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  1. #1
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    Sep 2008
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    Salinas, CA
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    Default exhaust manifold porting?

    I heard you can modify the flow of stock exhaust manifolds while there off and still have them look stock. How much should one expect to pay get this done? Could someone do it themselves. Also, is it even worthwhile if your leaving everything else stock?
    I'm just curious because I plan on my nailhead looking completely stock, but it woulds be nice to put some sneaky/.unnoticable upgrades on it.
    Adrian Migotti
    1968 Riviera
    1962 Electra 225 4 door (FOR SALE)
    1957 Super Riviera Sedan

  2. #2
    Join Date
    Apr 2005
    Location
    Twin Cities, MN
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    2,684

    Default Re: exhaust manifold porting?

    I ported my factory manifolds. All I used was a knock off Dremel, a small carbide burr, and a drill w/a few grinding stones. Take a look through my past posts, I know I posted a few pics in a thread not too long ago.

    EDIT: Here's the link...

    http://www.v8buick.com/showpost.php?...0&postcount=11
    Andy

    1962 Buick Invicta, 407 Nailhead,
    Nitrous, ST400 manual VB trans,
    V6 ST300 Converter, 3.23 Posi

  3. #3
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    Sep 2008
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    Default Re: exhaust manifold porting?

    Quote Originally Posted by CameoInvicta View Post
    I ported my factory manifolds. All I used was a knock off Dremel, a small carbide burr, and a drill w/a few grinding stones. Take a look through my past posts, I know I posted a few pics in a thread not too long ago.

    EDIT: Here's the link...

    http://www.v8buick.com/showpost.php?...0&postcount=11
    Sweet so basically you just make the opening bigger? Anything to look out for? Did you feel or hear a difference?
    Adrian Migotti
    1968 Riviera
    1962 Electra 225 4 door (FOR SALE)
    1957 Super Riviera Sedan

  4. #4
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    Twin Cities, MN
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    Default Re: exhaust manifold porting?

    I slightly enlarged the port, and basically smoothed out the bumps on either side. I'd concentrate on smoothing and blending - that's where you'll see the most gains.

    I can't comment on how just the manifolds helped, but going from stock manifolds and a single 2 1/4in exhaust to ported manifolds and a dual 2 1/4in exhuast, it was one helluva difference.
    Andy

    1962 Buick Invicta, 407 Nailhead,
    Nitrous, ST400 manual VB trans,
    V6 ST300 Converter, 3.23 Posi

  5. #5
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    Salinas, CA
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    Default Re: exhaust manifold porting?

    Quote Originally Posted by CameoInvicta View Post
    I slightly enlarged the port, and basically smoothed out the bumps on either side. I'd concentrate on smoothing and blending - that's where you'll see the most gains.

    I can't comment on how just the manifolds helped, but going from stock manifolds and a single 2 1/4in exhaust to ported manifolds and a dual 2 1/4in exhuast, it was one helluva difference.
    Ok sweet. I'm still debating the exhaust thing myself, it still has the completely original exhaust and muffler and its all pretty rust free.
    Adrian Migotti
    1968 Riviera
    1962 Electra 225 4 door (FOR SALE)
    1957 Super Riviera Sedan

  6. #6
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    Apr 2005
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    Twin Cities, MN
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    Default Re: exhaust manifold porting?

    Quote Originally Posted by 68riviera430 View Post
    Ok sweet. I'm still debating the exhaust thing myself, it still has the completely original exhaust and muffler and its all pretty rust free.
    Mine still had the original system too, but after almost 50 years, it was time to replace it.
    Andy

    1962 Buick Invicta, 407 Nailhead,
    Nitrous, ST400 manual VB trans,
    V6 ST300 Converter, 3.23 Posi

  7. #7
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    Sep 2004
    Location
    Michigan, USA
    Posts
    15,050

    Default Re: exhaust manifold porting?

    If it's in good shape I'd leave it alone for now and focus on the other items you have planned. Best not to get up to your neck in too many things at once. Just the cosmetic stuff you're planning is going to take a long time. The thought of breaking off some 45 year old manifold bolts and having to pull the heads for repair would make me think twice.

    Devon
    Fuel & Brake Systems Engineer
    "I can live with doubt and uncertainty and not knowing. I think it's much more interesting to live not knowing than to have answers which might be wrong." - Feynman
    "Good data is precious. The problem I have is when some damned fool fails to use it properly." - Slingerland

  8. #8
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    Dec 2009
    Location
    Brew City Wisconsin
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    3,343

    Default Re: exhaust manifold porting?

    Its never too soon to start spraying down those bolts. Sounds like you are going to take them off sooner or later.
    William
    1966 Wildcat


    IF ITS GOOD, IT AINT CHEAP. AND IF ITS CHEAP, IT AINT GOOD!

  9. #9
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    Default Re: exhaust manifold porting?

    Quote Originally Posted by DaWildcat View Post
    If it's in good shape I'd leave it alone for now and focus on the other items you have planned. Best not to get up to your neck in too many things at once. Just the cosmetic stuff you're planning is going to take a long time. The thought of breaking off some 45 year old manifold bolts and having to pull the heads for repair would make me think twice.

    Devon
    Gah, I know, but they're gonna have to come off in the detailing anyways so I can get them sandblasted and painted. Not a full exhaust though
    Adrian Migotti
    1968 Riviera
    1962 Electra 225 4 door (FOR SALE)
    1957 Super Riviera Sedan

  10. #10
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    Jan 2004
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    Lawrenceburg, Tn.
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    Default Re: exhaust manifold porting?

    Adrian,,,,,,
    You need to ck out my list of cheap tricks stickey in the wrenchin secrets section if you havent already.... I have done all those and they work....
    Doc "Widely unknown"

  11. #11
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    Default Re: exhaust manifold porting?

    Quote Originally Posted by william.ali.kay View Post
    Its never too soon to start spraying down those bolts. Sounds like you are going to take them off sooner or later.
    Started today, gonna shoot for a week, maybe week and a half of spraying twice a day
    Adrian Migotti
    1968 Riviera
    1962 Electra 225 4 door (FOR SALE)
    1957 Super Riviera Sedan

  12. #12
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    Default Re: exhaust manifold porting?

    Forgot,,,,, to port the exhaust manifolds , I use some exhaust manifold gaskets as a pattern to size the holes... and like Cameo says you can use a dremel and carbide burrs or like I do use a air or electric die grinder and some 6'' carbide burrs.... makes for speedy operation and smooth results , then if you want to really smooth the final cut up use one of those porting kits that you get from summit....but dont put the exhaust manifold gaskets on the engine, just hang them up on the wall,if you install them they will leak sooner or later,, buick didnt use them at all,,,,,, and of course you will want to do the ''Doc dual plane" mod on the intake manifold for a good hp increase,,, for just a little money and effort....and when the carb is back on the intake you cant tell that it has been done.... Buick used 2'' exhaust pipes on the head end of the exhaust system but restricted the system by coming out of the muffler with 1 3/4'' pipes back to the bumper... they claim that the exhaust cools off as it goes back and a smaller pipe is ok.... I opened up the collars at the exhaust pipe and had some 2 1/4 pipes made and used mufflers that matched and then tail pipes that are 2 1/4'' to the back bumper... like 68 riv said , it made a bunch of difference....
    Last edited by doc; 02-21-2010 at 06:05 PM. Reason: mo info
    Doc "Widely unknown"

  13. #13
    Join Date
    Feb 2004
    Location
    Northeast Kansas
    Posts
    606

    Default Re: exhaust manifold porting?

    Doc, et al:

    What do you about opening up the exhaust manifold where it goes into the exhaust pipe? There's a ball flange on the end of the manifold that fits into the flare on the end of the pipe. No matter what sized pipes you use from the manifolds back, or how big make the ports, there's still that bottle neck where the manifold dumps into the exhaust pipe?

    This has been bugging me for some time now. I've got the new bigger pipes, and know how to open the manifold ports, but my thinking is "why?" if there's that bottle neck at the end of the manifold.

    Thanks in advance, Ed

  14. #14
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    Default Re: exhaust manifold porting?

    i took the carbide burrs and opened it up as much as possible... without risking breakage.... but as far as your question, back in the days before headers were readily available, the bigger pipes were put on and the theory was that it created a venturi effect that helped the exhaust scavenging...
    Doc "Widely unknown"

  15. #15
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    Default Re: exhaust manifold porting?

    Quote Originally Posted by doc View Post
    i took the carbide burrs and opened it up as much as possible... without risking breakage.... but as far as your question, back in the days before headers were readily available, the bigger pipes were put on and the theory was that it created a venturi effect that helped the exhaust scavenging...
    I thought the venturi effect was big into little, not little into big. Does it work both ways?
    Andy

    1962 Buick Invicta, 407 Nailhead,
    Nitrous, ST400 manual VB trans,
    V6 ST300 Converter, 3.23 Posi

  16. #16
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    Mar 2006
    Location
    Southern Wisconsin
    Posts
    3,752

    Default Re: exhaust manifold porting?

    After seeing a picture of some ported BBB manifolds recently for sale on this site, it looked to me like the exhaust pipe flanges were so thin that they would crack very easily if the pipe was tightened up too tight, or even with very much movement of the pipe. Since I have been thinking about doing this to mine, I remembered some of the cars I have worked on in the past. One that came to mind was a Chevy 327-300hp which has 2 1/2" exhaust pipes. These manifolds used a full exhaust donut rather than a cast in flange and the manifold itself was cast as basically an inverted flare the same as the pipe is flared. So, off to the parts store I went and bought a pair of these donuts. I haven't started on mine yet but I plan to machine the flange off flat and then cut the inverted flare into it. I'm not certain I can get it to fit a 2 1/2" and may have to use a 2 1/4" but I believe this could also work on the nailhead manifolds. Just an idea since I haven't proven it yet, but I see no reason why it wouldn't work.
    Bill

  17. #17
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    Default Re: exhaust manifold porting?

    The venturi effect is when a given area is squeezed down some and then flairs back out .... all carbs do this to speed the flow up.... works the same on the exhaust side...
    even if you do nothing to the exhaust manifolds and just put bigger pipes on , there is some venturi effect...the biggest restriction that I have found in buick exhaust systems is the reduction in pipe size at the muffler... ie; 2''in and 1 3/4'' out.... i went from factory specs to 2 1/4'' in and 2 1/4'' out,,, made a lot of difference on my riv....
    Doc "Widely unknown"

 

 

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