OREO Speedwagon

I just read Ganey's exhaust topic.

:eek:

It basically said that if I do away with the cat and run duals with some low restriction mufflers, I can get up to 45 more HP. Wow.

I live in a non emissions testing state and I know of a place that would "forget" to put cats on if I were to take it to them and have duals ran.

So, I have a couple of questions:

1) Is this true? Up to 45% more by running duals, no cats, and better mufflers?

2) Any suggestions for affordable mufflers that aren't too restrictive?

3) How about headers? It's a stocker now, but I plan on piece mealing it's build up. Can they refit the exhaust if I were to put headers on later? Or should I do the headers before hand?

Thanks all!

Fevre

45 hp and 45% is a bit diff, think your stock is about 180 so that would give 80 more hp if 45% as oppossed to the more realistic 45 total hp. I have not douobt it would esp if you cat is old.

turtlevette

NO

GDaina

Depends on the rest of the internal components...but as a rule, yes, stock exhuast is very restrictive, adding 2.5" X pipe and free flowing mufflers will give you a good kick in the pants, not to mention added fuel economy...adding headers would with the above, that h.p. figure is attainable

OREO Speedwagon

Turtlevette - wow. thanks.


;)


[Modified by OREO Speedwagon, 10:18 PM 3/17/2004]

68shark

Think there are many posts on "true dual" exhaust where those that have switched from the 2 into 1 cat exhaust to the '74 and prior true dual setup report substantial gains in power. If you don't have an emissions issue, ie. testing to pass, go for it!

OREO Speedwagon

I think I'm going to do it. I plan on adding an intake and carb, but with such a restrictive exhaust, I don't think it would make sense to do it now.

So, I think I'm going w/ the duals pretty soon. I'm wondering what it would take to put the headers on. How bad is it to DYI?

GrandSportC3

:withstupid:

verskel

#1 - you will definitely add enough power to 'feel' the difference.
#2 - you have many options (check Summit Racing) from Flowmasters to Magnaflows to Flowtechs to Dynomax......etc. etc.
#3 - you can always add headers later but if you're getting the exhaust done at a shop, they sometimes discount the header installation if done at the same time. ;)

verskel

Lazy poster ! :lolg: :lolg: :lolg: :jester

What a way to rack up your # of posts...... :rofl: :rofl: :rofl:

I mean....this guy.... :lol: :lol: :lol: ok, I'm thru :jester :leaving:


[Modified by verskel, 4:02 PM 3/17/2004]

JScott81

One comment - one question

First, one of my other vehicles is a 97 4X4 Expedition. I considered putting duals on and was told that I may actually loose a % of my power due to the system being too free flowing. The system is designed to have a certain amount of back pressure to fuction correctly. Is there any truth to this and if so, is the case similar with older systems like on the C3?

Question: My 81 vette is brand new to me. I have taken it out for a few short test drives and found that it is very sluggish. The engine roars but the car feels like I'm dragging an anchor behind me. The cat appears to be original the muffs are not but they have been on for quite some time. Do you think the cat could be clogged enough to rob most of the power from the 350? How best to check the condition of the cat?

stingraymaniac

the old cats took alot of power even when they where new,so when it has sat there
for meny miles it dosent get better!
remove the cat and buy dual exhaust with an xpipe then you should feel the increase.

OREO Speedwagon

Well, the thing is, I can't find a shop that will put the headers on for me. So, I may just have to do it myself. And from what I've read, it ain't no fun.

;)

stingraymaniac

not so big job to put some headers on the car
took me 10 minutes to take loose one of mine on my 74

verskel

Based on past experience the cats always rob your engine of power.

There does need to be some 'back pressure' but not too much. In order for you to notice a loss in performance on a vette you'd need to run straight pipes with no mufflers on an '81 .....and then.....maybe....it might flow too freely. :rolleyes:

All mufflers have some back pressure inherent in the slowing down of exhaust gasses by diverting the direction (physics 101). In a nutshell....I wouldn't worry about "not enough" back pressure.

Also, the higher the compression of an engine......the less back pressure / restriction.....the better. :thumbs:

Fevre

Have heard if you hit with a mallet that can break loose some of the crude but since you are uncertain of its age I would just yank the sucker and put a new free flow one in or go duals. With new EFI engines you have to reprogram the computer but the lack of backpressure is not the cause, it is the computer not getting the signals it needs/likes.

OREO Speedwagon

yeah, I've been going through the archived threads and it's starting to look less bad. Remove the ac, alternator, and starter seems to be the place to start.

I might do this pretty soon. The Dynomax coated headers seem to be pretty popular, so I may check out a set of those.

:yesnod:

verskel

Well, you're especially right if it's an A/C car and even after you get the headers on.....spark plug changes can be a @%$^&$ :cuss

Others here may disagree, but I don't believe the gains from headers on your '76 (provided it's stock) will be great enough.....maybe 10-15 hp.
The stock Corvette manifolds are very, very good and much better than stock manifolds on a plain chevy or camaro. :yesnod:

Fevre

First find someone who will do up an exhaust for you, since you have a cat some shops will not touch it without one.

ZD75blue

If you can talk to the techs that would be doing the installing most of them dont have any problems doing it after buisness hours... for "Non road use" :yesnod: