weber carbs and fuel pressure

[PEZi]

So for christmas i'll be snagging a Weber 38 DGES... but for those of you running webers i want to know if you're running fuel regulators and such... i suck at all things electrical so i'm looking for any help i can get

i'll be doing all new fuel lines... pump... and carb... maybe even the tank if i can find a small one for cheap... but like i said i suck at EVERYTHING electrical

[damn]

So for christmas i'll be snagging a Weber 38 DGES... but for those of you running webers i want to know if you're running fuel regulators and such... i suck at all things electrical so i'm looking for any help i can get

i'll be doing all new fuel lines... pump... and carb... maybe even the tank if i can find a small one for cheap... but like i said i suck at EVERYTHING electrical

When i put my 34/34 on i installed a fpr becuase that is what was recomended in the carb manual but when i installed everything my fuel pressure was WAYY off! when the dial was set to 3.5psi it was only reading 2psi of fuel pressure at the gauge. I removed the fpr and the stock pump is providing a steady 3.5-4 psi of fuel pressure at all engine rpm's.....The fpr was actually clogging my fuel system.

Heres the fuel pressure gauge im using: http://www.autozone.com/autozo...ectre

If your looking to get a new fuel pump i would recomend this pump...Mr. Gasket Micro-Electric Fuel Pump - 2-3.5 PSI - 42 GPH part #MRG42S

http://paceperformance.com/ind...RG42S

With such low volume pumps as long as you have a gauge about 2in before the carburetor and it reads at least 3.5psi of pressure at all times but never excedding more than 4psi you wont need a fpr.
Modified by damn at 9:27 PM 12/7/2009

[PEZi]

good stuff... thanks man

[PEZi]

so... i'm bumping this because i've been looking into some more of the weber recommendations... and it says to NEVER let it exceed 3.5 psi

i'll obviously look at the pressure via a gauge in order to see where mine flows at... but it looks to me, from what i've been reading, that running the setup you (damn) had with the FPR is actually right... but the removal of the return line is how you fix the low psi that you were getting

i'll keep looking into this... but what are some of the others of you running that have webers?

[breadbox]

I just ordered a weber Carb for my truck, Hopefully its everything I'd hoped it'd be.

[PEZi]

oh it will be man... assuming you get it set up right... i've been digging into this for a while now so that i get mine set up right...

here's a few things to look for:the PSI never to exceed 3.5psithe jetting set up properly so you're neither too rich or too leanand BUMP THE TIMING UP!!! do it 1-2 degrees at a time and listen for pinging... once you hear the ping knock it back down 1-2 degrees so it no longer pings... also... don't forget to run premium gas

they also say to start with fresh... BRAND NEW plugs and to check them after each adjustment to test for lean/rich issues... i personally won't be doing this cause my plugs are expensive and in good condition still... and i just can't afford to replace them

[damn]

Honestly the fuel pressure is not going to matter much as long as it is right around 3.5 psi of pressure! When it goes over say 4.5 or 5 psi then you get hard starting or flooding. If your pressure fall's under about 3psi you will run lean and the truck will run like it has no power.

I learned the sweet spot is right between 3.5psi-4psi. Get a fuel pressure gauge and rev the engine up a few times to see if your fuel pressure is dropping off at higher rpm's. The stock OEM pump should be more than enough to supply the correct pressure.

Also you guy's need to know these carb's are jetted on the rich side for safety so make sure you know what your doing if your going to jet it leaner and advance the timing. Dont want to develope detanation!

[PEZi]

yeah... on mine i'll have to jet it leaner because of high altitude

i'll be doing lots of trial and error with the timing advance on it

[damn]

If you tell the guy your altitude im sure he will jet it accordingly before shipping it to you.

Also i was never running a return line on my truck.
Modified by damn at 8:56 PM 12/23/2009

[PEZi]

nah... its from webercarbsdirect... it just gets shipped as they made it with all the stock settings... it's already on its way lol

i'm wondering why your pressure was so low then... it seems odd that a regulator set at 3.5 psi would flow at only 2

[damn]

nah... its from webercarbsdirect... it just gets shipped as they made it with all the stock settings... it's already on its way lol

i'm wondering why your pressure was so low then... it seems odd that a regulator set at 3.5 psi would flow at only 2

Guess it could have been a faulty regulator? But since it is running at the correct pressure now there is no need to use one.

[PEZi]

yeah i got no idea man

[breadbox]

just so I am clear....

Why do you say use premium? Doesn't octane rating have to do more with engine compression then timing?

[damn]

just so I am clear....

Why do you say use premium? Doesn't octane rating have to do more with engine compression then timing?

With these engines you dont have to use premium the compression ratio is way to low and the weber carb comes jetted on the rich side anyway.But bumping up your timing too much could cause detonation so you have to be carefull about that plus you have to remember the vaccum advance will add even more timing onto what you do.

[turbojunker]

nah... its from webercarbsdirect... it just gets shipped as they made it with all the stock settings... it's already on its way lol

i'm wondering why your pressure was so low then... it seems odd that a regulator set at 3.5 psi would flow at only 2

I had a Weber 45DCOE on an RX7, and I used one of those cheap a** dial type regulators. I checked it against a gauge and it was about 1.5 psi lower than I had it set at.

[PEZi]

Why do you say use premium? Doesn't octane rating have to do more with engine compression then timing?

its just a personal preference... i think you can add in a little more advance with it

[PEZi]

so... i talked to a local carb guru (he's been running carbs on autocross cars for 30 years now)

he told me that what damn is saying about the carb running at 4 psi is something some people have done in the past but he strongly recommends you don't run above 3.5 psi

here is his reasoning behind it... and to be 100% honest... i've seen the work this guy does and trust him more than anyone when it comes to carbs

Believe Weber when they say 3.5 psi, I really prefer more like 2.5. Lots of fuel pressure just eats the inlet needle and seat and you get very erratic float level control. Fuel pressure regulators aren't that expensive, especially when compared to five quarts of synthetic oil diluted by gas, and crank bearings destroyed by running in a gas/oil mix instead of straight oil!

[damn]

so... i talked to a local carb guru (he's been running carbs on autocross cars for 30 years now)

he told me that what damn is saying about the carb running at 4 psi is something some people have done in the past but he strongly recommends you don't run above 3.5 psi

here is his reasoning behind it... and to be 100% honest... i've seen the work this guy does and trust him more than anyone when it comes to carbs

So he is going against even weber and saying they should run 2.5psi? Mine ran like crap at 2.5psi think about it. Weber recomend's 3.5psi i talked to John at weber north america on the phone and he said to run between 3.5-4psi i guess you can run whatever float's your boat but im trusting the builder's of the carb.

[PEZi]

so that guy works for weber?

i think they need to come up with a real number somewhere cause one of their online tutorials says 3.5psi MAX....

but yeah the guy i know has been tuning webers for a long a** time on lots of different race cars... and the results are very good

[PEZi]

here's one of his projects... its got dual side draft webers running 2.5 psi with a 3 psi max.... its not slow

http://www.photostockplus.com/...nt=45

[damn]

Havce you got your carb yet? Im wondering how the 38 work's might get me one if its a good carb!

[Nissan_Boy85]

About the fuel preesure...I call complete and udder BS. I've been running around 5 to 5.5 pounds of pressure for about 8 months. I say let it flow

[seang]

About the fuel preesure...I call complete and udder BS. I've been running around 5 to 5.5 pounds of pressure for about 8 months. I say let it flow

Could that possibly cause it to run rich?

[PEZi]

Havce you got your carb yet? Im wondering how the 38 work's might get me one if its a good carb!

yep... sure did! not gonna put it on till i get all my new lines and a regulator and a gauge ready to go with it tho

About the fuel preesure...I call complete and udder BS. I've been running around 5 to 5.5 pounds of pressure for about 8 months. I say let it flow

you said you were having some running rich issues tho right? that could be the problem... just to be safe check your oil and make sure there's no fuel smell to it

with that said... psi and flow rate are not the same obviously... as long as the pump keeps flowing low psi numbers aren't something to worry about

[PEZi]

i totally forgot phleb posted this... nothing to do with fuel pressure necessarily... but a great guide for the tuning process itself

zerothread/376140

[damn]

About the fuel preesure...I call complete and udder BS. I've been running around 5 to 5.5 pounds of pressure for about 8 months. I say let it flow

That's 2psi over what the carburetor needs in order to function properly. 1/2 psi below or above 3.5psi isnt going to make a difference..But when you start going 1psi and over on a carburetor that has such low volume requirements your going to run into problem's!

Think about it 5.5psi is about 58% more fuel pressure than what the carburetor needs to function properly! Hell 4.5 psi is what 28% more and that is just 1psi difference!

You guy's have to keep this in mind before you decide to run even 1psi more or less than the 3.5psi requirements! Do you want your engine running around with 28% or 58% less fuel? Or more 28% or 58% more fuel??

Keep your fuel pressure between 3.5-4psi better to have it running rich than lean. Worst case is your running with 14% more fuel which is what a 1/2 psi more fuel would be.

[Nissan_Boy85]

I have to run the preesure that high due to the fact that I don't have the right size jets and so I can run over 45 MPH. Soon as the rebuild is completed it's getting a look over and tuned again.

[flinterman2000]

4 psi is pretty ideal. I used a Mitsuba electric pump (which is the standard pump for the L28 engine) on my 84 Galant super saloon running a 32/36 DGV on a Z20 with no problems, minimal tuning was necessary. Phleb is right. Make sure there is no vacuum leaks before tuning.

[flinterman2000]

To help with your problems hard left cornering, use this circled in red

[PEZi]

To help with your problems hard left cornering, use this circled in red

i messed with that a bit a while back... didn't do anything i removed it and it helped a lot but its still not gone

i got to thinking about it a bit... and finally realized what was happening and i'm hoping for sure the new carb fixes it... with the hitachi... the fuel in the bowl was being dumped into the manifold under left cornering... basically it just empties the bowl into the mix and sputters out... then once it all clears again it runs properly

the weber should do the trick as i've never heard of anyone having this problem with one