[Jerry C]

I need some help from the master engine builders. I have two 1.9 engines, both are in good shape. One is a 72 the other is a 73. One will go in my GT stock, for now, the other will be built for some HP. I would like to know if one has better natural parts that the other. That is does one have better rods, crank block or head? Do I need to mix parts? I am thinking I want to bore a block to become a 2.0L and do the big valve mod with the hot street cam. I can build the engine no problem, but I don't know what are the best parts to start with. I need some help

 

[RallyBob]

Unless the '72 is a late '72 (which is essentially the same as '73), then I'd use the earlier engine. Sometime in late '72 (through '75) Opel changed their head castings to a 12-bolt design, adding two small bolt holes at the timing cover area to reduce leaks. Trouble is, they also changed the metallurgy of the head, and started flame-hardening the exhaust seats for use with unleaded fuel. The flame hardened seats crack regularly, rendering the heads into useless pieces of junk.

So, if you can determine if the head is a 10-bolt style on the '72, I'd use that one. The blocks are essentially identical, no harm using either there.

Bob

 

[Jerry C]

Thanks Bob, The heads are 12 bolt. The guy at the local speed shop tells me he can machine out the old seats and replace them. He said it is not a problem to do on Opel head. Is that true?

 

[RallyBob]

The cast iron is still different on the later heads. Even by machining the seats out and replacing with aftermarket seats, the risk of cracking is high due to the brittle cast iron. Hit 230 degrees once and they're usually toast.

When I used to sell big-valve heads, I refused to modify late heads unless the owner signed a waiver, since they might last 5 years, or they might last 5 minutes. It would suck to spend $800 or so and have it be junk shortly thereafter.

Bob