AQ130 heads cracking?

[joe_merchant]

Looking at this thread, http://www.marineengine.com/boat-forum/showthread.php?t=379194, there's a comment that there are many AQ130 heads out there that are cracked. I'm wondering where they typically crack, what causes this, and what would be the indication, other than water in the oil?

I have an AQ130D with 175 lbs compression in the first three cylinders and 135 in number 4. It's running fine and I haven't done a leakdown test yet but my first guess is an exhaust valve. Was planning on running it this season and pulling the head for a valve job in the fall. The comment about it being common to find cracked heads on this engine have me wondering if it wouldn't be better to just look for another head and have it ready to go instead of doing a valve job on the old one. I realize this is a little bit of "crystal ball" work but wondering if there is some common experience that some of you can share.

Thanks

 

[boatdoc55]

The 130/170 engines have an iron head as we all know and it is very common to see cracks between the exhaust and intake valves. Pretty inexpensive to clean one up and have it mag'ed at a good auto machine shop. The cracks show up real good and in many cases you can see them with the ***** eye.
Remember these engines are of the era of GOOD gas and have some pretty good compression so when putting one back together I always go with the later head gaskets as they reduce some of that compression and will last a bit longer on this stuff they call gas nowadays. I also don't give them as much timing as we did way back when.