351 cleveland running rich

[Corey 12]

Hey guys, having a bit of a problem with my 351, I think its running rich, I'm having a bit of trouble starting it, it's idling really bad and has a really strong smell of fuel, I pulled the aircleaner off today and everythings covered in fuel under there, I'm thinking it's the powervalve, any other suggestions or am I completely off course here?

 

Cheers, Corey.

[gerg 10,871]

Power valve only opens an extra jet under load. It will not cause fuel to spill out of the boosters at idle. If there's fuel dripping out of your boosters or float bowl vents, you have a float issue or stuck needle. Foam plastic type floats can become saturated with fuel over time, and brass ones can spring a leak or collapse. Either one will cause the bowl to flood and piss fuel out of the boosters or float bowl vent.

[Corey 12]

Cheers mate, i replaced the power valve anyway because i had one there the same size, it seemed to fix it for a minute or two then went shit again, I guess that would say its a needle or float problem as you said, right? Is there any way I can test these or do I just replace them and see how it goes??

Cheers.

[gerg 10,871]

You didn't mention if they were the black foam ones, the cream coloured hollow plastic ones or brass. I'd fill a small container with petrol and pop one in there. If it floats say above the seam along the side of the float then it's ok. If it sits lower then I'd replace it. There are specs available for the required weight of one. Too heavy = chuck it. Brass is easiest to test. Just shake it and listen/feel for fluid sloshing inside. If yes, it's buggered. You can solder up any holes but at 20 bucks each, just get new ones. If the needle/seat is the unscrewable type, pull it out and have a look at the rubber face on the needle. Blow it through to make sure there are no bits of crap in there. If it's the other non-adjustable type, you will have to pull it apart too but adjusting is done with the bowl off, and with it turned upside down, the float should sit level with the top of the bowl. Bend the float tab with a small flat screwy to adjust.

[Corey 12]

So it caught fire today, luckily my work truck was parked next to it and theres a fire extinguisher behind the cab, i only put it there last week and after today I went and bought one for the effy, i replaced the floats and it was still running shit, i was watching it run and all of a sudden it started pissing fuel out of the rail between the bowls, then the car decided to backfire and the whole lot caught, so after i cleaned the stain in my pants i found the o ring had split, probably my fault pinching it after putting the bowl back on, anyway luck was on my side and nothing was damaged, but the car is still running like shit, so ive replaced the power valve, the floats and checked the needles, i cant work out why its doing this i changed nothing it just started running like shit, whoever fixes this gets a bunch of roses sent their door, seriously.

[Butcha 111]

What sort of carby is it mate?

[Corey 12]

Holley dp, previous owner told me its a 700

[Butcha 111]

Check your timing retarded timing can makes fumes stink and car hard to start. Check ignition leads and coil are in good nick and the coil is recieving full 12v. Chuck on some new spark plugs. Check you have no vacume leaks and all the hoses are good. Disconnect bake booster hose an block it off see if it makes a difference.

[Butcha 111]

Actually just re-read your first comment you said that everything is covered in fuel under the air cleaner..few things come to mind either fuel is coming out the vent tube, car is backfiring up the carby which is timing related or you have major reversion caused by leaking valves or a valve that has started to push through the collets can normally feel it if you put your hand over the carby while giving it a rev or can see the mist come back up. Also look down the throats at idle and make sure the boosters are not dripping (float or needle and seat).

[gerg 10,871]

Blocked air bleeds will make it suck raw fuel instead of emulsion. Even a high float level will cause fuel to drip out. Without it in front of us, it's really hard to pick what the problem is.

[Corey 12]

K so now i have no idea what its doing, this morning it ran out of fuel in the front tank, no worries so i flicked over to rear, and what do you know it starts running normal again, my first thought was that i got a bad tank of fuel, but correct me if im wrong, bad fuel wouldnt make it run as rich as it was am i right? Anyway i filled the front tank up again, still running sweet, drove to my girlfriends house (about 50kms) I get around the corner from her house and it starts running shit again, would i be right in thinking there is something wrong with the front tank thats upsetting it? Im going to fill the rear tank tomorrow and run it on that for a while and see how it goes....thanks for all your replies i wouldnt know where to start without your suggestions, cheers

[gerg 10,871]

Does each tank have its own pump or just a changeover valve? Could the suspect tank have breather problems, becoming pressurised and over-fuelling the carby?

[Corey 12]

Im fairly sure its just a changeover valve mate, but I'll have a look this arvo and double check, I dont think its a breather problem i pulled both caps off and neither of them sucked air when i took them off

[bear351c 10,273]

Could spray a little Ether (Aerostart) around the carb and intake manifold, if engine revs rise....got a vacuum leak.

Check leads, timing, fuel pump as suggested.

 

(Not going to say anything about the brand of carby)

[Corey 12]

Yeah i gave the aerostart a go and no luck there. I didnt get a chance to check the pump or anything today, but im gonna have a second look at the plugs and leads again tomorrow, i might post a picture of one of the plugs, maybe one of you guys will see something i dont

[bear351c 10,273]

Running LPG at all ?

[Corey 12]

No mate it used to but its all petrol now

[Corey 12]

K so i just pulled the plugs and they are all a really powdery black, correct me if im wrong but this only confirms its running rich right?, another thing i noticed straight after turning the car off i looked down the throat of the carby and i can see fuel dripping, i dont know how to explain where its dripping from as i dont know much about these, so heres a picture:

Cheers, corey

[Corey 12]

Another update, i just had a mate who happens to be a mechanic come round and have a look, he set the needles for me and he reckons the back float wasnt doing its job, so we pulled the bowl off, gave the metal tab an adjustment, he set the needle low and gave it kick and it fired up and ran pretty well, still not perfect but a definite improvement, unfortunately he had to leave so i took it for a drive and found that under full throttle its backfiring a bit, what do you guys think?

[bear351c 10,273]

Still could be a fuel starvation problem, (pump, blocked filter etc), but you said you hadn't checked the timing.  As a general rule, when replacing a carby, I turn it upside down and set the float levels so that the floats are parallel to the ground. Idle screws out 2 turns, usually gets me started.

 

Backfiring could be a few things, ignition leads cross firing, cracked dizzy cap, ignition timing out, ........

[gerg 10,871]

They're your secondary boosters. That's where you fuel comes out under load. At idle and part throttle they shouldn't have anything coming out. Sounds like your mechanic mate was on the right track, dripping from boosters means that float is too high or the needle's not seating. Now that that's stopped, it seems like he's gone too far the other way and wound it down to the point where the secondary boosters are starving for fuel. If your floats are externally adjustable, wind the nut a quarter of a turn anticlockwise each time to raise the level a tad. You should check your bowl sight plugs to see if there is fuel touching the bottom of the hole, as this is the factory starting point for adjusting your levels.

 

Being a double pumper, you can somewhat isolate the primary from the secondary stumble by feeling the "step" in the throttle and how the engine behaves. If it goes ok before that step, your primary level is probably ok. See if it makes a difference when driving. Remember too that your secondaries supply a small percentage of idle fuel so if the jets are starving, your idle will be lean and lumpy.

 

Raise your secondary level and see what happens.

[Corey 12]

Thanks for all your help everyone thought I would update you all with how it went, it turned out to be the needle in the rear bowl, there is a seal about halfway down the needle that wasnt sealing properly, new needle and it runs like a dream again, cleaned it up and took it to my mates house for a bbq, went for a drive with my mate to the pub and busted an accelerator cable ! Some 60lb fishing line got us back it was an interesting trip though!

[gerg 10,871]

Thanks for all your help everyone thought I would update you all with how it went, it turned out to be the needle in the rear bowl, there is a seal about halfway down the needle that wasnt sealing properly, new needle and it runs like a dream again, cleaned it up and took it to my mates house for a bbq, went for a drive with my mate to the pub and busted an accelerator cable ! Some 60lb fishing line got us back it was an interesting trip though!

 

Nice to see you had a win. Yeah if that o-ring leaks, you get fuel flowing around the needle housing (bypassing the needle) and filling the float bowl regardless of what the level is set at.