87 454 exhaust manifold removal questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Jim85IROC · 12-28-2005, 01:17 PM

I may need to remove the passenger side exhaust manifold on my pickup (87 GMC 3500 454). I've got an extremely irritating exhaust leak on the passenger side somewhere, and after spending 2 days replacing the donut seal on the exhaust manifold collector, I've discovered that it wasn't the problem. Either the manifold is cracked or the gasket is in need of replacement. Either way, it looks like the manifold will have to come off.

What kind of a nightmare am I looking at? The truck's got about 100k miles, and is a winter-driven vehicle. I would really like to get this thing off without destroying the air lines or breaking any bolts off in the head. Any pointers would be much appreciated.

Russell · 12-28-2005, 01:20 PM

Unfortunately, my experience with 87+ manifolds is that you always break at least a few bolts, and the air lines are pretty much garunteed to break =/

Other problem is that as soon as you take that manifold off, it'll compress, and be really tough to get back on later =/

87 STEPPER · 12-28-2005, 01:39 PM

Im not too fam with the BBC exhaust and being that is on the pax side ya may have issues with the starter and it may need to be droped i dont know.

What i can tell ya is get some "PB Blaster" from the auto parts store and hit them bolts and air line fittings with it for a few days befor you attempt to brake any of them lose. this stuff works great for really tuff rusted bolts and nuts.

Sometimes it will help if you hit them with the penetrant when the eng is warm and then brake them lose this helps keep you warm too in the cold.

Buy the stock type gaskets to replace the old ones and just to let ya know there may not be any installed sometimes the factory wont use a gasket.

Clean the manifold with some sort of degreaser and do a good visual inspection of the manifold for cracks.

Good luck

Jim85IROC · 12-28-2005, 02:31 PM

great... this sounds like it's going to be a ton of fun.

Thanks for the info though guys. Now I need to decide whether to spend a weekend doing it myself or suck it up and pay a garage to fight with it.

piecesparts · 12-28-2005, 07:44 PM

If you break the bolts, go ahead and take the manifold off and then weld a nut to the bolt. The heat that is induced into the bolt as you weld it, will loosen the bolt from the cast iron head. The "PB Blaster" is a good idea, if you can't get that, then use "Liquid Wrench and heat the bolt and spray it onto the bolt to soak. Try getting it into the crack between the head and the exhaust manifolt so it will get to the threads.

Jim85IROC · 12-30-2005, 02:46 PM

I pulled the truck into the garage and started to evaluate things. I can't feel any air blowing around the donut in the manifold/exhaust pipe connection, which is what I just replaced earlier in the week. The good news is that it appears that my work was good, the bad news is that means it's something that's more work.

I felt around the manifold the best I could with the engine running, but between the fan blowing at mach speed and the fact that the manifold gets hot as hell almost instantly, it wasn't productive. The noise is definately louder under the hood than under the truck though. I checked the air tubes and they all appear to be ok, which leads me to think it's either a manifold gasket or a cracked manifold. It's so cluttered and tight down there though, I really can't see worth a damned, so I'm not sure what it is.

I managed to break free every exhaust manifold bolt that I can get to, but I can't get to the rear-most one, the one next to the dipstick tube, and the one holding the dipstick bracket.

I think I might punt this one off to my mechanic. After many hours of swearing and throwing tools, I'm sure I'll be able to get that manifold off, but I'm not so sure that getting it back on is going to be much fun, and with my luck I'll probably destroy the dipstick tube trying to get it out.

For the $20/hr my mechanic charges, I just don't think this one is worth the trouble.

piecesparts · 12-30-2005, 06:54 PM

To find a leak on a manifold there are two ways that I have seen that work, first, use amirror and a flashlight and look for darkened areas, exhaust carbon where the manifold and head meet. second with the motor running use a stethoscope with a hose on it and the noise will become real alive when you get close to it.

If your mechanic only charges $20.00 and hour, then we all need to drive to your area. The cheapest that we have in my area is $55.00 an hour. I have a lift in my shop, so finding things like that is easier than it is under a shadetree or in a shop on a creeper.

Jim85IROC · 12-31-2005, 01:03 AM

with a mechanic this cheap, it's always easier to send it to him. I do all of my own work on my cars, but since my truck is my only winter driver, I can't have much down time... plus, since it's a winter driver, it's rusty, cold, and wet. Not my idea of fun.

12-28-2005, 01:17 PM	#1
Jim85IROC Registered User Join Date: Dec 2004 Location: Readsboro, VT Posts: 502	87 454 exhaust manifold removal questions I may need to remove the passenger side exhaust manifold on my pickup (87 GMC 3500 454). I've got an extremely irritating exhaust leak on the passenger side somewhere, and after spending 2 days replacing the donut seal on the exhaust manifold collector, I've discovered that it wasn't the problem. Either the manifold is cracked or the gasket is in need of replacement. Either way, it looks like the manifold will have to come off. What kind of a nightmare am I looking at? The truck's got about 100k miles, and is a winter-driven vehicle. I would really like to get this thing off without destroying the air lines or breaking any bolts off in the head. Any pointers would be much appreciated. __________________ 1987 GMC Sierra Classic 3500 454 TH400 My Sounddomain Page

12-28-2005, 01:20 PM	#2
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Re: 87 454 exhaust manifold removal questions Unfortunately, my experience with 87+ manifolds is that you always break at least a few bolts, and the air lines are pretty much garunteed to break =/ Other problem is that as soon as you take that manifold off, it'll compress, and be really tough to get back on later =/ __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

12-28-2005, 01:39 PM	#3
87 STEPPER STILL PLAYS WITH TRUX Join Date: Nov 2002 Location: Melbourne, Fla. Posts: 2,764	Re: 87 454 exhaust manifold removal questions Im not too fam with the BBC exhaust and being that is on the pax side ya may have issues with the starter and it may need to be droped i dont know. What i can tell ya is get some "PB Blaster" from the auto parts store and hit them bolts and air line fittings with it for a few days befor you attempt to brake any of them lose. this stuff works great for really tuff rusted bolts and nuts. Sometimes it will help if you hit them with the penetrant when the eng is warm and then brake them lose this helps keep you warm too in the cold. Buy the stock type gaskets to replace the old ones and just to let ya know there may not be any installed sometimes the factory wont use a gasket. Clean the manifold with some sort of degreaser and do a good visual inspection of the manifold for cracks. Good luck __________________ ~~Bruce~~ MY 87 STEPPER MY 99 2D/WD TAHOE Last edited by 87 STEPPER; 12-28-2005 at 01:43 PM.

12-28-2005, 02:31 PM	#4
Jim85IROC Registered User Join Date: Dec 2004 Location: Readsboro, VT Posts: 502	Re: 87 454 exhaust manifold removal questions great... this sounds like it's going to be a ton of fun. Thanks for the info though guys. Now I need to decide whether to spend a weekend doing it myself or suck it up and pay a garage to fight with it. __________________ 1987 GMC Sierra Classic 3500 454 TH400 My Sounddomain Page

12-28-2005, 07:44 PM	#5
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: 87 454 exhaust manifold removal questions If you break the bolts, go ahead and take the manifold off and then weld a nut to the bolt. The heat that is induced into the bolt as you weld it, will loosen the bolt from the cast iron head. The "PB Blaster" is a good idea, if you can't get that, then use "Liquid Wrench and heat the bolt and spray it onto the bolt to soak. Try getting it into the crack between the head and the exhaust manifolt so it will get to the threads.

12-30-2005, 02:46 PM	#6
Jim85IROC Registered User Join Date: Dec 2004 Location: Readsboro, VT Posts: 502	Re: 87 454 exhaust manifold removal questions I pulled the truck into the garage and started to evaluate things. I can't feel any air blowing around the donut in the manifold/exhaust pipe connection, which is what I just replaced earlier in the week. The good news is that it appears that my work was good, the bad news is that means it's something that's more work. I felt around the manifold the best I could with the engine running, but between the fan blowing at mach speed and the fact that the manifold gets hot as hell almost instantly, it wasn't productive. The noise is definately louder under the hood than under the truck though. I checked the air tubes and they all appear to be ok, which leads me to think it's either a manifold gasket or a cracked manifold. It's so cluttered and tight down there though, I really can't see worth a damned, so I'm not sure what it is. I managed to break free every exhaust manifold bolt that I can get to, but I can't get to the rear-most one, the one next to the dipstick tube, and the one holding the dipstick bracket. I think I might punt this one off to my mechanic. After many hours of swearing and throwing tools, I'm sure I'll be able to get that manifold off, but I'm not so sure that getting it back on is going to be much fun, and with my luck I'll probably destroy the dipstick tube trying to get it out. For the $20/hr my mechanic charges, I just don't think this one is worth the trouble. __________________ 1987 GMC Sierra Classic 3500 454 TH400 My Sounddomain Page

12-30-2005, 06:54 PM	#7
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: 87 454 exhaust manifold removal questions To find a leak on a manifold there are two ways that I have seen that work, first, use amirror and a flashlight and look for darkened areas, exhaust carbon where the manifold and head meet. second with the motor running use a stethoscope with a hose on it and the noise will become real alive when you get close to it. If your mechanic only charges $20.00 and hour, then we all need to drive to your area. The cheapest that we have in my area is $55.00 an hour. I have a lift in my shop, so finding things like that is easier than it is under a shadetree or in a shop on a creeper.

12-31-2005, 01:03 AM	#8
Jim85IROC Registered User Join Date: Dec 2004 Location: Readsboro, VT Posts: 502	Re: 87 454 exhaust manifold removal questions with a mechanic this cheap, it's always easier to send it to him. I do all of my own work on my cars, but since my truck is my only winter driver, I can't have much down time... plus, since it's a winter driver, it's rusty, cold, and wet. Not my idea of fun. __________________ 1987 GMC Sierra Classic 3500 454 TH400 My Sounddomain Page



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