85 f150 intake exhaust leak

[kyleroth48625]

I have an 85 f150 with the 300 6 has an intake and exhaust leak on number 3 cylinder manifold bolts are tight as can be but as I look at it it seems to me like there is room for bigger washers on the bolts the factory washers don't look like they grab much of the manifolds and it did not leak for a long while after motor swap I'm fearing maybe the manifolds have warped I plan to pull the exhaust and switch to the efi style split manifold because I have a set sitting here for it off the old truck the motor was in anyone play with bigger washers or have just one cylinder leak like that.       Oh and from a past post thank you for all the suggestions for the timing jumping issues I never found the root cause but it had a bad computer for sure and wiring issues I swapped out to an hei cheap quick and painless and went to a non feedback carb to solve those issues

[mat in tn]

warped intake is possible. funny fix. maybe more of a happy accident. 25 years ago i had a warped intake on my 300-6. i pulled the intake/exhaust assembly off and from my inexperience i guess, i could not separate them from each other. i was having them  milled to be strait again so i dropped them off to be separated and machined. when i picked them up they were assembled and the guy said '' thats how i do it'' no more explanation or info. i felt screwed..that wont work with sandwiched gaskets. i used a newer gasket from the fuel injected 4.9 and , did i say 25 years? never looked back.

[FuzzFace2]

I used the factory washers when I went to EFI manifolds.
I also went with threaded studs over the factory bolts.
Only issue I ran into was the intake manifold dropped to low and caused a vacuum leak I just had to raise it up and been fine for 2 years now.
Dave  ----

[IowaTom]

I recently pulled the manifolds and head on my 300 in an '85 carbureted F150.  
The idle was very rough and I had no information on this engine as a replacement by a previous owner, so decided to take them to a local, good machine shop.  I noticed one of the gaskets - intake, I believe - had slipped on installation causing a leak and two valves were white.
An old trick is to spray carb cleaner or starter fluid around the manifold while the engine's running and before it gets too hot.  If you hear a change in rpm, you've got a leak somewhere.

[1986F150Six]

IowaTom wrote

I recently pulled the manifolds and head on my 300 in an '85 carbureted F150.  
The idle was very rough and I had no information on this engine as a replacement by a previous owner, so decided to take them to a local, good machine shop.  I noticed one of the gaskets - intake, I believe - had slipped on installation causing a leak and two valves were white.
An old trick is to spray carb cleaner or starter fluid around the manifold while the engine's running and before it gets too hot.  If you hear a change in rpm, you've got a leak somewhere.

Or, you can perform a "smoke" test.

https://www.ford-trucks.com/forums/1478167-vacuum-leak-detection-effective-and-inexpensive.html

[IowaTom]

GREAT information and well explained!  I love learning new things, thanks!