390 Exhaust Manifold Gasket change
 

I'll be changing out the exhaust manifold gaskets on my 390 to quiet down a NOISY ride; there's a big leak in the drivers side gasket that makes driving Patience almost uncomfortable. I don't have the resources yet for headers but would like some recommendations for what gasket and sealant would be best and also what can I expect? What am I in for? A week of misery? Two hours of simplicity?

It looks like there is some sort of metal gasket in there now; before taking things apart, should I just make sure that all bolts are tight?

I'll be sure to soak all bolts in PB Blaster for a few days before attempting to remove the manifolds, but do I need to disassemble to rest of the exhaust system (i.e., should I detach the collectors from the manifolds)? Also, presuming that all the bolts come out relatively easily, is this a pretty straightforward procedure?

Remember, I'm still relatively new to wrenching, don't have a complete automotive shop, and don't want to bite off more than I should chew, but I think this seems like something I--with my Haynes Manual and my limited knowledge--can do.

Just a couple of notes and FYIs:

1. The doughnut gasket is made of sintered metal. Meaning, it is cast with metal particles under high pressure. It'll crack (even new ones) if twisted or hammered (ask me how I know!). Fel Pro's part number is 60987.

2. Depending on how long the exhaust leak has gone on, the leaking exhaust gases may have pitted the manifold mating flanges. After disconnecting the head pipe, look and run your fingers along the seating surfaces to determine if it is reasonably smooth. The PO of my 70 "lived" with an exhaust leak requiring me to replace the passenger manifold. If it's deeply pitted, some JB Weld might be in your future.

3. I assume you have merged head pipes into a single exhaust tube. You'll have to loosen the passenger side in order to drop and rotate the driver's side. Oh, you're replacing both.. in that case get both head pipes positioned and started on each manifold before applying torque on the nuts upon reassembly.

4. Tighten the nuts evenly so the collar applies an even clamping force. Work evenly from side to side.

5. Use anti-seize and consider getting new outlet studs, nuts, washers, and ramp-lock washers. Two of my studs came out while trying to undo just the nuts.For the manifold bolts, use anti-seize on 'em too.

6. Disconnect the battery before working on your rig. It's just good practice.

7. I've never used sealants on the manifold outlets and no sealant on the manifold ports - just the gaskets. Again, evenly tighten the bolts. After a few heat cycles, go back and tighthen them snug - not gorilla tight. According to the manual, they only need btwn 18-25 ft.lbs.

8. The best tool to use is a ratcheting combo wrench... all sorts of strange angles you'll experience with a regular combo.

Just throw Percy's gaskets in and use Stage 8 header bolts and you will never have a problem. I have replaced header gaskets a few times and eventually learned there is a great gasket out there that will not blow out and Stage 8 header bolts wont back out on ya. Its all I use now and they have never let me down on all 3 trucks. Percy's gaskets are 2 layers of dead soft aluminum and seal very well, might want to warm the engine up and let it cool off and then re tighten but no matter what they are not gonna blow out on ya.

1. Thanks for the tip. I'm assuming (perhaps wrongly?) that I should be able to find this at my local NAPA or should I order it online?

2. Frankly, I have no idea how long the leak has been going on. But, for some reason, I DO have some JB Weld in my toolbox that I've never used. Follow directions, I imagine, or is there some special way I should use it?

3. Surprisingly--or perhaps not--this is a true dual exhaust set up so I'm imagining I can do it one side at a time, correct?

4 - 7. Gotcha. Thanks.

8. Fantastic! The boss-man at my new job just let me purchase a bunch of new tools and a set of standard and metric ratcheting combo wrenches were on my shopping list. Since my truck will reside in the shop, I get to use them.

This appears to be a well-detailed list from someone who's been in my shoes. THANKS. I'll let you know how it goes. Swapping out the exhaust manifold gasket is at the top of a LONG list of things I need to do to Patience now that I'm employed and have some financial resources to throw her way.

Fish

The doughnut gasket should be available at NAPA, Oreilly's, Autozone, etc.. it's a common part. However, I needed to visit four stores to get the two I needed. Shop now!

JB Weld - follow the directions and ya should be good.

Duals - cool! Much easier since ya don't have wrestle with merged head pipes.

It's really fresh in my memory cuz I went through all of it a couple of months ago cuz I had to replace the cracked driver's side manifold. Luckily I had the take-offs from my 73 (now wearing headers) for my 70.

You're most likely going to break some bolts, be prepared.

I'll need to drill and tap broken bolts to remove them, correct? Any idea what size bolts I'd need to replace those I've broken? Are they listed in the Haynes manual? I haven't looked?

Fish

Well here you go just ignore the part about the headers......yes this is my story.

This a story about changing from stock exhaust manifolds to fenderwell exit headers. Or if you are just changing stock exhaust manifold gaskets. Truck is a 79 F250 4x4 351M 4 spd.
The #1 thing in my book is to LUBE THE HELL outa those soon to be old exhaust bolts.
I would use PB blaster or Sea Foam Deep Creep. If the vehicle is not your daily driver, soak them as much a possible for like a week straight.
Use the red tube to get right in there, spray the top side of the bolt head and let it soak. This step is very important because you do not want to break off any of those bolts.
I have heard of heating up the bolts with a torch, good way to burn up your valve cover gaskets, and catch fire to your sprayed on lube, I always change them cold.
I even heard of starting the truck to heat up those bolts, great way to burn your hands and fingers. Remember LUBE LUBE LUBE, jack up truck to a comfortable working height, take off front tires. And do all the other safety stuff, block rear tires ect....
I start on the passenger side, it’s always easier. Do not try to "snap" torque the bolts loose, use a slow draw break torque. And use a quality socket, as straight on as possible.
If you break one, don't panic, you do not have to remove the head to fix this problem, at least I didn't, and I broke 3 on pass side and 2 on dvs side, on 1 truck and 2 and 2 on another.
If you do continue removing the rest of the bolts, hopefully with better luck. And then ditch that ol heavy stock factory manifold, do not throw them away those stock suckers are pricy especially the dvs side, why I do not know.
If there is any bolt left sticking out of the head after you remove the rest of them and the exhaust manifold maybe you can vice grip it and get it to break loose. Probably not, and you only gouge it up.
Some guys say they can weld a nut on there and get it out, those guys are luckier than me. If it’s broke flush with the head, just keep reading.
If you do break a bolt, use a GOOD QUALITY set of drill bits to drill it out. Use a center punch to make sure you start in the middle, VERY IMPORTANT. Start with a smaller bit and work your way up to a bigger one.
Match your drill bit to your tap size needed for the correct bolt size. 7/16 1/2 or 9/16 can't remember. I would then tap in new threads. As a tech note if you are going to re-tap the hole weld the tap into a old 3/8 drive socket that way you can get in there with a extension and get it tapped right the first time.
I WOULD NOT USE A EASY OUT, been there done that, broke it off in the hole, another long story.
If you are having trouble tapping in new threads, might be able to use a "helicoil" thread insert, easy to use, buy it in a kit, just have to drill out a bigger hole to insert the thread coil. Debur or run a tap in to clean out the old holes best you can.
Get new hardware, grade 8 or better, do not use the hdwr provided (junk) not enough washer face to the header flange. I got mine with a premade large washer, and use the lock washers with the little face to face lock teeth.
Not sure that they are called, got them and my bolts from Fastenall, use some thick header gaskets from Jeff's Bronco Graveyard, pricy but awesome. Make sure you use anti seize compound on the hardware.
DO NOT have any solvent on your hands when you install the gaskets, it will cause a hot spot on the gasket and burn it up. Passenger side inner fenderwell will need a bit of trimming or bend outa the way for now, trim later.
2 people makes this part a lot easier, while you wrestle the header into position, from under the truck, your helper will align the gaskets and start the bolts, all hand tight at first.
If you are having trouble getting it in, try taking off the shock tower, 3 bolts? Might give you more wiggle room, did for me especially on the dvs side. Evenly tighten down bolts, all the while making sure the header doesn't catch on anything.
Ck the clearance on the cab mount frame bracket to the collector area, grind the bracket as needed. Use a quality audioable Tq wrench, start at minimum working your way to max. STOP THERE, DRINK ONE BEER, AND GET READY FOR OTHER SIDE.
Ok on dvs side, remove dip stick and tube (plug pan to stop oil leak) and brake line coil from master cylinder to frame mounted proportional valve. Cap/plug all opening, brake fluid in the eye is a M...F....
Probably have to remove that brake line clamp plate from back side of shock tower, remember to take tower outa the way also. Bend/trim inner metal fenderwell and install in same order as passenger side.
Reinstall all the other stuff you took off, remember to re-bleed brakes. Make sure nothing is touching your headers, spark plug wires, fuel line ect...I would start the truck with open headers, so you can soak up the fruits of your hard labor.
Some smoke is normal from all the lube and the paint burning off YOUR new headers. Let truck idle, blip throttle to scare the neighbors, again make sure nothing is touching the headers.
Decide if you are man enough to drive it around the block, let idle till all the smoke quits. Shut off and do a torque ck on those bolts. CAREFULL THE HEADERS ARE HOT
The torque will be different due to the bolts being hot now, do a minimum tq ck. Start in middle and work you out.

A couple of years ago I had to remove the manifold from the drivers side of my 390. The bottom four bolts came out no problem at all. The four top bolts were a different story. I broke two of them off, even though I had been soaking them with penetrating lube for about a week. I put lots of anti-sieze on the threads before I put the new bolts in. I would suggest not torquing the bolts very much when reinstalling the manifolds. The book I have says 12-14 ft/lbs for the 352/360/390 engines so that's what I went with. Good luck.:)

Show me a man that has never broken off an upper manifold bolt on an FE, and I'll show you a man that pays someone else to do this job......

Shall I post my picture? Granted I've only worked on my FEs but I'm 2 fer 2 !!!!!

Booyah!... I must be walkin' on water!:-jammin

Sierra Hotel!

Only you could be that lucky, good for you, I say.

Guess I lucked out.... Changed mine a few months ago without issue. Decided for good measure to simply replace the bolts... If you do this be sure to grab grade 8 from your hardware store; they are the 'goldish' colored bolts.

When changing mine I noticed a crack in the passenger side so I really changed it twice. The studs came out of the replacement manifold so I redid that as well. The parts store didnt have an exact length so I had to go long and cut it with my grinder.