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1976 Ford 302 carburator problems (was lower re-build)

N

Neal Franson

Regular Contributor
My lower rebuild went well, and I installed it back on my boat and looks like it is functioning, but the engine is running terribly - it won't idle. I can just get it down to about 2000 rpm and it start to miss and it dies at about 1500 rpm. In taking off the spark arrestor, I see gas squirting out of this pipe above the butterfly and into the carb along with the gas from the jets in the venturi. I don't remember it doing this before. The pipe appears to be part of the carb base and is J-shaped with a hole on the end, The pictures in the manual look like the are U-shaped, and may be some kind of air-bleed device.
Also, I have a bulb pump on the fuel line that I use to get gas into the reserviour when it hasn't been run for a while and the gass goes into the carb, where I thought it would not go past the reserviour when it fills and the float shuts off the flow.
So there are two major outpoints with the carburator. It may have gotten damaged by the engine cover crashing down on it in the wind, but there are no visible cracks. I did rebuild it myself per the directions. I am tempted to put on my Chinese knock-off of an Edelbrock 1409 4 barrel marine carb that I bought last year, but would need a new fuel line from the pump.
 
Sounds like a vacuum leak to me....

Until you can control the flow of air into the engine, the RPM will continue to be elevated and no mixture adjustment will change the situation...

Glad to hear you go the drive back into working order.
 
other things that come to mind - make sure the box crashing down didn't break anything loose - carb is secured to the manifold.

remote control throttle cable is adjusted correctly and idle speed screw is backed out enough to get the throttle plate in the correct position...
 
I haven't done the test yet. But on the second manifestation, where I pump the bulb on the fuel line, and like the fuel pump, it pumps gas to the carburator. Wouldn't you expect it would just fill up the reservior and the float would stop the flow and it would be hard to pump? But instead, it gets pumped right into the venturi with no resistance. This is what made me think something was very wrong with the Holley.
 
Okay, so here is some data. The vacuum test was poor, either 12 or 15 in/hg. My tester zeros out at 3 and it was reading 15, so it was probably 12. Either way it is low.
Also, I found oil in the bilge and in tracing it down, it was leaking from the bottom of the front of the intake manifold and the timing belt cover. It may be where the vacuum leak is, or around there.
So, since I have to take off the carb and the intake manifold, I should probably repair and replace the original intake manifold, as I suspect that has something to do with my slow start problems, the new manifold being aluminum, and having much greater volume, being built for a four barrel 600 cfm, and my little 2 barrel is 500 cfm. The original one had a scar on the flat surface where the gasket goes, and the re-builder said to get a new one, or weld the old one. Others have said to go with the original. I do weld, so this is not a problem.
Now when I installed the intake manifold, all the Youtube guys (about five of them) all said not to use the cork spacers in the installation, but to just use a lot of the gasket stuff, about a quarter of an inch thick, and let it dry for a couple of days. Any opinion on this? It looks like this is where the oil leak is.
I also sprayed some starter fluid around the intake manifold to try to see more exactly if I could tell where the air leak is but couldn't tell any variation: I had to keep the rpms up to around 3000 to keep it running.
So tomorrow I will start taking it apart.
 
I doubt the vacuum leak is at the same place the oil leak is...

using RTV is standard practice at the front and back of the intake on V-block engines..a 1/4" bead to a bit fat...3/16" will be plenty...and overap it one half an inch onto the gaskets.
 
I tried welding the old cast iron intake manifold, but it was too rusty, and I blew a hole through from the bottom oil to the water passage on top, which is where the real rust was. The weld was not sticking to the rusty iron, I could peel it right off. It is about an inch by a half inch wide. So, it looks like I have to stick with the aluminum.
 
Some more data. I took the carb and intake manifold off and cleaned them up. I took the float section of the carb apart and it seemed fine. I blew into the fuel intake, and it seemed to shut off when I moved the float up to level. I couldn't blow though - maybe the bulb had more pressure than even the pump and it somehow blew on through? I saw no cracks.
The intake manifold seemed it needed more RTV, not less as it looked a little light where the oil leak was. It is hard to confirm if you have enough there, as it is under the thermostat housing. Most other places you can see it squirt out and clean up the excess. I bought a new gasket set.
I have no idea where the air leak may have been. I guess I'll put a little RTV around both sides of all the gaskets. Would it be better to just use RTV to install the carburetor instead of the gaskets? It has a double connection with the adapter for the two barrel.
I painted the outside of the aluminum intake manifold Ford Blue, so that it doesn't corrode so much.
 
I was thinking the bulk of the corrosion, in the manifold, would be in the water jacket...

I would be inclined to use Permatex #3 on the gaskets, and to use the gaskets under the carb.

If the heads' deck surfaces were milled a lot, the intake may require some trimming as well...I don't remember the threshold but sure whoever did the machine work could tell you.
 
I got my engine back together today, from the intake manifold to the carburetor, the thermostat housing and hoses, the distributer and electrical, and roughly timed. I did not try to start it, as I wanted to give the RTV a day or two to dry. I have pictures, but this website usually says my pictures are too big. I gave it a try, but no go. Anyway, there is a lot of Ford blue, as I decided to paint the oversized exhaust manifolds in the blue as well. Blue and silver. I'll let you know how it is running later in the week.
 
Well, it started right up, just had to adjust the timing and idle a bit and all is good... except when I went to raise the outdrive the tilt didn't function. It did it for a while when I reinstalled the outdrive but mysteriously started working again. I'll have to trouble shoot the electrical circuits.
 
It had 12+ volts to the solenoids from the switch and the tilt motor was new two years ago, so going towards the tilt motor, I found a frayed wire grounding it out and all handled now.
Just have to clean everything up, button up a few things and take it out next weekend.
 
Sometimes the solenoids on top of the intermediate housing will click but not pass current.
Next time it malfunctions, (presumably up), jumper across the 2 big terminals of the relay that has the green small control wire.
 
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