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!

that tells me that the intake is setting too far down in to the "V". On dry mockup I would want the bolt holes to be pretty much centered in the intake manifold holes and I would want the head and intake surfaces to be flat & I would not angle milled. thick paper gaskets on either side of the valley pan would be what I would mockup with to see if I can get the bolt holes back aligned & I'm thinking that will take care of the oil consumption. You are working with a "fixed" dimention valley pan which complicates things & I dont have the last word on this (been on SB's for decades) but hopefully this is will help. People have been useing valley pans dry with no issues (as did Ma) but everything has to be dead on for good sealing over time.

I hear you & I think I might have this backwards with the bolts being low in the holes vs. high in the holes. I really need to pull it apart again and take a look since I haven't had the intake off in a while.

I originally built this motor in about 1985, so my memory isn't too fresh on this. I'm am sure though about the half-dozen times I've re-sealed it over the years and that I tried the paper gaskets top/bottom once and couldn't bolt it up. That makes me think the bolts are low in the holes now that I think about it.

I HOPE they are sitting high since the intake would need to be "raised", not "lowered" which is a heck of a lot easier using gaskets.... but I think I just had it backwards in my first post.

And RapidRobert....do you know of a valley pan that is NOT fixed and does NOT require a head to be pulled off like the 440source ones? I do remember cutting a stock valley pan once, sealing the edges with RTV and trying to use "just" the paper gaskets years ago.

Have you tried just setting the intake on with no gasket or pan? Are the gaps even from bottom to top of the heads? How does the bolt holes line up then?

With unknown milling of the heads block and intake there's going to be some trial and error

Hey Rude, I think you're right. I really need to be SURE where it sits and not just go from memory. What I'm hearing on here and FBBO is I might just have to check, mill, re-assemble, re-check & repeat.

If it is just the intake that is off then it is a fairly easy fix. Either machine down the intake (or the heads) if it is too high or add gaskets if it is too low.

A more serious problem is if the machine shop decked the block without decking the valley walls. In that case it gets really difficult to get things to line up correctly since the valley wall will force the gasket up into the intake and mess up the alignment.

Yup, the walls at both ends of the block. The intake will sit on those ends, and the intake to block surfaces will have too much of a gap, and the bolt holes will be way off.

Here's some reading for you.


http://www.hughesengines.com/Upload/TechArticles/INTAKE_MANIFOLD_SEALINGJULY2015.pdf

Fortunately the ends of the manifold can be ground at home to clear the valley walls if needed.

This isn't a small block

Yup, little notches in the ends of the manifold flanges. Correct?

edit: A small block would need the walls cut down side to side of the block if the block deck was surfaced. Or the whole length of the front and rear ends of the manifold cut.

edit 2:

I keep thinking 'end of manifold' instead of 'end of flanges'. Oh well, trying to think of this situation while watching the hockey game isn't all that easy sometimes. lol

Well, I can see that the front/rear valley walls (where the metal bars & 3 bolts go front/back) have not been milled. I can see how that would distort the valley pan a little bit, but I always put a bead of silicone under the front/back of the valley pan & bolt that up last after the intake is bolted on & I haven't had any leaks in those areas...not good, but seems to be working. This is a 440 & the intake doesn't sit right down on the block, so it could we worse I guess.

WAIT A MINUTE....NOW I get it....the very corners of the big block intake can hit the valley rails....the notches make sense. I never thought of that.

OK, if I use Pittsburgh's (Hughes Engines) method to check the angle & "squareness" of the intake vs. heads, those washers are going to prevent me from seeing any valley rail vs. corners of the intake interference. It "seems" like I should check that first??? How do I go about checking that?

Pittsburgh...you rock. It hurt my head a little bit to understand it, but that looks like a great method to solve my problem. I think the only issue I might have is making SURE my 4 washers are EXACTLY the same thickness. THANK YOU

No problem and thank-you. I had this same issue with an Indy intake I modified to use on my Edelbrock heads. After doing some research I will be giving this method a try. I'm pretty sure Hughs sells the wax string.

It's a good solution. Yes, the washer thickness would be one problem but going with surface ground (precision) washers would get around that. One issue that they don't really speak to in the article is setting up the manifold or dialing it in for milling and holding it in a rigid manner to allow for machining. Both of those are critical to gaining from what was learned in the first step.

- EM

I lay the intake on the heads with no valley pan or gasket and take a feeler gauge and measure how much gap there is in each corner, top and bottom, front and back sides and write it down on the manifold with felt tip marker so I don't forget or get confused later, I also look at the manifold bolt holes and how they align with the bolt holes in the heads and go from there.
Once that is done take the manifold to a good machine shop and have them cut the intake to remove any angle and get clearances the same on the entire intake the same
You may need to have them remove some additional material later once it is straight on the heads to get the bolt holes align properly also
I like to see zero clearances on the bottom(all four corners) with no valley pan or gaskets and maybe up to and no more than .003 clearance at the top all the way across so the intake pinches the bottom up tight against the valley pan and or gaskets
IHTHs

Yeah, with the heads/block milled as you've stated .010 from the intake was just truing up the surface around the heat riser... ...I bet you'd easily seen triple that{if it stops there} before you could get some gaskets on there with the tin pan...

Anytime that I’ve had a problem with the bolts holes not lining up, I just sit the intake straight on the heads with no gaskets. If they line up better, the thickness of the gasket is about the right amount to remove. My machine shop has a tool they have made to help with the angle. If the angles are off, they need to be corrected. It is two parallel bars bolted together in a V. You lay it in the valley and square it up with the heads and set the angle. He machines the amount and correct angle and you are good to go. Had it done on several intakes and it comes out perfect.

So what do you all feel about enlarging/elongating the bolt holes in the intake? This is recommended in the Hughes link. It says to do it 1st thing, then go back & re-do it once the intake is fitted (if necessary)

As a racer and not a show guy numbers type of guy I’ve done it often. I oval them as needed up or down to make it easier for me

Enlarging the holes makes it easier to get the bolts in but doesn't get the sealing surfaces aligned.