Holley Fuel Pressure and Flooding - float settings, pressure Q's

[BenH]

Hello folks,

I know there are many threads that discuss things like this, I'd still like to voice my own experiences out loud and see what other's input is.

I am running a typical mechanical Carter pump feeding a Holley 750 with dual fuel feeds one each bowl, vac secondary not a double pumper. It is a mild build 440, new build, in a 65 Sat. The pump is not old, but not new to me, and I can't confirm it's accuracy or even it's rating since I don't see a part number (pretty sure there aren't multiple pressure types though for these?), it came on the 361 that was in the car originally, so I have a new one on the way for peace of mind that I will put on, M4845.

It is flooding pretty badly currently after just a few cranks, I doubt it's the fault of the pump, and I am almost certain when I take the carb apart I will find float setting and needle issues. It is a rebuilt carb with a fair amount of new parts including the front main bowl and I believe the float as well.

The thoughts still on my mind however are whether folks think it is really necessary to have an inline pressure regulator for Holleys? Holley's claim is any pressure in excess of 7.5 psi will cause flooding, and the Carter pump is rated 6-8 psi (certainly has to be a small margin of error there). I know this is nitpicking but I am just looking for opinions, the last engine I built was a 383 and I put a regulator and gauge on an identical setup and it was very happy.

Second question, anyone know what the measurements for setting correct baseline float height in a rebuild on a Holley are? It's flooding like I said and I'd like to start at a manageable point instead of trying to set the float height while it is puking gas, it just wont run like that and I don't want the excess washing down the cylinders and filling up the crankcase (been there done that).

Final question, the pump pushrods are the same from B to RB, yes?

I will update tomorrow when I pull the carb apart as well. Thanks in advance. The engine is otherwise ready to break in and this is the last thing in my way.

 

[451Mopar]

Just pull the needle/seat assembly out of the top of the carb bowl, make sure no trash is between needle and seat, and that the "O"-ring seals are in good condition (no nicks, broken, or missing.)
The floats seem to be good until the fuel pressure gets around 9 PSI, and the aluminum arm versions will start bending. The other types seem to take more pressure?

 

[BenH]

Any idea if anyone ever experienced a Carter thats quoted to max out at 8psi exceed 9?

Thanks for the reply.

 

[BB BELLA]

take the carb off and put it on a bench, rig a squeeze bottle with fuel and fill the carbs with it sealed to the fuel feed line, with the site plugs out fill the bowls and adjust floats [dump a bit and repeat till correct when fuel doesn't run out the site plug holes but you can see it at bottom of hole! get some clear plugs to check level when engine is being started, do not leave clear plugs in after adjustments are done.
make sure bowls are filled before attempting to start motor or a backfire can blow powervalve!
.02

 

[hunt2elk]

The new Carters are coming with way higher output pressure than advertised. The last 3 I bought were 10-11 psi, and supposed to be 7 psi max. Put a gauge in the line to verify what yours is doing.

 

[snakeoil24]

Two things you can do
1. Install the new style flat bottom needle and seat.
2. Install a bypass back to gas tank.”return”

 

[Dan64]

I just replaced a brand new Carter Strip super ( why don't they call them super strip instead?) fuel pump ,it was 11.5-12 psi. I called them and the guy i spoke to said "Don't use it, something wrong inside". I had horrible thoughts of it filling my crankcase with fuel and washing out my bearings so i replaced it. I would most definitely use a gauge and not just any cheapo gauge but a Aeromotive AEI-15632 ($46 bucks) It has the pressure equalizing pull pin on top to avoid false readings for when the liquid inside the gauge changes temp. Most gauges don't have this and can read as much as 3 psi under actual pressure when motor compartment/ gauge liquid get hot.

 

[BenH]

Well I guess I am going to get a regulator and gauge as well as correct the Holley issues and replace the pump.

I was very satisfied with a Holley 12-803 regulator on my last build, if the gauge follows the regulator in the system rather than precede it, you already have a baseline for where your pressure has been governed based off the regulator capability and the gauge doesn't really need to be a high dollar super accurate item in my opinion, as long as it gives out a reading in the neighborhood of 7psi. Especially gauges that only read from 0-15, shoot for a halfway point reading. I checked this setup with an overpriced Snap-On pressure gauge at my last shop and it was spot on, so I fully trust it.

 

[dadsbee]

Never had an issue with fuel pressure blowing the needles on a Holley, I just by the cheapest Carter fuel pump available..

 

[BenH]

Never had an issue with fuel pressure blowing the needles on a Holley, I just by the cheapest Carter fuel pump available..

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I like that pump advertising a solid 6psi, instead of 6-8psi. But I don't like that it is lacking the hard line fitting and just has 2 fuel nipples instead, my setup used a hard line to go behind the alternator.


edit: Ratings of 20 gallons per hour on the 4589 versus 33 gallons per hour on the 4845 is also something worth considering on a 450hp 440. Interested to hear opinions on that either positive or negative.