Will headers hurt exhuast flow?

[Mccoleman830]

I finally found c.a.r.b. legal full length headers from Hedman for my 78 K-15 PN# 66231. My question is, will long tube headers be more restrictive over my cast iron manifolds when routed into the factory "Y" pipe? It must be routed into the factory "Y" pipe because it has to be smog legal. I was told that since I can't run "true duels" then there isn't any point to buy headers. The reason why I want headers is to replace my cracked manifolds i currently have. Thanks for your help.

[ivorton74]

headers are supposed to improve exhaust flow...not restrict!! and more flow= more power.

[piecesparts]

The theory is that if you upgrade to headers, then you should open up the rest of the system to make use of the power gains that you can realize from the headers.

[Stepper86]

Why would dual pipes not be legal? If you put a cat on each pipe it should be fine, or?
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[piecesparts]

California smoggies will limit what you put on,but the use of a high flow aftermarket pipe will get you the flow that you need. Don't let the rules curb your desires completely. There are many legal high performance kits on the market.

[Restrorob]

I'd rather replace the stock manifolds over fool'n with cheap sorry Headman headers.

Amazon.com: Dorman 674-197 Exhaust Manifold:...
Amazon.com: Dorman 674-202 Exhaust Manifold:...


I just ordered a set yesterday from above for my buddy's Chevelle.....

[SCOTI]

Originally Posted by Stepper86

Why would dual pipes not be legal? If you put a cat on each pipe it should be fine, or?

The EPA & all of its extensions have no desire to validate what is acceptable & what isn't when it comes to replacement parts so they go w/'blanket' coverage (rules). You're only allowed to replace parts the way the factory equipped them. This means if it didn't come from the factory w/dual cats, it's illegal to put dual cats on it. The cat must also be in the same place on the exhaust as factory equipped.

So, even if dual cats would technically lead to cleaner emissions discharging from the tailpipe, they would still be illegal w/the current 'one-size fits all' mentality because the truck only came w/one. Exceptions are models offered w/varying options (f-bodies were available from the factory in both a single or dual cat configuration so it's technically acceptable to put 2 cats on an f-body that might have left the factory w/one as long as it's like the approved 2-cat set-up).

This is why it's hard (costly) to get emissions approved parts because the aftermarket manufacturers have to prove to the EPA that the replacement part does not defeat/reduce emissions control functionality.

Originally Posted by Mccoleman830

I was told that since I can't run "true duels" then there isn't any point to buy headers.

A good set of emissions compliant headers w/an aftermarket y-pipe routed into a larger ID cat & cat back exhaust will improve performance vs the stock manifolds, factory wimpy y-pipe, & small diameter single exhaust pipe. It will sound better too....

[Mccoleman830]

Thanks everyone for the input. The exhaust shop where I'm having the Y pipe redone stated that it should only cost $150 to remake the new Y pipe in 3" mandrel bent tube. Not a bad price, currently I have 3" tubing from my cat all the back to my 10 series flowmaster muffler.

[SCOTI]

Originally Posted by Mccoleman830

Thanks everyone for the input. The exhaust shop where I'm having the Y pipe redone stated that it should only cost $150 to remake the new Y pipe in 3" mandrel bent tube. Not a bad price, currently I have 3" tubing from my cat all the back to my 10 series flowmaster muffler.

Flowmaster sells a 2.5" Y to 3" outlet y-pipe for $40 through Jegs. If the $150 cost includes mandrel pipe from the headers to the y-pipe, that sounds about right.

[dugvera@gmail.com]

I wont buy anothet set of headers besides dougs thorley try y headers. I think your okay as long as they have a 3/8 flange but still. Look at doug thorley or dougs products. My $.02
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[Stepper86]

[QUOTE=SCOTI;5184063]The EPA & all of its extensions have no desire to validate what is acceptable & what isn't when it comes to replacement parts so they go w/'blanket' coverage (rules). You're only allowed to replace parts the way the factory equipped them. This means if it didn't come from the factory w/dual cats, it's illegal to put dual cats on it. The cat must also be in the same place on the exhaust as factory equipped.

I see, and here I was thinking that we have complicated rules in Europe

[SCOTI]

Originally Posted by Stepper86

I see, and here I was thinking that we have complicated rules in Europe

In my area of TX, several years ago we were going to switch to 'loaded chassis' style of testing for all year vehicles. This puts the vehicle closer to 'real world' loads which would yield more accurate tests. I think this type of testing would be ideal IF the vehicle was only required to pass the test to be 'legal'. Instead, it must pass a 'visual' inspection as well meaning all the various smog equipment pieces must be in place. If anything is missing (regardless of the impact on testing results) it won't pass.

In my book, the goal is cleaner air.
If my emissions controlled vehicle can still maintain the standards set by the government w/some parts changed or missing (or have even better results), it should be legal.

Of course, there are many who circumnavigate these restrictions & there are some places (shops) that might not verify every last detail as long as it passes the 'sniffer' testing. It pays to research testing options....

[Stepper86]

That is how we have it were I come from, pre -89 vehicles must have all smog equipment in place (if they had it from factory). But it is not tested for function, and many testers do not really make an extencive visual of the parts if the vehicle is othervise clean and tidy, if you pass the sniffer it´s okey.
On cars/trucks after -89 they will test the function(ECM error control etc..)and then do the sniffer.
They do loaded tests on diesels, but the way they test them is stupid. They start up the engine and rev it up to the limit for a period of time (I can only imagine how many they must have blown doing it )
No one drives a diesel that way, or any other engine for that mather. I think it should be done on a dyno, that way you would get some readings close to real life, but when ever you bring up the question with a tester they only shrug you off.

[Mccoleman830]

Originally Posted by dugvera@gmail.com

Look at doug thorley or dougs products.
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I called both Doug Thorley and Doug's Headers on the phone today. Both companies no longer build headers for this older truck in a smog legal design.

[dugvera@gmail.com]

Really? Man! sorry to point you in that direction. I have a set on my truck I love and just wanted to pass on a good quality product to you. I guess id just say make sure whatever headers you buy have a thick head flange.
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[Mccoleman830]

Originally Posted by dugvera@gmail.com

Really? Man! sorry to point you in that direction.
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No harm no foul. At this point summit racing has a cheap set of Edelbrock #68283. The only thing is it doesn't come with a carb E.O.# for my later year. It looks as if Hedman is the only way I can go.

[Stepper86]

Flowtech makes a shortie headder that is smog legal. Would probably be easier for you to combine with the Y-pipe than long headders. Another option would be to go with the stock manifolds from a early 90´s van/pickup, I do not remember exactly from what year they change design but they flow better than the ones on our trucks. If your engine is more or less stock you will hardly notice any differense with the headders any way.

[dugvera@gmail.com]

Originally Posted by Stepper86

Flowtech makes a shortie headder that is smog legal. Would probably be easier for you to combine with the Y-pipe than long headders. Another option would be to go with the stock manifolds from a early 90´s van/pickup, I do not remember exactly from what year they change design but they flow better than the ones on our trucks. If your engine is more or less stock you will hardly notice any differense with the headders any way.

This is true.
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[INSIDIOUS '86]

I beg to differ on not being able to tell a difference. I had some shorty headers made for a Camaro on my 305. Had all the air pipes and everything, I had bought a higher flow cat and a flow master y pipe with a large Gibson muffler the exhaust was change to 2.5 pipe from header to y pipe and three inch all the way back from the y pipe and three from the muffler. I spent about 600 on the whole system in 09 at a shop. I got rid of the computer distributor And fixed the timing and it ran a lot stronger throughout. Getting rid of the manifold restriction and heat riser and a low flow cat made a big difference. And I still passed visual and sniff test. Of coarse mine is old enough now that the 305 and emissions stuff are gone and a 3 xpipe and stroker motor took their place lol no more emissions for me
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[dugvera@gmail.com]

Originally Posted by INSIDIOUS '86

I beg to differ on not being able to tell a difference. I had some shorty headers made for a Camaro on my 305. Had all the air pipes and everything, I had bought a higher flow cat and a flow master y pipe with a large Gibson muffler the exhaust was change to 2.5 pipe from header to y pipe and three inch all the way back from the y pipe and three from the muffler. I spent about 600 on the whole system in 09 at a shop. I got rid of the computer distributor And fixed the timing and it ran a lot stronger throughout. Getting rid of the manifold restriction and heat riser and a low flow cat made a big difference. And I still passed visual and sniff test. Of coarse mine is old enough now that the 305 and emissions stuff are gone and a 3 xpipe and stroker motor took their place lol no more emissions for me
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For sure if all that work is done you'll notice some differances. A simple manifold to header swap is probably not going to show noticeable changes. Thats all I was saying.
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[INSIDIOUS '86]

Well consider the fact that a manifold opening at the flange is 2 1/4 at best not to mention the restriction the heat riser adds as well. The scavenging of the short tube header will slow the chamber to fill with more air fuel and less exhaust vs the log manifold that does not separate the cylinders. So even if there is t a great gain in power. The efficiency will def increase and so will mpg
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[dugvera@gmail.com]

Originally Posted by INSIDIOUS '86

Well consider the fact that a manifold opening at the flange is 2 1/4 at best not to mention the restriction the heat riser adds as well. The scavenging of the short tube header will slow the chamber to fill with more air fuel and less exhaust vs the log manifold that does not separate the cylinders. So even if there is t a great gain in power. The efficiency will def increase and so will mpg
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So....... very little noticable change from behind the wheel or even at the pump without opening up the entire system for full flow. And at that point you need to start thinking about how your going to compensate on the intake side of the system to feed the new opened up system. Im about to drop 6 bills on headers for my 66 and have a smog legal set on my 76. But would id advise someone to spend a bunch of cash on a set of headers when for very little outa pocket they can just replace the stock manifold. Perhaps save the money for an upgrade like an msd that actually will show noticable changes. Will they hurt? For sure not. Id hate to start a real argument here but do you think the engineers at GM would have known all they needed to do was bolt some cheap tubes to their motors that they would have a better overall product that all trucks would have started coming off assembly lines with headers years ago?
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[INSIDIOUS '86]

Wouldn't need to change the intake. The corvettes had a higher flow improved design header of sorts too. A manifold promotes faster warm up and is robust and lasts a long time. Faster warmup means less emissions over all witch meats the requirements Even so. You can't deny some cheap smog legal headers will improve things. I can't say it will do a whole lot as a stand alone upgrade but I've seen the factory y pipe and headers. Built to last not go fast. As for the argument I see no argument just two sides bringing valid points.
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[dugvera@gmail.com]

Originally Posted by INSIDIOUS '86

Wouldn't need to change the intake. The corvettes had a higher flow improved design header of sorts too. A manifold promotes faster warm up and is robust and lasts a long time. Faster warmup means less emissions over all witch meats the requirements Even so. You can't deny some cheap smog legal headers will improve things. I can't say it will do a whole lot as a stand alone upgrade but I've seen the factory y pipe and headers. Built to last not go fast. As for the argument I see no argument just two sides bringing valid points.
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Agreed. What a cheap set of hraders will do is get you very good at changing out gaskets.
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[SCOTI]

Originally Posted by dugvera@gmail.com

Agreed. What a cheap set of hraders will do is get you very good at changing out gaskets.

Manifolds can & do bring you similar results. Both of my square bodies had cracked and/or broken manifolds so they're not bullet-proof either.