Rather than hijack the other L82 performance thread that's going right now, I'm starting this one as my specifics are a little different.

What I have........
1979 L82 with 67,000 original miles
2.20 first gear 4 speed
3.73 rear end
Everything is stock, Lars did my carb a few years ago and I have set the timing and advance per his excellent papers. Basically all the ignition parts are recent. Smog crap is still there, including the air pump, but it is all disabled. Stock exhaust with the exception of a new cat and Magnaflow mufflers.

Suspension was gone thru a few years ago, so everything there is fine.

What I'm trying to achieve......
While I was impressed with how much the timing and carb woke it up, I'm now looking for even more. I don't want a fire breathing demon that will light up the tires in any gear, just some more fun when I mash the pedal. A big concern for me is because the car is still all stock, I would like to preserve the original look.

From my research, it seems the biggest bang is going to come from new heads. It also seems the 180/64 heads for my engine would be the best choice? Will the stock intake match up OK? Also, are the AFR heads worth over half again as much as the Darts for my application? I'm thinking not.

It seems the L82 cam is plenty good enough for what I want to do.

As far as exhaust, because of my concern about keeping the appearance of a stock engine, I would prefer to keep the stock rams head manifolds rather than go to headers. Would it be beneficial to go to true duals with a high flow cat in each side rather than the two into one that's there now? If it's going to be pointless to run the stock exhaust manifolds behind hi flow heads, then I will reconsider.

Any other upgrades I should look at doing?

What kind of performance increase can I realistically expect to see with these changes?

Lots of folks on here got some really good advice to share. Looking forward to taking advantage of it.

Thanks, guys

 

Conventional wisdom is that a good, free-flowing dual exhaust using the stock manifolds is better than headers connected to the stock exhaust system. On an L82, anything you can do to free up the exhaust is going to be beneficial.

Scott

 

I am in the same boat as you-78 L-82 4 speed, 3.70 gears, 66,0000 miles-everything internal to the engine is stock. The only changes over many 2.5 dual exhaust, roller tipped 1.5 comp cams rockers, zero emissions, Holley 4175 650 Qjet replacement. By far the biggest improvement you can make without changing engine parts is the exhaust. The emissions hardware and 2-1-2 exhaust with factory mufflers is terrible!-one of the worst exhausts ever put on a corvette! With the 2.5 inch duals and Shorty headers my L-82 did 233 RWHP on the dyno-that's like 40-50 HP over when totally stock. BTW-That is with a weak compression on cylinder #6 versus the other 7-looks like a leaking valve.

I am thinking of the AFR 180 64CC heads with the L-82 cam myself OR AFR195 64 CC with a howards roller cam. All about the money I want to spend and the time to make the swap. Changing just the heads using the L-82 cam is really very easy.

Hope that helps!

 

 

Power is made in the heads. Afr is worth the extra in my book. With this being said stock manifolds intake and exhaust would be a hindrance and I couldn't say that with those restrictions that dart etc wouldn't work as well because you'll only flow as much as your tightest choke point. Considering your thoughts on staying stock on the camshaft.. you might look into a cam shaft to work specifically with the stock intake and exhaust manifolds. I'd think that just a head change would make a noticeable improvement. You could always add 1.6 to 1 rockers to increase lift. If you had plans of building a non stock engine later then afr would definitely be the choice now so that you didn't have to buy different heads later. Good luck on your project. Blue

 

In 79 the rear would be 3:70 not 3:73. And the transmissions offered with the L82 were a close ratio which is 2.43 or wide 2.64. I never saw a reference to 2.20. Just a fyi.

I have a 78 L82 with a close ratio and 3:70 rear. 104,000 original miles. Presently I have a different cam, edlebrock rpm intake, original carb, open air element, original heads, and the original exhaust manifolds (no headers). I did install 2.5 true dual exhaust without the cats and magnaflow mufflers. As two others have said this would be the easiest gain and would look stock. My smog stuff is gone.
I dynoed 246rwhp beating JB by 13hp.

Ran in the 14's at the dragstrip and find I have plenty of power around town. I would think just the duals would make you feel better.

 

Good stuff, keep it coming

 

As Karol loves to point out, the major difference between my L-82 and his engine are his exhaust with no headers but magnafllow straight through mufflers with stock exhaust manifolds versus my shorty headers and Monza turbo muffllers (more restrictive but quieter mufflers) :lol
and Karol's aftermarket cam. I figure his cam and intake are worth 25 hp and my shorty's are good for 10-12 HP roughly, which gives Bill a 13 HP advantage.
FWIW-Karol's L-82 and my L-82 were dynoed on the same machine!

 

Heads and a retro hyd roller cam!! Paint the heads orange and they will look stock,,,,Unless your engine is blue....

 

Get the AFRs
If it were me get a performer eps, stealth or somethign similar, grind the name off spray it to look stock. You can make decent power without a huge intake. Should be plenty of fun..roller will just add to it and come on earlier too.
Ask Lars about a possible rejet once its done.

 

Headers are always an improvement over cast exh manifolds.

Cant help u with exh not knowing what u have to do to meet smog laws. U really need a custom exh shop to fab a performance exh under there. If u need to run cats and the inspector looks for one then sorry to inform u cant run dual cats. U can run dual cats if u want but thats not the original EPA qualifying equipment. Original was single cat and thats what an inspector will say u need. But some states only test the exh gas and dont inspect for the cat and other equipment - only u should know or find this out.
But for the case where they inspect u can have a shop fab a y pipe to 3" pipe that should fit through one of the cross member exh pipe holes. Plenty of legal 3" cats that will mate there and then u do whatever with the cat back sys. If u want to go 4" then u need to mod your cross member and a high flow cat inlet and outlet for the 4" pipe.
Now if no inspection then u can eliminate the cat and run duals with up to 3" pipe.

Hope this helps,
cardo0

 

More good stuff, thanks

I didn't realize the air tubes extended down into the exhaust manifolds. That's got to be a restriction there.

As far as smog, unless I get antique plates which I really don't want, I have to get it smogged every year. Pretty stupid, huh? I can't believe the people they hire at the smog stations would know the difference between two cats and one. They give a cursory look underneath with a mirror on a long pole and sniff the exhaust. What a joke.

I'm really wanting to keep the same cam. From what I am reading, unlike the L48 cam, it's pretty decent.

I stand corrected on the ratios......3.70 in the diff and 2.43 in the trans.

I'll definitely get ahold of Lars for his expertise when I decide just what I'm going to do.

Thanks, guys. I am open to any and all advice you can give me.

 

Its not a bad cam just a real old design. Something modern with better opening/closing events (with similar or even smaller specs) will pick things up.
You can always do heads see how you like things go from there. Make sure and let the head mfr know what type of cam you have so youre not running a 135lb hydraulic roller spring on a flat tappet.

 

What would be different about those opening/closing events that would make the new cam better?

 

Newer cams tend to have quicker ramp rates; this means the valves open more with less overall duration. More power with better low-RPM behavior. The caveat is increased wear on the lifter and cam.

If you look at the L-82 cam, it was about 224/224 duration with lift ~.450, modern flat tappet cams get similar lift out of durations in the mid 210s.

Roller cams allow for even more ramp rate.

In addition to that, they can also design for better exhaust gas scavenging, intake charge distribution, etc...

 

Thanks Shark Racer.

 

When comparing different camshafts, look at the duration at ,050" lift, and the advertised duration. The advertised duration will be a higher number, because it is measured at something like .006" of lift.

The smaller the number is between advertised and .050" lift, the faster the valves are opened. The faster they are opened, the longer they can stay open at full lift, for better cylinder filling.

On old-skool factory cams, this number will probably be around 70, old-skool aftermarket cams, like the Crane Energizer and the Comp Cams High Energy, tend to have this number in the high 50s, while newer aftermarket cams, like the Voodoo, and the Xtreme Energy grinds, can have this number in the low 40s, approaching the valve opening speed of a roller cam.

And that's why newer flat tappet cams perform better than old flat tappet cams...well, mostly why...there are a lot of variables.

Scott

 

Step 0: What you have done so far (carb/ignition)
Step 1: True duals (remove choke point of manifolds and 2-1-2 exhaust)
Step 2: Headers/cylinder heads (raise compression and increase air flow
Step 3: More aggressive valvetrain (improve air flow even more)
Step 4: Power-adder

If it were me, I would combine Steps 1 and headers from Step 2 as you will have exhaust system rework. If you are installing duals, you will likely have the tubes bent by a muffler shop. I had an excellent set of pipes installed with my Super Turbo mufflers and hedmann headers. Was loud driving there (open headers) but sure saved some time and $$$. Aluminized stainless pipes and my mufflers have lasted over 10 years with little if any rust.

I would also do the cam and heads at the same time as a top-end refresh as you will likely put fresh valve springs, locks, keepers, seals, etc. on with the new cam/lifters (especially if you go retro roller).

 

One thing about the exhaust manifolds, but I think the stock manifolds have a 2" opening where the exhaust pipe attaches to it, and you can get manifolds that are virtually identical to the stock ones but have a 2 1/2" opening, to eliminate that choke point. If you are insisting upon a stock appearance, it's worth looking into. Here's an example of what I'm talking about:

http://www.speedwaymotors.com/Corvet...FSHNOgodDhYAjg

Scott

 

Thanks Scott.