OST-093: My, My, Mystery
07-25-2022, 06:34 PM
Post: #1
OST-093: My, My, Mystery
Current build, so not a "Catching Up" thread.

[Image: AEU86 AE86 - OST-093: My, My, Mystery]


Essentially there are 3 types of 16V 4AG heads. There are 2 versions of the largeport, and of course the smallport.

The early largeport (1984-1987) was originally designed/built(?) by Yamaha, where the later ones(1987-1989) were changed and made by Toyota(?). You can see some of the changes in the following photos...



[Image: AEU86 AE86 - OST-093: My, My, Mystery]



If you watch Garage 4AGE's videos you may have seen the earlier head makes a bit more power. This is likely because at the bowls the earlier heads have a better shape as the bowl turns to the valve...

[Image: AEU86 AE86 - OST-093: My, My, Mystery]

... BUT there is more room in the floor of the later head (arrows).

I've come to the conclusion that the later heads were partially designed to better accommodate Formula Atlantic engine builders....... but that's another story...



The Mystery here is the head I'm working for OST-093. It appears that it is a mixed head, with some newer features, and some older features......

[Image: AEU86 AE86 - OST-093: My, My, Mystery]


more to come...... Wink

Dan -

You can |Sad .... OR you can ask for help!!!

OST Porting service - http://hachiroku.net/forums/showthread.php?t=19991
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Messages In This Thread
OST-093: My, My, Mystery - oldeskewltoy - 07-25-2022 06:34 PM
RE: OST-093: My, My, Mystery - banpei - 07-26-2022, 12:10 PM
RE: OST-093: My, My, Mystery - decryphe - 07-27-2022, 05:22 PM
RE: OST-093: My, My, Mystery - decryphe - 07-29-2022, 02:29 PM
RE: OST-093: My, My, Mystery - decryphe - 09-14-2022, 05:11 PM

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