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Porsche 944 NA with 944 S head

I am interested in building a engine using a 85.5 NA block and a 87 944S head. I have the NA block and S head and pistons. I know the pistons have to be changed to the S pistons.

I have heard some people say it can be done and some people say no.
Any feedback will be greatly appreciated!
Old 09-01-2018, 01:29 AM
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if the S pistons are the right size to fit the bores in your NA block (tolerance group), or the block can be oversized to fit them, then yes you can then put the S head on the NA block.

one complication - your 85.5 block does not have a provision for the timing belt tensioner used on the 16v cars. you can modify the block to accept that tensioner though.

what ECU will you use?
Old 09-01-2018, 05:59 AM
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Originally Posted by v2rocket_aka944 View Post
if the S pistons are the right size to fit the bores in your NA block (tolerance group), or the block can be oversized to fit them, then yes you can then put the S head on the NA block.

one complication - your 85.5 block does not have a provision for the timing belt tensioner used on the 16v cars. you can modify the block to accept that tensioner though.

what ECU will you use?
I think the pistons are the same size, but will
double check.

Is the timing Belt tensioner absolutely necessary?
If so How dificult to modify the block?

For the ECU I was told a 85.5 or later would work fine and
Would eliminate the need for a hall sensor.
Old 09-01-2018, 09:01 AM
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if you look at the front of the block you'll see 3 circles underneath the upper balance shaft. those three need to be drilled/tapped carefully for the S tensioner studs. not hard to do just don't drill too deep and keep it centered/straight. ideally use a tall drill press.

an 8-valve ECU will be totally wrong for the 16-valve head unless you can tune it - the 16v needs about 10 degrees less ignition timing across the rev range because it's a much better design.
Old 09-01-2018, 10:31 AM
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Quote:
Originally Posted by v2rocket_aka944 View Post
if you look at the front of the block you'll see 3 circles underneath the upper balance shaft. those three need to be drilled/tapped carefully for the S tensioner studs. not hard to do just don't drill too deep and keep it centered/straight. ideally use a tall drill press.

an 8-valve ECU will be totally wrong for the 16-valve head unless you can tune it - the 16v needs about 10 degrees less ignition timing across the rev range because it's a much better design.
I really appreciate your time and information! This project may be More complicated than I thought. I may be better off with a 89 2.7 engine
and add Rogue Tuning MAF kit.

I just want to get the most horsepower
that I can with out going broke.
Old 09-01-2018, 11:45 AM
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Originally Posted by DanR944 View Post
I really appreciate your time and information! This project may be More complicated than I thought. I may be better off with a 89 2.7 engine

and add Rogue Tuning MAF kit.



I just want to get the most horsepower

that I can with out going broke.


Donít we all. The struggle is real


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Old 09-01-2018, 02:56 PM
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get the MAF kit and the offset cam key, run the cam 4 degrees advanced.

with that setup (plus a little of my own tuning) i got the same power/torque from my early US 2.5L as that high-CR 2.7L made stock.

so i could see a 2.7L with the same mods making 175-180hp easy.
Old 09-01-2018, 04:03 PM
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Donít we all. The struggle is real


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Lol. For sure!
Old 09-01-2018, 08:29 PM
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Originally Posted by v2rocket_aka944 View Post
get the MAF kit and the offset cam key, run the cam 4 degrees advanced.

with that setup (plus a little of my own tuning) i got the same power/torque from my early US 2.5L as that high-CR 2.7L made stock.

so i could see a 2.7L with the same mods making 175-180hp easy.
Good Job! I think that will be the more sensible
choice. A lot of people have told me LS, but
I do not have that kind of money to spend.

Thank you for your time and knowledge!
Old 09-01-2018, 08:35 PM
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Originally Posted by v2rocket_aka944 View Post
get the MAF kit and the offset cam key, run the cam 4 degrees advanced.

with that setup (plus a little of my own tuning) i got the same power/torque from my early US 2.5L as that high-CR 2.7L made stock.

so i could see a 2.7L with the same mods making 175-180hp easy.
Great Job with getting your early 944 hp to the level of the 89 944 2.7 engine.
Do you mind telling me what Tuning you did to get the hp increase?
Old 09-01-2018, 11:10 PM
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just minor tweaking of the fuel and spark tables adding some here, taking some out there.
i was doing dyno tests with every little change i made to see what did what.

i had the DME tuner when I had the Rogue MAF kit.
there wasn't a lot of power gained by my tuning (maybe 2-3) but it made the car run nicer.

get the MAF, get the 4 degree offset key, and run the highest octane you can get at the pump. 91 minimum, 93+ ideally. check with Lindsey Racing if there is a different MAF kit for the 2.7L vs the 2.5, the larger bore and higher CR might affect the tune somewhat.
Old 09-02-2018, 05:35 AM
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Originally Posted by v2rocket_aka944 View Post
just minor tweaking of the fuel and spark tables adding some here, taking some out there.
i was doing dyno tests with every little change i made to see what did what.

i had the DME tuner when I had the Rogue MAF kit.
there wasn't a lot of power gained by my tuning (maybe 2-3) but it made the car run nicer.

get the MAF, get the 4 degree offset key, and run the highest octane you can get at the pump. 91 minimum, 93+ ideally. check with Lindsey Racing if there is a different MAF kit for the 2.7L vs the 2.5, the larger bore and higher CR might affect the tune somewhat.
Good deal Thank you for the information!
Old 09-02-2018, 11:42 AM
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As well as what v2 suggests regarding the MAF kit and the 4 degree cam offset cam key, wyit you could always fit some stock Euro 2.5 high (10.6:1) compression pistons. Would freshen the performance of that motor really well, a very noticeable gain!
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Old 09-02-2018, 12:36 PM
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As well as what v2 suggests regarding the MAF kit and the 4 degree cam offset cam key, wyit you could always fit some stock Euro 2.5 high (10.6:1) compression pistons. Would freshen the performance of that motor really well, a very noticeable gain!
I like this idea too! I could use the 2.5 block and install the Euro 2.5 pistons, instead of buying the 2.7 Liter engine. I know parts for the 2.7 engine are harder to find.
Old 09-02-2018, 06:33 PM
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try checking with user plyhammer - he usually has a 2.7L engine on hand for very good price.
less $ than it'd take to rebuild a 2.5 with the euro pistons.
Old 09-02-2018, 07:54 PM
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try checking with user plyhammer - he usually has a 2.7L engine on hand for very good price.
less $ than it'd take to rebuild a 2.5 with the euro pistons.
Okay Thank you. I will check with him.
Old 09-02-2018, 08:32 PM
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What would be the result of using the 944S pistons with my
NA block? I see the compression is 10.9:1 for the 944S pistons. Use the 8 valve head.
The tolerance group for both sets of pistons is 1.
I am going to double check tolerance group
Tomorrow. Would a DME/ECU from a 89 work best
With this setup? BTW I am working on a 84 944.
Old 09-03-2018, 10:06 PM
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944S pistons have a larger dish than 944 8v - the 944S HEAD has a smaller chamber with a net higher CR.

944S pistons under an 8v head would be 9.0-9.1:1 compression range, stock US 2.5 8v is 9.5:1 from 82-87 and 10.2:1 in 88.

you'd have to cut valve reliefs in the "S" pistons to clear the NA valves.

...do you have a nice set of 944S pistons available you're trying to do something with?
Old 09-04-2018, 01:13 PM
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Originally Posted by v2rocket_aka944 View Post
944S pistons have a larger dish than 944 8v - the 944S HEAD has a smaller chamber with a net higher CR.

944S pistons under an 8v head would be 9.0-9.1:1 compression range, stock US 2.5 8v is 9.5:1 from 82-87 and 10.2:1 in 88.

you'd have to cut valve reliefs in the "S" pistons to clear the NA valves.

...do you have a nice set of 944S pistons available you're trying to do something with?
Thank you again for your time and information.
Plyhammer sold his 2.7 L engine. I do have a lead
on another 2.7 L engine. Just got to get the money together.

Yes going to sell the 944S pistons. I have removed two from the block
and going to remove the other two.
Old 09-04-2018, 03:00 PM
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if you can find someone who can properly over-bore and re-condition the Alusil cylinders you could put 2.7L pistons in your 2.5 block/crank/rods. you'd get a 10.9 2.7L, the only real difference would be that you'd be using a standard (smaller ports) 2.5 head but i doubt it'd make a lot of difference.

you can get a suitable head gasket for this bore/block combination from Lindsey Racing/Cometic.

if you were interested in doing that, i've got a set of 2.7 pistons i'd trade for the nice condition 944S pistons.
Old 09-04-2018, 04:48 PM
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