I have a stock '78 L82 4 gear with 40K on the clock and an original (I assume) exhaust system, a front cross over pipe going into a cat with an exit pipe that splits into two oval mufflers located behind the rear wheels. This seems like a modest set of pipes. I'm not a big fan of headers but has anyone replaced this type of exhaust system with something that breathes a little better and how did it work out please?

 

Find something with mandrel bent pipes. And full dual exhaust. And drop the cat.

 

Check out Corvette Central. They have a line of dual exhaust systems that match the factory system at reasonable cost. You won't do much better than that, and they fit like the factory parts with good ground clearance.

 

I have a 78 L82 4spd. You can do this yourself ( also need the center hanger):
https://www.corvettecentral.com/c3-6...way-systems%2f

or in my case I wanted louder, with Magnaflow:
https://www.corvettecentral.com/c3-6...f%3fcount%3d45

 

Thanks much

 

The way to go. 2 1/2" pipe & Magnaflows is what I have...

 

Thanks for the feedback. The current exhaust system looks to be in perfect condition but I'm wondering if it is choking my engine. I've had quite a few chev/olds small block V8 engines over the years and most of them seem to have more HP than my L82. The engine runs well. It will accelerate but doesn't seem to have the grunt that I would expect from a 4 barrel engine in a relatively light car.

 

That factory exhaust is DEFINITELY choking your engine! Single best thing you can do is loose that horrible exhaust and Cat!

 

Hey Doc,
How you are? I haven't been on here in a while. Just waiting for winter to be over. last time we spoke you were having a "shake" or something in you front end ? How did that work out?
An experienced "Vetter" like yourself likely knows much about exhaust systems and most everything else regarding these old girls. What kind of output should I expect from these cars. The handling, cornering, stopping etc. far exceeds the Camaros and Cutlasses I had years ago but the acceleration isn't what I expected. Back in the day a buddy had a C3 with an inline 292 six cylinder that was wicked fast.
My car is pretty much showroom condition, completely stock and everything works, even the clock. It will go fast but not quickly. I'm thinking the carb or else the exhaust or am I expecting too much?
Your thought greatly appreciated.
Cheers Mate

 

Hi Mike, the shake was finally fixed. After replacing everything under the car. In the end it was twisted flanges on my half shafts. New Half shafts from Bairs Corvettes. All good.
Way back when dirt was new and Christ was still a Corporal. I bought my 77. Factory stock right down to the wing nut on top of the airfilter.
It handled, it stopped amazing!
Couldn't get out of it's own way! Little Ford Pintos would smoke me off the lights. It was truly embarrassing! The car had the look. The handling and fabulous brakes. It did have top speed, but it took half a day to get there!
One of the first things I did was pull the factory 2 into 1 though a horrible Cat then back to 2 and through 2 horrible mufflers off and dumped it in the skip bin! On went 2 1/2 inch Chambered exhaust, true duals. No bloody mufflers. That played havoc with the jetting in the factory Quadrajet. So some tinkering was needed there.
At any rate. With just a complete exhaust system and some jetting it went from snail to respectable.
IT WAS HUGE! No dyno mind you. But it felt like 100 HP. It was probably more like 50. But it really, really made a difference!
A lot has changed in my engine over the years. But I'm still running that Chambered exhaust. Car sounds fantastic. And goes pretty darn well.
(I did twist my half shafts).
Bottom line, best single thing you can do is lose that stock exhaust! Then your ready for future upgrades.
The stock Quadrajet is actually really hard to beat. Finding someone that knows how to rejet it can be fun.
But on this Forum we have Lars. Talk with Lars about possibly setting up your original carb. If your running a stock intake manifold there is nothing that will beat it.

 

Someone already mentioned @lars. Timing is also choking your car. He can help.

 

Thanks Doc for the quick reply and all the advice. Nothing as useful as the wisdom of experience!
Glad you got your ride back to normal, persistence pays off for sure!
When I bought my car from the original owner, an old guy like me, it came with a two inch high stack of paper, all from the Chev dealership. The previous owner put it in each spring for maintenance, mostly lubrication and adjustment, nothing beyond oil and once or twice new plugs but all stock set up. He liked the look and the handling but wasn't much into performance.
Back in the day when I was young and money was scarce, a long time ago, my first performance upgrade was to run straight duals with the old time "hush thrush" mufflers and back then there were no cats. I mistakenly assumed the GM would size the exhaust on the corvette so as not to choke off the engine on a performance car but I stand corrected. The old exhaust system will get replaced and become a wall hanger.
I do most of my own work so this shouldn' be too difficult. I sometimes use a mechanic who is an old guy like me and has worked at a GM dealership since day one. He remembers carburetors and races old time camaros so I'll ask him to do the carb set up.
Again, thanks for the advice and enjoy you Vette(s).
Cheers,
Mike

 

CanadianRover
Since you say you do most of your own work here is what I would recommend (assuming you don't have to deal with smog rules on your 78):.
BACKGROUND: I had headers on my 68 for probably 30+ years. I decided to go the ramhorns and a stock exhaust. I got some coated 2.5" Smoothie Ramhorns & the hear riser "spacer" on amazon. I bought Corvette Central exhaust pieces - either from Corvette Central (CC) or RPI-- whoever could give me the best shipping prices. Part prices were about the same. I got the full 2.5" downpipes for the 64-65 and then I got the remainder of the Corvette Central parts as the 2.5" intermediate pipes and mufflers. It all fit like a dream.
LATER I put in a fatter tranny and I could NOT easily squeeze those great fitting pipes around it and I knew that I would have to modify them.. I ended up making my crossmember a pass-under and then modified those pipes they would pass under.

SO - if I was starting now I would still do the 2.5" Smoothie Ramhorns and 2.5" CC mufflers (just because they fit so great and I don't need a loud exhaust) ..... however, instead of spending money on the downpipes and intermediate pipes I would spend that money on the appropriate Bowtie Overdrives Pass-Under crossmember and modify it to replace the welded-in crossmember. I would then get a muffler shop to fabricate the pipes from the Ramhorns to the CC Mufflers (they're gonna be about dang straight).. I say that because I ended up cutting & welding on the downpipes and the intermediate pipes when I made it all pass under.


.

 

I get a bit hexed when I hear people suggest that removing the catalytic converter will increase horsepower. It is against Federal Law to remove the catalytic from the system. Here in Northern Virginia they look for the cat and if it is supposed to be there they will require you to re-install one or pay a fine. My C3 doesn't need one and my C4 has a High Flow catalytic converter feeding the chambered exhaust spewing clean(er) exhaust. The C4 has all of it's emissions equipment and it is still functional. Between the new catalytic and the Chambered Exhaust the car gained something like 12 hp

My 1988 C4 is not exactly a Fast Corvette despite that fact it looks Fast. I replaced the original catalytic converter with an aftermarket Catalytic Converter from Summit that could flow several times the volume of the original unit. The rest of the exhaust is a Chambered Exhaust System and with that sound people assume it makes real power. I have a catalytic and was able to get 30 mpg on I-95 with my hot little L98 engine. I may not have the fastest car but I am still driving a Corvette and when the little cars rev their engines I just smile.

We can make all the power we want and still be within regulations with a little effort. The folks I know that removed their catalytic converters have to deal with a DRONE that will not go away. This is also the problem that can be aggravated by the exhaust system design.

 

Easy Tiger. OP is in Alberta. They don't care about a cat on an old car.

 

I just installed a test pipe from eBay in place of the converter on my white L82 , bolted right up in minutes

 

Thanks BKarot for this info, appreciated. The system you recommend looks like what I want. I also like something that's "made to fit" I can do mods but would rather not. I like a mellow sound but not too loud. My current system is a bit loud and after a couple of hours on the higheay it sometimes gives me a headache. I had a look under my car and it appears that the cross member is ported on both sides for a pipe. The price seems reasonable, actually less than I had expected.
Cheers
Mike

 

Thanks.
What does it sound like, is it loud?
Cheers,
Miks

 

Thanks for the feedback carriljc, appreciated.
2.5" Smoothie Ramhorns are aftermarket I assume?
Also, a fatter transmission would be a 5 gear or 6 gear? Something I'm also considering. When I get up to highway speed the engine is loud and revs high like it wants another gear or two.
Cheers,
Mike

 

Thanks for the feedback ctmccloskey, appreciated.
Not sure of the smog laws up here, likely if your vehicle was manufactured with a cat you are required to have one although there is no emissions testing and I don't know anyone who has ever been checked.
The cat may not be the only reason by engine is choked. I suspect a dual system, with or without cats will flow better.
Cheers,
Mike