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Exhaust port spacing/size: 1.6 vs 1.8

Old 07-19-2010, 06:34 PM
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Default Exhaust port spacing/size: 1.6 vs 1.8

I found this info regarding exhaust port spacing, and want to verify that it's correct.

The intake manifold, exhaust manifold, motor mount brackets and camshafts do not interchange because of the bore spacing differences.
Link to source.

I also found the 1.6 port measurements here, but so far nothing concrete for the 1.8.

Ultimately, what I'm wanting to do is have the option to cut the flange off a 1.6 tubular manifold and weld on a 1.8 flange if I end up with a 1.8 motor. I have a Mitsu flanged turbo and have found a cheap 1.6 mani for it, but not a 1.8, and was hoping they are close enough that this will work. I know I can buy a Garrett flanged mani for a 1.8 and an adapter plate, but that's still more expensive than doing it as described above if it's at all possible. I have yet to go to the Mazda dealer and overlay the manifold gaskets, but will do that if ultimately I can't find the answer. I figure somebody here will tell me it's not gonna happen though lol.

I also realize I can just swap the turbo flange on a 1.8 Garrett flanged mani, but the cheap 1.6 mani is a really compact log-style.
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Old 07-19-2010, 06:42 PM
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the port spacing should be close enough to swap the head flange. ARTech has my turbo manifold tacked up to a 1.6 flange right now and is fabbing everything up. when he is done he will be breaking the tacks and welding on a 1.8 head flange!
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Old 07-19-2010, 11:58 PM
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Originally Posted by matthewdesigns View Post
Ultimately, what I'm wanting to do is have the option to cut the flange off a 1.6 tubular manifold and weld on a 1.8 flange if I end up with a 1.8 motor. I have a Mitsu flanged turbo and have found a cheap 1.6 mani for it, but not a 1.8, and was hoping they are close enough that this will work. I know I can buy a Garrett flanged mani for a 1.8 and an adapter plate, but that's still more expensive than doing it as described above if it's at all possible. I have yet to go to the Mazda dealer and overlay the manifold gaskets, but will do that if ultimately I can't find the answer. I figure somebody here will tell me it's not gonna happen though lol.

I also realize I can just swap the turbo flange on a 1.8 Garrett flanged mani, but the cheap 1.6 mani is a really compact log-style.
Won't work. The port spacing is off. To give you a quick idea, the whole BP motor is 2"-3" longer then the B6 motor.

Originally Posted by WonTon View Post
the port spacing should be close enough to swap the head flange. ARTech has my turbo manifold tacked up to a 1.6 flange right now and is fabbing everything up. when he is done he will be breaking the tacks and welding on a 1.8 head flange!
Sean, take a good look at your photos, he sent you. Every port from the flange to your manifold, don't line up.

edit:::

Here you can see the gab distance there is.

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Old 07-20-2010, 12:08 AM
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i didnt pay that close attention to it my bad!


there op your question has been answered!
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Old 07-20-2010, 12:31 AM
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thats a sexy manifold.
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Old 07-20-2010, 01:50 AM
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Linked info above works out to 85.7mm bore spacing for 1.6.

I measured a 1.8 gasket a couple weeks ago and got 91mm bore spacing.
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Old 07-20-2010, 01:55 AM
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Thanks for the info guys, and for catching the detail in that photo wildfire! Looks like I'll be swapping turbo flanges if the need arises.
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