After Header install ?'s

[csdineley]

Hello

Well I finally got some headers after putting up with my cracked and leaking manifolds for awhile now. And today I got to test fit them before the snow started coming down. They're the cheap ebay stainless 3/4 chevelle headers. They fit well and look great. But I thought up some new questions.

1.) I need to have an O2 bung installed. Should I get it on the header collector or the reducer/ Y-pipe? Either way heated O2 or just a normal one?

2.) Collectors are 3" and came with reducers to 2.5". My stock exhaust is a 3" single stainless setup up from the cat all the way back. But the y-pipe is 2.5" so the question is should I have a 3" y-pipe made up or is there a befit of reducing it to 2.5" through the y-pipe?

3.) Once installed I need to find a way to get it up to the shop to have them weld up the bung and y-pipe. Any thoughts?

Thanks

[mopar346]

1. get a collector with a bung, yes a heated O2 is better and easy to wire.

2. reducing to 2.5 will creat back pressure which is good in most cases, I would stay with the 2.5 collector and y-pipe, course I would scrap it all for 2.5 or 2.25 true duals

3. ya drive it, if you have everything slip fitted it wont even be that loud, but I would have no concerns about driving it to the shop with open headers

[INSIDIOUS '86]

Originally Posted by mopar346

1. get a collector with a bung, yes a heated O2 is better and easy to wire.

2. reducing to 2.5 will creat back pressure which is good in most cases, I would stay with the 2.5 collector and y-pipe, course I would scrap it all for 2.5 or 2.25 true duals

3. ya drive it, if you have everything slip fitted it wont even be that loud, but I would have no concerns about driving it to the shop with open headers

So putting a wets sock in your mouth and running a marathon is better than open breathing?

No engine the world likes back pressure ever. Tuned pressure waves from headers are good not pressure.

So yes find a proper sized y pipe for your system.
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[mopar346]

Originally Posted by INSIDIOUS '86

So putting a wets sock in your mouth and running a marathon is better than open breathing?

No engine the world likes back pressure ever. Tuned pressure waves from headers are good not pressure.

So yes find a proper sized y pipe for your system.
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Not to disagree but I have known many cars over the years that ran better capped than uncapped, as well as many engines that dynoed better torque capped. It has always been attributed to back pressure, whether it was due to exhaust flow or not I cant tell you. I have also seen cars that ran strong and got lazy with only the exhaust being changed to a significantly larger pipe. Just real world experience no theories.

[INSIDIOUS '86]

Originally Posted by mopar346

Not to disagree but I have known many cars over the years that ran better capped than uncapped, as well as many engines that dynoed better torque capped. It has always been attributed to back pressure, whether it was due to exhaust flow or not I cant tell you. I have also seen cars that ran strong and got lazy with only the exhaust being changed to a significantly larger pipe. Just real world experience no theories.

I can see how one would attribute this to back pressure but that isn't so.
The case is most of the time an open header car will over scavenge the cylinder and lose intake charge out the exhaust. This usually means the headers are tunned for higher rpm not to mention open headers without any changes in jetting and tuning will usually kill power.

The headers job is to evacuate exhaust gasses as efficiant as possible while maintaining gas velocity and the collector is to straighten the gasses and straighten them as well as scavenge the pipe next to it.- headers in the basic sense shorter headers are better for top end and longer for low end. You also have tri-Ys,stepped tube, merge collectors, 180* headers and wave tuning to make enough options to put you in a coma with the possibilities
The mufflers job is to quite a vehicle. No other reason
Your pipes need to be properly sized for the engine output and rpm range.
A high output high rpm engine will like a 3" pipe to keep a good flow and velocity at high rpm whereas a 2.5 inch pipe on the same motor will help low end but you lose on the top. But in a normal street motor it will keep low end and maintain proper top end power. If your motor is kind of in between then there are various ways to optimize the exhaust by ways of H-pipe and xpipe and muffler flow and wether or not you run tailpipes. And believe me tailpipes can make a big difference.

So in a basic sense once you slow down your gas travel there is no real way to speed it up other than inducing pressure. So basicly adding a 2.5 y pipe isn't exactly ideal. Combined with a single pipe and shortie headers going from manifolds on a stock engine to this setup will net minimal gains IMO since that y-pipe is basicly going to size your whole system. Not to mention the biggest enemy of a single exhaust is low velocity through a high volume pipe and a single muffler, biggest evil being a single muffler. So a real good flowing muffler is needed to prevent back pressure to help keep flow and velocity.

Basicly if I was doing it (and I'm assuming a stock motor here since the manifolds are being used) I would add the headers and have a real smooth transition y pipe that uses the header collector diameter and merge to the exhaust pipe size and then a good high flow muffler to help the whole system do its job. Later add long tubes and a 2.5 system with an h pipe and a decent muffler. That system will work good up to 450hp
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[csdineley]

Thanks
I'd like to put a dual system on there, but it's not in the cards right now. To many other thing that need fixing first.

[piecesparts]

Too much free breathing makes for a lazy exhaust flow. If the piping is too long and too large, the gases will cool to fast and then cause a reversionary effect and not help sweep the cylinders out as the headers are designed to do.

[pwradder]

seeing that we're talking about a single exhuast 3'' is definatly not too big and if you're staying with it and not doing the duals for a while, it's what i would go with front to back. when the 02 sensor is installed try to keep it as close to the collector as possible.

[one low c10]

just curious if you had a link to the headers you bought. I am getting ready to order mine this weekend.

[csdineley]

http://item.mobileweb.ebay.com/viewi...d=271021552879
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[csdineley]

Ok next question to pop into my head. I seem to remember reading that you have to modify the A/C bracket to fit with headers. So does anyone have a picture of this?

[mopar346]

Basically there is a tab on the bracket that utilizes the front manifold bolt on the driver's side. Many people diregard this tab (or extra bracket) when installing headers which allow the pump to flex forward slightly cause premature belt wear. In most cases I have seen a spacer to take of the difference in thickness of the header flange verses the manifold is all that is needed, I have even seen header kits that come with one or an assortment. In some cases it may be necessary to notch the bracket for clearance.


Insidious, good info, what are your thoughts on header extension and way they even make them? I have been in the habit over the last 30 years (more so back in the day) of running header extensions in 2.5s on small blocks.

[Rich84]

What year truck do these fit?? 2wd or 4wd?? lowered or stock??

I figure they will turn blue pretty quick, but I used to like that look on my Harley..

[csdineley]

Well I can only speak for mine. Which is an 87 R20 2wd 350, th400.
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[Rich84]

The price just seems a little to good to be true...
Once you get them on let us know what you think.

[csdineley]

Well I finished up installing the headers today. Also got the O2 bung welding on. Still got to figure out the y-pipe. Most likely I'll just have to drive it up to the exhaust shop with headers open. I'm hoping the shop 2 miles up the road will do it, and not be crazy on the price! If not the next shop is 15 miles away.

[INSIDIOUS '86]

Have you looked at flow master y pipes? A lot of shops will just cut a hole in one pipe and weld another over the hole. Kinda like factory and this is not good at all
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[INSIDIOUS '86]

http://m.summitracing.com/parts/mpe-10798
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[csdineley]

Ok, so I got the y-pipe made up today. First impressions, much better then my cracked old manifolds.

[motornut]

Originally Posted by csdineley

Ok, so I got the y-pipe made up today. First impressions, much better then my cracked old manifolds.

looks good

[wyattglock]

Looks good!

[THE "10" SILVERADO]

I used u-bolt clamps to clamp mine up. As long as you don't overtigten and crush the pipe you should be fine. I might just drive it like this until I can get it welded because it doesn't leak.

[Rich84]

They look like they fit with plenty of room...Did they turn yellow??

[Auctioneerhere]

Did you put them on a 2wd or 4x4 truck?

[csdineley]

Yeah they yellowed, but I hear that's normal on stainless headers.
2wd

Haven't added a heated O2 yet. Seems to run fine with the stock one, is there a way I can tell when/if the engine gets into closed loop mode?