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Carburetor spacers

General engine tech -- Drag Racing to Circle Track

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ArizonaGuy
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Carburetor spacers

Post by ArizonaGuy »

Square bore carb spacers, specific to single-plane manifolds:

Four-hole, and open.
What are the benefits/drawbacks of each?
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Re: Carburetor spacers

Post by BradH »

6.50camaro
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Re: Carburetor spacers

Post by 6.50camaro »

Check 4 hole spacers that they match the hole pattern of the carb . Just went thru this with a cheap composite spacer . the holes were the right size but would not line up front to back with the carb . side to side they were ok, but front to back the bore centerlines were to far apart so there was a crescent moon shape of the spacer protruding into the flow path on all 4 bores . It was about .060 " . take that times 4 and it was probably hurting airflow quite a bit. Dan
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Re: Carburetor spacers

Post by steve cowan »

ArizonaGuy wrote: Tue Nov 16, 2021 12:15 pm Square bore carb spacers, specific to single-plane manifolds:

Four-hole, and open.
What are the benefits/drawbacks of each?
I don't think there is any draw backs,
I believe people don't redo the fuel curve to suit what spacers they test.
If you change a spacer and don't change jets/ bleeds and it picks up power what happened??
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Re: Carburetor spacers

Post by rebelrouser »

From the engines I have run on a dyno, it is just a crap shoot. I have had engines pick up 15 to 20 HP, have had engines lose HP with a spacer. I just think too many variables are involved to say one type of spacer is better than another. Also seen engines pick up a little on the dyno with a spacer, but that did not carry over to the drag strip. I will say that most times a dual plane intake likes an open spacer, and a single plane likes a four hole, but again not always does this work out. Used some of the wiz bang spacers like the super suckers, and the Reher-Morrison Anti-Reversion Plates. Again sometimes great results sometimes not so much.
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Re: Carburetor spacers

Post by BOOT »

Trial and error, track test to see if it's faster or drive it to see if you like it better.
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Re: Carburetor spacers

Post by 1980RS »

I don't care what a spacer does on a dyno, I care about what the car does at the track with them. Last year I ran my 468 that had a Holley 300-5 Strip Dominator in it and the 4 hole tapered spacer picked up a tenth and a half along with 1 mph. I then swapped on an RPM Performer and went to the track (same weather cond). Made a test pass with out the same spacer then added the same 4 hole tapered space slowed the car down and after jetting the car both ways leaner and richer it still ran slower. Pulled off the 4 hole and added a 1" spacer and the car ran within .003 of the single plane intake. Every combo like something different and some engine don't like a spacers at all.
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Re: Carburetor spacers

Post by rustbucket79 »

Yep, absolutely no rhyme or reason as to what works and what doesn’t when it comes to spacers.

What might help in some area could negatively impact in another.
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Re: Carburetor spacers

Post by HQM383 »

I wonder with spacers if it’s the way a spacer contributes to maintaining the atomization of the fuel, or put another way prevent de-atomization. This would all be very combination specific with the vacuum profile of the engine v the intake tract v carburetor metering abilities due to calibration and likely other factors. This hypothetically might make an open spacer prevent fuel smashing into intake walls. A 4 hole might atomize the mixture better with added velocity that was lacking before. This would make the spacer a truly ‘try it and see’ proposition as opposed to calculable ones such as determining cylinder head cc or carburetor cfm.
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Re: Carburetor spacers

Post by racear2865 »

Normally, when I try a spacer, it is to look at what that particular engines wants. If a 4 hole works, then engines needs more time to atomize fuel and more time to make turns. If it likes open spacer, it wants more plenum. Then I can back up and evaluate a look at another intake.
reed
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Re: Carburetor spacers

Post by Walter R. Malik »

ArizonaGuy wrote: Tue Nov 16, 2021 12:15 pm Square bore carb spacers, specific to single-plane manifolds:

Four-hole, and open.
What are the benefits/drawbacks of each?
You did not mention "cloverleaf" spacers or "tapered 4 hole" or 2 plane "equalizers" or thicknesses ... one or more will usually pick-up but, differently. Finding which one will be the best is a mystery until you try them all.
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Re: Carburetor spacers

Post by cjperformance »

My favourite spacer has an off/on switch and a couple of divider bars down the middle thats have little holes in them. Definitely feel the increase in Hp! 👍
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Re: Carburetor spacers

Post by MadBill »

Walter R. Malik wrote: Wed Nov 17, 2021 4:32 pm
ArizonaGuy wrote: Tue Nov 16, 2021 12:15 pm Square bore carb spacers, specific to single-plane manifolds:

Four-hole, and open.
What are the benefits/drawbacks of each?
You did not mention "cloverleaf" spacers or "tapered 4 hole" or 2 plane "equalizers" or thicknesses ... one or more will usually pick-up but, differently. Finding which one will be the best is a mystery until you try them all.
Speaking of tapered spacers, long-time members may recall me posting this 8-10 years back, but here it is again: a guy I know in the San Fran area was running a GT1 Corvette with an ex-NASCAR SB 2.2 358". After some routine service he felt it was down on power, confirmed by a chassis dyno test. When an in-depth search turned up no cause, he yanked the engine and shipped it back to the NC builder.

Fortunately, he had left the carb on the manifold so the builder immediately saw the problem: the the tapered spacer was installed pointy end up! He retested without the spacer and gained 10 HP. Then he installed it right side up and picked up another 10... #-o
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Re: Carburetor spacers

Post by agertz1 »

Seems like these spacers should also apply to 4bbl TBI units ? If an engine has too much stand-off inversion, a 4 hole, like a Super Sucker/ etc.
might help ? What about with an IR manifold ? #-o
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Re: Carburetor spacers

Post by plovett »

steve cowan wrote: Tue Nov 16, 2021 3:22 pm
ArizonaGuy wrote: Tue Nov 16, 2021 12:15 pm Square bore carb spacers, specific to single-plane manifolds:

Four-hole, and open.
What are the benefits/drawbacks of each?
I don't think there is any draw backs,
I believe people don't redo the fuel curve to suit what spacers they test.
If you change a spacer and don't change jets/ bleeds and it picks up power what happened??
This is my experience.
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