Head L48 L82, 74 through 77
Thread Starter
Burning Brakes
Joined: Sep 2005
Posts: 1,139
Likes: 109
From: B'ham Alabama
Head L48 L82, 74 through 77
According to my book, (Corvette Facts, 73 through 77), it shows ALL of the heads having the same number, 333882, for both the L48 and the L82 engine. I had always heard that the L82's had a better set of heads. However, according to my book, they are the same head. Is this right?
Melting Slicks
Joined: Mar 2007
Posts: 2,100
Likes: 12
From: Frederick Maryland
The Corvette Black Book shows essentially the same thing. A few other numbers, but that may be for California cars since they were different in some respects.
L48 and L82 differences were mainly in the rotating assembly (compression ratio, crank, pistons) and the block, cam, intake and carb.
L48 and L82 differences were mainly in the rotating assembly (compression ratio, crank, pistons) and the block, cam, intake and carb.
Le Mans Master
Joined: Jan 2007
Posts: 7,987
Likes: 3,333
From: Omaha NE
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
2022 C3 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
My black book shows 333882 for both L-48 & L-82 in '76.
My dealer sales brochure says the the L-82 has "special heads with larger valves"
My dealer sales brochure says the the L-82 has "special heads with larger valves"
Thread Starter
Burning Brakes
Joined: Sep 2005
Posts: 1,139
Likes: 109
From: B'ham Alabama
My "Corvette Black Book" and my "Vette Facts Book" BOTH say the same thing, 333882 for the L48 & L82 engines. However, just like you guys, I had alwayys heard and read that the L82 had "better" heads.
What is correct?
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
882 is a CASTING # ... more than one PART # uses same casting #.
It's how the casting is finished that determines part # ... ie valve size.
Other than valve size, There's no significant difference ... even then, L82's slightly larger valves don't amount for much "better". You can machine a L48 seat to accept a larger valve ... done everyday. You can machine a L48 rocker boss to accept screw-in stud & guideplate ... done everyday.
All 882 castings have same runner/port volume & shape and have same combustion chamber volume & shape ... just as do all 487 castings ... regardless of valve size.
Learn what's actually different ... learn if any difference is significant ... and try to understand how & why any such difference might be "better" ... & Don't believe everything you hear.
It's how the casting is finished that determines part # ... ie valve size.
Other than valve size, There's no significant difference ... even then, L82's slightly larger valves don't amount for much "better". You can machine a L48 seat to accept a larger valve ... done everyday. You can machine a L48 rocker boss to accept screw-in stud & guideplate ... done everyday.
All 882 castings have same runner/port volume & shape and have same combustion chamber volume & shape ... just as do all 487 castings ... regardless of valve size.
Learn what's actually different ... learn if any difference is significant ... and try to understand how & why any such difference might be "better" ... & Don't believe everything you hear.
Drifting
Joined: Nov 2004
Posts: 1,971
Likes: 7
From: Longwood Florida
YUP !! and smaller chamber to give slightly higher compression.
Over all the factory heads produce in the late 70 are not the best for performance... of course a machine shop can make them flow well... but you have a better starting point with a cheap 'brand new' set of vortec heads...
Over all the factory heads produce in the late 70 are not the best for performance... of course a machine shop can make them flow well... but you have a better starting point with a cheap 'brand new' set of vortec heads...
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
NOPE! ... L82 & L48 have same volume chamber ... L82's approx half-point higher compression is from L82 flattop piston that has more dome volume than L48's dish piston. Yes, L82 has slightly bigger valves. As before ... don't believe everything you ...
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Bigger valves, Bigger cam, Flat top forged pistons, Forged crank and 4 bolt mains are the only differences in the L82.
Melting Slicks
Joined: Jul 2005
Posts: 2,060
Likes: 46
From: winter haven florida
St. Jude Donor '12
this is an l-48 head off a 75. i dont think the previous owner ever changed oil 
. the motor was still running and didnt smoke when i did the rebuild though. no wonder they could only get 165 hp out of the 75 l-48.the heads ended up in the scrap pile at the machine shop. the vortec would be a much better choice for a mild build.
. the motor was still running and didnt smoke when i did the rebuild though. no wonder they could only get 165 hp out of the 75 l-48.the heads ended up in the scrap pile at the machine shop. the vortec would be a much better choice for a mild build.
Last edited by 2000FRCZ19; Mar 20, 2007 at 12:54 AM.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
this is an l-48 head off a 75. i dont think the previous owner ever changed oil . the motor was still running and didnt smoke when i did the rebuild though. no wonder they could only get 165 hp out of the 75 l-48.the heads ended up in the scrap pile at the machine shop. the vortec would be a much better choice for a mild build.
. the motor was still running and didnt smoke when i did the rebuild though. no wonder they could only get 165 hp out of the 75 l-48.the heads ended up in the scrap pile at the machine shop. the vortec would be a much better choice for a mild build.
Drifting
Joined: Jul 2002
Posts: 1,944
Likes: 20
From: The only Corvettes in Highett Victoria
....and wait, there's more........
63MAKO,
Also aluminum inlet manifold and aluminum finned rocker covers. Oh, and those little L82 badges on some models.
Regards from Down Under
aussiejohn
Also aluminum inlet manifold and aluminum finned rocker covers. Oh, and those little L82 badges on some models.
Regards from Down Under
aussiejohn
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,500
From: Little Rock AR
There weren't many parts that were common to the L-48 that would go into an L-82. Almost everything was upgraded in some way for added durabillity and HP. Some years used the same intake manifold but not all.-Mark.
Drifting
Joined: Nov 2004
Posts: 1,971
Likes: 7
From: Longwood Florida
I didnt realize the piston difference... GM did a lot of work to the L82 to get a low 15 maybe high 14 second vette.
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,500
From: Little Rock AR
The L-82 engine was realy a pretty good place to start with if you were into mods. The exhaust held it back a lot and the low compression/low performance heads held back a bit as well. All for the sake of clean air. Change a few things, recalibrate and it is 1969 all over again.
-Mark.
Safety Car
Joined: Mar 2005
Posts: 4,255
Likes: 82
From: Brampton Ont.
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
Melting Slicks
Joined: Jul 2005
Posts: 2,060
Likes: 46
From: winter haven florida
St. Jude Donor '12
i would have to agree completly here. i trashed these heads and did a lot more work with a better set of heads and got more than 2.5 times the origninal hp out of the rebuild.