OEF14vette

Hello Gents, i am getting to the point in my 5.3/ TH400 swap into my 74 Corvette to figure out what to do for exhaust... I know its conflicting but just want to here some legit opinions on the route to take. The engine is a stock displacement 5.3 with a Tick Performance Cam, 2.00" intake valves heads shaved .010". I already have 1-3/4" long tube headers and it is fuel injected. I know i want an X pipe in the exhaust somewhere space is a huge drawback on this thing. I am thinking 3" all the way back through some sort of bullet mufflers but want to know what you guy think. Also the car will be sprayed with a wet kit and is street/strip as in i drive it to work sometimes in the summer, cruise with it, but also run it hard at the track so looking for the happy medium of max performance, sound bada*s, but still be tolerable on the highway. Thanks in advance guys.

bad_408_vert

iTrader: (6)

Classic chambered exhaust systems

OEF14vette

As in Flowmasters or similar? Have a recommendation on pipe size? Some people say these things need to breath go 3" then i hear 2.5" is more then enough. But then my brothers stock 6.0 truck has 3.5" from the factory so that's why i was thinking 3" duals with an X pipe. Thanks

kingtal0n

iTrader: (1)

I think you will like the car better as a street car with dual 2.25" or 2.5" ID exhaust pipes.

A single 2.5" exhaust downpipe off a turbine is enough for over 400rwhp. The sluggish movement of slow moving exhaust will negatively effect low speed performance, as it subtracts from cylinder fill/VE at lower rpms.

LLLosingit

iTrader: (4)

I read this post and thought what drugs is this person on and then I look and see good ole Kingtal0n posted it and it all made sense. Do you actually believe what you post or are you just copying and pasting it from some other idiots post? What you just posted pretty much only applies to header primary size and collector size/length ...Not the rest of the exhaust system. When it comes to headers bigger isn't always better but from the collectors back as long as it's not restrictive there is no real gain or loss to worry about. If that were the case then open headers wouldn't make more power in almost every case over a full exhaust system. Edit: and not just any open headers, They have to be sized for the application...If the primaries are to big you will lose power. It's all about getting gases out through efficient scavenging, This is one reason you can gain with a crossover in a full exhaust system.

kingtal0n

iTrader: (1)

yawn. show me testing of engines back to back with different size exhaust systems, all else being equal. Then we will see whats going on.

words

farmington

iTrader: (14)

when you see the amount of power that can be made through an aftermarket 3" y pipe set up (which is in effect a SINGLE 3" pipe) 2.5" duals is plenty for this application. too many people think bigger is better, NOT.

xny1989

iTrader: (1)

I've got a pypes 2.5 stainless exhaust, with X-pipe and mufflers for my 72 GMC Sprint (El Camino) with a cammed 402. Sounds great and flows well.

LLLosingit

iTrader: (4)

I agree with the bigger not being better as long as it's not so small that it's restrictive, But the point I was making to the other person who replied is that bigger is not detrimental. Different header pipe sizes and length can change where power is made, After the collector doesn't really matter so much. Personally I like the sound of larger pipes with free flowing mufflers over small pipes with the same type muffler. The larger pipe seems to deepen the sound and not make it cackle as much.

OEF14vette

I appreciate everyone response and the points made, i think i am going to go with the 3" since i will be spraying the car and i am told nitrous likes a free flowing exhaust. I am also putting an X pipe in hopefully their worth the hype. The point of the larger pipe now is that i plan to do a larger Cubic inch engine late next year so why do it twice..

1970camaroRS

iTrader: (8)

You're a moron.

1970camaroRS

iTrader: (8)

Absolutely the correct choice. On my daily driver I run a 3" X-pipe, a pair of straight through mufflers and right out the side. It looks like this, and no...I'm not a good welder, but it doesn't leak and hasn't fallen apart:

Attachment 720795

Ran it on my more mild stock short block LQ4, midrange cam and same heads I'm running now. With the 1-3/4 headers it was pretty peppy down low. Now I run 2" primary headers (OMG, they're too big!) on my new motor. Still plenty peppy driving it around every day and it won't choke on the spray.

kingtal0n

iTrader: (1)

And you are a mad turkey


https://www.reddit.com/r/cars/commen...ngine_masters/

The video agrees with, and so do the people who watch it, everything I question about 2.5" vs 3" exhaust. That is, area under the curve. Its not always about the peak.

If a single 3" will support 500rwhp to my tires... then a dual 3" might support 900+ amirite? high five.

Get more mad. I would not be proud of that side exit mess.

LLLosingit

iTrader: (4)

This might explain your answer!

01ssreda4

iTrader: (96)

This is actually, absolutely correct. Ive had just about every single size of header on my car, from a stepped 1 5/8ths to now a full 2"/3.5". With each increase in size an area under the curve was softened, and an area over the curve was made better. It really depends on application. On my 6.0 Yukon, I chose 1 3/4s as I felt it was a good blend of characteristics, but still left me with useful torque for towing. I personally wouldnt go less then 3" for exhaust, I mean youre modding it for a reason, so why not make the change that helps the motor breathe in the upper rpms (where stock engines suffer).

Youve got a lot to learn there little whipper snapper.

1970camaroRS

iTrader: (8)

People talk about the "area under the curve" and I'm noticing more and more they include the power numbers under 3,000rpm. These numbers don't matter very much in reality unless you want to feel snappy up to 30mph and that's it. In my setup, I only need enough power under 3,000rpm at part throttle to get me up to the speed limit quicker than a Civic. In action, my car never sees 3,000rpm at the track. It sees 4,000rpm once since it's above 5,400rpm after the 1-2 shift.

1970camaroRS

iTrader: (8)

I.......don't understand you. You talk about the myth of exhaust velocity in the post-header exhaust system and how it will make more torque or more responsive or whatever. I post a video refuting this idea since the 3" clearly resulted in more power at every point above 3,500rpm and essentially the same power below that. Then you use the same video, plus some gibberish about "area under the curve", which is a poor argument in this case because the 3" has a much larger area. See here, 3" black line, 2.5" blue line.



Also, good luck making 500rwhp on a naturally aspirated engine. Funny how you bring a turbo to every knife fight and fail to realize it's apples and oranges. Here's an old post on the topic that is somewhat scientific/mathematical/theoretical that you might like to refute, re-imagine or twist any way you like.

https://ls1tech.com/forums/generatio...ml#post2987587

01ssreda4

iTrader: (96)

You're correct, for a car racing, bigger is better. But for people just driving around, like what I considered daily drivers the smaller primary headers/exhaust are noticeable. Actually I didnt notice until I started going up in size and the around town and part throttle started going away. Point being there is an application for each.

This is actually true, the further back, the exhaust cools and velocity is far less important. Headers have a direct effect on powerband (did wonders for my 6.0 yukon that was flat on its face by 5k) but exhaust further and further back has less and less of an effect.

1970camaroRS

iTrader: (8)

I daily drive my car with 2" primary headers. The only thing I noticed going from 1-3/4 headers was a lack of off-idle torque at low throttle input (like less than 4% tps) when backing out of a parking spot or leaving a stop light. Takes a tiny bit more throttle to get going, but it just means a change in driving style. But with an over-abundance of available torque and only needing a tiny bit of it to keep up with traffic, it's silly to think going over-sized kills driveability. The other thing I noticed was in tuning for under 3,000rpm cruise and part throttle acceleration. The signal to the wideband was skewed to a false lean a bit worse than the other header. Some of that is the function of the cam as well. Of course, I'm also running 4.30 gears and a 4,000 stall, so it covers up a lot of the over-sized header and big overlap cam. Getting closed-loop to function well in a day to day environment has been fun...

Full-Force

iTrader: (11)

You nailed it! I think some people confuse throttle response with torque or low end power. While I guess throttle response could be considered off idle torque or off idle power, off idle takes a fraction of a second to complete.