1997 pontiac Grand AM with the 3100.

I'm not sure of the entire sequence of events, but it leaked coolant and overheated and now it has a visbly cracked head on the front bank, right near the throttlebody. I can see it shooting out during a coolant pressure test. I'm not sure if the crack formed first and then it leaked and overheated, or if there was some other leak I haven't detected which led to the overheat and then the crack. The rear head doesn't appear to be compromised but it still has been subjected to the stress of overheating (car has also overheated in the past before as well).

If I were to replace both the front and rear heads with junkyard parts, what are the odds I would encounter some kind of valvetrain related problem? Could I just transfer over the pushrods and rocker arms to the new head and be done with it? My concern is some kind of nightmare scenario where I end up with valve noise or a burnt valve or something. This isn't my car, it is driven by someone's daughter so it has to have a dependable fix and not have weird noises etc. These engines have hydraulic lifters so I shouldn't have to mess with valve lash even with a head swap right?

5/18/2011 2:06:06 AM

First of all, Ray, how sure are you that it's the head and not an intake manifold issue? On the 3.1, the intake manifold actually extends under the valve cover about an inch. At the end, there's a visible seam. Lower intake manifold gasket failure and leakage is a pretty common thing, too, on these engines.

As far as head replacement goes, it's not that big of a deal to get some junkyard heads and have them reworked by a local machine shop, though you can expect to spend about 400 bucks to get the heads and have them worked. Then, expect to spend 175 for the head gasket kit.

At the very least, get your prize junkyard heads pressure tested and a light skim cut on the deck. Pressure test to determine if you have a hunk of shit head or not.

And that's still much cheaper than buying reman heads.

Your customer is going to have to expect to lay out in the neighborhood of 800 to 1000 for this to be done properly if you want to make any moneys on it.

Hydraulic pushrod motors are easy. Clean the deck, put head gasket on, put head on, torque head bolts according to spec. put intake manifold gaskets on, then drop your pushrods in, put your rockers on, and then finish all the other shit. The rockers on this engine are of a positive stop design and are nonadjustable. Don't worry about all that shit; the lifters will take out the slack.

In all reality, the 3.1 is a fantastically simple engine to work on and is actually rock solid. I've seen many of them with way over 250k miles on them. I've done quite a few head jobs on these over the years too. It's not that they suck...it's that there are just so damn many of them out there and the majority are owned by complete automotive morons that don't look after their shit.

5/18/2011 2:56:26 AM

Furthermore...I've seen damn few cracked heads on 3.1 engines (or 2.8 engines for that matter; same engine family)...and NEVER seen a head crack to the outside. Simply put, that's not where the thermal stresses are the highest. Heads usually crack between a cooling jacket and deck surface or the combustion chamber.

The more I think about it, the more I think about intake gasket failure. It's the most common failure on this engine family.

5/18/2011 9:34:04 AM

It sounds like the intake manifold should come off next for inspection purposes. The heads look to be about $50 each at the junk yard.

5/18/2011 9:53:28 AM

Yeah my money is on intake gasket as well. Any heads you get will need to be shaved, I've never encountered a set of those heads that weren't warped.

[Edited on May 18, 2011 at 10:25 AM. Reason : Don't mix up the pushrods, some are longer than others.]

5/18/2011 10:23:38 AM

I'm not a betting man but if I was that lower inake is pissing coolant everywhere. Those motors fucking suck.

5/18/2011 11:46:16 AM

actually they were pretty damn good motors, but really piss poor design/materials went into the intake gasket...

5/18/2011 6:04:05 PM