Sprint Exhaust and Stock intake on a 73 GT.
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Thread: Sprint Exhaust and Stock intake on a 73 GT.

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    New/Old Owner 1973 GT My location JimVonBaden's Avatar
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    Sprint Exhaust and Stock intake on a 73 GT.

    So I finally got around to installing my new exhaust from front to rear using a Sprint exhaust manifold, studs on the headpipe, new Bosal pipes all the way back, and a used Bosal mid muffler, and new Bosal resonator. Everything went fine, though with lots of cussing on getting out the old headpipe. :banghead:

    I also added a new radiator, new crank pulley and new (free) Hotspark and 3 ohm 40K volt coil. I reused the carb gaskets and installed the heat shield, but installed a new intake/exhaust gasket.

    Everything went well until I went to start the car. It will start and run OK, but it runs like it has a huge vacuum leak.

    I wasn't able to locate the leak, but I recognize the symptoms. It wont idle, or even run under 1500 RPMs, and it hesitates and sputters when revving the motor.

    I suspect the problem is the carb gaskets, but I did some research here and saw that some had to trim the Sprint to make it work with the stock intake. The leak seems much worse than a simple carb gasket.

    I am ordering new carb gaskets, but would like some input on what part of the Sprint manifold needs trimming?

    Thanks,

    Jim

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    Incurable Opelitus My location Wolfman3002's Avatar
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    Jim,
    There is a small bump on the middle runner of the Sprint manifold casting that will have to be ground off, as this is what interferes with the stock intake manifold. As you can see in the attached pic below, I didn't grind all of it off, but if I remember right, I also had to file a little of the lower inside edge of the base of the intake manifold also.
    Randy
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    1969 Opel GT (in the 70s), 1973 Opel GT (in the 80s), 1973 Opel GT (now), 1973 Opel GT (parts car)


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    New/Old Owner 1973 GT My location JimVonBaden's Avatar
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    Being that the intake is aluminum, would it be easier to remove the material from the intake? Also, how much needs to come off the intake even with the bump removed from the exhaust? It looks like there is a lot of material on the intake that can be removed.

    Thanks,

    Jim

    PS Would this create enough of an issue to prevent the intake from sealing?
    Last edited by hrcollinsjr; 06-19-2010 at 04:42 PM.

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    Detritus Maximus opelbits's Avatar
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    Quote Originally Posted by JimVonBaden View Post
    Being that the intake is aluminum, would it be easier to remove the materiel from the intake? Also, how much needs to come off the intake even with the bump removed from the exhaust? It looks like there is a lot of materiel on the intake that can be removed.

    Thanks,

    Jim

    PS Would this create enough of an issue to prevent the intake from sealing?
    Hey Jim-

    I had the same issue. I think I took material off the intake only, don't remember doing anything to the exhaust. The only problem is that my intake is unusable with a stock exhaust manifold (as if that is really a problem). It is definitely enough to cause a big problem.
    "No, it's not fiberglass."
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    New/Old Owner 1973 GT My location JimVonBaden's Avatar
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    Quote Originally Posted by opelbits View Post
    Hey Jim-

    I had the same issue. I think I took material off the intake only, don't remember doing anything to the exhaust. The only problem is that my intake is unusable with a stock exhaust manifold (as if that is really a problem). It is definitely enough to cause a big problem.
    Great, thanks. How much, and where, did you remove materiel from your intake?

    Jim

    PS Not worried about reusing it with a stock exhaust again.

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    Incurable Opelitus My location Wolfman3002's Avatar
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    Quote Originally Posted by JimVonBaden View Post
    Being that the intake is aluminum, would it be easier to remove the materiel from the intake? Also, how much needs to come off the intake even with the bump removed from the exhaust? It looks like there is a lot of materiel on the intake that can be removed.

    Thanks,

    Jim

    PS Would this create enough of an issue to prevent the intake from sealing?
    Jim,
    It is definitely easier to remove the intake manifold material. I didn't grind the bump on the Sprint all the way down because I was having a hard time, using just a dremel to grind with. However, I'd also be careful grinding the intake manifold too far, since you wouldn't want to punch through and give yourself another vacuum leak (one that would need a welder to fix!). I believe I just ground a 45 degree angle on the lower inside corner of the intake manifold, where it met the "bump" that was left on the Sprint manifold, taking off just the corner. unfortunately, I didn't take a pic, and the manifold is installed on the car right now. I probably wouldn't have had to take off near as much from the intake manifold if I had ground the Sprint manifold bump completely flat.
    Randy
    Wolfman (aka: Randy)
    1969 Opel GT (in the 70s), 1973 Opel GT (in the 80s), 1973 Opel GT (now), 1973 Opel GT (parts car)


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    New/Old Owner 1973 GT My location JimVonBaden's Avatar
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    Sounds good. I will know exactly where to grind since the two parts are rubbing together no.

    Sounds like I should grind a little of both to ensure clearance. I assume there is no worries grinding the exhaust manifold flush? Plenty of material?

    Thanks again!

    Jim
    Last edited by hrcollinsjr; 06-19-2010 at 04:44 PM.

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    Living in the past opelnut10's Avatar
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    sprint manifold/stock intake

    Quote Originally Posted by JimVonBaden View Post
    Sounds good. I will know exactly where to grind since the two parts are rubbing together no.

    Sounds like I should grind a little of both to ensure clearance. I assume there is no worries grinding the exhaust manifold flush? Plenty of material?

    Thanks again!

    Jim
    You can grind the hump on the exhaust down to flush, then grind the inside lip on the intake at a 45 and that will give you the clearance you need. If you have the exhaust off the car, cutting it down most of the way with a saws-all will save you a lot of work with the grinder, other wise the best method of attack is a burr tool chucked in high speed grinder. Good luck, but you do need to fix it to prevent further interference.
    Last edited by hrcollinsjr; 06-19-2010 at 04:44 PM.

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    Bump is gone on my Sprint exhaust manifold. I used a cut-off wheel, then ground (blended) the surface smooth.
    Last edited by hrcollinsjr; 06-19-2010 at 04:47 PM. Reason: A bump can't be flush and ground is past tense of grind.

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    Detritus Maximus opelbits's Avatar
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    Quote Originally Posted by JimVonBaden View Post
    Great, thanks. How much, and where, did you remove materiel from your intake?

    Jim

    PS Not worried about reusing it with a stock exhaust again.
    I ground down the bottom edge of the intake almost all the way across (the width of the center runner on the exhaust manifold plus a little) to make sure there was no interference and that there was a definite gap between the two manifolds for air flow. I ground it to a 45 degree angle until there was a sufficient gap, probably 1/8". The manifold is pretty thick there, just look at the ribs cast into the area that is normally covered by the exhaust manifold.
    I would imagine that some careful figuring and planning and you could use the four holes (now empty with no heat riser) to hold a heat shield between the two manifolds....hmm, another something for me to contemplate....
    "No, it's not fiberglass."
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    New/Old Owner 1973 GT My location JimVonBaden's Avatar
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    Quote Originally Posted by opelbits View Post
    I ground down the bottom edge of the intake almost all the way across (the width of the center runner on the exhaust manifold plus a little) to make sure there was no interference and that there was a definite gap between the two manifolds for air flow. I ground it to a 45 degree angle until there was a sufficient gap, probably 1/8". The manifold is pretty thick there, just look at the ribs cast into the area that is normally covered by the exhaust manifold.
    I would imagine that some careful figuring and planning and you could use the four holes (now empty with no heat riser) to hold a heat shield between the two manifolds....hmm, another something for me to contemplate....
    Thanks, and a good idea. I have some 22 gauge sheet that would make a great heat shield. I might see what I can do with that!

    Jim

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    Opeler My location krewzer's Avatar
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    I ground the hump off of my Sprint with a grinder. I also made two brackets, that held a heat shield, suspended above the intake manifold, (about 1/2 inch) where the 4 bolt holes are left unused. The heat shield was made from Weber grill parts. Lowes sells a stainless steel heat diffuser that make a neat shield, once cut to size and shape. I made a two piece shield, that the laps the exhaust manifold, in both directions.

    Wes

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    Detritus Maximus opelbits's Avatar
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    Quote Originally Posted by krewzer View Post
    I ground the hump off of my Sprint with a grinder. I also made two brackets, that held a heat shield, suspended above the intake manifold, (about 1/2 inch) where the 4 bolt holes are left unused. The heat shield was made from Weber grill parts. Lowes sells a stainless steel heat diffuser that make a neat shield, once cut to size and shape. I made a two piece shield, that the laps the exhaust manifold, in both directions.

    Wes
    Any chance you have some pics of the heat shield?
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    Quote Originally Posted by krewzer View Post
    ... The heat shield was made from Weber grill parts. Lowes sells a stainless steel heat diffuser that make a neat shield, once cut to size and shape. I made a two piece shield, that the laps the exhaust manifold, in both directions.

    Wes
    Weber grill parts? How good are they?

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    New/Old Owner 1973 GT My location JimVonBaden's Avatar
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    For those interested, here is how I fixed my clearance issue: http://www.opelgt.com/forums/general...rn-find-7.html

    I did not make a heat shield, just ran out of time. I will see if it becomes necessary. I did have a nice gap of nearly 1/4" when done, so adding one is completely possible.

    Jim

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    So another Opel friend of mine Keith and I were looking at what we thought was a Sprint exhaust manifold he had. (Turns out it was a Sprint manifold.) We compared it to a manifold off my 1971 GT and they look nearly identical except the manifold from my GT is cast iron instead of aluminum and where the Sprint manifold normally has that bump that people grind off, the stock manifold rises up to seat the intake manifold directly onto it.

    We both scratched our heads wondering what makes these two manifolds perform so differently? Does this extra area where the flat seating for the intake manifold to sit on created an extra pocket inside the exhaust thereby interupting the flow?

    Thanks, Neil & Keith

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    Southern Red Neck My location BQS4's Avatar
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    Quote Originally Posted by grslightng02 View Post
    We compared it to a manifold off my 1971 GT and they look nearly identical except the manifold from my GT is cast iron instead of aluminum
    Thanks, Neil & Keith
    All the sprint manifolds I have ever seen were cast iron also. If the sprint yall have is aluminum, I'd like to see a picture of it, if possible.
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    Member opeljohn's Avatar
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    Been reading this thread along with some others and thinking about my options for the future. Although I have managed a temp fix for the short term my GT will need to have the exhaust system redone. At that time I will need to fix and or replace the Intake Manifold also. One of the other little problems I have with my GT is the fuel boiling into the Carb throats in hot conditions, so I have been thinking about either a Sprint Manifold or OGTS Header. I have both in the garage but the Sprint Manifold will need some welding done to fix two broken off corners of old stud holes.

    I talked about this with Pete Anastos at the last Mother Road meet and it was his opinion that I might be happier with the Sprint Manifold. Pete has some race experience and said he found the headers hard to keep from needing to be retighened. Of course both will have different needs from the head pipe back.

    I tend to drive the GT on some pretty long trips so what ever I do needs to hold up. Would like to hear what others think of the two options.

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    Living in the past opelnut10's Avatar
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    Sprint Manifold vs Header

    Quote Originally Posted by opeljohn View Post
    Been reading this thread along with some others and thinking about my options for the future. Although I have managed a temp fix for the short term my GT will need to have the exhaust system redone. At that time I will need to fix and or replace the Intake Manifold also. One of the other little problems I have with my GT is the fuel boiling into the Carb throats in hot conditions, so I have been thinking about either a Sprint Manifold or OGTS Header. I have both in the garage but the Sprint Manifold will need some welding done to fix two broken off corners of old stud holes.

    I talked about this with Pete Anastos at the last Mother Road meet and it was his opinion that I might be happier with the Sprint Manifold. Pete has some race experience and said he found the headers hard to keep from needing to be retighened. Of course both will have different needs from the head pipe back.

    I tend to drive the GT on some pretty long trips so what ever I do needs to hold up. Would like to hear what others think of the two options.
    On a street driven GT the sprint manifold is very close to the header in performance with a 2 1/4" from the muffler and a 2" head pipe to the muffler. It is much less trouble to keep sealed and doesn't blow the gasket out between the head and manifold. The header is good for about 2 mph over the manifold at top end speed but it is a much bigger PITA.

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    Southern Red Neck My location BQS4's Avatar
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    John;
    Since I have a F.I. car, with the sprint as stock on it. The plenum won't fit with the stove section for the carb'ed cars, so thus the sprint manifold was made. Not long after I bought the car, I had to replace the gasket where the manifold meets the headpipe. This has been about 5 years ago. Not a problem so far, and as far as some one putting a sprint on their car, it's quite literally unbolting one, and bolting the other back in. As noted before, with the header, you have to cut off most of your headpipe, and have a "collector" welded in, this is after you bolt the header on and either have it towed to your muffler shop to have the collector welded on, or you can bolt the collector to the header, mark where it would fit in your current system, then cut you headpipe and do the "tomato can" trick of cutting the top and bottom out of a tin can, ten slit the side, wrap it over where the headpipe and collector meet, and hose clamp it down long enough for the trip to your muffler shop (been there done that...)
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