spoolin51

What is the advantage of putting a NA head on a 951? Is the swap worth the gains, and what all has to be changed ?

Cory9584

There is no performance advantage unless you do ALOT of porting and valve work to it, unless your talking about a 16v head. The only advantage i can think of is not having to worry about ceramic breaking off.

TonyG

Sorry.. I disagree.

The N/A head isn't cast around ceramic exhaust port liners. This means that the exhaust ports can be opened up, which means that you can obtain significant flow increases on the exhaust side of the equation.... which is far more important on a turbo engine than the intake side of the equation since you have pressure to force feed the intake side and make up for (relatively speaking) restrictive intake port design.

Even with stock 951 valve sizes, the N/A head can make substantially more power than you could ever get out of a ceramic port 951 head.

This is why all the big name 951 engine builders use N/A heads.


TonyG

spoolin51

Interesting..... Can this be any NA head or does it have to be something specific (944s) ?

lart951

I think Tony is refering to the 944 NA, the 944S is 16 valves and is a bit more complicated. The 944 NA is a straight swap, change the valves and you are ready.

spoolin51

Excuse my ignorance but what exactly would I change the NA valves to ? What about retainers... etc

lart951

You need the turbo exhaust valves they are filled with sodium to help in disipating the heat. If you do the swap to turbo valves might is well refresh the head.

spoolin51

True story..... Now lets see if i can find a cheap NA head

lart951

I sent you a pm

eniac

So is the N/A head only better after the exhaust side has been ported and opened up? What about stock N/A head vs stock turbo head?

TonyG

That's correct.



TonyG

TonyG

I don't know. Probably not much if any is my guess.


TonyG

blown 944

IMO the NA head is a much better choice. Having looked at a few turbo heads the ceramic liners are not always (not even close) lined up correctly with the valve seat creating a serious obstruction.

Personally I ported my liners to clean up the short side and to eliminate the obstruction. Looking back I should have just stuck the NA head on. I have a few cars and I wanted to keep them all operable .

If I were you
I would get a NA head
use the turbo exhaust valves ( that is debatable depending on cars use)
use the springs from the turbo head or get new ones

This opens up many possibilities for future porting that the Turbo head does not.

George D

This is why we used a 2.7 NA head when we had a 968TS factory head on the shelf for my 3.0 build.

George

Olli Snellman

I am also going to use 2,7L N/A head with my 3.0L 951, I managed to buy two unused heads from a friend in Germany. Valves will be Chevy BB ones.