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New diag info - 10 mpg & blowing raw fuel out my exhaust
https://slantsix.org/forum/viewtopic.php?t=47532		 Page 1 of 2
Author:  Fab64 [ Tue Jan 10, 2012 6:43 pm ]
Post subject:  New diag info - 10 mpg & blowing raw fuel out my exhaust
Hi all,

Some of you may recall that I bought an NOS Holley 2280 carb about a year ago (at the same time that Reed bought his). I installed it and the car seemed to run very well. I have no idea how long this carb was sitting on a shelf, but probably quite a long time. I've heard a few people on this board say that such a carb should be re-built before using. I did not do this.

Because of other work I've been doing (new rear end, front discs, etc.), the car was down for most of 2011. It's really only been back on the road since October, but I noticed I'm getting horrible gas mileage and seem to be blowing fuel out the tailpipe. Here are some pics of my driveway:

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Other than that, it seems to be running pretty well. The only time it has run badly is as I was going up a hill a few weeks ago. It started losing power, then completely died. I pulled over to the side, re-started it, and was able to get home. I haven't driven it since. Obviously, something is not right, but I'm not sure what it could be. Btw, my initial timing is 10 degrees advanced, with a max of 24 degrees mechanical. My vacuum is working correctly, and is providing about 11 more degrees. Is it possible that my accelerator pump is not adjusted correctly, and it's pushing too much fuel through? But wouldn't that also make it run poorly? I haven't checked the plugs yet, I'll do that this weekend. Is this something that could be caused by internal parts drying out over the last 30 years or so (while it was sitting)? Any and all suggestions appreciated. Thanks.

Roger
Author:  Joshie225 [ Tue Jan 10, 2012 6:55 pm ]
Post subject: 
That's just water and soot. If the car does run well otherwise I would start by checking the spark plugs and the float level.
Author:  ceej [ Tue Jan 10, 2012 6:59 pm ]
Post subject: 
You going to need to take it apart to find out. Get a kit for it. Holley brand if you can. They just work better.

Sitting makes me wonder. Mandatory ethanol where your at? If so, you probably have some cleaning to do.

The enrichment circuits are likely dumping fuel. could have something to do with the pump, but I'm thinking power valve is likely not operating correctly.

CJ
Author:  wjajr [ Tue Jan 10, 2012 7:18 pm ]
Post subject: 
10 Mpg is on the low side even for winter fuel blend. One item that will make engine run rich, and perform poorly at higher rpm is a sticking choke not pulling off fully. I suspect that where you live in a mostly warm climate the choke never is activated, except this time of year when temperatures drop into the fifties at night.

Forty years ago here in the Northeast we would see lazy choke often on used cars that came up from the south. Fuel injection has killed the choke problem, but drivers of old iron still can suffer this malady.

First start of the morning hand operate the linkage look for binding & sticking with air cleaner removed than perform a cleaning if needed.

Another cause of poor fuel mileage is as Josh said; incorrect float level and or sunken float.

Probably where your carburetor is NOS, never been refreshed, and the big one; sat all year filled with old gas (old gas is 60 days or older) it’s time to rebuild it.

When was the last time the valve lash was set?
Author:  Fab64 [ Tue Jan 10, 2012 8:01 pm ]
Post subject: 
Thanks, guys. Yes, it's usually pretty warm here, but the choke does come into play on cold starts. I'm pretty sure it's working correctly, but I'll double check to make sure it opens fully when warm.

I'm also not sure if Ethanol is used here. I'll have to look into that.

I'll check the float level this weekend, and pull the plugs.

Ceej, by "power valve" do you mean the accelerator pump? I'm pretty sure I'm getting a good shot of fuel, but I'll check again.

Valve lash was set when the engine was rebuilt three years ago. I doubt if I've even put 2,000 miles on it since then. I just realized I left out one important piece of information: the majority of miles since the rebuild was done with my old Carter carb. With that one, I was getting about 12-13 mpg. The only thing on the engine that changed was the new carb, so it would seem to be something to do with that.
Author:  ceej [ Tue Jan 10, 2012 8:43 pm ]
Post subject: 
The power valve is a vacuum dependent inrichment device. As vacuum increases, less fuel is allowed to flow through this particular circuit.

When your cruising along and stomp the go pedal, the vacuum holding the power valve shut goes shallow (Becomes a lower vacuum) and the spring associated with the valve overcomes it. This moves the valve to an open condition, flowing fuel into the associated port, booster or slot.

In a nutshell.

Most likely, your area is blessed with the curse of ethanol laced gasoline, lowering power, decreasing economy, and when left alone, drawing water into the fuel system. Ethanol has an affinity for water. Left for prolonged periods to gestate in your shiney new carburetor, water and ethanol mix with other crud and various compounds, like o'rings, gasket material, and aluminum.

When you open the carb up, be on the lookout for white powdery stuff and other guck in the bottom of the bowl.

CJ
Author:  SlantSixDan [ Tue Jan 10, 2012 10:10 pm ]
Post subject: 
All California gasoline is oxygenated, i.e., contains ethanol (pretty sure the other oxygenates, all ethers, are no longer used because of groundwater contamination issues with them). I don't see evidence of grossly rich running; soot spots like that are not abnormal on a carbureted car with no catalyst. If you haven't got actual black smoke out the tailpipe and the spark plugs aren't black, you're not running grossly rich. But 10mpg is way too low; I do suspect something's the matter, possibly with the economizer (power) valve, though the stall-out suggests a flooding problem possibly due to a sticking inlet needle and seat. Check if you like, but a Holley carb kit probably isn't available for this non-performance/non-aftermarket carb. I like the inlet needle and seat design Daytona Parts Company includes in their kits, www.daytonaparts.com . Oh, you will want to weigh the float; they're nitrophyll on these carbs and while I don't know for sure, I suspect some varieties of nitrophyll might not be fully compatible with current-day reformulated gasoline, so your float might be heavy. If so, replacing it should fix it fine. I don't know if there's a brass float available as there is for the 1945; I'm many miles away from my cattledogs.
Author:  Dart270 [ Wed Jan 11, 2012 6:32 am ]
Post subject: 
I would adjust the valve lash again, as it can tighten up on the first 1-2000 miles of driving. If you make only very short hops in your trips (<2-3 miles), then 10 MPG could be fine. I agree that checking the choke would be a good idea too. That is not much soot, in my book, if it is on initial startup in your garage.

Lou
Author:  Fab64 [ Wed Jan 11, 2012 8:44 am ]
Post subject: 
Thanks for all the replies, gentlemen. Hopefully, I will have more info to share this weekend.

One more thing: when I first got the car, it had a 1 bbl carb, which also spit stuff out the tailpipe. When I rebuilt the engine, I converted it to a Super Six. Before buying the current Holley 2280, I tried two different Carter 2 bbls, and neither one of them spit anything out.
Author:  Reed [ Wed Jan 11, 2012 10:03 am ]
Post subject: 
Have you verified that the choke adapter you made is still positioned correctly?
Author:  Fab64 [ Wed Jan 11, 2012 4:01 pm ]
Post subject: 
Quote:
Check if you like, but a Holley carb kit probably isn't available for this non-performance/non-aftermarket carb.
I found a carb kit in Walker's catalog - part 15702B, and it's available from Amazon (I haven't looked elsewhere yet).
Quote:
Have you verified that the choke adapter you made is still positioned correctly?
I think it's still good, but I will double check.
Author:  SlantSixDan [ Wed Jan 11, 2012 5:45 pm ]
Post subject: 
15702B is a Walker number.
Author:  wjajr [ Wed Jan 11, 2012 5:46 pm ]
Post subject: 
The amount of stuff spitting out the exhaust depends solely on humidity, and ambient temperature. Cool damp days will cause more condensation in exhaust pipe, and will take longer to heat that pipe enough above due point to remove vapor to atmosphere.

I see this puddle all the time under my carbureted cars, because the choke is a rather crude enrichment device compared to fuel injection, and we have a lot of cool damp weather.

Also if you make short trips, never getting exhaust system nice and hot, there will be a lot of moisture built up in the muffler, and its low spots. Once the exhaust system is loaded up it takes a while to boil all that water out. The black stuff is just carbon build up from running a little rich, the water picks it up and washes it out onto the ground.

Take that car out on the highway for a nice hour or longer ride at 60 mph, and get the moisture out of crank case, and exhaust system. Also there should be a 1/8â€￾ drain hole in the muffler’s low spot to help evacuate condensate.
Author:  Fab64 [ Wed Jan 11, 2012 6:48 pm ]
Post subject: 
Quote:
15702B is a Walker number.
Yes. I found this after I remembered you said Walker made jets for Holley carbs. Are you saying that Walker kits are no good?
Author:  Fab64 [ Mon Jan 16, 2012 4:18 pm ]
Post subject: 
Ok, I finally got a chance today to check my choke operation and look at my spark plugs.

First of all, here's a picture of my tailpipe (looks like it's running pretty rich):

Image

The choke seems to be operating correctly. I didn't lubricate or adjust anything before taking these photos. Here is a picture of it when the engine is cold, tapped the throttle, and it's closed:

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After the engine is warmed up, it's open all the way:

Image

I was really surprised by my spark plugs. I was expecting to see dark soot, but they actually look pretty good. Btw, plugs are Champion RN14YC (likely installed by my mechanic when the engine was rebuilt). Oh, I also noticed that spark plug washers are installed, contrary to Dan's recent advice stating that they should be left off. Anyway, here's #1 (probably the worst one):

Image

#1 - another angle (btw, should threads be wet like this?):

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#2:

Image

#3:

Image

#4:

Image

#5:

Image

#6:

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I don't have a new kit yet, so I did not want to open the carb up. I still plan to:

- see what gunk might be inside & clean everything
- pay particular attention to power valve assemblies
- check float level
- make sure float is not heavy or saturated with fuel
- replace needle and seat with Daytona parts, as Dan suggested
- check/adjust valve lash

Based on the condition of my plugs, I'd say I'm not running rich at all. So, where the heck is all my fuel going? Could my engine actually be burning that much fuel, and have such clean plugs? Is that a testament to how well my ignition system is working (strong spark)? I'm still running a Pertronix Ignitor-II ignition with their Flame Thrower coil, and have not yet converted to HEI.

Thanks for any additional input. I'll try to get a carb kit and needle and seat this week, and let you know what happens next.

Roger
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