Probably old question ; What is basic difference
between L48 & L82 to make 195 horse into 250.
I know it has 4 bolt mains in L82's but also higher compression from 8.5 to 9.0 right?
What is other changes, cam timing and distributor?
I have a feeling someone can tell us real simply,
the differences.
Also I have to say this forum is TREMENDOUS
boon to people getting into Corvette hobby....
The technical info here is invaluable to all the way you all share your experience and knowledge of these
wonderful cars .

 

Basically the L48 is about 8.25:1 compression, the L-82 about 9:1 with forged internals and a 4 bolt block. The L48 uses the baseline chevy cam, while the L-82 uses the L-82 cam with 224 degrees of duration. Its a decent cam if the engine had at least 10:1 compression. The L-82 has 2.02 intake valves while the L-48 has the 1.94. If you want to kick it up, I'd install a nice set of 62-64cc heads, fresh cam and lifters and maybe a Edelbrock performer intake and keep the Q-jet and stock distributor.

 

Scott M. ,
Excellent answer !!! I new some one would give me the insight I was looking for here. Once again this Forum SHINES!!!
I have done a few things like check the valves to bring balance to the valve timing and I set up the Advance as Lars lays out for small block Chevys. Swapping advance springs for better curve and that really helps. I have an Edelbrock Performer intake on it and a Holley
670 CFM Quadrajet replacement carb w/vacuum secondary.
I have played arround with primary jets quite a bit trying to dial in the carb. Here in central Oregon at La Pine we are at 4275'
elevation so vacuum is thin. I finally settled on 60 jets for primary.
Carb from Summit came with 62's and at first I was trying richer
and high altitude demanded I go the other way. It really feels good with the 60 jets now. The car came with a Super T-10 and a 3.08 rear so it is not real good coming out but as you get going after launch it comes on nice. I was wondering about changing to another meter plate in secondary and I have put an adjustable Spring kit
with lighter spring in and that seems to work better also.
Maybe this winter if I can switch to a better cam I might do that along with a new set of lifters . I want to keep it mild . I also got
Hooker headers with sidepipes that were there when I got it.
They are in decent shape too, Chrome is pretty good and I found a product that polishes away the Blue and Gold from the heat .
more later ......

 

The L-82 cam was the 350/350 cam. Like Scott said, w/ a little more compression, it works very well.

Also the L-82 has an 8" harmonic balancer. Forgot that it also had (at least in '73) a 2.5" double-walled exhaust.

Have you put lighter springs in the dist. yet? That will help.

 

L82 had better cam, Forged internals and better performance heads of the day with 2.02 vlaves, pushrod guide plates, screwed in rocker studs.
They were basically a 70-72 LT1 motor with lower compression and hydraulic lifters.

 

And a cast iron intake and a Q-jet.

 

Actually ..... I was going to suggest the ORIGINAL 69 350 CI 350 HP cam , INSTEAD of the L-82 . They are close ,but not the same grind.

They had different part numbers, I use to know the specs , but forgive me if I can't remember from 1977 . Anyway ....the old GM Chevy 350/350HP cam maynot be available any longer from GM, but its specs have been reproduced I'm sure by after market folks.. But, I tried BOTH out in a L-48 , back in 77 on a 74 L-48 engine. I used a set of 67 327 /300 heads that had like 10.75:1 .compression . high cpmpression with smaller valve...........I think the 350 HP cam had less lift , but mor duration and worked well with the smaller valves.. A local racer set up the rochester carb , a proper one will flow around 750cfm I don't know exactly how fast it was , but I would blow the doors off the local whimmpy doctor down the street with his 911

Oh ....I sold the 74 to a young sailor ........... when he test drove it, the guy could not wipe the grin off his face....

 

I got my info from my Chassis and Body Parts Catalog for Corvettes which listed the same P/N for 350/350 and the L-82 which was back then: 3896962.

 

Sorry , they used to be different , two very close but I had one of each they came in diffenent tubes with different part numbers. This were bought direct from the chev parts counter in 1977 . Idon't doubt the 350/350 isd now listed for the L-82 as well as a service replacement. But, originally there WAS A DIFFERence....just locate an ol mid 70's Chevy perforamce catalog ...I threw mine away 20 years ago. As zora used say they thought it was rerduntant. But the L-82 will work in a L-48 , but it works better with the large heads.

The L-82 cam shaft was developed specically for the 73-up L-82 /z28. the original 350-350 cam was from the 69 350cars.

Bascially all I was saying was the original 350/350 grind was a bit better suited for the L-48 with its smaller heads. The L-82 was more designed to work withthe 2.02 heads.

 

The L-46 and L-82 cams are good cams...for their day. They're designed to provide power at higher RPM levels, with torque peak around 4000 and HP peak around 5500. Depending on your trans and gears, you may want to consider a modern design in that same .450 lift range (max for your heads) that makes power lower in the RPM range.

You'll make more power with better driveability with a modern cam.

 

My 78 L-82 has an aluminum intake not cast iron. The L-48 in my year has a cast iron intake. The earlier L-82 probably had cast iron intake, though.

 

The Parts book I got the info from was May 1974. If you saw the two cams in different tubes w/ different P/Ns then I'll defer to you.

But I had this same discussion in 1975 w/ a guy who has forgot more about SBC engines than I'll ever know and he said the same thing when I told him that they had the same P/N. He later said that he checked both cams and they were the same.