Head L48 L82, 74 through 77
03-18-2007, 05:31 PM
#1
Burning Brakes
Thread Starter
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?
03-18-2007, 05:50 PM
#2
Melting Slicks
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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.
03-19-2007, 01:38 AM
#4
Le Mans Master
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2023 C3 of the Year Finalist - Unmodified
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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"
03-19-2007, 06:39 AM
#5
Burning Brakes
Thread Starter
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?
03-19-2007, 08:42 AM
#6
Le Mans Master
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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.
03-19-2007, 05:19 PM
#7
Drifting
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...
03-19-2007, 09:23 PM
#8
Le Mans Master
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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 ...
03-20-2007, 12:10 AM
#9
Race Director
Bigger valves, Bigger cam, Flat top forged pistons, Forged crank and 4 bolt mains are the only differences in the L82.
03-20-2007, 12:51 AM
#10
Melting Slicks
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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; 03-20-2007 at 12:54 AM.
03-20-2007, 02:01 AM
#11
Race Director
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.
03-20-2007, 03:59 AM
#12
Drifting
....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
03-20-2007, 08:46 AM
#13
Le Mans Master
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.
03-21-2007, 02:46 PM
#15
Drifting
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.
03-22-2007, 08:05 AM
#16
Le Mans Master
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.
03-22-2007, 05:00 PM
#18
Drifting
03-22-2007, 05:03 PM
#19
Melting Slicks
03-22-2007, 06:56 PM
#20
Melting Slicks
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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.