blown 944

Olli I love your thinking

pete95zhn

Mine's a NA head, ported for 48/44 mm stainless valves, LR springs and Ti plates.

Olli Snellman

Pete, do not keep them wondering for what enging those valves were designed for in the first place

blown 944

BBC exhaust

pete95zhn

BB Chevy by Ferrea.

Olli Snellman

Also intake if i can remember correctly ?

blown 944

Umm.. . I don't think so. 1.72 (close to 44 mm) is stock on some and 1.88 (48mm) is larger. Smallest intake is 2.06 on any stainless.


really, you guys should keep this quiet

Rogue_Ant

Wait, so you can use BBC exhaust valves for our heads? Does the BBC exhaust valve replace both intake and exhaust?


-Rogue

hosrom_951

With the new products out today, you don't have to go for 951 OEM exhaust or intake valves. There are several good products out there today, for a very competitive price compared with OEM Porsche.

I suggest you give CEP a call or 944 Enhancement about which valves to use, which brand, prices and so on...

Jeremy Himsel

I agree that the NA head is a decent choice provided that you also taking into consideration that when using an NA head for the porting ability on a turbo application it's important to focus in improving port velocity and low lift efficiencies to promote spool and reduce pumping losses as opposed to just hogging it out for total flow. It's important that your head guy understands this as I've seen a few turbo cars where the head guy thought a bigger port had to be better on a turbo car and it killed velocity because he ported chevy heads for 20 years. In a previous life (on NA's and Superchargers) I was always more worried about flow numbers through the head and relying on a good collector design and primary lengths to increase velocity and aid in the scavenging effect. Turbo cars don't rely on the collector creating the scavenging effect as much as they do by generating good velocity through the port and in the primaries. Not saying that a good collector design or "tuned" primary lenghts isn't benificial but you want this process started as far upstream of the turbine as you can get.

I also believe it's a good idea to use some sort of a thermal barrier like Swain Tech (however arguable) on the combustion chamber, valve face, exhaust port, and quench region to help retain heat and reduce the possibility of detonation. The exhaust-port coating is especially important to limit the amount of heat that transfers into the water jacket so the cooling system does not have to work as hard (cooler head temps reduce detonation) or transfer excessive heat to the intake ports. Although I've never captured it myself, it's said that the #4 is prone to localized boiling in the head that that's what we typically see #4 HG failures. Another benefit to the coating is that it also helps increase the exhaust velocity since a hot gas looks to travel to a cooler area. I wonder if the 996 and 997t's use ceramic coated liners? IIRC the air cooled cars did not, but the turbos were prety close to the ports.

lart951

Well, if any of you need a 88 944 n/a head, I know someone that has one for sale.

TonyG

The 996TT and 997TT do. But their exhaust ports don't have the huge hump in them like the 951's do either.


TonyG

RolexNJ

hosrom_951

Two things come to my mind about this:

1) Porsche knew about those 'humps' in the 951 head, but kept them anyway due to the fact that the wanted to 'tame' the 951 (which was priced half of what the 911T did at that time).

2) Porsche has better access to materials, machines and overall assembly. Maybe back then, having those 'humps' was a must, and today new techniques, technology (or whatever) eliminate that effect.

Guess it is one of those things....

Olli Snellman

One of the main reason why 951 had ceramic coated liners were emission questions. During that time cat technology was just about to start. To get cat work properly it was mandatory to get exhaust to it as hot as possible.
That is clearly written in 944 Turbo Information Technik manual from 1985 (page 10).