Once upon a time, I was an inexperienced Fiero owner... and I may have been a little overzealous with cleaning the middle intake manifold's mating surfaces with sandpaper / scotchbrite.
As I did not measure anything before/after, I don't know how much material I removed, or if I removed anything significant.
Apparently, sandpaper / scotchbrite may be too aggressive for cleaning these things, and can lead to flat surfaces becoming unflat.
I re-assembled the engine (with the thin cereal-box-like gaskets), and drove it like that for a few years, without noticing any problems... not that I would notice an intake sealing problem from the driver's seat.

Now, I have the engine apart (well, mostly buttonned up) for a rebuild, and I noticed that the bottom of the middle intake seems a little bit convex.
When I bolt down one corner of the manifold, there is a gap of 0.006" at the opposite end. Uh-oh, I said to myself.



I then found that tightening the bolt over the 0.006" gap allowed the gap to close. Good, the intake pieces are flexible enough to be forced together.

After tightening both ends, there are gaps in some places of 0.002".

Can the gasket handle this variation?
Ideally, I would not use RTV on the gasket, as I expect to have to pull the manifold for regularly for maintenance... so I don't want to deal with cleaning off RTV.

I could have the intake machined flatter by the machine shop that prepared my block, or I could look through my Fiero stash to see if I have an intake that hasn't had a retard go at it with scotchbrite.

What do y'all think about 0.002" gaps?

[This message has been edited by pmbrunelle (edited 01-01-2019).]

I'd say that is will within the tolerances for factory assembly. You can MIC the gasket if you like, but the 'crush' has to be a lot thicker than that.

The gasket material will easily soak up the 0.002" gap. That's part of the gasket's function.

Also, if you want the intake to be easily removable, you can give the gasket a light coat of motor oil. That will keep the gasket paper from sticking to the metal. But it will still seal.

Pray, tell.
What kind of maintenance needs to be done regularly that requires intake manifold removal?

That's a good question. The valvetrain components look stock-ish. It would be odd to have mechanical lifters under that.

Good to know that 0.002" doesn't strike you guys as being very much. I won't worry about it for now.

Just as a check when I do the final assembly, I'll measure how far down the intake moves, once the bolts are snugged. I'll use a dial indicator.

I'll keep the oil trick in mind.

quote Originally posted by olejoedad: Pray, tell. What kind of maintenance needs to be done regularly that requires intake manifold removal?

That would be the spray pattern inspection / flow check of the water injection nozzles.

Since this setup has zero track record, I should keep an eye on it until I gain confidence in it, or the engine blows up, whichever comes first.

That is the conclusion of this thread, in which you gave me some advice:
https://www.fiero.nl/forum/F.../HTML/141370.html#p7

Thanks, I had forgotten about the details of your build.
Looks like things are coming together well.

Yeah, well my threads regarding this project consist of a bunch of disjointed questions that come up as I hit different challenges.
Not so easy to follow.

Perhaps I should continue with a single build thread... it may provide better entertainment value to the forum members.

I do maintain a build thread on my local club's forum, and while the thought of maintaining two build threads (in two different languages) is somewhat horrifying, the Pennocks' group has been helpful when I've had questions, so maybe I should give back by doing a more interesting to read build thread.

Is my premise correct? Is a single project diary more valuable / fun to the forum rather than a bunch of separate questions?

Edit: I can think of an exception to this; when searching the Archives for tech info, it is easier to find information when it's in a standalone thread, rather than buried in someone's diary.

[This message has been edited by pmbrunelle (edited 01-01-2019).]