David L

What's the difference and are they cross compatible?
I think 1R is a 220 head and 2R a 250 but I could be wrong!
Many thanks

V2Rocket

no idea on the PN but all 8-valve 2.5L 944 heads, turbo or not, are interchangeable and functionally identical (except of course the fact the turbo head has sodium-filled exhaust valves and ceramic port liners but these do not affect performance if the turbo head is used on an NA car)

as long as the head PN starts with a 951 you have a suitable TURBO head regardless of year.

David L

Thanks Spencer. Mine is a 250 car and the existing part is 303 2R. I'm trying to find out if they are different. As there is a part no difference it seems logical they are . Question is how?

V2Rocket

not 100% certain, but i believe the part number (or casting #) was adjusted based on year of production.

but you would be perfectly fine using the 1R head if it is off another 944 turbo on your 250hp car. the ports, valves, springs, keepers, everything is the same from 86-91.

David L

That's encouraging, thanks
David

924srr27l

Its a little bizarre then really either the na head was and is so good? Porsche felt no need to work on it and change anything for a forced induction application ?


Unyet when they decided to up the 2.5 na capacity to 2.7 they decided to fit bigger valves? but this engine ONLY produced 3? bhp more than he 2.5 Unless they did that (Restrict) on purpose for some reason?


I'm well happy with the performance of my 944 2.5 (small Valve) head especially after the Stage II + 28cfm from 180 to 232CFM porting that Lindsey Racing did.


https://www.lindseyracing.com/LR/Parts/LRHEADS.html


This I'm sure this would work well in a Turbo Application also.


R

konakat

According to the PET the Turbo S did get a different head than the turbo in '88. 951-104-038-01 for the Turbo and 951-104-038-04 for the Turbo S.

V2Rocket

2.7 may have gotten bigger ports and intake manifold simply due to the added air volume needed by the engine at any given throttle position?

part number is different, but again, functionally identical.
you could put that -01 and -04 head side by side and look for differences without much luck.

924srr27l

Lindsey Racing did tell me the 2.7 Head doesn't flow that well, and that their flow guy said the 2.5 head design is better?


I wonder what 8 valve head they used on the 968 Turbo / S?


R

V2Rocket

2.7 head as stock flows better than a stock 2.5 head.
i dont have the numbers off hand but there is a chart comparing the two in the turbo forum if you look.

but a 2.5 head with some work can be made to match or exceed the stock 2.7 head.
its attractive to do that because the 2.7 head just for a core is a $1000 proposition whereas 2.5 heads are $50 or so.

the 968 turbo used a bespoke head...ports were sized like the 2.5 turbo but the coolant jacket on the front of the head matched the 2.7/3.0 block. they were regulation-limited for power output so decided to maximize torque output = no need for big ports.

924srr27l

That's exactly what I've had done, 2.5 head sent to the LR for work and modified to suit the 3.0 block and the whole tune maximised for torque,
190 ft lbs @ 2850rpm is sweet on the street.


R