My engine is sucking oil from the intake valley into the intake ports (440 six pack cast iron). I've struggled with this issue for years. I "think" the block was milled .040" & I "think" the heads were milled .020" (going from memory only 20+ yrs. ago). I do not "think" the intake face of the heads were milled.

The intake bolt are a PIA to line up & difficult to tighten. The bolts set at the very top of the intake manifold. I have oil in all the intake ports, the plugs oil up, I use a lot of oil & the engine smokes at high rpm. Over the years, I've re-sealed the intake at least 6 times. Valley pan only, "tried" using paper gaskets top/bottom of valley pan but I couldn't start a single bolt, RTV + valley pan, "shellac" sealer + valley pan.... I even tried cutting the intake sealing part off a stock valley pan, seal it to the heads with RTV & run a single set of paper gaskets to seal the intake/heads.

I've had this problem with BOTH my current six pack (cast iron) intake and a 4bbl cast iron intake. Years ago, I milled .010" of both intakes' head mounting surface (just a conservative guess) and sealing got better, but not really fixed. Now, with a lot of RTV and a stock valley pan, I can get the six pack intake to seal for maybe 6 months at a time...bolts still at the very top of the intake manifold holes....but then it starts sucking oil into the intake runners of the heads again. The engine is in a licensed, insured, running car.

My diagnosis is that I need to mill the intake manifold face (easier than pulling heads off) and likely "angle cut" the intake so that I take a little more off the bottom of intake runner where they meet the heads and a little less off the top of the runners so the valley pan gasket will get "pinched" just a little more at the bottom vs. the top.

So, my question is.... how do I figure out what to tell a machinist about how to mill the intake face correctly? I guess I "could" just do a conservative guess, machine, re-install, test & repeat....but is there a way to get it right the first time?

THANKS FOR YOUR HELP!

70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"