mfox20
Fort Worth, TX
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Joined: 10/11/2004
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I am working on a 1994 454 right side exhaust leak and decided to replace the stock manifold with a NAPA stock replacement. I am ready to install the new manifold and have a couple of questions for those that have done exhaust work on the 454's.
1. Gasket or no gasket when replacing? I have seen several post where gaskets were used with success and a few that say Chevy recommends no gasket.
2. Torque values and bolting sequence when installing new manifold?
Project is going well except for one broken bolt. I was able to get it out after drilling several times and using a square easy out/bolt extractor.
I would be happy to answer any questions for those thinking about trying to fix the typical 454 exhaust leak. I have a few pointers that could make the project go well.
Thanks in advance if you can provide some info.
Michael
1994 Four Winds 5000
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Joatha
Marietta, GA
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Joined: 07/19/2006
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I am one that recommends no gasket. I put a new one on mine in the summer of 2006 and didn't put a gasket on it. Its held so far. I have a buddy that rebuilds a lot of Chevy's and he doesn't use exhaust gaskets. I have done a number of Mopar motors myself and have done the same. Its his experience (and mine) that they tend to disintegrate over time and leak. I'm sure someone will disagree. But, that's been my experience. I've never had a problem with them leaking with no gasket.
25 ft-lbs will work pretty well as a torque setting. As far as order is concerned, I start with the middle bolts and work my way out alternating between front and back bolts. Also, I usually tighten to about 15-20 ft-lbs first and then go back and do the final tightening in the same order.
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RealtyRoy
NW Oregon
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Joatha has given you good advise but I'm one that likes using the gasket on the older engines. If there is any imperfections in the surface on the head where they meet than a gasket would be best. If you had a straight edge you could check it out.
Also, I always put a little anti-seize on the bolts before putting them in. If you ever have to do this job again you wont have to deal with broken bolts.
Good Luck!
Roy
May the roads and skies always be clear, and the firewood nice and dry!!
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sum1
So-Cal
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Sorry I can't give a specific reference for it right now, but I recall that the '91 Chevrolet Manual suggests cutting the web between the ports to reduce the forces exerted by thermal expansion and contraction. I also vaguely remember something about enlarging a couple of the bolt holes. Anybody with a better memory than mine? I'm also a fan of NevrSeize.
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Jakeman97
Florida / Massachusetts
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Joined: 08/29/2007
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mfox20 wrote:I am working on a 1994 454 right side exhaust leak and decided to replace the stock manifold with a NAPA stock replacement. I am ready to install the new manifold and have a couple of questions for those that have done exhaust work on the 454's.
1. Gasket or no gasket when replacing? I have seen several post where gaskets were used with success and a few that say Chevy recommends no gasket.
2. Torque values and bolting sequence when installing new manifold?
Project is going well except for one broken bolt. I was able to get it out after drilling several times and using a square easy out/bolt extractor.
I would be happy to answer any questions for those thinking about trying to fix the typical 454 exhaust leak. I have a few pointers that could make the project go well.
Thanks in advance if you can provide some info.
Michael
1994 Four Winds 5000
Hi Michael,
Not sure but this might help. "Chevy Big Block Torque Values" If not, would suggest you call or visit your nearest Chevy Truck Center and they will be happy to answer your questions right from the shop manuals.
Jakeman97
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fuzzbutt
Pittsburgh
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Joined: 11/17/2006
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I had to have mine fixed last year. 94 Chevy 454 also. They used the copper gasket set. The old mainfold face had some deformities from blow by. They cleaned up the face and the new gaskets sealed it up just fine.
Good luck!!!
John, Sherry & Sabrina
+ Mowgli (Keeshond) Sunny (Sun Conure) & Lily (Cockatiel)
94 Winnebago Adventurer 34'
04 Nissan Murano
98 Subaru Forester
92 Honda Gold Wing
Now.....bring me that horizon.
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mfox20
Fort Worth, TX
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Thanks to all for the input.
Based on the link from Jakeman97(Chevy Big Block Torque Values), it looks like 25 is the right torque value. Several have confirmed to start in the middle.
Now I just have to decide: gasket or no gasket. I may start with no gasket and add it if it starts to leak. Now that I have a little experience on this right side I could get the gasket installed in about an hour.
Thanks again and I will update the post with the results when installation is completed.
Michael
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Troubleshooter
Anchorage, AK
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Joined: 05/02/2002
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Per the Unit Repair Manual for the 1991 7.4L (454CID) engine.
Exhaust Manifold bolts/studs to be tightened to 54 N.m (40 ft. lbs.)
No gasket used between the block and the manifold.
No specific sequence for tightening the bolts/studs on the 7.4L engines, however I personally would use a "X" pattern, starting from the center, and working to the outside.
Bill
2002 Discovery 3126E CAT
2004 Saturn VUE
Mountain Master Tow Brake
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Flyfisherman128
Broadalbin, NY
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Joined: 08/09/2005
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I did mine at 25 ft-lbs like the book says, they loosend after two years. Dont forget to re-torque after a couple of outings.
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bacollins
Lawrenceburg, IN
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Joined: 11/21/2004
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My manual states that for '88 - '94 engines, center bolts 26 ft/lbs, outer bolts 20 ft/lbs. It's a good idea to clean the threaded holes in the head with a bottom tap and use new bolts/studs, use anti-seize liberally on the threads. I personally prefer gaskets on the manifolds, especially on the older engines, racing type gaskets from Summit or Jegs are good. Check the torque after a couple of heat cycles.
'92 Itasca Sunflyer P series Chevy
'99 Wrangler Toad
'99 Cherokee Toad
'00 Yamaha WR 400
'05 KTM 450 EXC
'92 Honda 750 Nighthawk
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