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Old 01-18-2011, 07:10 PM   #1
MarkBullis
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Default What's the difference between L48 and L82?

Hey guys... what was the difference between the L48 motor and an L82? I know the 82 had more power, but what was the difference?
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Old 01-18-2011, 07:51 PM   #2
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Quote:
Originally Posted by MarkBullis View Post
Hey guys... what was the difference between the L48 motor and an L82? I know the 82 had more power, but what was the difference?
The differences probably vary by year but essentially boils down to the following:

Crank L82-forged L48-cast
Pistons L82-forged L48-cast
Intake L82-Alum L48-iron
Cam L82-performance L48-std (performace is just a generalization the L82 cam is a higher perf cam than the L48 but in comparison to aftermarket cams isnt all that splendid)
Valves L82-large L48-small
Block L82-4bolt L48-2bolt
Compression L82-8.9:1 L48-8.2:1 (1978)

there are other changes for example in 78 the L82 exhaust was 2 1/2" while the L48 was 2 1/4" (IIRC)
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Last edited by fauxrs; 01-18-2011 at 07:54 PM.
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Old 01-18-2011, 07:52 PM   #3
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Quote:
Originally Posted by MarkBullis View Post
Hey guys... what was the difference between the L48 motor and an L82? I know the 82 had more power, but what was the difference?
Cam and compression ratio (pistons).
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Old 01-18-2011, 08:01 PM   #4
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L34

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Old 01-18-2011, 09:35 PM   #5
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L34

Beat me to it.
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Old 01-19-2011, 09:54 AM   #6
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The Rods and Oil pan are also different.
Plus the Aluminum valve covers.
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Old 01-19-2011, 10:16 AM   #7
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completely different, L-82 was a true performance engine. L48 was a nice station wagon engine
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Old 01-19-2011, 10:18 AM   #8
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completely different, L-82 was a tuned down smog engine. L48 was even more so
Fixed it for ya.
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Old 01-19-2011, 10:51 AM   #9
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In 1978, dual snorkel vs. single
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Old 01-19-2011, 10:56 AM   #10
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All of the above with the correction that both intake manifolds are cast iron. Exhaust after the manifolds on a 73 is 2 1/2 inches versus 2 inches on an L-48. Intake and exhaust valves are different and lift and duration of the cam are greater on the L-82. The iron block castings are identical. Tach redline is greater on the L-82 (5600 w/o AC on the L-82 versus 5300 L-82). Rear ends installed at least in 1973 tended to be greater in L-82 4 speed cars such as the GS4 3.70 which resulted in more revolutions to the rear wheels per crankshaft revolution.
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Old 01-19-2011, 08:36 PM   #11
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Quote:
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All of the above with the correction that both intake manifolds are cast iron.
Actually, I know in 78/79 the L-82 used an aluminum intake. In 80, I believe everything or nearly everything switched to aluminum.

L-48s, cast-iron 78/79
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Old 01-19-2011, 10:59 PM   #12
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both sucked. one just worse then the other....
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Old 01-19-2011, 11:04 PM   #13
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ha ha! both sucked. ha ha! wait a minute what am i laughing at i have an l 48. wahaaaaaaaaaa!
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Old 01-19-2011, 11:17 PM   #14
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"L-82 was a true performance engine" haha
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Old 01-20-2011, 04:47 AM   #15
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Quote:
Originally Posted by fauxrs View Post
The differences probably vary by year but essentially boils down to the following:

there are other changes for example in 78 the L82 exhaust was 2 1/2" while the L48 was 2 1/4" (IIRC)
Hey fauxrs:

Check out your webpage out of curiosity...you did some serious work on that 78. Looks great! What's your background...engineer? Nice display of data in tables. You must have a penchant for detail.
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Old 01-20-2011, 05:43 AM   #16
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Quote:
Originally Posted by Evil Empire View Post
"L-82 was a true performance engine" haha
Starting in 78, the L-82 had an aluminum intake not cast iron, as noted already. Also, check out the Super Chevy artice below, about the Gross HP of a bone stock L-82 and compare those numbers to the "mighty" LT-1 Gross HP numbers and torque from 70-72 and the L-82 is right there in terms of gross HP numbers-apples to apples. Add to that the 0-60 and 1/4 mile numbers from 1978/79-6.5 sec for the 4 speed and 6.6 for the automatic, only 2 cars tested by Road and Track were faster-Ferrari Testarossa and Porsche Turbo-5.5 and 5.0 respectively. In the late 70's the L-82 was a true performance engine relative to what was available from any manufacturer-foreign or domestic.

http://www.superchevy.com/technical/...ver/index.html

Quote-"In stock trim on our dyno, the 9.0:1 L82 produced 313 flywheel (gross) horsepower at 5,500 rpm and 355 lb-ft of torque at 3,800 rpm. The engine produced adequate torque relative to the horsepower rating, but it wasn't exactly what you'd describe as earth-shattering."

The L-82 will easily make 400 HP by changing the heads and cam-not hard.

The 70/71 LT-1 was 330/350/370-The mid range LT-1 had 37 more HP-Not earth Shattering 350-313=37 Gross HP gain! In Net HP that difference is probably about 10-12 HP Net! The 1972 LT-1 had 255 Net HP and the 1973 L-82 has 255-Wow! 74 L-82 with true duals 250 Net HP. A 78/79/80 L-82 will certainly make 250-255 Net HP with a true dual 2.5 inch exhaust (more with headers) and no cat. Is the LT-1 a better engine-certainly but not by much!

This same kind of nonsense is probagated about the 427 435 Gross HP big blocks. Yes they are fast for their day but so was the L-82 but it does not stand a chance against a modern LS3 not to mention an LS7 Z06-not even close. Different eras!

Hopefull, this information will put to rest that the L-82 is some knid of "dog" compared to the "high horsepower" SB engines of the late 60's/early 70's-it simply is not true.

Last edited by jb78L-82; 01-20-2011 at 08:08 AM.
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Old 01-20-2011, 09:32 AM   #17
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Quote:
Originally Posted by fauxrs View Post
The differences probably vary by year but essentially boils down to the following:

Crank L82-forged L48-cast
Pistons L82-forged L48-cast
Intake L82-Alum L48-iron
Cam L82-performance L48-std (performace is just a generalization the L82 cam is a higher perf cam than the L48 but in comparison to aftermarket cams isnt all that splendid)
Valves L82-large L48-small
Block L82-4bolt L48-2bolt
Compression L82-8.9:1 L48-8.2:1 (1978)

there are other changes for example in 78 the L82 exhaust was 2 1/2" while the L48 was 2 1/4" (IIRC)
Well i've got a 1977 with 4spd... with out taking the engine out, is there anyway i can tell which one i have?
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Old 01-20-2011, 10:26 AM   #18
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On my 78 L-82 the fifth digit of the VIN number is a 4 but a 77 it is an X:

Decoding VIN Numbers


Do you need to determine if you Corvette is really an L-82? Here's a simple way to decode your VIN number. However, this only works for 1973 - 1980 Corvettes.

First, here are a few facts about VIN numbers:

Each Corvette has a unique Vehicle Identification Number and they are assigned in sequence, starting with one, during production.

The last 6 digits of the VIN make the Corvette unique. This number is the Production Sequence Number.

Position
Description Code
1 General Motors Division 1 = Chevrolet
2 Car line or series Z = Corvette
3 - 4 Body style 37 = Two door coupe (1973-1977)
67 = Two door convertible
87 = Two door coupe (1978-1980)
5 Engine type 1973: J = L48; 350ci, 190hp
T = L82; 350ci, 250hp
Z = LS4; 454ci, 275hp
1974: J = L48; 350ci, 195hp
T = L82; 350ci, 250hp
Z = LS4; 454ci, 270hp
1975: J = L48; 350ci, 165hp
T = L82; 350ci, 205hp
1976: L = L48; 350ci, 180hp
X = L82; 350ci, 210hp
1977: L = L48; 350ci, 180hp
X = L82; 350ci, 210hp
1978: L = L48;350ci, 175hp, 185hp
4 = L82; 350ci, 220hp
1979: 8 = L48; 350ci, 195hp
4 = L82; 350ci, 225hp
1980: H = LG4; 305ci, 180hp
8 = L48; 350ci, 190hp
6 = L82; 350ci

Last edited by jb78L-82; 01-20-2011 at 10:29 AM.
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Old 01-20-2011, 11:56 AM   #19
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L-48s did not have smog pumps (Xcept CA and high altitude)
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Old 01-20-2011, 01:34 PM   #20
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Quote:
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L-48s did not have smog pumps (Xcept CA and high altitude)
My non-CA, low altitude 80 had a smog pump....
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Old 01-20-2011, 01:34 PM
 
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