Fuel Consumption/Carb Prob...

[BiggusJimbus]

Everything was running great until the last day of my last trip.
I've got a 750cfm Holley 4010 carb on my 455 Olds that has worked perfectly to date.
However, My fuel consumption suddenly skyrocketed. I mean to like 30 gph. I've pulled the cover off the carb and checked the floats, no prob. The needles seem to be sealing correctly. I am pretty sure that the gas is just dumping into the motor, as the runners in the intake manifold were literally wet with gas.
Any ideas as to what is going on here?
I'm running the dreaded Holley Blue Pump at about 5.5 lbs of fuel pressure. According to Holley, the needles should be good for up to 8 lbs.
Help please, as I am going to try and get some use out of the boat this weekend, and can't afford a gas bill like that.
Thanks in advance for any help.
Jimbus.

[Hotcrusader76]

Sounds like you're due for a seasonal tune-up...No?
How long ago since the carb was rebuilt? Looks like you should check into some new plugs, wires, cap/rotor, etc, etc..ya know..tune-up type stuff.
As far as the excessive fuel consumption, it sounds like a multitude of problems...tune-up, leaking carb, fouled plugs...
Hope this helps you out.
~Ty

[BiggusJimbus]

Picked up new plugs.
Opened up the carb. It's clean. No muck. flipped the cover over and blew in the fuel inlets. The valves are sealing properly.
Nothing looks particularly dirty or varnished.
It's not running bad. But the gas is going somewhere. If it's not better tomorrow, I guess I'm going to have to dig deeper into the carb.
Plugs didn't appear to be fowled, much to my surprise. I know I was running a little rich. I am running some pretty hot plugs.
Anyway. I guess I've got to do more investigation.
[ September 04, 2003, 09:54 PM: Message edited by: BiggusJimbus ]

[Snowboat]

Has the oil level in your pan risen?
[ September 04, 2003, 09:08 PM: Message edited by: Snowboat ]

[BiggusJimbus]

Nope. Hmm. That's something I ought to check out.
I doubt that was the problem. It was happening while I was running. I could literally see the fuel gauge needle move.
I think I checked the oil and it was clean, but I'll double check that.

[BiggusJimbus]

Good thought,
But the oil is the correct level, color and smell. No gas or water there.
That's a good thing.
I'm pretty sure it is dumping right down the carb. I guess I'll have to take a closer look at it while it is running.
It's a dead simple carb design. I'll go over the setup carefully tomorrow.
Hmmm. This is perplexing. The carb only has about 40 running hours on it, for that matter, everything in the boat does. As I said, it was running very nicely up until it started chowing down gas.
I was hoping somebody would be able to say your problem is X, but I know these carbs were never very popular. I've had a couple over the years that have, up until now, worked perfectly.

[Rexone]

Most common carb leakage problems:
Leaking needle valve due to dirt or damage OR excessive fuel pressure.
Sunken float due to saturation or leakage.
Bad Power valve (common)
There are others but I'd check these out first. If it still seems to be running good it's probably not ignition. Is the transom black?
Good luck :)

[BiggusJimbus]

Rexone:
Most common carb leakage problems:
Leaking needle valve due to dirt or damage OR excessive fuel pressure.
Sunken float due to saturation or leakage.
Bad Power valve (common)
There are others but I'd check these out first. If it still seems to be running good it's probably not ignition. Is the transom black?
Good luck :) Needle valves seem to be functioning correctly, but I'll get some replacements anyway. Cheap insurance.
Probably pick up a couple power valves as well, although this model carb doesn't have the blowout problems of the earlier holley's
Floats are good, I tested them.
I'm pretty sure there are no ignition problems, as I said, it still runs pretty well. The transom does get a little black. I know I've been on the rich side, at least on the idle circuit.
I think that I am most suspicious of the power valve, so that may be my first order of business.
Thanks for the suggestions.
Jim.

[LeE ss13]

Another cause for excess fuel consumption with a Holley carburetor is that the main body gets warped where the metering block mounts. It exposes the power valve vacuum chamber to fuel passages. It's easy to check. Just remove the bowls and metering blocks and lay a small straight edge or even a business card across the main body. If it is warped, it will need to filed or machined flat again. When fuel is being leaked through the vacuum passages that feed the power valve, it goes unseen. Meaning, you won't see it spilling out the booster venturis when the engine is running. It is coming out the bottom of the carb where the vacuum passage is. Just a thought.

[Hotcrusader76]

Good point LeE ss13....
But this is a 4010 carb, very different than the 4150 style you described. Nonetheless great info.
~Ty

[FastRat1]

i'm surprized ur plugs werent fouled...why the hot plugs??...r u burning oil??...i see no reason to run them...put the stock plugs bk in there..or maybe 1 range colder...they work fine in my BBC...just trying to be helpful...but i would diffently look at the carb real close..as ev1 above has stated
Ron

[LeE ss13]

Hotcrusader76:
Good point LeE ss13....
But this is a 4010 carb, very different than the 4150 style you described. Nonetheless great info.
~Ty I've got to start reading more carefully. OK, how about, pull both Power Valve covers off. They must both be dry and flat. If they are wet, the power valve is leaking. If they are dry and they are not flat, they will leak vacuum and the power valves will run full rich all the time. Just another thought.

[BiggusJimbus]

I'm running slightly hotter, and slightly more gap than stock plugs. As, I have much better than stock ignition. The plugs I picked up are one step cooler. But I'll be running a .045 gap. I have the Mallory MBI and Promaster coil. Really, it has worked splendidly.
I'll pick up some new power valves and needle valves and get those in there. Thanks for the info on what to look for with the PV.
The carb doesn't have so many hours on it, but It's still been sitting for about 8 years, and I could easily imagine the rubber failing in itl.
Thanks for the help, folks. I'll let you know how it goes.
I'll be at the Shasta Cat Attack starting this afternoon, so I suspect there will be plenty of rides available if I can't get sorted.
Gotta get out of this cold weather. Should be a beautiful weekend.

[kojac]

Biggus Jimbus
But I'll be running a .045 gap. I have the Mallory MBI and Promaster coil. Really, it has worked splendidly
Are the power valves the right #rating for the vacauum you are pulling? If for instance they are rated 8.5 and you are pulling 6 to 7 inches of vacauum at cruising then the power valves would be open and using more gas. Check your vacauum while cruising and make sure it is in line with the power valve #. You want to make sure that they don"t open until you need them.
We dynoed a 468 chevy and tried gapping the plugs at .045 up from .035 and lost 11 horsepower???
using MSD coil,6AL box and MSD plugwires.
Went back to .035 and got it back.
You probably won't see the ll horsepower difference on the boat.
I'd love to hear about other experiences.
Kojac

[kojac]

kojac:
Biggus Jimbus
"But I'll be running a .045 gap. I have the Mallory MBI and Promaster coil. Really, it has worked splendidly"
Are the power valves the right #rating for the vacauum you are pulling? If for instance they are rated 8.5 and you are pulling 6 to 7 inches of vacauum at cruising then the power valves would be open and using more gas. Check your vacauum while cruising and make sure it is in line with the power valve #. You want to make sure that they don"t open until you need them.
We dynoed a 468 chevy and tried gapping the plugs at .045 up from .035 and lost 11 horsepower???
using MSD coil,6AL box and MSD plugwires.
Went back to .035 and got it back.
You probably won't see the ll horsepower difference on the boat.
I'd love to hear about other experiences.
Kojac

[FastRat1]

my 2 cents...i use the AC projected core-nose plugs in my 427 BBC with a magneto ign...1 step colder than stock...gapped as they r from the box...n/p at all...they work great for me...no load-up or mis-fire
Ron

[Rexone]

BiggusJimbus:
The carb doesn't have so many hours on it, but It's still been sitting for about 8 years, and I could easily imagine the rubber failing in it.The 8 year deal is likely your problem. Rubber and gaskets as well do not like sitting around 8 years. Likely you just need some fresh parts. :)

[H2OT PURSUIT]

Just a thought, but maybe you could borrow another carb and try it out just to verify that it is a carb problem. I got the impression that it was fine one day and terrible the next. If it were a tune up issue wouldn't it have come on slowly?

[BiggusJimbus]

Well,
Turns out I had a couple of small problems, but ultimately, I think I had something blocking the needle that cleared out before I got to it.
My choke wasn't operating correctly, which will lead me to ditch it, as I don't really need it with the boat. The other is a small vacuum leak that strangely enough, I couldn't hear.
Anyway, I'll be doing a rebuild and cleaning/replacing anything even mildly marginal and will quit worrying about it. It ended up working fine after some fooling around on Sat. morn. Part of it was I really needed somebody to sit and watch it while underway, and I got the correct person in that spot.
Thanks for the help everybody.
Now back to the regularly scheduled prop vs. jet or Corrected vs. uncorrected arguments. ;-}