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.

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...

quote Originally posted by TopNotch: Many of you have probably know about the D-shaped exhaust ports on the head...

I wonder why the exhaust ports were actually made smaller in these heads? Seems like an odd thing to do with heads that reportedly flow better.

quote Originally posted by Patrick: I wonder why the exhaust ports were actually made smaller in these heads? Seems like an odd thing to do with heads that reportedly flow better.

The main restriction is the valve bowl. I'm guessing that they just matched the port more closely to the bowl. This might cause better "scavenging". And, I'm no expert on this, but I think that for a normally aspirated engine, there's an optimum ratio of exhaust to intake size. When I compare it to other engines, the exhaust on the older head looks big compared to the intake.

See https://www.fiero.nl/forum/Forum2/HTML/074087.html
Same head. list different intake. see post https://www.fiero.nl/forum/F...HTML/074087.html#p19

Another useless Red X thread...

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

Interesting to know that a 90 Grand Am manifold will fit, but I'm still going to use my 88 duke manifold. I've already drilled and tapped the head for the two bolts by the EGR port. And it will be easy to modify the manifold for the other two different bolt holes. Besides, I already have two 88 duke intake manifolds (in case I mess up one).

And if any one is wondering about the pristine looking 88 duke head in my pictures -- well, it's not so pristine. It has a crack in the area of one of the exhaust valves. Which is why I got another head in the first place. I had taken it to a machine shop for them to check out, and they found the crack, after acid-washing it to make it look so clean.

quote Originally posted by TopNotch: Interesting to know that a 90 Grand Am manifold will fit, but I'm still going to use my 88 duke manifold. I've already drilled and tapped the head for the two bolts by the EGR port. And it will be easy to modify the manifold for the other two different bolt holes. Besides, I already have two 88 duke intake manifolds (in case I mess up one). And if any one is wondering about the pristine looking 88 duke head in my pictures -- well, it's not so pristine. It has a crack in the area of one of the exhaust valves. Which is why I got another head in the first place. I had taken it to a machine shop for them to check out, and they found the crack, after acid-washing it to make it look so clean.

Why not use the whole S-10 short block?

quote Originally posted by FieroG97J: Why not use the whole S-10 short block?

Because I already had my block bored and new cam bearings put in when I found out that my old head was cracked, and I had to get another one.

quote Originally posted by FieroG97J: Why not use the whole S-10 short block?

Does not fit.

quote Originally posted by KurtAKX: Have you tried overlaying your head gasket yet to make sure you don't actually have one of the new "U" style heads, which look almost identical but have one of the head bolt holes moved about .750"? It'd be a shame to put a lot of work into that head and then find out you've got the wrong thing.

I have a VIN A head. It will fit a VIN R block exactly. The VIN U heads aren't any newer than the others -- just different.

[This message has been edited by TopNotch (edited 06-01-2011).]

quote Originally posted by TopNotch: I have a VIN A head. It will fit a VIN R block exactly. The VIN U heads aren't any newer than the others -- just different.

I didn't mean to imply that the "U" head was any newer, I just consider all the "half-moon" exhaust port heads to be "new-style", and among them there are definitely two different head bolt configurations machined from the same casting number... just wanted to make sure that you were working over a head which had the VIN A/E/R head bolt pattern, otherwise you'd be extremely disappointed.

Most of U engine won't work. Shorter overall length in head and block than R & A engine. See link above.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

Continuation of this thread here: https://www.fiero.nl/forum/Forum2/HTML/118800.html