Modifying a Stock 2.4 Exhaust Manifold for a GT
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Thread: Modifying a Stock 2.4 Exhaust Manifold for a GT

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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Modifying a Stock 2.4 Exhaust Manifold for a GT

    I like the 2.4 exhaust manifold that my engine came with. I've had 2.0 headers. Yawn, been there, done that. I want to make the stock one work on my GT. But the darn exit end is angled a little to the passenger side and not straight down. How can I make this thing work on a GT? The only way available to me is to drive it with no headpipe or anything to the muffler shop, dodge the cops because the car will sound like a locomotive with no muffler, and tell'em "Here, make a muffler system for me that will work."

    That sucks.

    Can I have the end of the manifold cut off and welded on at the normal GT angle? Is this logical?

    What other options do I have?

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    Opel Key Master My location opelspyder's Avatar
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    Does your manifold have the O2 sensor port on it? If so the manifold I put into the CA Opel seems to point in the right direction. The pipes are quite a bit bigger, and yes, maybe you could make a temporary one to be muffled, but I will drive it to the muffler shop to have the head pipe made
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    Opel GT Source has an adapter to install a standard 1.9L manifold on a 2.2L or 2.4L engine. P/N 11033 adapter is approximately $50.00. I would call OPGTS and inquire. Not sure if the OPGTS adapter is for the intake or exhaust manifolds?

    I have an European Sprint Exhaust Manifold from Germany for the 1.9L. I might sell it if somebody offered me $150.00 plus shipping. At the slow rate that my GT updates are progressing, I will probably install a 1975 Sprint Exhaust Manifold.

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    Tennessean Site Supporter My location hrcollinsjr's Avatar
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    Quote Originally Posted by The Scifi Guy View Post
    The only way available to me is to drive it with no headpipe or anything to the muffler shop,...
    Shame you won't be able to see the neato flames coming out but I'm sure you'll see evidence when you pop the hood or maybe before.

    Driving with an open header is one thing. I wouldn't recommend driving without a headpipe, doesn't have to be full length but I would want it to at least exit under the car.

    JM2CW,
    Harold

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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Yes, it has the O2 sensor.

    I even bought a 1.1L headpipe offa ebay so that I could bolt it to my spare sprint manifold, then take that assembly and the 2.4 manifold to the muff shop, so that they could copy and integrate the angle, length, and other issues into the 2.4 exhaust they'll make. The RallyBobster says I should go for 2.5" pipe for the 2.4's exhaust sytem.

    Anybody see any flaws in this game plan?

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    Member Team Unter Puff's Avatar
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    Do you have a stock exhaust manifold, or a header. Install the non-problematic exhaust only for the drive to the exhaust shop. Then have them fab up a system for you.
    1970 GT - Why can't I find any of my nuts.

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    Southern Red Neck My location BQS4's Avatar
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    Quote Originally Posted by The Scifi Guy View Post
    Yes, it has the O2 sensor.

    I even bought a 1.1L headpipe offa ebay so that I could bolt it to my spare sprint manifold, then take that assembly and the 2.4 manifold to the muff shop, so that they could copy and integrate the angle, length, and other issues into the 2.4 exhaust they'll make. The RallyBobster says I should go for 2.5" pipe for the 2.4's exhaust sytem.

    Anybody see any flaws in this game plan?
    Gordy;
    I'm not sure, but, I don't think the 1.1 head pipe will bolt up to the 1.9 manifold.
    "Yes, I do have a rifle rack in my Sportwagon"

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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Here’s pics of my oem 2.4 exhaust manifold and my Sprint manifold. You can see that the exit of the 2.4 has the two runners(?) oriented about 80 degrees different with the two runners exiting the manifold front to rear, instead of the oem GT right to left orientation. I was incorrect about the angle of the 2.4’s exit being off to the right. It’s not. The last pic shows the two manifolds sitting flat on their exits with the exhaust ports against each other.. As you can see, the exhaust port-to-exit angle is 90 degrees on both manifolds. You’ll also notice the exit of the 2.4 is almost centered between cylinders 3+4, whereas the oem/sprint’s exit is almost parallel with cylinder 3’s exhaust port.






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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    I’m all confused and frustrated now. Here’s the pics of the two headpipes I have. I was told that the newer looking one is a 1.1L GT one. The other is the home made one that my GTX’s original 1.9 motor came to me with. Gene’s right, the 1.1 pipe doesn’t match the Sprint’s holes(unless I just used the two in the middle to hold it to the Sprint manifold). The 1.1 pipe doesn’t come anywhere near matching the huge 2.4 manifold’s flange. So, assuming that the 1.1 headpipe is the same virtually exact shape as a 1.9 GT’s headpipe, I laid the two headpipes together with flanges absolutely parallel and square with each other. Then I clamped them, square and true, to a thick flat hunka steel plate I had to see how they would line up side by side. Way off! Now I’m all confused as to which one mimics an oem 1.9 GT exhaust systems angles and clearance issues the best. The 1.1 seems wrong to my eye and the home made one has me totally befuddled. I KNOW that the home made one was in a GT with a 1.9 engine, it fit lousy, but it fit. But it seems so different than the 1.1 that now I don’t trust the new one’s dimensions.

    Whatta PIA!

    I refuse to fail at this quest. I refuse to have to do what everybody else has to do and use an OGTS header/headpipe or have RallyBob or someone make a cool azz custom one. I have nothing against either alternate choice. I’d love to have a cool azz RallyBob headpipe/header, but it’s harder to make the oem one work and that’s the whole point. Do what few people have done, just for the sake of doing it.

    Who wants to send me a rusty, nasty, used 1.9 GT headpipe for little more than the cost of shipping?

    My plan is to then bolt it to the Sprint and then bolt the Sprint and the 2.4 manifolds side by side and level to each other to a board and take it to the muffler shop. I’ll have them make a flange to match the 2.4 and somehow construct a 2.5” exhaust the mimics the angles of the oem set up.

    How’s that sound? I’m a rookie at this custom exhaust crapola.






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    Opel Key Master My location opelspyder's Avatar
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    It honestly sounds like you are making it out to be more than it is worth. A 1.9 headpipe will not bolt up to the 2.4 manifold, it is too small. Both pipes you have there appear to be a 1.9, the new one looks like it is from a Manta/1900. Anyways here are some pics of a 2.4 manifold from underneath...it looks to be a pretty good straight shot. Now I have an original flange, with the pipes cut off, and obviously they will not work due to the curve in the pipes, but If I were going to do this, this is what I would do. 1st, Cut these pipes off the flange and draw out a new one on paper with the correct hole size for the two pipes. 2nd, have a new flange made. 3rd, weld two pipes straight down from the original one with a 90, and maybe even run flex pipe, or run somewhere with a tubing bender to bend the pipes where you mark them, take it back and mock it up. You just want a crappy temporary setup...let the exhaust shop make one that is pretty. Pictures show in the car, and the pipe with flange. I'm not necessarily at that point I want to get into making the flanges, but it will be a couple months it will happen. For that matter, you can draw one up with what you have as well. The bolts are a lot bigger in that manifold as well, thats why I think you are wasting your time getting a GT headpipe
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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Keith, I'm in no hurry with this and it'll easily be 6 months or more before I'm ready to tackle the engine end of my car. If you're willing, or the situation permits, I'd love it if you could have two of the final design made and I buy one of them from you.

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    Opel Key Master My location opelspyder's Avatar
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    Will do! I wish the car was at least rolling, or I would go ahead and trailer it to the muffler shop and get it done before paint...just won't happen. I may have a few made so you can use one for getting over to the shop and they can have a fresh one to work with
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    Southern Red Neck My location BQS4's Avatar
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    Gordy;
    Not to throw another "monkey wrench" in this, but, you should know, the the "sprint" manifold most people want, actually had two different sizes of where the head pipe bolts up. There's the smaller one that came on our 75 F.I.'ed cars, and there's a euro version that overall looks EXACTLY the same, except the flange where the headpipe bolts up is bigger.
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    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
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    I'm going to be fabricating a custom headpipe to fit a 2.4 CIH exhaust manifold to a GT. The prototype will be a 2.25" main tube diameter, but I will be building a jig that enables me to make them in either 2.25" or 2.5". I'll be posting up pics here when the prototype is done then I'll be listing them in the ad forums, on a one-off build basis.
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    Quote Originally Posted by RallyBob View Post
    I'm going to be fabricating a custom headpipe to fit a 2.4 CIH exhaust manifold to a GT. The prototype will be a 2.25" main tube diameter, but I will be building a jig that enables me to make them in either 2.25" or 2.5". I'll be posting up pics here when the prototype is done then I'll be listing them in the ad forums, on a one-off build basis.
    The next sound you hear will be Gordon yelling as he does cartwheels across his yard!
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    Just Some Dude in Jersey My location The Scifi Guy's Avatar
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    Cart wheel sounds:


    Tumble........tumble.........tumble..........tumbl e...........tumble.........squish........Dammit! Dog poo!




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    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
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    Part of the deal with Gordon was I would build his headpipe custom, but would use it as a template in order to build a jig fixture so more could be built down the road.

    I contracted to have a bunch of 3/8" thick steel flanges water-jet cut for future head pipe builds, and just got them last week.

    Note the difference between the 1.9 flange size with 1.625" tubes, and the 2.4 flange with 2" tubes!

    I ordered the tubing bends last week so pretty soon we'll have some of these built up.
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    Southern Red Neck My location BQS4's Avatar
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    Which motor(s) and models would this be good for Bob?
    "Yes, I do have a rifle rack in my Sportwagon"

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    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
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    Well, like the thread title states...Opel GT with a 2.4 exhaust manifold fitted!
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    Southern Red Neck My location BQS4's Avatar
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    Quote Originally Posted by RallyBob View Post
    Well, like the thread title states...Opel GT with a 2.4 exhaust manifold fitted!
    D'oh, sorry was half asleep when I was reading this.....my bad:banghead:
    RallyBob likes this.
    "Yes, I do have a rifle rack in my Sportwagon"

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