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Getting a L-82 into the 13's?

OldSkool

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Jul 21, 2005
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51
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Newport, RI
Hypothetical question here.

I don't yet have a Vette, but I'm considering getting a C3. I don't know a heck of alot about them, so I'm trying to do some research. I know alot of them were relatively underpowered, and since I don't believe in slow Vettes (or stock 350's!), I'd definitely be modding it. While not as fast as I'd ultimately like to go, I think that running in the 13's is respectable, and not too crazy a goal.

Say I had a '75 or '76 L-82 with a 4-speed. What would I need to do to get it to break into the 13's in the 1/4? Now I know these engines only came with about 200hp, but if I'm not mistaken, the L-82 has a 4-bolt block, higher compression, and better heads (2.02) than the L-48. Please correct me if I'm wrong, btw.

Assuming the engine is in good shape with reasonable miles, would I be able to accomplish this w/out getting into the internals? I'm thinking headers with a free flow exhaust w/high flow (or no) cats, GM Vortec heads with matching intake, and a good carb might do it, with the right tuning. I'm not sure what gears these came with, so a gear swap might be needed too, but nothing too low, as I'll need to drive this on the highway.

Does this sound feasible? Or will I need to do a cam swap also? If so, does the engine need to come out to do that?

And how much power can the stock driveline take? I'd imagine plenty, since they installed big blocks in these cars. A 13 second small block is probably barely scratching the surface.

Thanks for any info. Like I said, I'm a Vette novice, so any help or suggestions are greatly appreciated.

Mike
 

socor7

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Apr 12, 2004
Messages
79
Location
Denver, Co
Corvette
1976 White with red Int 4 speed
cam swap and gears

not sure about the 13 second part but you can do a cam swap with out pulling the engine, but does require to pull the radiator. I just did an engine swap (cracked block from an over bored stroker motor) and replaced it with a 330 hp gm crate engine and it takes the hp and torque very well. both parts very easy to do. most of the power loss on the late 70's vettes were due to lower compression ration my 76 was 8.5:1 and from all the emissions stuff like smog pumps and erg valves. I think it would be very possible but it would be very helpful if you did a cam swap, pending on if you have a l48 or l82.


drew
 

L48

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Jun 16, 2005
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247
Location
Wadsworth OH
I have a 350 Chevy with a stock rebuild bottom end (oil pump may be one step above stock), casting 3970010, with 882 heads in my 76 Trans Am. (These are the same castings as my L48.) It is a street car with 700R4 automatic and 4.56 gears. It runs 12.60's with open exhaust. The heads have the stock valves (1.94 intake) and have been ported by me with a 3 angle valve grind. I was running low 13's before I added roller rockers, a bigger cam (.480 lift) and a K&N. The cam I had before was a dual pattern .442/.465 lift with 214/224 duration @ .050 lift. With this cam and catalytic convertes the car passed Ohio emissions testing (e-check) so it was quite streetable. It has Hooker supercomp headers, a single plane intake with a 750 Holley on it. I also run manual steering and brakes to save weight.

btw - I run the stock compression ration of 8.5:1 and I run on 87 octane.

That car is about the same weight as the 75 Corvette I now have.

I am not sure it is possible on the stock cam, but if you add a cam change to your list I think it is quite possible. The key is good heads.
 

OldSkool

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Jul 21, 2005
Messages
51
Location
Newport, RI
Thanks alot for the info. Sounds like one quick T/A you got there. Pretty impressive that it passed the sniffer test too.

It's good to know you can get the cam out with the engine still in the car, it makes a cam swap much more appealing now. If I have the heads off, I might as well do the cam, right? I just didn't want to yank the engine untill it's time for a full rebuild.

But like I said, this is assuming I get a car with a engine in good shape. Actually, this is assuming I get a car at all! I'm just doing research right now and kicking around ideas.

My plan would be to get a good driver I can tool around in for the rest of the season, and then do the cam/heads over the winter to have it ready to go back on the road for the spring. I hope to find something in good shape that doesn't need a ton of work. Basically just something needing a minor refurbishing to be a nice car.
 

Glensgages

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Black '82 Coupe
OldSkool said:
Hypothetical question here.

Say I had a '75 or '76 L-82 with a 4-speed. What would I need to do to get it to break into the 13's in the 1/4?

#1- intake/carb, probably along the lines of a Holley 650 double-pump #4777, and a 'decent' intake:
Victor Jr. works well, without giving-up bottom-end punch.

#2 camshaft, probably in the .480" lift, 230* at .050"-range, moving useable power up to 5800-6000 PM.

#3- exhaust, as you have already mentioned, without the catalytic converter, in the 2.5"-diameter range.

#4- cylinder heads with smaller combustion chambers, getting the compression-ratio up to about 9.8 or higher. Edelbrock aluminum heads are hard to beat (for the money), and offer advantages over the Vortecs 'down-the-road'.....

#5- rear-gearing, probably at-least 3.70s, and stickie tires that can handle the kind of power you'll be making.
 

patsnitrovette

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Dec 15, 2001
Messages
348
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absecon,newjersey
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1973 electronblue LS1
Glensgages said:
#1- intake/carb, probably along the lines of a Holley 650 double-pump #4777, and a 'decent' intake:
Victor Jr. works well, without giving-up bottom-end punch.

#2 camshaft, probably in the .480" lift, 230* at .050"-range, moving useable power up to 5800-6000 PM.

#3- exhaust, as you have already mentioned, without the catalytic converter, in the 2.5"-diameter range.

#4- cylinder heads with smaller combustion chambers, getting the compression-ratio up to about 9.8 or higher. Edelbrock aluminum heads are hard to beat (for the money), and offer advantages over the Vortecs 'down-the-road'.....

#5- rear-gearing, probably at-least 3.70s, and stickie tires that can handle the kind of power you'll be making.

i had everything he said but i used an rpm air gap intake and sportsman 2 heads(72cc) and ran 13.70's at 108mph,traction limited .Havent run the fuel injection setup yet.
 
7

78 L82 4spd

Guest
Oldskool -

Sounds like I have the car you are trying to buy!

I have a 1979 L-82 4 speed with a freshly rebuilt motor - everything that you were looking for and/or highlighted above. {I know my user name says 1978 - that's what I was looking for when I started!}

I have not run it at the track but it pulls real good. I will send you an Adobe Acrobat .pdf of the car that I had made up in a private message.

Stephen
 

MMM

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Clayton, NC
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'63 Coupe, '72 Convert, '02 Z06
I had a '75 L-82 Convertible, with the wide ratio four speed and 3.55 rear. All work I did to the engine was with the intent of keeping it stock appearing. When finished the car ran consistant 14.2's in the quarter. This was with worn out stock tires (I didn't want to wear out my new ones). I am sure with a little more tuning the car would have broken into the high 13's. What did I do?
- Internally - pocket ported the heads with a three angle valve job
- Installed a L-79 cam (350hp /327cid stock cam). This change
may have not helped much, but I just like the L-79 cam, FEEL
it is easier on the valve train than the L-46/L-82 cam. I also
installed new lifters.
- Externally - All emissions equipment was disabled, but left in place. This
included the EGR, AIR system, EFE and ported vacuum
system.
- Removed the cat and installed a true dual exhaust system,
actually a '74 L-82 system.
- Left the primary metering rods and jets stock
- Changed the secondary metering rods and rod hanger, rods
gave richer mid-range and hanger was higher causing the
rods to lift earlier.
- Converted vacuum advance to manifold vacuum and
recurved distributor advance to '70 LT-1 specs.
The throttle response of this engine was instantanous and it pulled hard to 6500 rpm which was my self set limit. The engine looked dead stock, original air cleaner, ignition shielding, emissions equipment, etc. It still idled very smoothly and had great low end torque. I am not a big fan of aftermarket equipment. Most of the aftermarket equipment manufacturers cannot afford to put the engineering into their equipment that GM can. My experience is that aftermarket stuff usually comprimises drivability for top end power and you may not even see any improvement there.
My $.02 worth.
Good Luck,
Mike
 

OldSkool

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Joined
Jul 21, 2005
Messages
51
Location
Newport, RI
Thanks for all the info, now I know where I need to start if I were to get into this project.

MMM, I have to say I disagree w/you about aftermarket parts, but I have to give you credit for getting such good results using factory parts. Almost anyone can get good results w/aftermarket parts, but it takes hard work to do it w/stock stuff.

One more question: would I be better off starting w/a L-82 car, or does it even matter?
 

Glensgages

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757
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State-of-Confusion
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Black '82 Coupe
OldSkool said:
One more question: would I be better off starting w/a L-82 car, or does it even matter?

I'd think, since you are considering a stick-shift car, the L-48s may've come with a wide-ratio transmission, while the L-82s may've come with a close-ratio gear-box:
I believe automatics of that era were equipped with THM350s for L-48s, and THM400s for L-82s.

L-82s generally had forged pistons, 4-bolt blocks, and steel crankshafts;
L-48s generally had cast pistons, 2-bolt blocks, and cast-iron cranks.....
either bottom-end will survive what you'll do to it, running 13s, but if you decide that only 12's will do, you'll be pushing the boundaries of what it'll take.
 

Glensgages

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Black '82 Coupe
L48 said:
Everything I have read about the '75 indicates the automatic L48 had a 400 tranny. Mine does. I can't speak for the later years.
I have no-reason to doubt that.....
wasn't exactly 'sure' WHEN the THM400 was an L-82-only piece, but thought it was in the '75-'76 range.
:beer

Pretty-sure it was THM350/L-48 by '77-'78, though:
a buddy looked-over a very low-mileage '77 L-48 that had the 'supposedly-original' transmission, that was a THM350.....
 

ernbuild

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Joined
Mar 30, 2004
Messages
82
Location
BRISBANE/AUSTRALIA
Corvette
91/ZR1
L82s a great start

OldSkool said:
Hypothetical question here.

I don't yet have a Vette, but I'm considering getting a C3. I don't know a heck of alot about them, so I'm trying to do some research. I know alot of them were relatively underpowered, and since I don't believe in slow Vettes (or stock 350's!), I'd definitely be modding it. While not as fast as I'd ultimately like to go, I think that running in the 13's is respectable, and not too crazy a goal.

Say I had a '75 or '76 L-82 with a 4-speed. What would I need to do to get it to break into the 13's in the 1/4? Now I know these engines only came with about 200hp, but if I'm not mistaken, the L-82 has a 4-bolt block, higher compression, and better heads (2.02) than the L-48. Please correct me if I'm wrong, btw.

Assuming the engine is in good shape with reasonable miles, would I be able to accomplish this w/out getting into the internals? I'm thinking headers with a free flow exhaust w/high flow (or no) cats, GM Vortec heads with matching intake, and a good carb might do it, with the right tuning. I'm not sure what gears these came with, so a gear swap might be needed too, but nothing too low, as I'll need to drive this on the highway.

Does this sound feasible? Or will I need to do a cam swap also? If so, does the engine need to come out to do that?

And how much power can the stock driveline take? I'd imagine plenty, since they installed big blocks in these cars. A 13 second small block is probably barely scratching the surface.

Thanks for any info. Like I said, I'm a Vette novice, so any help or suggestions are greatly appreciated.

Mike

Hi mike .I have a L82 in my 78, and yes they are different from the stock 48s.
They have 4 bolt mains+ heavier rods +forged pistons+long duration cam +bigger valves and better heads. Its a good start to building a tough engine.
I run a roller ,lumpier cam, roller followers and rockers, pro street heads,steel flywheel, all balanced, power plus manifold ,650 holley with mech/secondaries
and proform throttle body, with custom made extractors and MSD dizzy.
All up around 550 HP, with close ratio t10 gearbox.
If i could get all the power to the ground, doing the maths she would be a 10 to 11 second 1/4 miler. As it stands, it goes like hell in a straight line.
From what ive heard the tranny and diff are not a problem, cant say the same for handling though.
Have fun hope you get a vette soon,
regards ernie.:lou
 

OldSkool

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Jul 21, 2005
Messages
51
Location
Newport, RI
Thanks for the info. Ern, it sounds like you got one nasty Vette there. Must be a blast to drive.

Sounds like I'll be keeping my eye out for an L-82. I'm not going to be too picky with hte tranny though. A 4-speed would be fun, but an auto will probably be better at the track.

Mike
 

KANE

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KY
Corvette
Dark Blue 1982 Trans Am(s): Polo Green 1995 MN6
OldSkool said:
Sounds like I'll be keeping my eye out for an L-82. I'm not going to be too picky with hte tranny though. A 4-speed would be fun, but an auto will probably be better at the track.

I'd buy a C3 without any special options or packages- that way I'd know I wasn't ruining anything of historical value. Then, I'd get a an SD430. It is the Scoggin-Dickey remake of the famed ZZ430. I'd run EFI and top it off with a modified for GEN I small blocks LT1 intake. I'd run a T56 swap or a 700R4 tied to either a 3.42(M) or a 3.73(A). I'd gut the front and rear suspension and replace them with VB stuff.

I wouldn't mess with rebuilding the original engine unless I really wanted to do it. The new stuff is cheap if you know where to find it. Ebay can help you save some money too as there is ALWAYS someone trying to dump something.
 

OldSkool

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Messages
51
Location
Newport, RI
Sounds like a great plan, if I hit the lottery. That's just a bit more money than I'm able to spend right now. That's why I want a nice driver with a solid engine that I can hop up a bit to enjoy right now. I figure if I can find a strong runner, I'll just do some basic mods so that the car can get out of it's own way before I'm ready to go all out on a complete rebuild.

The closest race track is about 2.5 hours away, and I'm not into street racing, even if there WAS a street racing scene around here. Right now I just hope to have a nice driver that will put a smile on my face when I hit the go pedal. And an exhaust that'll set off car alarms. Too many yuppies w/BMW's and Porsches around here, I gotta show them what's up. I don't care if they're faster than me, you can't beat the rumble of a Chevy V8.
 
G

grapeknutz

Guest
The best way IMHO is to get a set of decent heads ( not vortec ) or get the stockers ported and flowed. Then with the flow numbers go to a good cam manufacturer and get what they recommend and you will be very close to that goal.
 

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