This vacuum leak has ruined my motivation for my car (long post)

Izyk

Izyk

New member
So this is going to be a long post and I am going to go over everything that I have done to try and find my vacuum leak. I have posted this many many times and have tried many many things so I am going to go everything I have tried.

So I have just finished rebuilding the 250 inline 6 engine for my 1970 Ford Maverick and the build was a success.. or so I thought. After I finished it I got it running somewhat ok.. the carb has some hesitation but it still ran. I took it on a test drive and drove it maybe a mile and it was running good until I pulled back into the driveway and it start to run terribly and then shut off.
I tried to start the car back up but it didn't want to run at all and would shut off when I gave it any gas and would only run if it was incredibly rich. Of course just my luck I had a vacuum leak. I went back and forth searching for what could be the issue and even got a new carb in the process because the old one had definitely caused me issues before.

I finally got it to run and somewhat handle throttle although still running rich so I parked it after driving it around the yard to test it out. Once parked again however the vacuum leak somehow got worse once again. So I started to go everything.

I check and replaced every line, checked every port and adapter I could find and still nothing. I took the lines that were going to the distributor and blew through them to see if the diaphragm in the distributor was fine and I couldn't blow through them so the diaphragm was fine.

I took some brake cleaner and sprayed it around the carb and flanged and it made my gauge jump from 15 to 20 and the engine started to run better so I figured thats what it was. I took off the new carb and put the old one back on and I double gasketed the spacer because I figured the spacer was probably warped but after doing this the vacuum had somehow gotten worse.

I thought it was odd and I put the new carb back on and it didn't changed anything and the car wouldn't even start at this point. So I went and I bought a weber adapter and threw on a Weber 32/36 with the new adapter (along with the needed fuel pressure regulator) and I was still having the same issue. The vacuum gauge was still reading 15 and when I gave it any gas it immediately would drop to 0 and shut off. But the car would still run although very rich. So rich that my spark plugs were coal black and it was started to pull fuel down into the oil pan... Not good (I've been trying to run the engine the least amount possible due to this issue.)

I went out a few days later and the car wouldn't even start at all. Hooked up the vacuum gauge and when cranking it barely reads ten. Nowhere near close enough for it to run. Ok so I retraced all my steps and blocked all the vacuum ports to see if it was one of those but it didn't fix my issue. I went over every gasket everywhere and they are all fine and yet I still have a massive vacuum leak somewhere.

At this point I am at a complete loss... After trying 3 different carbs, 2 different adapters, test my distributor, going over every gasket and every vacuum port I cannot find this leak and I have completely given up on this car because I FINISHED the engine rebuild 3 months ago. I have spent probably 20 hours in total searching for this vacuum leak and I cannot find it and I have given up.


I have posted this a dozen times across many forums so I am going to answer some questions most people have.

No it does not have a break booster or air conditioning. There are no vacuum lines that lead to under the dash. All the vacuum lines in this Maverick start at the engine.
I have replaced the vacuum line that leads to the transmission control valve and even when I block it off it doesn't fix it.
The intake doesn't separate from the head. It is casted as one piece. (Although since we are on a ford six forum most of you probably know this.)
The head was machined so the intake flange for the carb spacer is not warped.
I have a brand new pcv valve connected with a new line for it.
The current vacuum rating for the engine is 10 when cranking and will not start.
The current carb attached is the Weber 32/36 stock.
The original carb was a Carter RBS. The first 2 carbs I tested were Carter RBS carbs.
 
The engine will start and run if you have 10 Hg when cranking.

What is the fuel pressure when it did run?
Sounds like the carburetors aren't getting fuel either from a clogged fuel filter or clogged pickup in the tank.
We recently have had others with similar problems from rust and other debris in the gas tank after sitting a long time.
Did you try disconnecting the fuel line and seeing how much gas flows into a can when you crank the engine?

You haven't mentioned anything about the ignition timing?
 
Last edited:
Had a similar problem with my original 200ci engine. Previous owner had tried a couple different carbs. Didn’t fix the problem. We took off the electronic ignition and reinstalled points and condenser in the distributor. This corrected our issue. What are you running for a distributor? Electronic ignition or points/condenser? I know this sounds like a simple fix, but might be worth a try.

One other possibility…crack in the head/manifold?

Good luck. We feel your pain.
 
Hi, I would open up one of the carbs and see if there is any dirt or debris in there. Dirt would explain running rich and flooding if the needle was stuck open. If you find any dirt the tank needs to be taken out and cleaned or replaced. Can you gently blow into the fuel line from the fuel pump and hear bubbles in the fuel tank? I would check the fuel line and rubber hoses for a pin hole which would prevent the fuel pump from pumping fuel. I would run a short rubber hose from a gas can under the fuel pump and see if the engine runs. Did you check for spark? I would run an inline spark tester to verify. Unless you have a major vacuum leak, the engine should start and run. Good luck
 
Are you running a 2-1 adapter? or had the head machined for a 2 brrl base plate? Check those mating surfaces for trueness.

All Small Six - Holley 2300 Tuning

Howdy guys! So i believe i got my leaks sorted out, the car seems to run better and has much more power! Anyhow, I gotta tune this 2300 now and it's throwing me for a loop a bit. Its a 350cfm street avenger. So far it seems to want 64 jets to run a good cruise, but WOT is like an 11 on the...
fordsix.com fordsix.com
Post #14, leaks at baseplate.
 
Have you tested the two small plugs on the front and rear of the cast manifold if they are leaking?
 
pmuller9 said:
The engine will start and run if you have 10 Hg when cranking.

What is the fuel pressure when it did run?
Sounds like the carburetors aren't getting fuel either from a clogged fuel filter or clogged pickup in the tank.
We recently have had others with similar problems from rust and other debris in the gas tank after sitting a long time.
Did you try disconnecting the fuel line and seeing how much gas flows into a can when you crank the engine?

You haven't mentioned anything about the ignition timing?
Click to expand...
The gas tank and the fuel pump and all fuel filters are brand new. It will fire with 10Hg but it shuts off immediately. I have tried adjusting with fuel pressure on it in every direction it will go and has not solved the problem. Along with the air/fuel screw

I have tried messing with the timing but it just made the car not want to run at all. It will kind of run if I advanced it all the way but I don't want to do this and cause any damage.
I have taken the distributor out and took it back a took and forward a tooth but had the same result and made the engine not want to run at all so I know the timing is right. When I did get the engine first fired up after the rebuilt it ran great and didn't have any issues with the timing.
 
frozenrabbit said:
Are you running a 2-1 adapter? or had the head machined for a 2 brrl base plate? Check those mating surfaces for trueness.

All Small Six - Holley 2300 Tuning

Howdy guys! So i believe i got my leaks sorted out, the car seems to run better and has much more power! Anyhow, I gotta tune this 2300 now and it's throwing me for a loop a bit. Its a 350cfm street avenger. So far it seems to want 64 jets to run a good cruise, but WOT is like an 11 on the...
fordsix.com fordsix.com
Post #14, leaks at baseplate.
Click to expand...
I keep having people tell me its the baseplate and I honestly think it is but it just doesn't make any sense on why it would be. The head was machined, the mating surfaces are extremely smooth mate seamlessly. I have tried to different carb baseplates (with one of them being new) to no avail even with double gaskets and thick gaskets so It makes no sense on how it could be leaking still.

The current baseplate is a 1-2 barrel adapter. The head is machined for a 1 barrel baseplate. I guess will try to test it for trueness. If it is the head, I guess I'll have a few words for the machine shop lol
 
Last edited:
Goldie said:
Had a similar problem with my original 200ci engine. Previous owner had tried a couple different carbs. Didn’t fix the problem. We took off the electronic ignition and reinstalled points and condenser in the distributor. This corrected our issue. What are you running for a distributor? Electronic ignition or points/condenser? I know this sounds like a simple fix, but might be worth a try.

One other possibility…crack in the head/manifold?

Good luck. We feel your pain.
Click to expand...
It has points and a condenser with both of them being new. I would really hope the head isn't cracked because it was expensive to get it done since everything on it needed replaced.
 
B RON CO said:
Hi, I would open up one of the carbs and see if there is any dirt or debris in there. Dirt would explain running rich and flooding if the needle was stuck open. If you find any dirt the tank needs to be taken out and cleaned or replaced. Can you gently blow into the fuel line from the fuel pump and hear bubbles in the fuel tank? I would check the fuel line and rubber hoses for a pin hole which would prevent the fuel pump from pumping fuel. I would run a short rubber hose from a gas can under the fuel pump and see if the engine runs. Did you check for spark? I would run an inline spark tester to verify. Unless you have a major vacuum leak, the engine should start and run. Good luck
Click to expand...
The tank is brand new but I suppose I can try to test it.
 
If you open the throttle by hand does the accelerator pump squirt a fair amount of gas into the carburetor?
 
Izyk said:
It has points and a condenser with both of them being new. I would really hope the head isn't cracked because it was expensive to get it done since everything on it needed replaced.
Click to expand...
I hope not too, for your sake, Izyk! On occasion, we have purchased new points/condensers and have had them be junk right out of the box. Good old Chinese parts everywhere you look now. We purchase a lot from NAPA because we have a master-installer discount, and I can't tell you the number of parts we end up returning because they are faulty and need to be replaced under warranty.
 
If the tank is new, leave it. Any rubber fuel line, be sure it's not disintegrating internally. A verification of the mechanical fuel pump is highly suggested. Debris can hang them up in either valve, causing insufficient pressure, or flooding pressure. . . Usually two gaskets together will always leak. I understand you're trying different fixes, to isolate the source.
 
At this point, I would take a close inspection of the ignition.
A couple of things that can give grief here is a faulty condenser or one with the wrong capacity.
Check the coil's primary supply voltage; make sure it's not dropping down below its threshold. Take a voltage reading at the coil positive with the key on/engine off, then while cranking and a final one with it running.
Or, has the coil itself is going/gone bad. Pull the coil wire and carefully hold it apx 1/4 inch from the head while cranking the engine, you should be getting a nice blue spark consistently.
 
Hi, some guys here, including me, have been asking about the spark. The condensers are always in question. You may have a defective condenser that will cause weak or intermittent spark. I would try the old condenser, or get a new Eichleln condenser from Napa, or change to Pertronix ignitor and coil. The problem could actually be as simple as the coil being wired backwards, or a bad ground in the distributor. Also, have you rechecked the point gap, and watched them open and close as you spin the engine? I would not be surprised if at least part of the trouble is ignition. Good luck
 
Valve adjustment is correct ?
Cam Break in ?
Static timing ?
I like to use grease on the carb gaskets, really helps to seal them.
Double check those "freeze out plugs" on the ends of the log manifold ?
Sparkplug spark is hot blue and makes a sound ?
 
B RON CO said:
Hi, some guys here, including me, have been asking about the spark. The condensers are always in question. You may have a defective condenser that will cause weak or intermittent spark. I would try the old condenser, or get a new Eichleln condenser from Napa, or change to Pertronix ignitor and coil. The problem could actually be as simple as the coil being wired backwards, or a bad ground in the distributor. Also, have you rechecked the point gap, and watched them open and close as you spin the engine? I would not be surprised if at least part of the trouble is ignition. Good luck
Click to expand...
I've tried 3 different condensers and 2 different points, 2 different distributors and 2 different ignition coils
 
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