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Author Topic: Anatomy of a Better Duke Head  (Read 16378 times)

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TopNotch

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Anatomy of a Better Duke Head
« on: May 28, 2011, 09:28:21 pm »
I'm rebuilding the engine in my 88 coupe, and when I'm done and it's running, I'll do write-up on it. But for now, I thought I'd tell you about the head I'm putting on it. It is a 91-93 type VIN A head, as used on S10 trucks, etc.

Many of you have probably know about the D-shaped exhaust ports on the head:

The top head is a normal 88 duke Fiero head. The lower one is the S10 head. Here's a close-up of the exhaust ports:


But the exhaust port difference is only the beginning. Look at this view of the valve openings (S10 head on the left):

Here, it's easy to see that the valve openings are larger, especially the intake opening. The intake opening is also deeper. This head is going to flow a lot better.
is going to flow a lot better.

This next picture illustrates a problem I'm going to have:

The holes to mount the intake manifold aren't in the same place. In the next picture, I have a duke gasket over the S10 head to illustrate this.

The intake and coolant holds match exactly, and the extreme left and right bolt holes are the same, but the other ones are different. I can modify the intake manifold for the top two holes that are different, but I'll have to drill and tap the head for the holes beside the EGR port. There's plenty of metal there to allow that.

This next picture illustrates another difference in the two heads. The S10 head uses longer valve springs (S10 spring on the right):

And, of course, it has longer valve stems because of the longer springs:

These longer springs will support a higher lift cam better than the short springs could.

More to come when I get the engine back together and in the car...
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85GT

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Re: Anatomy of a Better Duke Head
« Reply #1 on: May 30, 2011, 08:59:00 am »
good luck Pat  :) :)
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Raydar

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Re: Anatomy of a Better Duke Head
« Reply #2 on: June 30, 2011, 10:25:14 pm »
Regarding the port mismatch on the intake... Is using the S10 intake a possibility? Might it even be beneficial?

Also, I'm surprised at the shape of the center exhaust ports. I thought I remembered my 88 Duke having the two center ports "siamesed" into one big port. Of course, that was 12+ years ago. I could easily be mistaken.
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TopNotch

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Re: Anatomy of a Better Duke Head
« Reply #3 on: June 30, 2011, 11:07:00 pm »
I have to use my intake manifold because of other modifications already done.
The exhaust manifold is siamesed, not the ports on the head.
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Raydar

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Re: Anatomy of a Better Duke Head
« Reply #4 on: July 01, 2011, 09:59:10 pm »
Quote from: TopNotch on June 30, 2011, 11:07:00 pm
...The exhaust manifold is siamesed, not the ports on the head.


I know the manifold is siamesed. I was just thinking the exhaust ports were too. Maybe I'm thinking of a different year. Or maybe I had a different year head. :/

I did have to remove my manifold to get it welded. It was in a previous life, though.
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