downpipes for stock manifolds

mrhand

New Member
May 17, 2022
11
Have an '81 with a 350 and currently has an older but perfectly funtional dual exhaust system with headers. I want to replace the headers with stock exhaust manifolds but the only downpipes available are these 2.5" stainless ones from Pypes DGU14S.

I need aluminized pipes in 2.25" so I can weld to my existing system. A couple of online exhaust places wont duplicate these pipes for me in aluminized 2.25", why I dunno.

Anyone have a source for aluminized 2.25" pipes for stock manifolds? I don't have a trailer to take the car to have custom pipes made someplace.
 

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Tony65

Member
Jun 27, 2015
47
Eastern Ma.
That kit does not look like what I remember small block chevy manifold / head pipes looking like. mrhand's picture is what I remember, one @ 90 degrees, the other at about 45 degrees. I've welded some stainless to plain steel with a mig welder (L56 wire) with the incorrect C02/Argon.. it was dirty, but worked ok. You probably should check with Pypes to see if any issues welding their material to alumanized pipes. 2-1/2 to 2-1/4 adapters are available, so wouldn't worry about them being 2-1/2".
 

hd_cat

Veteran Member
Sep 6, 2013
134
United States
If you're set on using stock manifolds, the Pypes downpipes are a better bet, then when you decide to upgrade and buy the Pypes system later, you won't have to use an adapter. I have the complete Pypes 3" stainless system with Flowmaster Mufflers, tough to beat, especially with their polished stainless tips!
 

snowdog

Member
Nov 14, 2002
50
Lexington, KY
Just FYI Uhaul rents a fairly decent car trailer, you gotta have a truck. Also if you want to move back to old school manifolds, hooker and others make high flow factory exaust manifolds that look ausome and factory.
 

jeff swisher

Veteran Member
Apr 26, 2018
1,949
Yukon Oklahoma
I a pinch you can make your own down pipes if you have some straight tubing.
You will need a hammer and another piece of pipe or a 4x4 board.

You lay the end of the pipe on the 4x4 just hanging over 1" or so and take your hammer and hit the pipe from the inside and flare your own flange on that pipe.

Years ago i would go to a muffler shop and talk to one of the guys doing the work and ask him if he could build me a flange.
He would say did you go inside and talk to anyone.
NO I did not.
Good give me 5 bucks and a couple minutes and i will make you a flange and do not talk to anyone else.

:)

I weld stainless to mild steel and galvanized and aluminized all the time and no issues.
Mig or arc welder is what I use.

If you weld steel to cast iron you ca do it with gas and brass brazing rod.
You can also port the exhaust manifolds larger and slick them up.
Been there and done that.
 

76z28

Veteran Member
Jun 29, 2009
2,541
bakersfield
Just FYI Uhaul rents a fairly decent car trailer, you gotta have a truck. Also if you want to move back to old school manifolds, hooker and others make high flow factory exaust manifolds that look ausome and factory.
Not only this, but they are also 2.5 inch exits rather than the poor 2.25.
I just pulled off factory exhaust manifolds without air tubes for headers. Maybe I am crazy, but I would rather have the extra sound and power.
 

krabben1

Veteran Member
Lifetime Gold Member
May 16, 2007
8,429
( . Y . )Delco
That kit does not look like what I remember small block chevy manifold / head pipes looking like. mrhand's picture is what I remember, one @ 90 degrees, the other at about 45 degrees. I've welded some stainless to plain steel with a mig welder (L56 wire) with the incorrect C02/Argon.. it was dirty, but worked ok. You probably should check with Pypes to see if any issues welding their material to alumanized pipes. 2-1/2 to 2-1/4 adapters are available, so wouldn't worry about them being 2-1/2".
Yeah,I saw that they were both 90s.
A simple pie cut on the bottom and weld whats there fixes that.
I usually just use the pypes downs,and either use whats there if its my stock manifold,or cut them off and weld the header receiver,whatever it may be.
 

Postmech

Member
Aug 14, 2016
54
Alabama
The front pipes from a 1974 Z/28 worked on my 1978 Z/28. if Walker still makes them, they should work for your application. Had to cut the Donut gasket ring off the pipes to work with my factory manifolds but they bolted up fine and looked factory. Slid right over the front pipe of the factory resonators. Was a little loud but later added a homemade balance tube and it sounded great.
 




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