to make it short
the 16V head works (but not the stock one without mods)
It makes more HP on high rpm but less torque on lower rpm
the stock rods are not good for this kind of HP.
Porsche and the racing treams experienced Problems with the 968 T RS which raced unrestricted in le mans.

all in all for street use it may work but for Autobahn use or hard racing driving I would not sugest it.

everyone is free to use what he wants. i try to protect some people to throw away their money.... better build it right from the beginn.
The 8V head can provide you enough torque and HP so that you blow (for sure) the tranny, the clutch and the axles) so if you go to 16V you have even more problems.
If you mean just a low boost 16V head then it is ok.
It is not ok for 400+ HP

Konstantin

 

Konstantin,
Yes, we are talking about 400+ hp.
If the 16V head is used, you can get 400+ (flywheel) HP with the right turbocharger and only 9 psi, if compression is lowered to 9.0 to 1 (head spacer will work just fine with only 9 psi).
The tranny, clutch, axles.........use 951S parts.

 

IMHO it's better for the drivetrain with the 16v head since you don't get the same monstreous torque as you do on similar hard tuned big displacement 8v engines.

 

There is a reason I have not responded to any of d993's comment. Like said earlier, its easier to talk when its not your money. Do it, prove it and then talk.
Raj

 

Raj,
Nice response.
If everyone had that attitude, all 968's would still be producing 240hp (or less).........

 

.........somehow I sense a guilt over excessive $$$ spent. Like a "hmmm.........I didn't think of that".

 

Why THINK when someone else instills it in you and charges BIG $ for it?

 

Buddy, I do my own work and built my own. So preach it to someone who spent that kind of $$$. I think you have me mistaken for some of those other turbo guys.
Atleast I can say I have done both, what do you have on your resume?
Raj

 

I'll back Raj up on that. He does his own work and I trust implicitly what he says, because he can back it up with personal experience. What have you done, d993?

There have already been a lot of well reasoned posts on this thread why an 8 valve head was used. If those aren't good enough, I can think of a couple of other forums where it would be more appropriate for you to post your "information".

Regards,

 

If all you need to turbo a Porsche is a thicker head gasket there are thousands of young 944NA owners with a dollar and a dream who would be doing this.

 

It's pretty clear (to me) that d993 is not seeing the point about turbocharging a 8V vs 16V. This is not an issue of "monkey-see, monkey-do" - it's a matter guys here on Rennlist who have built or are looking to build these engines "correctly." The mantallity of "use a thicker head gasket - it'll work" vs "use the proper parts for the job" is what's being debated.

Some tuners use shorter rods, some have probably looked into a thicker head gasket to drop the CR, but at the end of the day, to maintain the combution chamber characteristics that the Porsche engineers designed you've got to use the "proper" 104mm turbo pistons - 16V or 8V. It's clear that "minor" details like squish area are not of a conern to you.

For the 8V 3L application, the 951 parts needed are much more readily available and are more cost effective than many of the custom parts (intake, exhaust/crossover) needed for a 16V application.

As already stated, if a thicker head gasket is all that is req'd then everyone in the 944/968 community would have done it already.

d993, you talk as though the thicker head gasket route is a far better, more cost effective option for turbocharging a 16V engine compared to the 8V - correct piston, modified 951 or 2.7 head option.

Obviously, you haven't spent a red cent on your thicker head gasket idea and can't back up what you are saying. In my opinion, what you fail to recognize is that even with a thicker head gasket 16V application, the 8V option is still a more cost effective option and it's built with the "correct" parts.

 

Points made. Now a question for the experts. I'm exposing my ignorance to all of you, please bear with me, why must static compression be reduced to run optimal turbocharged applications? Of course, to allow higher boost reliably! But why so? My understanding is that static compression + boost compression will result in effective compression, by reducing one we can raise the other and vice versa. Why not simply running stock compression 11:1 with lower turbo pressure to achieve the same effective compression than 8:1 bottom end with 15-20lbs boost? I know my deduction is incorrect, otherwise everyone would do it this way, but I need to understand why.

Thanks for helping a clueless soul..

Regards,
Chris

 

Damn! All I needed was a thicker head gasket?? My wife is gonna kill me if she finds out I didn't need all them fancy engine parts!

Seriously, I believe most people invested in owning and modifying these silly cars are interested in the process as much as anything else, and subscribe to the school of thought that "anything worth doing is worth overdoing," or at least "doing right." Addressing the CR issue via spacer seems a quick fix approach which ignores many other factors involved in more properly executing the conversion, and goes contrary to the mindset of those involved in these very projects. These cars, and the projects they spawn are usually a labor of love to their owners. Owning and messing with these cars, and the word "economy" have no business being together. If it was all about a cold speed per dollar calculation, we should all be driving something else.

 

Does any one here experienced problems with a thicker head gasket? Because if no one has experienced problems, how can we disregard the idea without testing it? I made a 968 16V turbo conversion myself. I decided to take the shorter rod way to lower the compression, and I remember a lot of people talking about the squish area. I have run up to 20 psi of boost without the most remote sign of detonation on street gas. I suspect that the pentroof design of the 16V head diminish the tendency to knock. The bottom line is that we can assume some things based on theory, but the thruth is that all the theory in the world cant susbstitute testing. I'm not saying that messing with the squish area is the right way, but that there are some ways that may not seem correctly but that can yield very good results.

By using the 16V from my 968 I saved the cost of buying a 2.7 8V, but incurred on the expense of a new intake manifold and the modification of the 968 exhaust header flanges to fit the 951 crossover pipe. That made the 16V conversion a little more expensive. Going with the 8V will save you some money and the problem about the fabrication of the intake manifold and exhaust header modification. By using the 16V head I do not need to mess with the timiming belt and sprockets. How much reliable will be the 16V head over the years to come have to be seen.

But hey, Porsche did not made the 2.7 head for turbocharging either!

 

On a much more mundane note, can someone educate me about the 968 block's oil cooler/thermostat housing set-up. Based on PET, it looks like the the 968 block uses the 951 style housing without the cooler inside, correct? If so, will a standard 951 housing set up bolt right up? Will a late-style 951 OPRV also work?

My Tom C pistons are finally in route I understand, so am gearing up again.

(Raj, there was no oil housing on the block you sent, right? It's been too long to remember, and I can't find one among my parts.)