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-   -   3psi carb fuel pressure positive results. (https://www.offshoreonly.com/forums/do-yourself-boating-budget/315437-3psi-carb-fuel-pressure-positive-results.html)

Jetfiremuck 07-18-2014 09:31 AM

3psi carb fuel pressure positive results.
 
For what it's worth. I've spent many hours frustrated with multiple removal/carb combos trying to solve a booster dripping gas at idle. This prevents smooth idling, loading up etc. replaced , cleaned,recleaned carb used original Holley seats floats etc with no joy. Fuel pump pressure was 5psi constant no spikes.
Finally spoke to an old school carb pro . He stated that all the Holley 4160 and the like were designed for leaded gas originally and the use of E 10 and higher concentrations is causing most of the problems with poor running etc.

My result was installing Holley fuel press regulator with gage. Set at 3psi. It's a completely different world. No leak overs smooth idle great throttle response no bog.

I'm passing this on to help those that had the same frustrations I had. I tried all carb adjustments.

Black Baja 07-18-2014 09:55 AM

Sounds like something is wrong with the metering block...

SB 07-18-2014 10:00 AM

Guage correct ? Sounds weird to me, but, what ever works is what works.

I have had some issues like that, not excatly that, with the real large needle and seats but none with the normal .110's or smaller. I usually have no problems up to 8psi or so, but prefer say 6-7psi.

Glad you have it fixed.

jbraun2828 07-18-2014 10:18 AM

Should have at least 6psi. I had problems like that on an old boat with holly 850's. Could set the floats right and would drip gas at idle. I bought 2 new carbs and it ran perfect. People say you can always re build a carb, I had mine done 2-3 times and just couldn't get it right.

Jetfiremuck 07-18-2014 10:59 AM


Originally Posted by SB (Post 4155391)
Guage correct ? Sounds weird to me, but, what ever works is what works.

I have had some issues like that, not excatly that, with the real large needle and seats but none with the normal .110's or smaller. I usually have no problems up to 8psi or so, but prefer say 6-7psi.

Glad you have it fixed.

Thanks for the info.
As I mentioned this was my experience. I live in Fl and it may be the gas had a higher ethanol content. I run a 460 jet .I did change out metering blocks etc,
If you You Tube 'predator carb rebuild ' there is a shop that rebuilds carbs, and he mentions the same 3psi at the carb while engine running. I think vapor pressure has a lot to do with it too.

Griff 07-18-2014 12:20 PM

Change the 4160 metering plate to a 4150 metering block.
Dripping fuel is a sign of improperly adjusted floats or a bad needle/seat assembly.

IMO, 3 psi is not enough fuel pressure. It should be 5-7psi. What you have done is put a bandaid on a problem.

BUP 07-18-2014 12:27 PM

Agree about the needle and seat. Most carb engines need 5 to 7 psi. and seem to work very well at 5.5 to 6.5 psi for stock & slightly modified marine engines. At 3 psi on the top end you have a really good chance of running lean. I would not even run a stock OEM V-6 carb marine engine at 3 psi, plus its out spec by any of the marine engine manufacturers.

Jetfiremuck 07-18-2014 01:06 PM

My whole purpose of posting was to help someone who tried everything as I did to resolve this booster issue. As stated I bought Holley branded products, needles seats and floats. Changed float bowls and so on. 3psi stopped the problem on my carb. I've run at 4500rpm with no issues. I've since changed to a predator carb and the throttle response on that 460 is amazing using that carb.


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