i hear you, i wanna keep the smog equipment intact, i think that is gonna be the key to getting top dollar for these cars in the future, and with only 230hp out of the box, every little bit helps, but to each his own

 

I don't think a 78 is going to become a high priced collector car any time soon. I would just put the old manifolds and smog pump in a box and store them away. Do the carb and distributor setup as advised and put on a set of good Jet Hot coated headers. The Sterling coating from Jet Hot is their best coating. It really holds up and lowers the under hood and floor board temps. Put duals with 2 1/2" pipe. an X pipe will help with drone and can add some power. There are lot's of opinions on mufflers here.

You probably have the dual snorkel cold air intake air cleaner. This isn't a bad setup, I would keep it.

 

This is my thought with my 76 and exactly what I've done.

Pros: increased power and better exhaust note.

Cons: prone to leaking, if not maintained,
Not original. Some headers hang low.

Use a decent product and have them either ceramic coated or jet hot coated. The ball flange collector's are suppose to fight collector flange leaks, I've not personally used a set yet but my next set will have them. Look for a thicker flange that mates to head, off the top of my head, 1/4" & 3/8" are the flange sizes and the thicker flange is less prone to warpage. Currently I'm running hooker comps. Good fitment and don't hang to low, but they have a flat flange collector and 1/4" head flanges.

Good luck.

 

I put long tube s/s headers on my stock 350. I had them coated at Jet-Hot. I also installed a Magnaflow true dual system with x-pipe and low restriction muffs.

I noticed a real difference in the seat of the pants acceleration of the car. My guesstimate: 20-25hp was unleashed with the free flowing exhaust.

 

Was not an option, they were standard.

 

I used a full replacement dual exhaust system from Corvette Central Exhaust. It came with ceramic coated 1 5/8" block-hugger headers that use a ball-and-socket collector, and a nice thick flange. 2 1/2" aluminized pipe all the way back to Magnaflow mufflers. Complete system from the header gaskets all the way back to the tailpipes, Cost about 600 bucks and some change about 5 years ago, maybe a little more now. I'm pretty happy with it.

http://www.parts123.com/parts123/yb....ort~1~cadefibQ

The conventional wisdom says that you are better off with a nice, free-flowing 2 1/2" dual exhaust system using the stock manifolds, than with headers using the stock exhaust system, just FYI.

Scott

 

Stock 78 l-82 was rated at 220 Net HP, about 180-185 RWHP. With Mcjacks shorties, no pollution control at all, 2.5 duals, and Monza turbo mufflers with very few other very minor mods, my L-82 did 233 RWHP on the dyno with a weak #6 compression cylinder. You do the math, but those numbers are BIG increase in net HP!

 

I would say that 220 net horsepower would probably give you more like 150-170 rear wheel horsepower, if that. That makes your 233 rear wheel horsepower even more impressive.

Scott

 

Headers used to be my favorite mod, especially first time mod because you can't hardly lose. You get more low end torque, midrange, really more torque everywhere, and even improve your gas mileage. But there is some drawbacks (PITA's) associated with headers that my father used to complain about, and the older I get, the more I realize he is right:

Con #1: You will be experiencing exhaust leaks from time to time, and generally will be replacing gaskets both at the engine and collector, from my experience, at least once a year give or take.

Con #2: The collectors hang down too low, causing ground clearance problems, especially an issue on Corvettes and other low riding cars. It's funny until it happens to you, going down the road 80 mph, hit a bump in the road, then all the sudden your car just got louder. You look in your rear view mirror about that same time and see metallic objects dancing in the street. You've just blown up your collectors.

Con #3: Too noisey (they add noise over exhaust manifolds) and have "tinny" sound. Personally I don't have an issue with this. But my neighbors do.

Pro #1: One of the best bang for your buck HP/TQ mod out there, not that difficult to install, but a lift is really nice to have. Can be done without one though.

Pro #2: Increase in torque everywhere, high, low, and midrange.

Pro #3: Increase in mpg. How many mods out there result in an increase in HP AND gas mileage?

I'd say as a rule of thumb if your car is a daily driver and you depend on it to get to work/school, I'd stay away from headers. If its a weekend warrior then ok. If any of the cons above you can't tolerate then I'd avoid them. The problem is when you go to modding an engine you almost have to have them. You won't get near the increase in power with a cam install without headers for example.

What I considered doing on my truck is just throw a whipple blower on the engine, keep the stock manifolds, and call it a day.