Carb spacer for my setup? - Vintage Mustang Forums
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post #1 of 30 (permalink) Old 05-13-2019, 07:39 PM Thread Starter
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Carb spacer for my setup?

Hello everyone,
I am installing a 600cfm Holley 4160 on my 302 with a stock Ford cast iron 4 barrel intake manifold. The engine is stock, so 4800rpm power peak and roughly 5200rpm redline. I do have long-tube headers and a 2" dual exhaust.

I've heard that the main benefit of a carb spacer is increasing plenum volume, which increases higher rpm power at the expense of lower RPMs. I know that they can also keep the carb cooler, especially if you get a plastic one.

Seeing as my engine won't be revving especially high, and that I have an iron intake (which doesn't conduct heat as much as aluminum, so shouldn't heat the carb as much?) how much benefit would I get from a carb spacer? And should I get one of the open ones, or one that has 4 holes (which should match up with the 4 holes in the Ford intake)?
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post #2 of 30 (permalink) Old 05-13-2019, 07:44 PM
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I don't think you will benefit much from a spacer. If you're having a problem with hot fuel a spacer might help. If not, I wouldn't bother.

I would consider not installing a 600cfm carb. A 500 would be better for the application you have described.

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post #3 of 30 (permalink) Old 05-13-2019, 08:38 PM
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I am a BIG fan of the stock aluminum 4 hole spacer that has the correct PCV port and an Autolite 4100, one of the best-atomizing reliable and easily-adjusted carbs ever built, and flow just right for the 289-302 up to 6000 in warmed-up trim, about 90% volumetric efficiency. Ford got it right 50 plus years ago and it still rings true. The spacer does add a little length to the overall intake runner, helps low to mid range grunt I believe, and Ford wouldn't have put it on there if it wasn't useful.

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Last edited by myfirstcar66; 05-13-2019 at 08:41 PM.
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post #4 of 30 (permalink) Old 05-13-2019, 08:44 PM
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I think your 600cfm 4160 will work great.
Carb spacers are cheap. Try one. You might like it.
https://www.summitracing.com/parts/sum-g1408/

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post #5 of 30 (permalink) Old 05-13-2019, 09:09 PM
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I've got a Edelbrock 500 cfm carburetor with less than 500 miles on it gathering dust. Given todays gas and fuel percolation, I'd run as much spacer as possible.
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post #6 of 30 (permalink) Old 05-13-2019, 09:29 PM
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I run a 2" 4 hole Phenolic, had it on my 289 now it's on my GT40P. The biggest benefit you'll get is a cooler carb chances are you will run out of valve spring before you notice much else
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post #7 of 30 (permalink) Old 05-13-2019, 09:52 PM
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I’m using a phenolic spacer for something like a 428. It’s very thin and has the nipple for the PCV hose along with a thermal insulator I bought at Carlisle a few years back. It all seems to work fine. I have a picture of the box it came in somewhere.

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post #8 of 30 (permalink) Old 05-13-2019, 11:05 PM
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I've always gone with "4 hole for torque, open for revs".
Thought it was the accepted rule.
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post #9 of 30 (permalink) Old 05-13-2019, 11:40 PM
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Quote:
Originally Posted by 2nd 66 View Post
I run a 2" 4 hole Phenolic, had it on my 289 now it's on my GT40P. The biggest benefit you'll get is a cooler carb chances are you will run out of valve spring before you notice much else

2" spacer? What kind of intake and air cleaner do you have on that? I run a 1" and I only have about a 1/2" clearance when the hood is closed.


As for the OP: I also agree that you'll get some benefit for the carb being cooler. For what it's worth I'm also running a 4-hole spacer to (supposedly) increase lower end torque.
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post #10 of 30 (permalink) Old 05-13-2019, 11:50 PM
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Quote:
Originally Posted by Nailbender View Post
I've got a Edelbrock 500 cfm carburetor with less than 500 miles on it gathering dust. Given todays gas and fuel percolation, I'd run as much spacer as possible.
Costs a little more on the front side to buy non-ethanol gas , but I don't have nearly the long-term -sitting starting, hot starting or percolation issues that I do with the 10% corn alcohol gas. Also don't have nearly the issues that I did with the Edelbrock.
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post #11 of 30 (permalink) Old 05-14-2019, 12:13 AM
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I just added a 1 inch spacer to my edelbrock 650 on my 289. I also added a heat sleeve to the fuel line and I didn’t notice any performance but it cured my vapor lock problem
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post #12 of 30 (permalink) Old 05-14-2019, 08:06 AM
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Jet down what you have or get a smaller carb
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post #13 of 30 (permalink) Old 05-14-2019, 09:14 AM
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Quote:
Originally Posted by 66ryan View Post
2" spacer? What kind of intake and air cleaner do you have on that? I run a 1" and I only have about a 1/2" clearance when the hood is closed.


As for the OP: I also agree that you'll get some benefit for the carb being cooler. For what it's worth I'm also running a 4-hole spacer to (supposedly) increase lower end torque.
Edelbrock F4B 14x3 drop base you must not have seen my teardrop hood
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post #14 of 30 (permalink) Old 05-14-2019, 12:31 PM
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Modern ethanol-containing gasolines tend to vaporize easily resulting in vapor lock and/or percolation. Even though cast iron doesn't conduct heat as well as aluminum, a hot intake manifold will transfer some heat into the carburetor. If you find that your idle gets progressively worse in hot weather and the exhaust fumes cause your eyes to burn, you may be experiencing percolation. Vapor lock occurs in fuel pump and prevents it from being able to pump fuel, thereby causing it to stall and impossible to start until the engine cools down (when the fuel vapor condenses back into liquid). Intake manifold heat helps street-driven vehicles run better, even in hot weather, so I would not disable it to keep the intake manifold cooler.

I would add a 4-hole phenolic spacer with just enough height to allow your hood to close. See Vapor Lock.
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post #15 of 30 (permalink) Old 05-14-2019, 02:35 PM
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Quote:
Originally Posted by fraso View Post
Modern ethanol-containing gasolines tend to vaporize easily resulting in vapor lock and/or percolation. Even though cast iron doesn't conduct heat as well as aluminum, a hot intake manifold will transfer some heat into the carburetor. If you find that your idle gets progressively worse in hot weather and the exhaust fumes cause your eyes to burn, you may be experiencing percolation. Vapor lock occurs in fuel pump and prevents it from being able to pump fuel, thereby causing it to stall and impossible to start until the engine cools down (when the fuel vapor condenses back into liquid). Intake manifold heat helps street-driven vehicles run better, even in hot weather, so I would not disable it to keep the intake manifold cooler.

I would add a 4-hole phenolic spacer with just enough height to allow your hood to close. See Vapor Lock.
Copy and pasted from your link ."To get the utmost performance from a race car, the intake manifold needs to be as cold as possible but these cars usually don't run well year-round on the street."
I have that passage block off on my engine ,I don't drive it in the winter so But it does run pretty well on the street from mid April till mid October


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