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The 944S head is the weakest of the 16v heads. I have cracked a few of the S2 heads, the 968 heads are the strongest.
Originally Posted by 333pg333
Welcome back Chris.
So how/when are they cracking? During port work? Clamping? Headlift? High boost applications?
I'm using the S head as it bolts straight onto my 2.5L block and as it's 'built' already.
Originally Posted by Chris White
They crack at the spark plug hole on highly stressed engines.
So, Chris White, the most reputable builder of 944 engines that I know of, cracked few S2 heads and says these heads crack at spark plug hole on highly stressed engines?
FYI, S and S2 heads also crack around the spark plug holes on NA applications.
Now quantify the term "highly stressed application".
This issue is not related to the engine being turbocharged or not.
Ah so something that has cracking issues on NA is super reliable for use on turbos, and not only that, it is superior by all means, am I getting this right?
btw...I did state pretty much that exact information previously in this thread, so it's no secret.
Not really sure what you're trying to 'Win' here Voith? Yes, it's possible that some of the 16v heads are going to be vulnerable compared to the 8v, but there are enough examples of people who have had very good success with the 16v heads. I don't think anyone is uncovering any secrets in here. 'Caveat Emptor' as such...
It proves my point that 4v heads are weaker and more prone to cracking than 2V heads.
So in this respect, 2V head is superior and in turn more reliable.
You initially argued that 16V heads were weaker because they feature less material between ports, and that they ran warmer around the plug tip area. This is true on several other types of 4+V heads, but has not been recorded on 944/968 16V heads. If this very issue has ever been reported over the 13 years I have been on this board (and others), I apologize if I missed it.
It is even less conclusive to dismiss the 4V head because of issues related to the cam chain tensioner, that is not related to the engine being turbocharged or not, though I will concede that stiffer valve springs should add strain to the tensioner assembly. With this being said, several seem to be running stock 16V NA springs on their 16V heads without issues, so?
Guys Voith is right, the 16v head is terrible and you should never use them ever!
If anyone wants to sell their crack prone 16v head I would love to take it off your hands. I'll take all the risk and you can feel good someone else was willing to buy it from you and not just be a lump if aluminum lying around the shop with nowhere to go.
Guys Voith is right, the 16v head is terrible and you should never use them ever!
If anyone wants to sell their crack prone 16v head I would love to take it off your hands. I'll take all the risk and you can feel good someone else was willing to buy it from you and not just be a lump if aluminum lying around the shop with nowhere to go.
Voith i know what you are saying. More parts typically means less reliable, But i think you are not comparing the efficiency aspect to your logic. If you can run less boost and get the same power you are actually stressing the parts less. So with power being a constant 400 hp on an 8 valve vs 16 valve you have less stress on a 16 valve. Am i right?
I ran a turbo'd S2 head for about 4 years with the car tuned for 400rwhp and had no issues with cracking. I over built it for my application and ended up swapping it out for a 968 head that I kept a lot closer to stock.
Another data point for the S2 head is that at least one of the two 968 based Doom engines used one. Initially it was used as a test bed engine then ultimately made it into a hill climb car. The engine ended up cracking two cylinders during a race at Pikes Peak. I'm a little foggy on the numbers now, but the engine was set up for higher rpm, and was making something like 900hp. I would say that's a high stressed application, and the S2 head managed to survived when the block did not.
A friend of mine bought that particular engine, and when the head was refreshed, all it needed was a cleaning and a couple of valves needed to be lapped.
You can break just about any part if its assembled or applied incorrectly. Even if you get those two correct, you can still break parts with improper tune, misuse, or neglect.
03-29-2015, 07:09 PM
