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Username Post: What's the difference between the L48 and the L82?        (Topic#218541)
60 Bel air 
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Posts: 18
60 Bel air
Age: 36
Loc: Castle Rock, Colorado
Reg: 05-07-09
06-05-09 03:44 PM - Post#1711738    

What's the difference between the L48 and the L82 Corvettes? I know it has to do with the engine, but whats the difference? I recently purchased a '75 Stingray L48 and was wondering. Any info helps...

Thanks
1960 CHEVY BEL-AIR 2 Door Hardtop w/ 454cid, Turbo 400, 9" Rear, and still a project

1975 CHEVY CORVETTE Stingray 350cid, Auto, all original


 
YeniPenny 
Dedicated Enthusiast
Posts: 5813
YeniPenny
Loc: Biloxi, Ms
Reg: 11-26-01
06-05-09 05:59 PM - Post#1711798    
    In response to 60 Bel air

The L-48 was the base engine. (from memory), It had approximately 190HP. The L-82 was the high performance engine having 220HP most of the years it was available. The last year for the L-82 was 1980.

 
wagonmaster 
Senior Member
Posts: 8370
wagonmaster
Age: 65
Loc: Loganville, Ga.
Reg: 04-28-00
06-05-09 06:21 PM - Post#1711805    
    In response to YeniPenny

In 1975 the L-48 had 165 HP while the L-82 had 205 HP. Those engines had more camshaft and useable RPM as a result, don't remember what, if anyting, else they had to make them different.
Hey T @!


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Joe


 
bowtiefan 
"7th Year" Silver Supporting Member
Posts: 2103

Loc: Vacaville, CA
Reg: 02-19-04
06-05-09 06:32 PM - Post#1711817    
    In response to wagonmaster

I think that most years, the L-82 had an aluminum intake and a bigger carb. Internally, the L-82 was a 4 bolt main whereas the L-48 was a 2 bolt.

Ken
38 & 39 2dr sedan, 41 coupe, 54 convertible, 56 Nomad, 57 210 2dr sdn, 70 Camaro RS, Corvettes; 57, 61, 65 396 coupe, 67 427 convert, 69 & 72 T-top, 88 coupe,91 ZR-1, 07 Z06, 07 Silverado, 09 BMW 135i convert.
http://www.picturetrail.com/ken58


 
60 Bel air 
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Posts: 18
60 Bel air
Age: 36
Loc: Castle Rock, Colorado
Reg: 05-07-09
06-05-09 07:59 PM - Post#1711858    
    In response to bowtiefan

Thanks for the info....If I was to install a Edelbrock intake manifold, a 650 cfm Edelbrock carb, and headers w/ side pipes would I notice a nice gain? Would it be worth the money if I planned on keeping this car for a while?

Thanks
1960 CHEVY BEL-AIR 2 Door Hardtop w/ 454cid, Turbo 400, 9" Rear, and still a project

1975 CHEVY CORVETTE Stingray 350cid, Auto, all original


 
wagonmaster 
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wagonmaster
Age: 65
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Reg: 04-28-00
06-06-09 07:12 PM - Post#1712374    
    In response to 60 Bel air

It would if you added headers and a high performance exhaust system. You'll need a '74 -back crossmember to run real dual exhaust or modify yours to allow the left side exhaust. SHould really wake it up!
Hey T @!


In Memory of Mike McVeigh- The "Mad Spring Wacker" He roams the Forums of CT forever in our hearts and minds!

http://www.picturetrail.com/wagonmaster55

Joe


 
1974monte454 
Contributor
Posts: 289
1974monte454
Reg: 03-02-09
06-08-09 09:54 PM - Post#1713717    
    In response to wagonmaster

i talked with a corvette guy, said he tried everything with his L-48 to try and make power out of it, he said he upgraded the ignition, added headers, dual exhaust, intake, but he put a L-82 cam in it and that did the trick. i drove a 73 stingray with a L48 in it and i must say, it was rather depressing, the performance that is.
1974 454 Monte Carlo (factory)
1977/74 427 Monte Carlo
1985 K20 4 speed
MK3 USCG


 
wagonmaster 
Senior Member
Posts: 8370
wagonmaster
Age: 65
Loc: Loganville, Ga.
Reg: 04-28-00
06-09-09 02:36 PM - Post#1714063    
    In response to 1974monte454

Our 1974 L-48 ran really well with minor mods, It was no big block killer, but it would hold it's own and got great mileage!
Hey T @!


In Memory of Mike McVeigh- The "Mad Spring Wacker" He roams the Forums of CT forever in our hearts and minds!

http://www.picturetrail.com/wagonmaster55

Joe


 
Richard Martin 
Dedicated Enthusiast
Posts: 5145

Loc: Davis Islands, Florida
Reg: 06-12-03
06-09-09 02:56 PM - Post#1714077    
    In response to 60 Bel air

The '75 L82 had 4-bolt mains, forged crank, forged alum. pistons, a hi-perf .450/.460 lift cam, and 2.02/1.60 valve heads. The L48 had 2-bolt mains, cast crank, cast alum. pistons, standard perf .390/.410 lift cam and 1.94/1.50 valve heads. The '75 L82 could still be considered a high performance engine...the L48 was available in several Chevrolets including the Nova. The L82 was a $336.00 option in '75. 2372 installed according to Corvette Black Book.
-----
Richard

 
Smokey 
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Smokey
Age: 65
Loc: "Small town USA"
Reg: 12-06-99
06-09-09 07:45 PM - Post#1714259    
    In response to wagonmaster

Hey Joe both my 75's had the crossmember for the daul exhaust. I don't know what the prodution number was so I can't say if they were early 75 car's or not.
How I remember is that I ran dauls on both of them from the're stock unmolested two into one convertor configuration.
The first one I had was a L-82 and was a strong runner for a smog car
'67 427 Chevy C-10
'79 454 surburban
'89 454 1 ton dually
'03 V-Star 1100


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YeniPenny 
Dedicated Enthusiast
Posts: 5813
YeniPenny
Loc: Biloxi, Ms
Reg: 11-26-01
06-10-09 08:55 AM - Post#1714483    
    In response to Smokey

Smokes, I have a 78 L-82 that has the notched crossmember for duals and it is for sure an original car. I had real duals put on about 17 years ago.

 
wagonmaster 
Senior Member
Posts: 8370
wagonmaster
Age: 65
Loc: Loganville, Ga.
Reg: 04-28-00
06-10-09 06:51 PM - Post#1714846    
    In response to YeniPenny

Cool! I had a good friend that had a '77 without the dual exhaust cross member. We used an older one to convert his to duals. Don't recall where I heard it, but I was under the impression that all '75 up did NOT come with the dual exhaust cross member.... Good info that they didn't here.
Hey T @!


In Memory of Mike McVeigh- The "Mad Spring Wacker" He roams the Forums of CT forever in our hearts and minds!

http://www.picturetrail.com/wagonmaster55

Joe


 
1974monte454 
Contributor
Posts: 289
1974monte454
Reg: 03-02-09
06-12-09 10:31 PM - Post#1716175    
    In response to wagonmaster

starting in 75 monte carlos dident have the dual exhaust cross member
1974 454 Monte Carlo (factory)
1977/74 427 Monte Carlo
1985 K20 4 speed
MK3 USCG


 
pgtr 
Senior Member
Posts: 344

Reg: 11-21-03
06-30-09 06:57 PM - Post#1726758    
    In response to 60 Bel air

  • 60 Bel air Said:
What's the difference between the L48 and the L82 Corvettes? I know it has to do with the engine, but whats the difference? I recently purchased a '75 Stingray L48 and was wondering. Any info helps...

Thanks



Congrats on your purchase!

The L48 replaced the L75 in 1969 as the base '300hp' Corvette engine. It continued in this capacity largely unchanged thru 1980. It was also an optional engine on a few other Chevrolets such as the Camaro.

The L82 came out in 1973 - essentially it replaced the L46 (last seen in 1969) as the '350hp' optional engine. It also was avail thru 1980.

The 300 and 350 hp terms are relative to the days before SAE Gross HP ratings. In '72 all HP ratings changed to SAE NET and subsequently dropped.

There may be some year to year variations but here's a list from memory:

THe L82 had the old L46 cam. The L48 had a milder cam which produced great torque and a good idle.

L48 had a cast iron intake, L82 had lighter aluminum.

L82 and L48 have slightly different timing curves.

L82 and L48 have slightly different heads w/ the L82 having larger valves.

L82 has forged pistons, L48 cast.

L82s have rod guides.

SOmeone else mentioned the 2 bolt/4 bolt diff.

L82 has a larger balancer than the L48.

The L48 has a cast crank - I don't recall on the L82 off hand...?

You're L48 is a VERY GOOD engine. They put these engines in Corvettes for a longer period than any other and with good reason (69-80). Enjoy!

 
pgtr 
Senior Member
Posts: 344

Reg: 11-21-03
06-30-09 07:08 PM - Post#1726768    
    In response to 1974monte454

  • 1974monte454 Said:
i talked with a corvette guy, said he tried everything with his L-48 to try and make power out of it, he said he upgraded the ignition, added headers, dual exhaust, intake, but he put a L-82 cam in it and that did the trick. i drove a 73 stingray with a L48 in it and i must say, it was rather depressing, the performance that is.



When comparing an L48 to an L82 ensure that other differences don't muddy the issue such as powerteams inclusive of transmission/axle ratios. Often L48s came w/ automatics and the standard axle ratio. L82s often came w/ 4 speeds and various performance axle ratios.

Ignition won't make a noticeable difference. (though I would always recommend an upgrade to electronic if it's pre HEI).

L48s in stock trim produce excellent torque so mods like dual exhaust and headers won't necessarily wake them up.

Essentially cam and valves are the significant difference from an L82/L46 for producing HP. THe L46/L82 cam often does the trick although I'd consider a more modern dual profile cam similar to the venerable L82/L46 cam.

THe distributor should be properly curved for ANY engine beit L48/L82 from the smog era.

The other stuff would be pretty standard fare in any engine rebuild like an L48 - maybe hypereutectic pistons, a valve job, etc... E.g. any typical performance oriented rebuild of an L48 would essentially render it identical to an L82. However I'm a fan of the L48s torque in 'mostly' stock trim without chasing after HP figures.

 
pgtr 
Senior Member
Posts: 344

Reg: 11-21-03
06-30-09 07:10 PM - Post#1726770    
    In response to bowtiefan

  • bowtiefan Said:
I think that most years, the L-82 had an aluminum intake and a bigger carb.



Same carbs - QJets in all of them. Different part#s, possibly a slightly different jet or rod but same carb otherwise. Great carb - equally at home in a grocery getter, a tow vehicle or a performance application.

(The L82s predecessor, the L46 had a Holley)


 
BT74 
Member
Posts: 102
BT74
Loc: Salem, New Hampshire
Reg: 08-12-04
07-02-09 03:21 PM - Post#1727827    
    In response to 60 Bel air

Not sure about the 75, but the 74 L48 put out 195 HP, the L82 was rated at 250 HP and the 454 was rated at a whopping 20 HP more than the L82 (270 HP)
Essentially, the L82 was the low(er) compression version of the LT1 of the late 60's:
010/020 high nickle block, 4 bolt main, windage tray, forged crank, forged pistons, shotpeened rods(much like the "pink" rods, but without the pink paint),882 heads with pushrod guideplates/hardened pushrods, mine actually had 1.94 valves rather than the 2.02s, and in 74 the intake was cast iron. The compression ratio was 9:1 on the L82, and I believe the L48 was rated at 8.5:1. In 74, the heads had stellite valves(ex) and hardened seats, so it could handle unleaded gas, but it was the last year without a cat, so it ran on leaded.

 
pgtr 
Senior Member
Posts: 344

Reg: 11-21-03
07-02-09 08:47 PM - Post#1728029    
    In response to BT74

HP changed from year to year esp after changing to SAE Net ratings.

L82 is not a lower CR version of the LT1. The LT1 was produced from '70-72 w/ solid lifters, different cam etc and fundamentally is a different beast. THe last LT1s had the same CR as L82s. The L82 is, as stated earlier, a very close replacement of the L46 and in fact used the exact same cam (which also works well in an L48).

Early L48s had higher CR - 10:1.

Later (71+) L48s had 8.5:1

L82s had 9:1

  • BT74 Said:
Essentially, the L82 was the low(er) compression version of the LT1 of the late 60's:
010/020 high nickle block, 4 bolt main, windage tray, forged crank, forged pistons, shotpeened rods(much like the "pink" rods, but without the pink paint),882 heads with pushrod guideplates/hardened pushrods, mine actually had 1.94 valves rather than the 2.02s, and in 74 the intake was cast iron. The compression ratio was 9:1 on the L82, and I believe the L48 was rated at 8.5:1. In 74, the heads had stellite valves(ex) and hardened seats, so it could handle unleaded gas, but it was the last year without a cat, so it ran on leaded.




 
Silversurfer74 
Forum Newbie
Posts: 11

Age: 36
Loc: Sheldon, IA
Reg: 07-06-09
07-08-09 03:57 PM - Post#1731330    
    In response to pgtr

What would a 250 hp L82 have been rated at under the old rating system?
Thanks,
Adam
Thanks,
Adam
"Wisdom is knowledge gained through experience."


 
wagonmaster 
Senior Member
Posts: 8370
wagonmaster
Age: 65
Loc: Loganville, Ga.
Reg: 04-28-00
07-10-09 03:43 AM - Post#1732169    
    In response to Silversurfer74

No, that would have been the new "net" HP rating that began in 1972. It was 250 net HP.
Hey T @!


In Memory of Mike McVeigh- The "Mad Spring Wacker" He roams the Forums of CT forever in our hearts and minds!

http://www.picturetrail.com/wagonmaster55

Joe


 
Silversurfer74 
Forum Newbie
Posts: 11

Age: 36
Loc: Sheldon, IA
Reg: 07-06-09
07-10-09 06:56 AM - Post#1732235    
    In response to wagonmaster

Let me put it this way my L82 was rated under the net rating system at 250 hp. Hypothetically if this same engine were produced prior to the introduction of the net system, what would the factory have rated it at for hp?

Anybody know? And is there a formula for figuring the difference?
Thanks,
Adam
"Wisdom is knowledge gained through experience."


 
wagonmaster 
Senior Member
Posts: 8370
wagonmaster
Age: 65
Loc: Loganville, Ga.
Reg: 04-28-00
07-10-09 07:14 AM - Post#1732243    
    In response to Silversurfer74

If you added back the compression and hi-rise intake it would be very close to the 350 hp engines of previous years. Without those...310-320 + or -. Hope this helps.
Hey T @!


In Memory of Mike McVeigh- The "Mad Spring Wacker" He roams the Forums of CT forever in our hearts and minds!

http://www.picturetrail.com/wagonmaster55

Joe


 
Silversurfer74 
Forum Newbie
Posts: 11

Age: 36
Loc: Sheldon, IA
Reg: 07-06-09
07-10-09 01:52 PM - Post#1732390    
    In response to wagonmaster

Thanks for the info! Does that mean when I look at crate motors advertising high hp numbers that I can expect a much lower actual (installed) hp number also?
Thanks,
Adam
"Wisdom is knowledge gained through experience."


 
YeniPenny 
Dedicated Enthusiast
Posts: 5813
YeniPenny
Loc: Biloxi, Ms
Reg: 11-26-01
07-10-09 02:12 PM - Post#1732404    
    In response to YeniPenny

Since we are getting numbers all over the board, here are a couple of links to the Corvette Action Center listing specs:

This one is for 78 and includes the L-48 and L-82:

http://www.corvetteactioncenter.com/specs/c3/1978/...

This one is for the 75 model:

http://www.corvetteactioncenter.com/specs/c3/1975/...

Specs for all other years are listed there also.

 
pgtr 
Senior Member
Posts: 344

Reg: 11-21-03
07-10-09 07:25 PM - Post#1732561    
    In response to wagonmaster

Yes - I'd second Wagonmaster's response. It's essentially a low compression newer variation of the L46 which was 350hp.

However take away the high compression and that takes some away.

As for the 'old system' of rating HP - it wasn't much of a 'system' which is to say you really can't duplicate it systematically (why they were encouraged to get rid of it). They did a lot of stuff back then - they'd essentially blueprint the engine, take off all the accessories, advance the timing, feed cold air to the intake, feed water to the inlet... In fact I think they didn't use the air cleaner and may not have used the stock exhaust. So those old ratings were fairly unrealistic for the average mass produced engine coming down the line. But they certainly helped sell cars.

There have been threads in the past either here or elsewhere discussing the various tricks and techniques used to rate HP back in the day. Interesting but it's a good thing it's done more systematically today I think.

Bottom line is those gross ratings did NOT reflect a random engine coming down the assembly line, installed in a car with accessories installed and loaded.

 
Silversurfer74 
Forum Newbie
Posts: 11

Age: 36
Loc: Sheldon, IA
Reg: 07-06-09
07-13-09 05:36 PM - Post#1734430    
    In response to pgtr

You guys have been helpful in educating me about the differences in rating systems as well as the main differences between the venerable L48 as well as the potent L82. Thank you all.

Silver-

 
gz 
Forum Newbie
Posts: 12

Loc: Oshawa, ON
Reg: 05-27-09
07-27-09 05:47 AM - Post#1742603    
    In response to Silversurfer74

new here so pardon the question, I was always under the assumption the short block was the same for 1971 to 1977 LT1 / L82 applications, ie block, crank, pistons, rods, etc. I know the biggest change was 1973 when they dropped the aluminum intake and Holley to gain EGR applications, but did not think bottom end wise much was different. Appeciate your thoughts.

 
pgtr 
Senior Member
Posts: 344

Reg: 11-21-03
07-27-09 08:39 PM - Post#1743129    
    In response to gz

  • gz Said:
new here so pardon the question, I was always under the assumption the short block was the same for 1971 to 1977 LT1 / L82 applications, ie block, crank, pistons, rods, etc. I know the biggest change was 1973 when they dropped the aluminum intake and Holley to gain EGR applications, but did not think bottom end wise much was different. Appeciate your thoughts.



Not quite sure what you are asking... you wish to have someone compare the '70-'72 LT1 to the '73+ L82?

Again the L82 was essentially the same as the L46 predecessor - NOT the LT1.

The LT1 was a different beast - higher CR and SOLID LIFTER cam profile producing higher RPMS than the L46/L82s.

AFAIK the aluminum intake was NOT dropped by the L82 after 73. The L82 always had an alum intake and QJet AFAIK. However the LT1 would have similarly had a forged crank as the L82.


Edited by pgtr on 07-27-09 08:42 PM. Reason for edit: No reason given.

 
wagonmaster 
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wagonmaster
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Loc: Loganville, Ga.
Reg: 04-28-00
07-30-09 03:58 PM - Post#1744955    
    In response to pgtr

  • Quote:
AFAIK the aluminum intake was NOT dropped by the L82 after 73. The L82 always had an alum intake and QJet AFAIK. However the LT1 would have similarly had a forged crank as the L82.



I have heard this more than once. I can state that the intake on the 1973 L82 was painted red, not natural aluminum colored, if it was aluminum at all. We always thought (assumed?) that they were cast iron, since they were painted red from the factory. No proof either way, just the paint information from the date/time in question.
Hey T @!


In Memory of Mike McVeigh- The "Mad Spring Wacker" He roams the Forums of CT forever in our hearts and minds!

http://www.picturetrail.com/wagonmaster55

Joe


 
Richard Martin 
Dedicated Enthusiast
Posts: 5145

Loc: Davis Islands, Florida
Reg: 06-12-03
07-30-09 06:06 PM - Post#1745031    
    In response to wagonmaster

From Alan Colvin's book: Corvette by the Numbers 1955-1982:

Intake # 458520 1978 L82 220 horsepower 350

page # 233

"This aluminum intake was only used on the 1978 220HP engine. It was the the first aluminum production intake installed on a small block Corvette engine since the 1972 LT1."


1979 and later L82's used similar alum. intakes with different casting numbers. 1977 and earlier L82's had iron intakes....the same painted iron intakes that were installed on the base L48 engines. All the casting #'s are also available in Colvin's book. This info is also backed up by the Corvette Black Book.
----
Richard



 
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