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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old September 16th, 2017, 10:56   #1
00013cave
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Default ALH head on AHU block?

Like the title says. Not sure if this has been answered somewhere else but doing some research for a future project. Want to use a good AHU block but use an ALH head so i can have a VNT, unleaking valve cover etc
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Old September 16th, 2017, 11:10   #2
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I've read it doesn't fit. A search will bring up the details.
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Old September 16th, 2017, 11:18   #3
00013cave
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thanks
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Old September 17th, 2017, 22:20   #4
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They're quite different, definitely won't fit.

There's nothing about the head that gives you the ability to use a VNT. All 8V heads have the same exhaust ports.

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Old September 18th, 2017, 06:46   #5
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Ports and bolt spacing are different - just do an image search on ALH AHU head gasket, and you'll see that they don't match.

VNT on an AHU? many have converted. Generally requires fabrication work on the rear engine mount, and a tune of course.
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Old April 11th, 2018, 13:37   #6
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Intake/exhaust port spacing is the same. Intake/exhaust bolt spacing is the same. Head bolt spacing is the same. Coolant port spacing is the same. Oil supply to the head is the same. Here is an image that has the differences highlighted in red and green. I believe all of the differences are oil drains that allow oil to drain from the head to the block. I feel unsure about the one with the blue arrow. Can someone confirm? I believe they could all be tig welded shut and then the head surfaced. The green area would need to be filled in as shown and machined to the correct AHU profile for the front center drain. It's probably doable and somewhat tempting due to the better availability of ALH heads and the much improved sealing of the ALH valve cover. It would be a lot of work and easy to trash a good head if it was messed up, though.

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Old April 11th, 2018, 15:36   #7
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Quote:
Originally Posted by libbybapa View Post
due to the better availability of ALH heads and the much improved sealing of the ALH valve cover.
nice outline.
id have questions as to whats going together there, quite a few. but one of the only points you brought up, for all that work, youd need to do (most) yourself. you have a better sealing valve cover. heheh.
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