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I am wanting to up the horsepower on my 350, factory exhaust. factory all. I'm thinking about going with Pypes to run true duals. They come with and without the cat. cov.. Does anyone have a ideal on how much HP with be lost by going with the cat. cov. Also on headers, can you get the same amount of HP out of side mount headers as with all others? Any knowledge would be appreciate.
I am wanting to up the horsepower on my 350, factory exhaust. factory all. I'm thinking about going with Pypes to run true duals. They come with and without the cat. cov.. Does anyone have a ideal on how much HP with be lost by going with the cat. cov. Also on headers, can you get the same amount of HP out of side mount headers as with all others? Any knowledge would be appreciate.
You should pick up a fair few horsepower, 20-25 if not more, on a stock L82, by going to true dual with long-tube headers. You’ll do even better on midrange torque.
Sidemount headers have a number of sharp bends to get to the sides, so they aren’t as good for horsepower as straight back. They certainly sound unique, of course.
A catalytic converter of an appropriate size with modern construction will be a minimal loss. I’ve run my car with test pipes for a few months when the one of the current cats blew out, and I didn’t feel a difference in power. Nor did I notice a change when fresh catalytic converters were installed.
You should pick up a fair few horsepower, 20-25 if not more, on a stock L82, by going to true dual with long-tube headers. You’ll do even better on midrange torque.
Sidemount headers have a number of sharp bends to get to the sides, so they aren’t as good for horsepower as straight back. They certainly sound unique, of course.
A catalytic converter of an appropriate size with modern construction will be a minimal loss. I’ve run my car with test pipes for a few months when the one of the current cats blew out, and I didn’t feel a difference in power. Nor did I notice a change when fresh catalytic converters were installed.
On my white 1980 L82 I just removed the Catalytic Converter and installed a “test” pipe ( straight pipe ) in its place along with a distributor curve kit , seems to make a noticeable improvement but I haven’t ran it at the track yet so no data other than the butt-o-meter but this will be my base line when I do run
On my black 1980 L82 I installed some 64cc chamber Promaxx 183 aluminum cylinder heads, Comp roller tip rocker , Edelbrock Performer, Comp XE262 cam slightly less duration than stock but a touch more lift along with side mount Hedman headers going to 2.5 inch side pipe with one not tight 90 degree bend going through 2.5 inch Cherry Bomb glass packs , with a 700R4 transmission it ran a 13.64 at 102.87 Kilkare a month ago
I just received some Hedman headers from Jegs today for rear exhaust to replace the side exit headers / side pipes do to noise , I’ll be converting to 68-74 dual exhaust but can’t imagine it being anymore powerful than the side exit
if you look close at my black L82 you can see the side pipes
On my white 1980 L82 I just removed the Catalytic Converter and installed a “test” pipe ( straight pipe ) in its place along with a distributor curve kit , seems to make a noticeable improvement but I haven’t ran it at the track yet so no data other than the butt-o-meter but this will be my base line when I do run
You're saying you did the "test pipe" and distributor curve kit at the same time when you noticed the improvement? It's also worth noting, the single OEM cat, if it's still even functional, are a massive flow impediment vs a modern converter.
Re-curves from OE timing wake these motors up a LOT. I can vouch for that as well.
To be clear regarding my post above - my setup was twin 2.5" modern cats, and changing only those (to and from empty cats), I did not notice a difference.
Are you saying that with cats. installed, you noticed no difference in HP with no cats.?
Correct. True dual with empty cat shells after a blowout vs true dual with new cats.That's not to say there isn't a measurable difference on a dynamometer, but I certainly could not feel it when I drive the car.
Others have claimed 2-3 hp, which in a 400 hp build is not as consequential as driving in the middle of the day vs the end of the day in the summer.
I'm considering a exhaust system from Pypes, with the cross pipes, and I can get it with or without their cats. If I will only lose a total of 4 HP, or even as little as 8 total, I think I will go with their cat.system. Was that 2-3 per side or total?
Last edited by 401KVette; Jun 9, 2021 at 07:01 PM.
I'm considering a exhaust system from Pypes, with the cross pipes, and I can get it with or without their cats. If I will only lose a total of 4 HP, or even as little as 8 total, I think I will go with their cat.system. Was that 2-3 per side or total?
That's a good idea, because you never know when or if, anti-pollution requirements could change, so with the "cat system" in place, you're legal, and the cost has already been covered.
I'm considering a exhaust system from Pypes, with the cross pipes, and I can get it with or without their cats. If I will only lose a total of 4 HP, or even as little as 8 total, I think I will go with their cat.system. Was that 2-3 per side or total?
I believe total. Either way, I'd look at the decision as a tradeoff between the cost of catalytic converters against the benefits to the environment. Horsepower wouldn't enter the equation for me.
I went with a 700R4 on my black 80 and Pypes said it wouldn’t fit the 700 transmission or 82’s that come with a 700R4 , something to consider if you plan on OD in the future
You should pick up a fair few horsepower, 20-25 if not more, on a stock L82, by going to true dual with long-tube headers. You’ll do even better on midrange torque.
Sidemount headers have a number of sharp bends to get to the sides, so they aren’t as good for horsepower as straight back. They certainly sound unique, of course.
A catalytic converter of an appropriate size with modern construction will be a minimal loss. I’ve run my car with test pipes for a few months when the one of the current cats blew out, and I didn’t feel a difference in power. Nor did I notice a change when fresh catalytic converters were installed.
Looking at my side mount headsets, I'm not seeing alot of sharp bends.
1980,l82. Headers:
