Oil leak from 390
Thread Starter
|
Elder User
Joined: May 2008
Posts: 619
Likes: 1
Oil leak from 390
What I thought was leaking from a valve cover gasket turns out to be something else. Thinking from the leak pattern, the intake manifold gasket (rear part) has failed. I can't think of leakage from anywhere else - the rear main and front main seals are bone dry. Is this a common source of leakage from the FE motors - the intake manifold gasket? Mine is technically not the 1974 390 but a 1967 version, so intake may be a little different.
Second question - is the intake / valley gasket pretty easy procedure for these engines? I have experience w/Ford SB and Chevy SB/BB but not these motors.
Thanks-
Second question - is the intake / valley gasket pretty easy procedure for these engines? I have experience w/Ford SB and Chevy SB/BB but not these motors.
Thanks-
New User
Joined: Aug 2014
Posts: 8
Likes: 0
Intake manifold gasket leak at the rear is the most common leak for a 390. It is a cork gasket and over time it squeezes out. Best way to hold it is remove the manifold and clean the surfaces real good. Use a center punch and put a row of center punch holes along the surface on the block. Use the old style permatex that hardens. This will anchor the gasket. I done it to a 76 F-250 with a 390 ten years ago and it still has not leaked a drop.
Postmaster
Joined: Oct 2010
Posts: 4,656
Likes: 4
From: Northern and Southern Cal
Care must be taken to align every surface.
I actually prefer to use a silicone bead where the cork usually is. That way the cork (that I don't use) cannot move.
But many do as described above and dimple the top of the china wall to hold the gasket. Just depends on your experience, everybody is different.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
Dimple the china wall with a punch. You can go the extra mile and also dimple the corresponding surface on the intake.
Position the intake dry to gauge how thick to lay on the RTV. Anywhere from 1/8- to 3/16ths-inch thick is typical.
Clean/degrease both surfaces and lay on the RTV centered on the china wall. Wait about 15 minutes to let the RTV take a set, and then lay the intake square and down. On an FE, install the distributor to align the intake and then torque the intake bolts to spec.
Position the intake dry to gauge how thick to lay on the RTV. Anywhere from 1/8- to 3/16ths-inch thick is typical.
Clean/degrease both surfaces and lay on the RTV centered on the china wall. Wait about 15 minutes to let the RTV take a set, and then lay the intake square and down. On an FE, install the distributor to align the intake and then torque the intake bolts to spec.
Thread Starter
|
Elder User
Joined: May 2008
Posts: 619
Likes: 1
Couple questions (apologies):
1. Assume you don't need to remove valve covers for intake clearance?
2. Why 'dimple' the wall? For what purpose?
3. Did Ford or Felpro not make the rear gasket thick enough so that you have to use permatex? I used to use dabs at each corner but never along the block.
4. What do you mean by install distributor first to align intake? Wouldn't you want to install and torque to spec the intake after intake is down?
1. Assume you don't need to remove valve covers for intake clearance?
2. Why 'dimple' the wall? For what purpose?
3. Did Ford or Felpro not make the rear gasket thick enough so that you have to use permatex? I used to use dabs at each corner but never along the block.
4. What do you mean by install distributor first to align intake? Wouldn't you want to install and torque to spec the intake after intake is down?
New User
Joined: Aug 2014
Posts: 8
Likes: 0
The dimples give the gasket a "anchor" spot. This is the only way to hold the gasket from working it's way out. On your engine you will find the gasket has squirted out. The gaskets are the proper thickness when new but the heat makes them work out. Good old permatex will cement them down providing you make the dimples rough enough to embed into the gasket. Trust me it works, mechanics have been doing this for years. Personally I trust the cork gasket with permatex more than I do silicone. Don't be shy on using the permatex, slather it on good as in this case you are cementing the gasket down not just holding it in place until it is tightened.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
Dimpling the walls gives the RTV some "feet" to hold onto... moreso than a slick surface. In a sense, they provide friction.
Your call whether you do so.... I am just sharing 30+ years of experience under the hood.
EDIT.... If the RTV oozes out to a point that it is more than just a bulge, that is an indication that ya used too much.
Trending Topics
Thread Starter
|
Elder User
Joined: May 2008
Posts: 619
Likes: 1
So other than the dimpling suggestion and a few others, is the basic procedure in the factory service manual? What RTV is preferred (permatex #1 or 2?)
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Rezvani's Latest Post-Apocalytic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
New User
Joined: Aug 2014
Posts: 8
Likes: 0
Postmaster
Joined: Nov 2012
Posts: 2,806
Likes: 8
From: Langley, BC
I'm not saying that what you're doing is wrong. If it works, great. But a lot of people skip the gasket altogether and that works too. It really doesn't matter as long as a seal is made.
Postmaster
Joined: Nov 2012
Posts: 2,806
Likes: 8
From: Langley, BC
FE intake is 80lb and aluminum aftermarket is about 15lb.