jb78L-82

1978 L-82 220 NET HP/1979 L-82 225 NET HP (Only Difference from 78 L-82 is freer flowing mufflers). Exactly the same engines

1978 L-48 185 NET HP/1979 L-48 190 NET HP-Same exact engines-Mufflers again

Difference-35 Net HP

1978 L-82 4 speed 0-60 MPH 6.5 sec
1978/79 L-48 4 speed/auto-7.8-8.2 0-60 MPH

Big difference!

TCracingCA

Put headers on it and keep everything else the same except for the tune! Change those and take it to someone who can put a real crisp performance tune on it!

Then sell it when you are ready, with the old exhaust manifolds throw into the deal!

Alwyn678

Bingo

GUSTO14

Clearly there were many differences between the L48 and the L82 in every year. In 1978, some of the significant differences in the engines were; Most of these contributed to the additional 35 horsepower the L82 produced over the L48. The intake manifold (other than the weight advantage of the aluminum L82 manifold) did not contribute to it.

But if you can find an aluminum L82 manifold that doesn't cost too much, it's a worthwhile addition for the weight savings.

GUSTO

jb78L-82

I have added some more details to Gusto points about the differences between the L-48 versus the L-82 in 1978. The point about the L-82 intake being aluminum versus the L-48 cast iron intake is true but the intake on these cars is pretty good since changing to an aftermarket one that will fit under the stock hood is worth VERY little gain.....maybe 5-6 HP from Performer RPM versus the L-82/edlebrock Performer, at best.

Clearly the L-82 makes the additional 35-40 NET HP with better flowing cylinder heads, higher lift/duration cam (the L-48 cam specs are pretty pathetic-Standard GM passenger car specs....(L-48 engines are out of breath at 4,000 RPM with a 195/205 duration versus the L-82's which pull to 6,000 RPM redline fairly easily with 222 duration), higher compression ration (8.9 vs 8.2), and bigger exhaust (2.5 inch Y pipe versus 2 1/4 inch for the L-48).

Keep in mind that a 73-80 L-82 is pretty much the same motor/specs as the 1971 LT-1 rated at 330 GROSS HP but with emission gear, 2-1-2 catted exhaust starting in 1975, emissions tune including severely retarded ignition timing and carb tuning, very high temp operating coolant temps etc. Strip all that away from an L-82 and add 2.5 duals with free flowing mufflers without a cat, you pretty much have a 71 LT-1 and the same performance. I did that to my 78 L-82 4 speed starting in the mid 80's and was very pleased with the performance increase from these great engines until the rebuild/upgrade in 2014....

Norcoastal

So basically what I'm seeing here is there are a number of upgrades and every one contributes to incremental added hp.

I've added a true dual exhaust which could give me 5 hp and if I add an aluminum performer intake that could add another 5, so with very little work, I can add 10hp.

At 185 hp to start and adding at increments of 5 and 10 hp, over time I could have a fairly well performing motor and I can do it one step at a time.

This is very encouraging.

7t9l82

San, seek counciling if you think.port matching will provide that much of a power increase.
The L-82 intake is the same as the cast iron garbage only lighter..
.if you need to paint the car to sell it there goes your profit. Keep it and make it what you want and let someone else pay too much for a chrome bumpers car.
The late model are great and are just as .much fun and way cheaper.
​​​​​

mobird

There are some that will increase the horsepower in leaps instead of in tiny baby steps. The big one is HEADS! The L48 has terrible flowing stock heads. Pick up a pair of Vortec heads (do a search on this site, there are hundreds of threads about Vortec heads) and a cam (Lunati 60102 would be a good candidiate) and you have a solid 50+hp increase. Couple that with a good flowing exhaust (with HEADERS! Not manifolds) and a decent aluminum intake, and that motor will be putting out close to double what it did stock.

7t9l82

A true dual.exhaust will give you quite a bit more than 5 h.p. <br />Where do people get these figures? It's as bad as watching some of these TV shows around here?

mobird

Especially with headers! I would guess it more like 20 hp.


Have you ever played some of the racing video games? They are all set up like that, intake adds 5 hp, exhaust adds 5 hp, turbo adds 10 hp, etc... so I think a lot of people think that's actually how it works, instead of being a combination of parts equaling better flow into and out of the motor.

jb78L-82

I can tell you from personal experience with my 78 L-82 that a totally stock internal L-82 with 1.52 comp cams roller tipped rockers only, true dual 2.5 inch exhaust with Monza turbo mufflers, McJacks shorty headers, no emissions at all did 233 RWHP on a dynojet. Considering that a stock 78 L-82 was rated at 220 NET HP and is roughly 180-185 RWHP when new, my results with a dual exhaust added 42-48 RWHP!!!

Karol, on this forum, with his 78 stock L-82 with a cam only of unknown origin (not the L-82 cam) with stock 882 heads and everything else internal stock L-82 with a 2.5 inch duals, magnaflow mufflers with ramhorn manifolds produced on the same dynojet 248 RWHP!!!! That increase is roughly equivalent to 60 RWHP!!!!! with a cam and exhaust.

I would not expect the same increases on a base engine L-48 for a variety of reason, but the L-82 has tremendous HP potential with relatively little effort..............

mobird

Dang, that's even more than I thought! I'm guessing it's because the L-82 has a good flowing intake, decent cam, and heads that flow at least a little better than the L-48 heads, plus a little more compression, so the big choke is the exhaust, so freeing that up uncorks a lot of power!


On the L-48, I doubt it would be quite that (as you said), so I'm sticking to my 20hp guess till someone proves me wrong


I can tell you from experience that switching to headers and true duals on my L-48 was worth a chunk of power, you could definitely feel the difference!


The biggest change in power by far though was the Brodix aluminum heads and Lunati 268 cam (I did both at the same time). Literally felt like double the horsepower of stock (and it probably is fairly close!)

jb78L-82

In 2014, I completely rebuilt/upgraded my L-82 with JE forged Racing 9:1 pistons. AFR 180 64 CC CNC aluminum heads (total compression with 1094 .015 gasket 10.2:1), Howards roller cam (.525/.525, Duration 219/225, LSA 110), Long tube Headers 1 7/8 inch with 3 inch collectors and the car is a 355 L-82 monster now. I reconditioned the L-82 OEM Forged crank, reconditioned the L-82 forged OEM rods, mildly ported the L-82 aluminum intake, etc. The engine is killer now....425-450 Gross HP!. The combo of parts was selected for strong low end grunt, tremendous mid range torque with excellent sub 6,000 RPM HP. I could not be more pleased with the outcome. Transformed the C3 into real sports car with the 4 speed and 3.70 gears. BTW-I know what serious power is (I am not delusional with the L-82 355) since I have a 10C6Z06 bought new with 4,200 miles on it as well.

mobird

That's awesome. Two totally different animals there. My brother has an LS2 GTO with full bolt ons that put 402hp to the rear tires. Everytime I drive his car I always think how crazy quiet and calm it is at normal cruise, like a completely normal car. But plant your foot and it takes off like a rocket!


My vette on the other hand is always being snorty and raring to go. It crackles and pops at idle, and it almost never just "settles down". But that's why I love it!


I'm sure your vette and C6Z are similar in that way!

cv67

Its the character of a rowdy Gen1 that completes these imo

The amazing thing on a bigger LSx is how tame they are and how broad a powerband they can have

Still addicted to huge solid cams that are still lumpy under 3k. Efficent or not its pure hot rod stuff that brings me back.

Best mod ever to any sbc is sticking a bigger arm in it...friend I used to look up to who was a vette fanatic used to give me hell about my overcammed 350s forever. Wasnt until he gave me a ride in a well thought out but mild 383 LT1 93 Ruby it sunk in. He was the NCRS type his cars looked factory perfect but had every internal mod in the book, even extrude honed intake/exh manifolds
Very tame but woulda smoked what I had at the time

jb78L-82

Definitely the C6Z06...perfectly sedate until you get on it! The 78 L-82 355 is very similar though with the 219/225 duration cam..it idles perfectly smooth, better than the L-82 cam (.450/.460, duration 222, LSA114) and cruises just like the OEM L-82 just has tons more low and mid range grunt..Step on the throttle and the front end of the car noticeably lifts under 3/4-WOT throttle...amazing!

mobird

I'm with you on that! I have (multiple times) considered an LS swap in my vette, but then I remember it's not a daily driver, it's a weekend fun car! And it's hard for an LS to compete in the grin-factor with a Gen 1 with a lumpy cam! I'll have to take a video of the exhaust note for you guys, Doug's headers and Side pipes with STS baffles. Thing sounds amazing at idle and SCREAMS at high RPM. I love it.

Krystal

The biggest problem with the L48 are those heads........followed closely by a flat as the midwest plains cam shaft.

BOTH ARE GARBAGE and don't let anyone try to tell you otherwise.

Heads with smaller chambers will get you the compression you need and virtually ANY OTHER DESIGN will flow better than the worst ever emissions head found on the L48.

A 1980s era aluminum Corvette head has the smallest Chambers and cam bump your L48 to near 10:1 compression........but a set of iron Vortecs will cost less to buy and flow far better ......even though the slightly larger chamber volume only gets you to 9:1 Compression they'll make more power too.

Then that cam shaft swap.......no big mystery here. A lack of lift and short duration in the stock L48 cam was all geared toward passing new tough emission requirement and not focused at all on making power.

Heads and a cam swap along with the headers, aluminum intake and carb swap.........easily hakes an additional 100HP.......... you won't make enough to take down the newest performance cars.........but the difference between a 16 second car in the 1/4 mile vs a car that can run in the 14s is still NIGHT vs DAY different.....all in a good way.

derekderek

and there are zillions of used eddy performers and such out there for 50 bucks. but paint, seat covers, door panels and redye the rest. you can usually repair cosmetic cracks in dash pads trim etc. paint. even a 400 buck Maaco job is a comeup. you obviously can't do a top dollar job on a 78 you are walking away from. value. the number in your head around 4k as-is? edit. old nthread, but apparently Mobird was here yesterday. you still thinking about cleaning up interior. this guy just bought a 72 and it came with 78 door panels. odd color, but... https://www.corvetteforum.com/forums...nels-help.html

san

Im pretty sure your not as smart as you think you are. Keep your smart *** remarks to yourself. I guess all the thousands of motors built didnt really need all the percision done to them. The original poster asked what could be done cheaply for horsepower gain.