Exhaust for 1998 L29

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Erik the Awful

Supporting Member
Supporting Member
Joined
Aug 9, 2019
Messages
7,621
Reaction score
15,533
Location
Choctaw, OK
I watched Engine Masters' episode on cheap mufflers and bought a pair of 2.5" Cherry Bomb Salute mufflers for my 350. They seemed to be right at that point of not dragging down power while also not being ear-bleedingly loud... and they're too loud for me. I already have hearing damage, so I don't want a loud exhaust. On the plus side, they're not an obnoxious "blat", more of a constant thunder.
 

TexasAggie

I'm Awesome
Joined
Nov 22, 2020
Messages
143
Reaction score
126
Location
Fort Worth, TX
But unless you are450 to 600 hp I recommend a single 3"

Reasoning? More backpressure for better throttle response and low end grunt? I figured I'd keep the dual 3" since that is how they ran it from the factory. I'm currently all stock on the engine by will eventually rebuild to something with more power so figure I may as well build the exhaust for it now.
 

Frank Enstein

Best. Day. EVER!
Joined
Jul 15, 2018
Messages
2,005
Reaction score
3,431
Location
Canton, Ohio
No backpressure but the proper size pipe for best scavenging.

imagine each exhaust "puff" as a cotton ball.

If the pipe diameter is correct the cotton ball will seal to the pipe walls and create a vacuum behind it to help pull the next "cotton ball" into the pipe which creates a vacuum behind it and rinse and repeat.

If the pipe size is too small the cotton ball turns into a "hot dog" and there isn't enough room for the vacuum to form.

If it's too big it doesn't seal and again no scavenging.

At higher rpm the pulses happen more often and turn into "pancakes".

This is why the collectors are larger in diameter. The pulses are coming 4 times as often.

That is also why you lose bottom end torque when the pipe size is too large.

Having the pulses arrive evenly helps the scavenging. This is where 180 degree headers and equal length headers have an advantage.

So introducing back pressure into a system with tubing that is too large slows the puffs down flattening them into pancakes so they seal to the pipe wall and gain scavenging back.

Obviously this is an oversimplification but it helps to visualize how this works.

On a highly tuned racing engine that operates in a narrow rpm range you can delay the exhaust valve opening and gain power.

Hope this helps.
 

EKOBS

Newbie
Joined
Jan 6, 2022
Messages
14
Reaction score
7
Location
Buffalo, New York
The Burns Merge collectors are impressive but on a stock engine they might not make much difference, But every little bit helps!

If there is a Tri-Y header I always recommend that. Any engine under 8000 RPM will see gains with that type over a 4 into 1 header.

180 degree headers are even better but good luck getting them to fit!

I recommend a proper Y or at least an X pipe. The gains can be dramatic.

For this I would do dual 2.5" into a single 3" Y pipe

https://www.summitracing.com/parts/flo-y250300s

with a WLK-17769 muffler

https://www.summitracing.com/parts/wlk-17769

and the biggest glass-pack after as a resonator.

This tail pipe kit


That would be optimum for 300 to 400 hp.
Thank you for your response. Your idea regarding Tri-Ys is very interesting. The ‘collectors’ that came on my headers (JBA #6822s) do not seem like the best solution and if I were to cut those off this presents the opportunity to turn them into Tri-Ys. By the way, I have been using the stock Y pipe into the cats and then the flomaster tail pipe kit you mention and it may be a little loud for some but I‘m o.k. with it.
 

EKOBS

Newbie
Joined
Jan 6, 2022
Messages
14
Reaction score
7
Location
Buffalo, New York
No backpressure but the proper size pipe for best scavenging.

imagine each exhaust "puff" as a cotton ball.

If the pipe diameter is correct the cotton ball will seal to the pipe walls and create a vacuum behind it to help pull the next "cotton ball" into the pipe which creates a vacuum behind it and rinse and repeat.

If the pipe size is too small the cotton ball turns into a "hot dog" and there isn't enough room for the vacuum to form.

If it's too big it doesn't seal and again no scavenging.

At higher rpm the pulses happen more often and turn into "pancakes".

This is why the collectors are larger in diameter. The pulses are coming 4 times as often.

That is also why you lose bottom end torque when the pipe size is too large.

Having the pulses arrive evenly helps the scavenging. This is where 180 degree headers and equal length headers have an advantage.

So introducing back pressure into a system with tubing that is too large slows the puffs down flattening them into pancakes so they seal to the pipe wall and gain scavenging back.

Obviously this is an oversimplification but it helps to visualize how this works.

On a highly tuned racing engine that operates in a narrow rpm range you can delay the exhaust valve opening and gain power.

Hope this helps.
This is exactly the goal of this project, to create an exhaust which properly scavenges the engine. In order to do this I’m willing to do some fab work and welding, I’m even willing to make a couple pressure wave termination boxes if necessary. I have the luxury of space since this is a rear drive only crew cab.
 

Frank Enstein

Best. Day. EVER!
Joined
Jul 15, 2018
Messages
2,005
Reaction score
3,431
Location
Canton, Ohio
If you want to put on the SCUBA tanks and deep dive into exhaust theory have a a look at this;


Flowmaster used to make 4-2-1 collectors but they have been discontinued. I did see some on FleaBay though.

The JBA shorties have a "Fire Cone" (pyramid) in the collector to reduce turbulence. They are the only ones that do to my knowledge.

If you REALLY want to go down the rabbit hole on exhaust tuning Engine Analyzer by Performance Trends will teach you a bunch.

Exhaust tuning can be a big help but intake tuning can give enormous gains if you get it right.

Get the intake tuning wrong and it goes bad FAST!
 

kennythewelder

Officially Retired, B31-3 (6-G) certified welder.
Staff member
Super Moderator
Joined
Jul 14, 2014
Messages
6,500
Reaction score
9,100
Location
Louisiana
Any thoughts on shorty vs long tube?

Thanks
Craig
You talking about headers. Well, ok, here it is in a nut shell. Long tube headers are better everywhere except at very low RPMs. Very low, up to maybe 1000 or so. Shortys are a lot easier to install. They are a direct replacement for the OE exhaust manifolds. I have a set on my 97, 5.7L, and I like them. Also if you have a 4x4, the transfer case is in the way to install long tubes. And, shorty headers go in from the top of the engine compartment, and long tubes go on from under the vehicle, or that is how they are designed, anyway
 
Top