: 2334 | Location: OKC, OK | Registered: February 15, 2008Reply With QuoteReport This Post
DRR S/Pro
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Plenum should match the cubic inches , but then comes the heads, manifold runner length, size and taper. No easy feat.

Kasse Manifold was a test piece and prob not exactly what was needed but still offers a big picture. It is havac inside.


Raceless in California!
 
Posts: 4485 | Location: Vacaville  | Registered: January 07, 2004Reply With QuoteReport This Post
DRR Sportsman
Picture of TD3550
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This...




Balancing 101 lol...

This message has been edited. Last edited by: TD3550,
 
Posts: 1409 | Location: Under a Truck | Registered: August 23, 2013Reply With QuoteReport This Post
DRR S/Pro
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quote:
Originally posted by TD3550:
This...




Balancing 101 lol...



L I K E ! Button!





Raceless in California!
 
Posts: 4485 | Location: Vacaville  | Registered: January 07, 2004Reply With QuoteReport This Post
DRR Pro
Picture of chasracer
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I have one of the suckers on mine and I'm pretty sure that it's not doing a thing for me. But considering that I would have to re-do a lot of stuff to take it off - it stays on there.

Now, the one time that I really experienced a spacer that was working I was in the wrong car. I raced SS/OA for a short period of time and one of the bad parts was that we had to use an original carb. Our car was a '55 but of course a lot of cars can fit that class. One of the better cars in the class was actually a '56. I had a time run against that car one day and I tree'd the driver by a solid 15 but at the 60 I was staring at the '56 taillights as it went by me. Later that day I went after some fresh plugs from one of the sellers in the midway and I happened to see that '56 with the hood up so I took a walk in that direction. Sitting on that engine was the tallest set of spacers I have ever seen cobbled together and it was just short of the height of a tunnel ram to keep the carb under the hood. The owner/driver said, yep it increases the CFM of that 500 carb to almost a 750 - I don't know if he was right about that or not but the damned car definitely wasn't being hurt by it.
 
Posts: 1135 | Location: The problem is not the problem. The problem is your attitude about the problem. Savvy?” ~~ Captain Jack Sparrow ~~ | Registered: August 21, 2000Reply With QuoteReport This Post
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