I just fired up my new 440 and it ran like crap. When I first fired it up I had fuel coming out both carb vents . I adjusted the floats what felt like all the way down ( turned nut clockwise ) before it stopped pumping fuel out of the vents ( Mechanical pump ).I haven't had a chance to pull the float level plugs to check the level with the motor running yet. The motor runs really rough like it has a couple dead cylinders but the exhaust temps ( taken at the header flanges ) are fairly consistent about 325 - 400 F. It idles just OK but when I rev it it has that dead cylinder shake to it. It did pop through the carb when I first tried to start it the dist was 180 out. I screwed the mixture screws all the way in and the motor died so I think the power valve is ok. The carb is a Holley 4780-5. The motor is new and everything on it is new or rebuilt. Is this a carb problem or could it be something else?

Motor info:
452 peanut plug heads
9.7:1 compression
Hughes whiplash muscle car cam
Performer rpm intake
MSD-6 AL
Stock dist
Blaster coil
Holley 4780-5 Carb. This carb was rebuilt by a meathead that put the metering blocks on backwards

im not happy with my holley carb to..keep on it, im sure all it needs is tuned up and adjusted properly.

I just pulled a spark plug and it's black and wet.I only ran this motor for 20 minute break in and then maybe another 5 minutes after that. The plugs are Autolite 23's is that too cold for this motor ?

What kind of pressure is that pump putting out?

hi
what is your fuel preasure ?

you do not want over 7 psi max 1

what pump ?

what is timing set to?

idel speed start at 800.

vac with trans in d warm is ?

Holley 4780-5 Carb. This carb was rebuilt by a meathead that put the metering blocks on backwards


and did you take it apart and check thing out before firing up the engine....

the needle and seat probably had dirt in it...usually tapping on the housing will unclog it..or brake cleaner will work too...

I tried tapping on the bowls but they continued spraying the next time I started it. it's a stock mechanical pump my Holley inline gauge is reading 3-4 psi while the engine is running.

I did take it apart to switch the metering blocks around and everything looked OK but I didn't go over every part like maybe I should have.

I'd go thru the carb & just me I'd take off the intake & regoop the cam/lifters

The timing was at 34 - 35 at 2,000 rpm with the vacuum advance disconnected and plugged during break in. After break in I set it at 10 with the vacuum line disconnected to try and figure out what was going on.

No you're good there Bro.

What should I look for in the carb ? I've re-built a few Holley's but I'm not even close to being an expert on them so any guidance would be a great help.

You'd wanna correct his mistakes (the blue no stick gaskets are good) then invert each bowl & set the float level w a drill bit(s) (forget the dimentions). On a real wild cam I'd rather use the drill bits for a first/last adjustment. EDIT alot of people overtighten jets and undertighten PV's, not crazy just a bit

Take the bowls off. Turn them upside down and adjust the needle and seat to where the floats are level. This will get you real close.

What are the primary jets? Aset of 70/72s would be a good starting point. What is the power valve. Take a vac reading, divide that number by 2. Thats the power valve you need.

It's going to run poorly until you get the timing dialed in. Been there, done that. Trust me. I can't see that whiplash cam liking only 10* of initial timing. I ran more initial than that with a stock cam.

Try bumping your initial up to like 16 and go from there. Then play with the timing and see how much timing you can add before the engine starts to fight against the starter. This happens when the engine is hot and you crank the starter. You will be able to tell when you get to this point. Then back the distributor off a hair and lock it down. After that you will probably need to recurve your distributor to get the total timing to 36-38* all in somewhere around 2600-2800rpm.

Remember, timing affects fueling. Fueling does not affect timing. So obviously you get the timing setup correctly first. Half-assing it to do the cam break-in is fine, we all do it that way. But now is the time to get that setup correctly before you try additional carb tuning IMO.

340Shorty ... The power valve is a 6.5 primary jets are 71 secondary jets are 85

Daytona ... The fuel squirting out of the bowl vents has me going after the carb first after 30 minutes of run time the plugs were wet and black so I think the floats are screwed up. Adjusting the the float level externally had little to no affect so something must be wrong in there. I plan on pulling the bowls off this morning and checking the floats then I will fire it up and work on getting the timing right. I hope it will even run after fuel soaking the plugs.

Pull the needle/seat assemblies and clean the rubber seats. You might have some garbage in them that may not have allow them to close. Then re-adjust your floats.

Im assuming you double checked that you dont have a plug wire(s) crossed?

Yes I checked the plug wires to make sure I don't have any crossed and double checked and I will check again before I start it again.

First of all set the floats, upside down and level is indeed a good starting point.

Idle metering screws at 1 1/2 turns out.

Next, your rear jets are WAAY too big. Mid '70s would be more like it. Stock is 76, and most Holleys are set up pretty close out of the box.

then work on timing.

R.

Also keep in mind you said you have a stock distributor. Stock distributors have WAY too much timing built into them. That's why IMO when you set your total to where you want it, you won't have enough initial for it to want to run cleanly.

It's a double pumper and the rear jets are 9 sizes too big. The double pumper secondary opens with the throttle, not by engine demand. So at anything beyond a little above idle you are getting way too much gas.
Add to that the fact that your first run had the floats set waaaay too high and you can see where overfueling problems may crop up. Yuck's approach is good but I'd change it one way: Before you do anything else get a set of 76s in the secondary metering block! Also if your floats are plastic see if they will actually float in gasoline or if they are full of gasoline and sink. This could be half or more of your problem. If they are brass see if they slosh. Submerge the brass floats in hot water and watch for bubbles. The hot water will expand the air inside and if there's a leak there will be bubbles.

R.

In my reading on Holly carbs, on a vac carb the rear jetting can vary up to 10 sizes larger than the front if they are changeable.
this has worked very well in my apps

I dont run DP carbs but on them the secondary jetting is the same size as the primaries.

of coarse there may be curcumstances where this doesnt apply.

My floats are brass and they are dry nothing inside of them. I set the floats to level as suggested and will re-adjust them once the motor is running. I had it running and had no fuel leaking into the air horn so I think the floats are ok now most likely a little low. I'm in the process of changing the plugs so far I have 2 that were firing ( the 2 center plugs on the drivers side) but I still have 2 more plugs left to be changed. The secondary jets are 85 those are the Holley factory size jets.

I found 2 more plugs that were running for a total of 4 good ones and 4 bad ones the 2 centers on the drivers side and the 2 back ones on the passenger side . I'm getting ready to start it now. I will stay out of the secondaries until it's good and warm just in case those jets are too big.

OK, I dug deeper. The 4780 and 4780-1 had power valves in the secondary meteroing block and indeed had 76 jets in the secondary. Later 4780s, the 4780-2 and up, had no rear power valve and 85 jets in the secondaries.
So you should be good to go.
It's good to hear your floats are definitely OK.
R.

before you fire it crank the idle screw up. Then slowly back it off and see what happends. If you start to have gas pour out of the vents you have a float or fuel pressure problem. I'll go with float. Something is dirty or they are just too high. After you fix that you can re-set the timing. Too much rear jet, timing off and wrong PV aren't going to cause fuel to come out of the vents.

He said it appears the floats are set right now, no more fuel geysers.....
R.

Ok I just ran it again and it ran like crap again. I didn't have any fuel dumping out of the carb so that's a plus. But it wasn't running on all cylinders. From the exhaust temps it looks like the cylinders that didn't run before the new plugs are now running but the ones that did run before the new plugs are not running now. I'm getting spark to all of the wires. I checked them by putting my timing light pick up on each wire and pulling the trigger and all of the wires had a blink or a signal. The wires, cap, plugs and rotor are new so I don't understand what's going on here..

I checked the floats and they are perfect. I took the sight screws out and had no fuel coming out but when I shook the car side to side a little trickle of fuel would come out.

If you had enough fuel in it to make plugs fouled and wet, I'd be looking at the oil in the pan to make sure it's not diluted or you'll have more than carb problems!!

I smelled the oil yesterday after I saw the fuel soaked plugs and it didn't smell like gas at all and it looked clean too. Is this starting to sound like a cam problem ? should I start another thread ? or keep going on this one ?

It's better to stick with one most of the time. That way we can see what's been covered already.

Ok I will keep going with this one. I took the valve covers off and all of the intake push tubes are bent and some are completely off the rockers. One is broken I think and is laying down in the valley. What would cause this ?

what brand plugs are you running

I'm using Autolite #23 plugs.