390 FE Ford Vacuum Leak Killer! Why the FE Fords burn the number 4 & 5 exhaust valves.

As I pulled the 1968 Mercury with the 390 Ford FE in it around to empty the trunk it lost the power breaks and made me think of this video. This is actually an issue on all the old vacuum power brake systems that do not have a filter on the vacuum line to prevent fuel vapor from entering the power break booster. So, after sitting for 15 years in a field the rubber diaphragm in this 69 Mercury has rotted away to the point it has totally failed now.
What I thought was vacuum lines under the dash that had failed turned out to be inside the power brake booster. Good thing it happened here in the driveway, but its a fairly easy fix that will get this car back up and running in no time.

[vrmgt]

shouldn't there be a one way check valve on the booster to prevent air leaking back to the engine?

[musclecarmitch]

Great video and explanation on the FE vacuum! I have a nightmare of a vacuum leak chasing on my Corvette's, thankfully most all the lines and actuators have previously been replaced, but headlights, wiper door and all that stuff sure can be a pain!

You probably saved me tons of headache ! I have a 390 mercury cougar GT and I have both a "brake" light on and the vacuum headlights that won't come down. I could hear a hiss behind de carb but now i'll check the booster! Might have to change it.

[rodrij]

I have a 390 in my 76 Ford F250. I have a definite vacuum leak. I'll try the brake booster line and see if that's it.

[timwindsor]

Very informative video brother. Thanks for sharing. Keep the content coming. Hope you have an incredible weekend. Much love and RESPECT

[WilliamMunny-ds]

Im new to Ford FE 390s but i think the number 5 Piston is front drivers side. you probly mean pistons 3 &4 valves?

[MattsRageFitGarage]

It's funny you mention the amount of Ford vehicles in the area. My grandparents and dad are from just west of the Sandpoint area, and a few years ago we went back there for the fun of it just to get out of the house for a few days. I could not believe the amount of 67-72 F series trucks still driving around, it's like the land time forgot for those things. Most were beat up badly, but that was the most common truck to see there for anything old. The next most common truck was 90's dodge pickups, hardly any chevy's or 80's anything though in comparison.

[Blu_Grit_Garage]

Hope to see you at the 2024 NNN. Glad you caught the problem before leaving last year.

[deanstevenson]

🥝✔️, same with my 1981 3.3 liter, a 200 Ford used a common MAN Vaccum T, one to the booster off of the log intake. Same noise.

[Donna-lt]

Hey. What is the bottom gasket on the intake manifold of a 390 f250 called

[prayfawind]

i have a 390 in a 66 Mercury, that has smoke coming out of the oil cap, any suggestions on how to fix please?

[patrickfitchjr.]

Can you help me fix the typical Ford carburetor issue that seems to happen? Acts like it can't get fuel. Gets hot, starts to sputter, then stall out and don't want to start. Please anyone, what is the problem with these. 3 of these now all with 360 or 390 and same issue.

[johngaughan]

When I bought my Mercury with a FE it had several vacuum leaks. Probably that's why mine runs on 6 cylinders until is warms up. Slowly gathering parts for a new motor.

[johncools]

Which part of Idaho sir? I'm in the post falls area and just picked up a 66 comet. I'm looking at putting a 390fe in it but don't know a ton about the big blocks.

[roberts]

any part number for this filter? id like to add to my fe 428.

[Terminxman]

This is why I put at least the brake booster to my carburetor, I don't like the idea of everything vacuum related being run off of the #4 cylinder intake runner

[SonOfAHerbert]

I’ve got an f150 with a 360 that is sensitive to throttle when cold starting and will often stall when you tap the accelerator. It stays running ones it’s warmed up a bit. Could this be a sign of bad A/F mixture or vaccine leak?

[DanEBoyd]

Is that an Irish Mercury?
When the booster died on my old '82 Mustang GT, (probably because my young dumb arse probably chucked that filter) I thought I could live with it. Nope. A week later I got a new booster. Another thing with those is a bad booster can hit the back of the master cylinder with vacuum, drawing brake fluid through the rear MC seal and into the combustion chambers, where it will make your engine run like crap.

[lynnrunningdeerB]

Quick fix. Install a vacuum motor in it somewhere😁.