C-3 1980 L-82

[Keith]

Hi,
I picked up a 1980 L-82 with 92K miles on it. The motor's pretty noisy and I was thinking of having it rebuilt. Most people told me that if it was the L-48 they would just tell me to buy a crate motor, but since it's an L-82 it was worth rebuilding. My question is if I rebuild it, what are some things I can do to get more horsepower out of it without getting crazy? Doesn't changing the intake or cam make it no longer an L-82, then making rebuilding it pointless (as opposed to buying the crate motor)? I'm not planning on a full restoration or show car, just a nice driver.
FYI- all the emissions have been removed.
One more question. Someone put a Holley carb on it and it's been suggested that I find a stock Quadrajet to replace it. Thoughts?
Thanks!

[Joe L.]

Re: C-3 1980 L-82

Keith-----

I'd rebuild the engine to its original L-82 specs. This engine should have plenty of performance when it's in as-new condition.

I'd also return it to its original emissions configuration. The fact that this has all been removed could be a CAUSE of performance problems and NORT a cure for them. Emissions systems on these cars are too integrated to remove components and expect .f good performance. That includes the use of an original carburetor.

[Keith]

Re: C-3 1980 L-82

Thanks...
What about headers? Someone suggested them. I had been thinking about getting the emissions back. I picked up a GM 1980 shop manual and I was going to start making a list of what's missing, including finding the right carb.
Thanks again.

[Duke W.]

Re: C-3 1980 L-82

Consider that the L-82 is basically a lower compression verison of the '69 L-46 that was rated at 350 gross horsepower.

At least 50 HP is lost with the heated inlet air and single catalytic converter. Also, Since your engine was designed for regular unleaded fuel you can back date the pistons to '69 for 11:1 and use premium. Use the OE cam or an exact reproduction. It has a rather late phased inlet event that kills enough low rev compression to keep it out of detonation without having to retard the timing excessively.

Get smart on how to improve SB heads or find a professional who can rework them for you, and depending on whether you have to be emission tested, do something about the inlet and exhaust system AFT of the manifolds. Stay away from headers.

Duke
Duke

[Keith Willey]

Re: C-3 1980 L-82

Thanks!
Sounds like good info. I'm not very well educated in engine rebuilding/performance, but I will bring that info up to the Vette place I will probably have rebuild it.
I will probably have to replace the exhaust manifolds because of leakage, so you would recommend a stock replacement? I would probably keep the cat but go to a better one.

[Joe L.]

Re: C-3 1980 L-82

Keith----

I ABSOLUTELY NEVER recommend the use of headers for a street car. They do provide significantly increased power, but they also create a LOT of other problems. Some of these include excessive heat in the passenger compartment, excessive heat in the engine compartment, reduced life of engine peripheral components due to heat, much higher maintenence, exhaust leaks, and on-and-on. Forget them. Period.

[Peter M.]

Re: C-3 1980 L-82

Duke,

Could you elaborate on the following:

- why you suggested avoiding headers

- "Get smart on how to improve SB heads or find a professional who can rework them for you" - do you have recommendations on what to do to the heads to get better performance? I'm thinking about my 71 Lt1 heads actually.

Thanks

Peter

[Duke W.]

Re: C-3 1980 L-82

Use OE or reproduction manifolds. A modern monotlithic cat will have less restriction than the original bead bed type.
You should get Dave McLellan's book - lot's of good info on C3 engines and what it took to meet emissions targets.

Duke

[Duke W.]

Re: C-3 1980 L-82

The bolts loosen, the gaskets can leak and blow out, and they radiate a lot of heat to the engine compartment and cowl due to the increased surface ares.

The old Chevrolet Power Manuals and How to Rod Hot SB Chevies (HP books) have good sections on porting. There are others that are more modern. Brouse Classic Motorbooks.

Duke

[Michael C.]

Re: C-3 1980 L-82

Duke,
Please elaborate on the "heated inlet air". Are you referring to EGR or the ducted air scheme for the air cleaner, or maybe something else. I'd like to understand this a little better. Thanks.
Mike

[Duke W.]

Re: C-3 1980 L-82

I believe your L-82 has two inlet schnorkels and each has a themostatic spring that draws some air from a "heater" around the exhaust manifold. These devices maintain an inlet air temperature to the carb. air horm of about 100 degrees, and you loose about one percent power for every 10 degree increase in inlet air temperature.

Like I said, I'm not sure or your specific configuration. If they are set up to disable the heated inlet air at WOT then there would be no loss of WOT power.

BTW, I recall that Dave McLellan in his book said that the early single converter Corvettes had about 11 psi backpressure. This is a huge amount of backpressure - probably 40-50 HP.

Duke

[Keith Willey]

Re: C-3 1980 L-82

Duke,
So it sounds like you would be in favor of keeping the emissions off (since I'm not looking for show points)?
Are you in favor of the stock carb? Someone put a Holley on mine.
~keith

[Duke W.]

Re: C-3 1980 L-82

If your car doesn't have to be emission tested, then it becomes a personal choice as to whether you want to maintain compliace with emission configuration.

Personally, I don't feel like a criminal for making some "adjustments" to my cars that only see a few hundred miles per year.

I would recommend that you make minimal changes including the carb. The Quadrajet has a flow rate of 750 CFM and the design facilitates good idle and part throttle fuel metering.

Most of the emission control devices - AIR, CCS, EFE, TCS, etc. are "add-on" and can simply be removed or disabled. Details are in your shop manual. My philosophy would be to minimally affect visual appearance, but have the functional configuration as close to a '69 L-46 as possible.

As I previously stated the single OE converter is the biggest power robber. A single monolithic bolt in replacement will improve the situation, but the most effective improvement would be to backdate the exhaust system to a full dual configuration.

Duke

Duke

[Keith Willey]

Re: C-3 1980 L-82

Thanks to all who responded. I'll take your advice and talk it over with my vette guy.

Glad to be back in the club!!