I was hunting for an exhaust leak on my '95 F-150. It has to be upstream of the O2 somewhere because it has caused the gas mileage to drop in the toilet. It's a 300 inline six so the intake and exhaust bolt down together. I got the intake and exhaust manifold off and UGH...



That may be my exhaust leak on the #4 port, but look at the disgusting intake ports. This is what happens with crankcase vapors and EGR gasses combine in a "dry" intake. It's a fuel injected engine but the way the injector is situated it sprays directly over the top of these deposits with no way to clean them.

Just cleaning these out should gain me about 10 HP back. It's got 198k on the clock. I expected to find that kind of sludge under the valvecover but it's actually remarkably clean, as is the inside of the pan. I guess the PCV is working, perhaps a little too well! It's gonna be going back with a header and I think I'll be putting a catch can on the PCV to see if I can keep this from happening again.

Think about this... it took 198k to do that.

I would think passing some SeaFoam through the intake would keep it from happening.

All for the header.

Deep down inside, I love big old inline 6's...

Those 300 sixes are tough little motors.

Offenhauser makes a nice intake for them that uses a 4 bbl carb. I'm sure a Holley FI system would fit and work well too. There is a load of power hiding in there.

Oh its a great engine just a lousy manifold design. Gonna try and make the EFI live happily with the header, if that doesn't work I'll go with a carb. The whole point though is to gain my economy back, mpg has fallen 3mpg in 6 years. I can hear the exhuast leak so I think it is just tricking it into running too rich.

For some reason the picture won't load for me.

I bet cleaning that and the better flowing headers will do wonders for getting your fuel economy back

Matthew

there are literally tons of parts available for the 300 six. It's a great engine, as Brian noted. Very durable.

Now the picture loaded....nasty build up in there!

what was your final decision on the exhaust?