You don't even have to jack up the motor, just slip them in from underneath.
78 stock L82
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 751
Likes: 0
From: Lufkin Texas
78 stock L82 Exhaust Question
Does anyone know the Horse power differance between staying with my original exhaust manifolds or going to Headers I plan to run 2-1/2
duals all the way back either way. Also If I go with headers are ceramic coated better or not.
duals all the way back either way. Also If I go with headers are ceramic coated better or not.
Le Mans Master
Joined: Oct 2004
Posts: 5,269
Likes: 54
From: Orlando Florida
St. Jude Donor '05
You have to get rid of the stock manifolds, they are the worst part in that exhaust system. Duals from the manifolds back won't be a lot better than what you have now, with headers you can expect 30HP more than stock, it's going to feel and sound like 80HP more 
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 751
Likes: 0
From: Lufkin Texas
Originally Posted by RedBad1979
You have to get rid of the stock manifolds, they are the worst part in that exhaust system. Duals from the manifolds back won't be a lot better than what you have now, with headers you can expect 30HP more than stock, it's going to feel and sound like 80HP more
Thanks I just did not know how much of a pain in the rear headers would be to install or keep the gaskets on.
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
OK, so what are the best headers out there? Which ones does the forum recommend? I already have a set of Madvet duals that neck down to 2" at the manifolds. I would want to hack off the neckdowns and mate up what's left to something 
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
how about a conservative estimate .....with headers and dual exhaust and no cats....a 10-15% increase...really depends on how clogged the old cat was.
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Here is an option without the pain of headers....
http://www.castheads.com/corvette_systems.php#manifolds
I have Headers on my 69...but considering these for the 78 L-82..if I can slip by smog check...
http://www.castheads.com/corvette_systems.php#manifolds
I have Headers on my 69...but considering these for the 78 L-82..if I can slip by smog check...
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Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Contrary to popular belief, the rams horn exhaust manifolds are not that bad. Many street rodders use them as an alternative to headers.
The advantage of headers is at higher rpm, where they allow the system to breathe more freely. However, they offer no advantage in the lower rpm range, where you're trying to produce more torque.
Having said all of that, the choice is yours. Personally, I had my exhaust manifolds ceramic coated -- I find headers to be a leaky, noisy PITA. The exhaust system is 2½" duals with an h-pipe near the oil pan.
The advantage of headers is at higher rpm, where they allow the system to breathe more freely. However, they offer no advantage in the lower rpm range, where you're trying to produce more torque.
Having said all of that, the choice is yours. Personally, I had my exhaust manifolds ceramic coated -- I find headers to be a leaky, noisy PITA. The exhaust system is 2½" duals with an h-pipe near the oil pan.
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
Here are specs for a new GM engine that seems similar to the L-48. The engine puts out essentially 250hp. Bolt up some accessories and hook up a restrictive exhaust system (such as the mid/late 70's) and the hp dropped to approximately 180hp. That's 70 hp. How much was lost with the accessories and how much was lost from the exhaust?
Horsepower¹: 249 HP @ 5,000 RPM
Torque¹: 304 FT/LBS @ 3,500 RPM
Redline: 5,200 RPM
Comp. Ratio: 8.50:1
Heads: Cast Iron, 76 cc Valves: 1.940” I, 1.500” E
Camshaft Lift: Hydraulic; 0.390” I , 0.410” E
Duration @ 0.050”: 195° I, 202° E
Block: 4 Bolt Main, 2 Piece Rear Main Seal, 4.000” Bore
Crankshaft: Cast Iron Nodular, 3.480” Stroke
Note¹ - Numbers are for a engine that had a cast iron intake, Q-Jet Carb., HEI distributor, 1-5/8” headers and open exhaust installed prior to dyno testing.
Horsepower¹: 249 HP @ 5,000 RPM
Torque¹: 304 FT/LBS @ 3,500 RPM
Redline: 5,200 RPM
Comp. Ratio: 8.50:1
Heads: Cast Iron, 76 cc Valves: 1.940” I, 1.500” E
Camshaft Lift: Hydraulic; 0.390” I , 0.410” E
Duration @ 0.050”: 195° I, 202° E
Block: 4 Bolt Main, 2 Piece Rear Main Seal, 4.000” Bore
Crankshaft: Cast Iron Nodular, 3.480” Stroke
Note¹ - Numbers are for a engine that had a cast iron intake, Q-Jet Carb., HEI distributor, 1-5/8” headers and open exhaust installed prior to dyno testing.
Burning Brakes
Joined: Apr 2000
Posts: 1,076
Likes: 0
From: Dixie TN
headers
Originally Posted by toupstrio
Does anyone know the Horse power differance between staying with my original exhaust manifolds or going to Headers I plan to run 2-1/2
duals all the way back either way. Also If I go with headers are ceramic coated better or not.
duals all the way back either way. Also If I go with headers are ceramic coated better or not.
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Originally Posted by bobs77vet
how about a conservative estimate .....with headers and dual exhaust and no cats....a 10-15% increase...really depends on how clogged the old cat was.
An easy 30HP with duals. Add a K&N Filter for another 25HP.
Install ROLLER ROCKERS and you got another 30HP. See...it's EASY. Ya just gotta change parties
Dep
Le Mans Master
Joined: Sep 2000
Posts: 9,078
Likes: 7
From: DFW TX
Cruise-In VII Veteran
St. Jude Donor '07
You guy's never stop. 
Don't forget the stickers, there good for a 1/10th in quarter.
Don't forget the stickers, there good for a 1/10th in quarter.
Originally Posted by DJ Dep
Aww c'mon Bob. Don't be so dang Conservative. Be a LIBERAL!!!
An easy 30HP with duals. Add a K&N Filter for another 25HP.
Install ROLLER ROCKERS and you got another 30HP. See...it's EASY. Ya just gotta change parties
Dep
An easy 30HP with duals. Add a K&N Filter for another 25HP.
Install ROLLER ROCKERS and you got another 30HP. See...it's EASY. Ya just gotta change parties
Dep
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Originally Posted by Budman78
You guy's never stop. Don't forget the stickers, there good for a 1/10th in quarter.
Don't forget the stickers, there good for a 1/10th in quarter.Why...I remember when EVERYONE had an STP sticker on their car. Good for an instant 10HP boost.
Dep
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Originally Posted by toupstrio
Does anyone know the Horse power differance between staying with my original exhaust manifolds or going to Headers I plan to run 2-1/2
duals all the way back either way. Also If I go with headers are ceramic coated better or not.
duals all the way back either way. Also If I go with headers are ceramic coated better or not.
