NEED HELP with Gas Motor! AHHHHHH...

[timbuk]

put the moter from the burb in the bus! Sounds like a sticking float or a needle valve problem if you go to a 4 bbl let us know how you like it compared to a 2 bbl i got a 2 bbl on my 65 and often wonder.....

[timbuk]

yes downsouth i have also heard this about the 4 bbl myth on a bus lets see if the experience gets wind of this and replies im sure you will burn it if the secondaries are in all the time,they do in my cars!

[paul iossi]

put a fuel pressure guage on it and find out exactly what is going on with the fuel pressure, to high or to low?
if it looses pressure, is it sucking air from pinholes in the rubber fuel lines that connect the steel lines at the tank and engine?

double check all of your electrical connections, grounds at the body and frame as well as at the engine,
1) your comment about the factory ignition system not working suggests opens or high resistance in the primary wiring
2) MSD is great stuff when it's working, how ever the factory electronic ignition should be more than up to the challenges of a stock engine, after 2 MSD box failures my jeep is running stock GM HEI, all the NASCAR cars run 2 MSD systems, primary and backup, you have to ask youyself why, hint it's great when it's working.

back to the fuel system, before you replace the carb, your engine can only pump so much air and efficiently use so much fuel, make sure to size the replacement carb to the engine size.

think industrial powerplant not racecar.

good luck

[paul iossi]

carburator stuff;
to start with your "industrial engine" is designed to maximize torque at reletively low rpm, probably 4000 rpm max, not to be confused with a high speed performance engine turning 5000rpm +

think of your engine as an air pump, if it is 100% efficient, it can only pump 360 cu in of air per revolution, in reality an industrial engine that is optimized for torque is probably only 75% volumetrically efficient.
1 cu ft = 12x12x12=1728 cu in
engine displacement x rpm /1728 = cfm = volume of air that the engine can pump at 100% efficiency
360 x 4000 =1440000 / 1728 = 833.3 cfm of air that your engine can move at 100% efficiency, in reality you only need a 750 cfm carb to feed your engine.

all carbs are a combination of several systems, cold start (choke),idle, low speed, mid range, high speed and enrichment(accelerator pump), a 2bbl carb has and uses all of these systems, a 4 bbl carb has and uses all of the systems on 2 bbls plus 2bbls that are high speed and an enrichment circuit that are used at wide open throttle, ie, the last 10 % of throttle.

you need to be aware that if/when you start changing the intake and carb to increase performance you will also need to change the camshaft and exhaust to maximize the intake changes, in doing so the low end performance/driveability will be compromized.

my vote would be to keep it stock and enjoy the trip as well as the destination. if you really want more power keep your eyes open for an old motorhome with a big blogk 413 0r 440 ci engine with a 727 torqueflite automatic trans to put in your bus.

hope this info helps

[Joe Monstermaker]

Have you tried running without tightening the gas cap, like Smitty suggested? A plugged fuel tank vent can cause exactly what you're experiencing.
So can vapor lock. You said the motor has been redone... has the fuel line been moved at all? Does it run anywhere near a heat source?
If you can positively eliminate those issues, then I'd start looking at a carb rebuild or replacement.

[sportyrick]

Climbing a hill and/or turning it off after a drive and having to wait to get it to start sounds like vapor lock or a heat soaked coil or condenser. Climbing a hill creates a lot of heat and can soak the engine compartment and boil the gas or break down electrical thingies resistance. Now my bus was getting vapor lock in 20 degree weather so it can happen at any temperature. Did the fuel line get changed in any way, moved closer to an exhaust manifold? Put some hose over it, just spiral split it and slide it on and see if that makes a difference. Most of the time on later model stuff there is a sock on the fuel pickup in the tank whether it has an in tank pump or not, I have had them covered with fine silt and you couldn't see till the gas dried out and then it became visible, that mesh is so fine it won't pass water so it only takes some dust to stop it up. When you pull a vacuum on any liquid it lowers the boiling point, hence vapor lock or in other words your fuel boils and you get no liquid but just gas. If you are pulling fuel up to the engine and you have a restriction in your fuel line you will lower the boiling point. Remember your blood will boil in outer space because of the lower boiling point in a vaccum. Another thing that doesn't like heat is a condenser, do you have points and a condenser? You should look for a change, you changed something and it's probably right in front of your nose. I doubt it's the carburetor, they either work or don't, 80% of carburetor problems are ignition. A puff of black smoke tells me your ignition momentarily stopped working, your carburetor didn't take a quick nap. Maybe you changed some wiring around? Your new fuel pump is faulty and isn't up to snuff? Pinched a fuel line when installing the engine? Fuel line is grounding the engine and is under an electrical load? I had and old Ford tractor and it would run fine for a while but then it would quit for no reason and wouldn't start at all, bad coil. Heat, heat heat, what's changing because of the heat? sportyrick

[the_experience03]

I kind of like sportyrick's theory. Where are your fuel lines running? With a mechanical pump putting vacuum on the line from the tank the fuel is MORE likely to boil. Vaporous fuel is pretty tough to pump and meter correctly.

As far as ignition goes, a heat soaked module will usually cause it to just cut out completely, no to lose power. A dying, heatsoaked coil, on the other hand, will cause the symptoms you are describing. The factory coil is designed to run through a ballast resistor. For cranking it's fine to put a full 12 volts to it to get a hotter spark, but when you wired in the MSD stuff I think there's a good chance you left it getting 12 volts all the time. Old canister coils will quickly die if you do that because they overheat. Swapping to a newer style e-core coil or maybe one of MSD's high performance coils could help a lot.