Bass GT3

Re the intake, not an issue. What would be idea is a chart type affair, that lists each configuration, it's swept capacity and it's strengths & weaknesses.
ie, X block + Y head= 3 ltr/ high rev motor/ poor low end etc
There seems to be too many variables here!! I always thought the 2.7 was the short lived 16valve model??
Waaaay to hard!

Chris White

Here is the engine ‘menu’ and some general observations!
944 NA & 944 turbo 2.5 liter 8v – basic turbo and NA configuration - 100mm bore
944S – 2.5 block with 16v head – block and crank same as other 2.5, head very similar to the later 3.0 16v head - 100mm bore
944 na 1989 2.7 – 1 year only engine – 8v head made to fit 3.0 block but with 2.5 crank. Larger intake ports, larger intake valves than a 2.5 8v head. 3.0 block same as S2 16v block. - 104mm bore
944 S2 – 3.0 16v head. Block, crank and head are different than the 2.5 – but with the same mounting points. Virtually all external parts bolt on the same. - 104mm bore
You can fit a 2.7 head on a 3.0 block (that’s what the factory did)
For a small sum ($350 +/- US) you can get a 2.5 head modified to fit a 3.0 block.
The plus of using a 8v head on a 3.0 turbo is that you can bolt on all the ‘normal’ turbo parts – intake and exhaust and such. 16v head needs a custom intake and exhaust manifold
The 8v head makes very nice midrange torque and will flow quite well stock and amazingly well with mods. The 16v head will outflow the 8v head at higher RPM and due to the lighter valve train can run higher PM as well.
To me the plus of the 16v is the ability to run higher RPM – well into 7k – but the draw back is that you need to really look at the oiling system to run high rpm – if you want to run over 7k I would recommend a dry sump set up (not cheap!!!)
All else being equal the peak torque / HP of the 16v will be 1k higher rpm that the 8v

Bass GT3

Chris,

Thanks for that. makes more sense now. Re the dry sump. I won't go this route without it. I've custom dry sumped my 2ltr screamer, and am well aware of the bearing issues on these engines. Especially as i will be on 10" & 13" super sticky 1 lap slicks!!
I also don't have any problems making custom intakes & exhausts. So i really wanted to just look at the engine/head combo's on their own merits.
Given what you've written, i may go the route of a modded S2, with al new rods & pistons, light flywheel etc. jenvey ITB's and a well chosen turbo should see it home. And dry sump of course.

Thanks,

Steve

Chris White

I like the way you think.....https://rennlist.com/forums/showthre...eferrerid=1956

fast951

Interesting thread. It appears that by summer's end we will have a few 16V engines (2.5L, 2.8L, 3.0L, 3.1L) that we can compare.

I'm in the process of building a few turbo engines: 2.5L 16V based on a 944S engine, a 3L 16V based on a 944S2 engine and a 3L 8V based on a 2.7L engine. All will have the Alusil blocks, custom pistons, all with a 8:1CR.
The 16V engines will share the exhaust, intake and cams. The headers will be stock 16V headers, the crossover is a modified 951 unit. It'll be interesting to see the results.

The 2.5L 944S engine will be the first to complete. I will use the Stage 3 turbo on it, this will give us a good comparison between the 8V and the 16V engines.

One thing I like about the 16V is the fact that it is not prone to detonation like the 2.5L; the 16V head as is flows better than the 2.5L and 2.7L head.
The 2.7L head, in stock form, flows better than the stock 2.5L head. The 2.5L can be made to flow much better than stock, but it can get expensive.

The 16V heads will require some work/upgrades to live well in a forced induction configuration.