Gas milage goes up too.

Expect you know on a Corvette like yours duals run straight back from manifolds or headers.
The iron manifolds are not that bad on stock engines especially if you have to run cats.
The more hp one has the more headers help.

Now, one can keep the stock carb & cam this to over 300HP easy, even 340 or more if everything else is right!

Merry Christmas

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Cheers
Ganey

CORVETTE 77 385CI 6.3L Hi-Perf. Sus.
http://ganeys.home.sprynet.com/

you exclude the 82's in you posting, is this because they have stock headers? Does anybody know how these headers compare to aftermarket ones?

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Andy
Fremont, Northern California
Two tone '82, Hypertech Stage II chip
Edelbrock cam, K&N air, high flow exaust,
Monza style mufflers.
Click here for my Vette on the WEB

Best Headers & 3" Converters to 2 1/2 duals.
I would try to run headers or manifolds, duals, 2 hi flow cat. converters, crossover pipe, Dynomax mufflers.

If not possible, hi flow cat & try no mufflers or Dynomax. Your ex. manifolds are some of the best available so changing manifolds or to headers is not cost effective.

Cat & single ex. quiets, remove mufflers, too loud for you, then add even short glasspacks or turbo mufflers. Test- Remove cat & use test pipe to see diff., then you will know what you want.

See I will never buy a muffler thread in Aftermarket.

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Cheers
Ganey

When you talk about 214hp for '81 Z28, where do you get that from? Wasn't the rating 180-190hp?

The headers give another 15hp, so shouldn't it go to 256 instead of 246?

Thanks buddy

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1980 355/300hp
USS Corvetteforum SSB Gold Crew
Damage Control Off. Ltjg

*Corvette: The Only Sports Car That Matters*

Headers help mainly at higher rpms. The 82 will not turn high rpms w/ stock Cross Fire manifold so headers would not be cost effective & would expect 0 to minimal gain.
Would expect the other exhaust mods to help 82 some.

Monty is 82 expert & says the fuel system is capable of 300 HP, but not the manifold.
I posted on 12-2-99 on Cross Fire Mods - Update about using 2 4bl manifold if 300 HP is enough & cam for it. There is also a Holley 670cfm injector & manifold.

If you want to run gears or higher stall converter, try this cam TPIS 700-134 221/230 .454/.454 112 LS.

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Cheers
Ganey

CORVETTE 77 385CI 6.3L Hi-Perf. Sus.
http://ganeys.home.sprynet.com/

Yes, I think the 81 Z28 was less hp. These figures are engine on dyno complete exhaust, no accessory. Expect you know different dynos will show different figures, so the exact figures are not as important as what the changes show. If someone has not seen this type of info. before, it is enlightening, don't you think?
Yes, you are correct, have fixed to 256.

Redvetracer
Put a description of headers here. I don't think many look in Parts Sale/Wanted section.

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Cheers
Ganey

CORVETTE 77 385CI 6.3L Hi-Perf. Sus.
http://ganeys.home.sprynet.com/

Use your rams horn manifolds or factory "Shorty style" headers from c4. from the manifolds run a 2 1/2" mandrel bent y-pipe (will require fabrication) merge the two legs of the 'y' into a Flowmaster merge pipe. this pipe has a smooth transition from 2- 2 1/2" to 1 - 3" - connect to 3" high flow cat - use another flowmaster 'y' and use 2 1/2" pipes to low backpressure mufflers.

This should be the equal of a dual 2" system. The only difference being the resistance of one cat vs. two. Should be very close though as (1) 3" pipe has greater x-sectional area than (2) 2" pipes.

All this and its smog legal too!

This is what I plan to do when I get round to the engine/exhaust/driveline work.

redvetracer-----send info on headers - i may be interested.

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White 1978 L-82
4-Speed
Soon to be burgundy

Zr-1 glass bumper

what I meant the the '82 seems to me the only shark that has stock headers installed from factory. Don't know if they are good but maybe that is one reason the '82 is measured 200hp instead of lees hp in the previous years.
And BTW, you are right, the other exaust mods helped alot!

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Andy
Fremont, Northern California
Two tone '82, Hypertech Stage II chip
Edelbrock cam, K&N air, high flow exaust,
Monza style mufflers.
Click here for my Vette on the WEB

[This message has been edited by andy82 (edited 12-21-1999).]

Ganey, you are damn right! The difference one can make with exhaust upgrades on these so-called 'smog motors' is incredible.

BTW, I have been kicking around this theory for a while now. See if you can follow and then comment:

If we look at the '71 hp ratings (the only ones that showed both net and gross) we see 330 gross for the LT1 and 255 net. I know it is not an exact science but the conversion rate seems to be approximately 1:0.77. So lets accept a rounder 20% power loss with net.

Using that, lets convert the net hp ratings of the L48s from 1975-1980 to approximate gross as well as add 20% for true duals and no cats (so as to even the score with the 68-74s):

Year Net Appr. Gross True duals gr.
1975 165 206 247
1976 180 225 270
1977 180 225 270
1978 185 231 277
1979 195 244 292
1980 190 238 287

Now if you look at the base hp for 1968 through 1971 (gross numbers), you will see base numbers from 270 to 300. If we take these numbers at face value, the L48 is as good as any base engine offered previously and does not deserve the bad rap.

After all, it was the smog laws that put on more accessories but the engine didn't change (yes, I knoe compression dropped but that didn't do much).

What do you think?

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1980 355/300hp
USS Corvetteforum SSB Gold Crew
Damage Control Off. Ltjg

*Corvette: The Only Sports Car That Matters*

Previous years 75-80 have ratings for L82 from 205 to 230 HP.
Highest net is 255 HP @ 5600 72 350 no cat. w/ duals.

Highest small block gross is 375 @ 6200 327.

I have no exp. w/ 82, don't have size info. on your ex., do not expect your ex. is better than the rams horn manifolds.

Consider this I beat new GTOs, etc. repeatedly w/ 57 Chevys w/ 283, 307, 302, w/ 30-30 solid lifter cam, dual ex., rams horn manifolds like Corvette has. Stock 57 carbs, aftermarket air filter, supertuned. Stock gears about 3.36.
Used 4.56 Posi on the fast cars.

Why not tell what you did & results for 82 guys?

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Cheers
Ganey

quote "Highest net is 255 HP @ 5600 72 350 no cat. w/ duals."

There you have it: true dual exaust w/o cat and headers seems to be the ultimate solution. Note: HP Numbers also dropped significant with intro of smog legal equippment.

I for my part have to be smog legal, but noticed a difference by just changing to high flow cat and tips instead of rear mufflers.
I'd love to see dyno results although I can't compete to many other folks here in the forum but just for the heck of it...

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Andy
Fremont, Northern California
Two tone '82, Hypertech Stage II chip
Edelbrock cam, K&N air, high flow exaust,
Monza style mufflers.
Click here for my Vette on the WEB

Based on more info., a long time ago figured for engines rated net about 200-325 HP one could take net & add 30%.
Now you want to add for duals, I think your 20% dyno may be optimistic. See Ex. 2 the 20% included headers.
15% may be a lot to add.
If one adds 30% then adds 15% the total is about the same as you have. So different methods about same total results!

PS I have been running way behind on this thread because it takes so long to key in answers.

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Cheers
Ganey

much more header than I need unfortunatly.

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White 1978 L-82
4-Speed
Soon to be burgundy

Zr-1 glass bumper

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Eddie Hernandez
1975 Corvette Coupe
Meriden, CT

Thanks.
http://www.randomtechnology.com/ is supposed to be the best. Suggest asking them, they have e-mail at site.

I think you would be much better off to run duals & 2.

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Cheers
Ganey

CORVETTE 77 385CI 6.3L Hi-Perf. Sus.
http://ganeys.home.sprynet.com/

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Demar
76 L-48
http://www.angelfire.com/in2/demar/index.html
Terre Haute, Indiana

I don't run that type because I want 4into1 full length headers for max. power & rpms, the headers point straight back & the pipes go straight through the crossmember & straight back making gentle curves around the spare. There is also a crossover pipe.

This is ideal. There are about 2 ways to improve this. One is to remove spare & avoid the gentle curves. The other can not disclosed since it needs to be sold to an exhaust co.

I think to run the side pipes you must really like them. All the turns does not help. One should run a crossover pipe w/ it. Expect the shorty headers to be a little better than the rams horn manifolds. Still, it will work & a lot of guys like them. If you did a topic on this probably the side pipe guys would say do it, ask about pros & cons. Anyway I am not trying to talk you out of it. At least you don't have to worry about cats, however those sharp turns are probably as bad.

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Cheers
Ganey

Having the muffler at the end is ideal.
Total ex. system loss w/ above system w/ headers & turbo mufflers can be less than 15!

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Cheers
Ganey

I have had a Firebird 400 Conv. & a Trans Am similar to your Camaro, however it has been years. Expect you know you have the large live axle in the way that you will have to loop over to be legal. Basically you want to make as straight as possible, gentle curves as possible for any car. Anyway will not match Vette system.

One way to deal with the live axle cars is to run pipe straight back, add mufflers & forget the tailpipes over axle. I barely attached the mufflers to pipes & suspended the mufflers front & rear so that a hard jab on the throttle would blow the mufflers off & leave suspended out of the way. This is especially good if one does not have headers. This should be done after staging. Too late now, Gotcha!

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Cheers
Ganey

CORVETTE 77 385CI 6.3L Hi-Perf. Sus.
http://ganeys.home.sprynet.com/

I have an 80 model vette which runs the exhuast under the transmission crossmember. This makes it real easy to swap from stock type exhaust to the so called off highway duals in about an hour. I can change back quickly if needed.

On your Vette the Dynomax Cyclone headers flow great & fit great!

I am glad you like this topic, anybody else?

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Cheers
Ganey

CORVETTE 77 385CI 6.3L Hi-Perf. Sus.
http://ganeys.home.sprynet.com/

The problem is that the intake manifold's intake port, where it meets the head, is about the same size, maybe even smaller in some areas as the stock, stainless steel headers. The stock headers can be improved somewhat with a little grinding work. The welds where the individual tubes are welded to the flange are sloppy, blocking at least a full 1/4" of the tubes. With a die grinder, this weld can be grinded flush, the air tubescan be grinded flush on the inside, and some general port matching will improve flow. The stock cat, as long as it isn't plugged or melted will flow plenty for the crossfire.

If I were just starting to mod a crossfire, the first thing I'd do is open up the intake manifold to match the heads, at least as much as is possible with out going through the bottom of the manifold. Comp Cams makes a .450" cam for the L83, this along with porting will produce the biggest improvement, in my opinion, without pissing the ecm off.

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1982 White 383 DFI SuperRam
Park Ridge, IL
11.895/120.121mph 438HP/478TQ

Thanks for adding your 82 experiences.
What is dia. & length of 82 stock header pipes?
I was thinking about the intake problem & guessed the dual 4 manifold would work good.
Have you seen this from Brandon vette84? http://www.flash.net/~famviz/monster
He posted in Aftermarket, CrossFire/Carb Conversion, maybe he will tell more of his exp.
Sounds like he did not cam it.

74Vette69

Familiar w/ that Vette, besides Q-J, etc. it is running auto & 3.08, can build.

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Cheers
Ganey

CORVETTE 77 385CI 6.3L Hi-Perf. Sus.
http://ganeys.home.sprynet.com/

Dynomax is good too. The reason I didn't go with them is that they don't make a California smog legal header for my 78.

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http://www.orderofthedragon.com/
91 green convertible
Flowmasters Power Chip K & N Filter
1978 Pace Car
Eldelbrock manifold, cam & timing chain, Magnum Roller Rocker Arms, modified exhaust 300+ HP
Sensei Earl
Bakersfield, Ca.

Sensei Earl

Nice to see ya over 300!

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Cheers
Ganey

The 82 stainless steel headers have a diameter ranging from 1 1/4" to about 1 1/2". The primary's are narrowed at the 90 degree bend a little, and the sloppy welding narrows it quite alot, but that can be corrected with some grinding. The length is comparible to a set of shorties, about 1-2" above the oil pan flange.

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1982 White 383 DFI SuperRam
Park Ridge, IL
11.895/120.121mph 438HP/478TQ

Thanks.
They say better late than never!

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Cheers
Ganey

I'm writing everything down that i learn here on the forum and including it in my specs for my upgrades. I have set engine specs down (even posted them on my web site) but I think they will be changing for a stroked 350 (3.835" stroke - approx. 396 cu in) torque monster instead of the more revvy 355 i was planning.

engine specs can be found at http://www.geocities.com/MotorCity/Downs/3057/enginespecs.html

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White 1978 L-82
4-Speed
Soon to be burgundy