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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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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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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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I've got a Edelbrock 500 cfm carburetor with less than 500 miles on it gathering dust.:wink: Given todays gas and fuel percolation, I'd run as much spacer as possible.
 

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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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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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I've got a Edelbrock 500 cfm carburetor with less than 500 miles on it gathering dust.:wink: 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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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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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:shrug:
 

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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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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 :shrug: But it does run pretty well on the street from mid April till mid October
 

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I added a 2" 4 hole spacer a while back for the added plenum volume theory. 2"+1" OE spacer so its at 3":). Everything else is stock 4V w 450cfm Holley, the hood is cut with a CJ scoop so its kinda cool to see the air filter through the inlet, not much else though. I don't think it added anything up top to be of use.
Im leaving it on till paint is finished, hopefully within a month, i'll revisit the idea and get a better test with it and without. im pretty sure it did cost some low end response.

On the low end cost it might be that I couldn't reuse a 2" air cleaner spacer. That is a piece that sits right atop the carb, its meant to raise the air cleaner for clearance but a side benefit is that it forces the air to be in a straight downward flow before it gets to the carb. that thing made a noticeable improvement for me. Reminded me of the Engine Masters filter shootout when the "salad bowl" made improvements.

Im saying if you have 2" and $8 to spare try one of these under your air cleaner:grin2:
https://www.amazon.com/Mota-Performance-A10205-Cleaner-Resistant/dp/B002ZMFXLW/ref=sr_1_5?crid=6LSEUCJ8Z307&keywords=air+filter+spacer+carburetor&qid=1557866082&s=gateway&sprefix=airfilter+spacer,aps,187&sr=8-5
 

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I would add a phenolic for sure, i tested my 289 w & w/o the spacer years ago with a IR temp gauge (can't remember the readings) but also noticed I couldn't put my hand on the carb/lean on the carb after the car was run w/o a spacer, too hot. Added the thickest phenolic spacer that allowed air cleaner to hood clearance and could then put my hand on the carb after running and it was warm but not hot. A reduction in fuel temp/carb temp is always good.

I went with the 4 hole as I want low/mid more than WOT performance for the street.
 

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Eh. I'll keep running my Victor Jr. I already have it port matched to my heads and I don't want to do that again not to mention having a Vic Jr paper weight at that point. Bought it and ran it for the drags and I'm just going to keep running it even though I'm mostly street now.


With stock heads and cam the only benefit you might get from running a spacer will be a bit cooler carb and that will definitely help.
 
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