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 Post subject: Fuel Pressure Regulator
PostPosted: Thu Oct 08, 2009 11:36 am 
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2 BBL ''SuperSix''

Joined: Thu Sep 10, 2009 11:50 am
Posts: 17
Location: Los Angeles
Car Model:
I'm installing a regulator so that I can use a Holley 5200 carb. Where does it go in the fuel line? I would assume, before the filter.

If I'm reducing the pressure at the carb, am I increasing the pressure somewhere else? Will this cause a leak, or rupture the pump diaphragm?

Do I need a "fuel tank return"? This is an inexpensive Mr. Gasket regulator, so there is no fitting for a return.

What else do I need to know?

I especially would like to hear from people who have successfully used the Holley 5200 and Weber carburetors.


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 Post subject:
PostPosted: Thu Oct 08, 2009 11:59 am 
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Board Sponsor & Contributor

Joined: Thu Oct 31, 2002 5:39 pm
Posts: 24486
Location: North America
Car Model:
H'mm. What fuel pressure are you trying to achieve? I have found FPRs to cause more problems than they solve on systems with mechanical fuel pumps.

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 Post subject:
PostPosted: Thu Oct 08, 2009 2:40 pm 
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2 BBL ''SuperSix''

Joined: Thu Sep 10, 2009 11:50 am
Posts: 17
Location: Los Angeles
Car Model:
3.5-4.5 PSI seems to be the consensus. Would I be better off with an electric fuel pump?

With the stock setup, the engine acts and smells like it's getting too much gas.


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 Post subject:
PostPosted: Thu Oct 08, 2009 2:58 pm 
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EFI Slant 6
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Joined: Fri Apr 21, 2006 4:47 pm
Posts: 374
Location: SF CAL
Car Model:
sounds like a carb rebuild is what you need more then a pressure regulator. or maybe just an adjustment to the fuel air mixture

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 Post subject:
PostPosted: Thu Oct 08, 2009 3:26 pm 
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Board Sponsor & Contributor

Joined: Thu Oct 31, 2002 5:39 pm
Posts: 24486
Location: North America
Car Model:
Quote:
3.5-4.5 PSI seems to be the consensus.
Then you're in luck, because the stock ordinary unmodified un"regulated" slant-6 fuel pump produces 3.5 to 5 psi.
Quote:
Would I be better off with an electric fuel pump?
Even bigger pain in the rear than a FPR with a carburetor.
Quote:
With the stock setup, the engine acts and smells like it's getting too much gas.
Sounds like the carb is faulty and/or improperly adjusted. Lowering the fuel pressure would be a band-aid; I think I would turn my efforts and attention to the carburetor itself before I'd add extra parts to the fuel system, though if you want to be precise you can put a fuel pressure gauge in the line between pump and carb and see what you read.

One "extra part" that would be a good idea to add would be a vapour-bleed fuel filter (Wix 33054 or NAPA Gold 3054, Purolator F20030). In addition to the inlet and outlet nipples, it has a 3rd nipple which is a vapour return. It has a 0.060" orifice and takes a ¼" hose, which you must route safely back to the fuel tank (a hassle, but not impossible). This helps alleviate high fuel pressure that develops between the pump and carb after shutdown.

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 Post subject:
PostPosted: Thu Oct 08, 2009 10:48 pm 
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Supercharged
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Joined: Thu Jan 27, 2005 8:32 pm
Posts: 7834
Location: Portland-ish
Car Model: Fiat 500e
I used a Holley 5200 carb with a stock mechanical fuel pump. No leakage or float sinking problems at all.

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 Post subject:
PostPosted: Fri Oct 09, 2009 12:25 pm 
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2 BBL ''SuperSix''

Joined: Thu Sep 10, 2009 11:50 am
Posts: 17
Location: Los Angeles
Car Model:
"I used a Holley 5200 carb with a stock mechanical fuel pump. No leakage or float sinking problems at all."

A-ha! That's the answer I was looking for. I will concentrate my investigation elsewhere.

I've got 5 of these carbs, all carefully rebuilt. All have serious vacuum leaks at the throttle shaft, which, I am told, is impossible.

My current unit was purchased as NOS, and it, too, had a vacuum leak. I had it re-bushed. The carburetor expert thought I was a fool, but it made a big difference.

I've spent a lot of time and effort rebuilding these carburetors to the specs. I think the next step is to take a hard look at the needle and seat. I've already replaced it once.

Thank you for your input, everyone. You may have saved me some trouble. I know that there are several members of this forum that use this carb, and I would love to hear their perspectives.


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