What are the chances of Cracked Heads?

[mongo]

I'm working on a 99 Grand Am with a 3400 in it. The motor had an obviously blown head gasket. I checked the heads for warpage and they were right on the edge of being O.K. but I decided to have them machined anyway. I took them into the shop and it was $140 to mill the two heads and another $140 to pressure test as well.

So far I have just told them to mill the heads and NOT to pressure test. How common are cracks in these heads? Is it reasonable to assume that a pressure test is not needed since I found the exact point where the gasket blew? I know that a pressure test is always recommended but if a crack in the head is not a common failure, I won't worry about it for now...

[robertisaar]

i suspect iron heads of cracking, but it's not very common to have a cracked aluminum head....

[mongo]

Thanks for the reply. That is what I was thinking since I cannot find much reference on the net pointing to these heads cracking very often....

When the machinist quoted me $280 to mill AND test, I asked him what rebuilt heads went for since I thought it was about that price. Lo and behold... that is the EXACT price for a set of fully machined and tested heads with freshly ground valves and new seals.... on-line anyway...

[SappySE107]

Ive had quite a few cracked aluminum heads, between the seats and between the intake and spark plug. 140 to mill is a ripoff, just like 140 to pressure test.

[robertisaar]

Ive had quite a few cracked aluminum heads, between the seats and between the intake and spark plug. 140 to mill is a ripoff, just like 140 to pressure test.

you also deal with more heads than most...

[Weatheralls Auto]

I have seen a few cracked, but they were external one the end leaking coolant.

[SappySE107]

Sure, most people deal with 2 heads. I still see too many cracked heads on percentage for me to believe that its not very common. On vans, its even more common for the rear head to crack.

[Weatheralls Auto]

Sure, most people deal with 2 heads. I still see too many cracked heads on percentage for me to believe that its not very common. On vans, its even more common for the rear head to crack.

^^^^^^
I agree, due to the heat I believe.

[mongo]

Well.... I was trying to keep this on the cheap as it is my Son's girlfriends car. It had a blown head gasket and was overheated twice but supposedly shut down immediately when the high temp was noticed. I can get heads off eBay for $99 each that have supposedly been milled and tested. Now that I am dumping $140 into the set just for the milling, I am getting in WAY over her budget.

The going rate here in St.Louis appears to be $280-300 a pair to mill, clean, and pressure test a set of V6 heads.

I know I am rolling the dice by not having EVERYTHING done at once, but I would like to know my odds before I spend a bunch of money she doesn't have... I DON'T WANT TO DO THIS JOB TWICE! But I don't want to blow an extra $140 that I don't need to if the odds are good the heads are fine...

If they have been blowing exhaust through a crack between the valves, it should be fairly visible I would think...

[mongo]

Hey Sappy! Where are the most common places for these particular heads to crack? Is there one spot that goes first or are there many places? The webbing between the intake and exhaust valves see the most logical places to me....

I think I am going to go ahead and use these heads "as-is" after they are milled... unless I find an obvious crack on them visible to the naked eye (after a thorough cleaning)...

[1988GTU]

You could ship that head here, have it resurfaced, AND have it shipped back to you for under 120.00. To have it pressure tested and to have both heads done would be most likely under 240.00.



Check the #5 chamber over really well. Clean the area really good, throw some pencil dust on it and wipe it off. If there's a crack, you should see it.

[mongo]

Why number 5? Is there something about that cylinder that causes it to run hotter than the others?

[1988GTU]

The lower intake coolant port on cylinder area often fails... It's what I commonly noticed and deal with. Can't do much about it other than run clean coolant & metal lim gaskets.

[robertisaar]

Why number 5? Is there something about that cylinder that causes it to run hotter than the others?

IIRC it's the last cylinder to recieve coolant, so it should run the hottest...

[SappySE107]

Ive had quite a few cracked aluminum heads, between the seats and between the intake and spark plug. 140 to mill is a ripoff, just like 140 to pressure test.

There