1974 318 in motorhome.new plugs,wires,distributor,rebuilt 2bbl carb,replaced fuel filters,voltage reg.when i put into gear and apply gas it misses like crazy.idles rough.tried spraying carb cleaner around intake manifold all that did was give the engine a good bath.gonna check pvc and brake booster vaccum tomorrow.what am i missing???????

 

Check your wires u cld have 2crossed, mopar has two wires that if crossed it will run but have those symptoms.
also dbl ckeck your carb Air bleeds all you need is a small piece of gasket or dirt I even found a smoll hair once in a new carb, start with these.... others will chime in

 

Removing those or any tubes and plugging then start and idle will give you that answer.

Adjust idle mixture screws? Does pump shooter squirt gas when throttle moved?

 

I would bet this is a problem with one or two cylinders. Did it do this BEFORE you replaced all this stuff?

If so, check for a spark plug that you somehow either did not get gapped, was dropped, or even cracked. Suspect crossed plug wires. Might be a bad plug wire

Maybe you got the cap on "crooked" and the rotor hit and damaged.

Check the firing order

Check under the cap. Pull and examine the rotor carefully, and the inside of the cap. Make certain it fits tight and correctly.

Check all 8 plugs visually

If no improvement, devise a simple "cylinder balance test." Get a grounded probe, IE screwdriver and clip lead grounded to block. Pull the dist. boots up to loosen the wires.

Pull one wire out at a time and GROUND the cap tower to prevent spark crossfire. The engine should "sound" the same with each cylinder and a tach should drop the same RPM.

CHECK CAREFULLY for cylinders 5 and 7 reversed

 

It could just be poor timing/bad chain, make sure that's checked

 

maybe misses aint the right word.more like surging.when i start giving it i little gas kinda feels like its loading up or surging.all plugs good and gaped.wires in correct place.no vaccum leaks. rotor new,cap new.electronic ign. new.brake booster vaccum good.my dad passed away and just started workin on it so i dont know how long it was running bad.maybe something internal i dont know.thank you guys for your replys.im bout ready to wave the white flag....LOL!!!!!

 

what and where are the air bleeds? pumping gas in ok when i pump gas peddle.

 

Air bleeds (not knowing what carb) in general when looking down the throat, are usually on top of, or near the pump shooter. Two very small (guitar wire size) holes, they allow air to enter and mix (emulsify) with the liquid gas just before it is sucked up the tube to the venturi. If plugged more gas than what is needed will enter the venturi causing a rich condition.

Usually on a rough idle breakaway surge condition imbalanced idle screws would be the suggested first thing to check then idle mixture.

Do you know if both screws are turned out about the same number of turns? If you turn them both in together until seated does the engine stop?

 

Mopar single fire V8 dist cap wiring
My dad made this saying about small and big block dist cap wireing. To reduce wiring confuseion. “the small block has the dist in the wrong place, in the back of the engine. BUT the shaft rotates the right way clockwise. The big block has the dist in the right place, in the front of the engine BUT the shaft rotates the wrong direction counterclockwise. Both wire #5 and #7 on both ALL ways have #5 before #7 on the cap AND block. And most / some stock V8s have the firing order cast in to the intake manifold. And more info: if the cap has a vent hole next to the center tower. Plug it with JB-weld.

 

I was taught the hole was there to vent ozone from the Hell storm of sparks going on inside the cap. Why plug it? Is it a water thing?

 

this is a holley 2 bbl carb.air fuel mixture screws are turned out 2 full turns.i put wire down air bleeds no difference.its got good gas.filters are clean.....thank you guys very much for responding i could sure use the help.I JUST DONT GET THIS THING!!!!!!.....should be pretty easy.....i dunno i just dunno!!!!!

 

there is some kind of a cap on intake manifold right next to carb on drivers side. what is that?

 

That is a vacume port if..its on top of the intake runner i usualy plugit as its a area that can cause a odd flo to that no. 7cylinder. Double check it make sure its seald
a wire down the air bleeds does not always clear the debree ...if its a small piece try compresed air to blow the piece back into the float bowl
the carb was rebuilt by you or did u purchas a remanufactuerd carb ?

 

Does it have EGR? Check each manifold vacuum carefully. EGR valve might be stuck open

Did it run this way BEFORE you started working on it? This is not clear.................

 

You can check the timing chain for slack by turning the crank back and forth with a wrench or by hand and the belt (fan if no clutch).

One way you'll come against valve train resistance, then other way until you feel the same. That amount of movement will be the slack in the chain, and if it's 15 degrees or more no tuning will make it run properly.