Interesting find on my new project car! Questions...
 

I just bought a 79 911 widebody. I already knew it had a 1980 "3.1" block, but the rest was unknown. It had a Holley Pro-jection TBI kit on it with a custom intake manifold. The TBI kit was not operational, so I went ahead and removed it, along with the engine shroud. As I was doing some clean up on the engine I noticed that it has 3.2 heads on it with the date code 2/86!

I was already going to do a 3.2 intake with a Bitz EFI kit on it anyways, which will make things a bit easier, but my question is, how will this effect performance? I know the 3.1 had the 3.3 turbo cylinders with some kind of high compression pistons from the factory. I have verified that the engine still has the larger cylinders.
So, what can I expect?

Do you have pics of the engine and engine bay?

Anyone??

http://forums.pelicanparts.com/uploa...1388359985.jpg
http://forums.pelicanparts.com/uploa...1388360013.jpg

3.2L heads flow real well, bone stock

OTOH, you can expect that a PO who would eff up by using that manifold and carb may have effed up elsewhere too

I assume you will do a full teardown anyway...

I did a compression test, and all cylinders were 178-180, and no broken studs, so it does not make any sense to tear it down.

You need to do a leak down test. I'm sure that the motor was not getting the same amounts of fuel to each cylinder with that manifold setup.

Based on what I see in those pics, yes, tear it down and check everything. That manifold is a serious WTF?

I would check the cam timing also in addition to checking that it's correct you may
also find the cams have been changed
I agree on not tearing it down if the leakdown/comp is good and it's not leaking oil

What is a "3.1" ? I've never heard of that displacement.

I have to say in all my years of P ownership I have never seen or even heard of a TBI setup on a 911! WTH?

Big ports on a 3 L engine will make for sluggish response at low engine speed. This can be overcome with a higher compression ratio. I suggest getting it running as you planned, drive it and decide if you can live with it. The compression ratio might have been bumped already.

if it's a real SC 3,1 ... i would not modifie it.... my 2 c

the porsche 3.1 engine is 9.5:1 with 3122cc's
the porsche 3.2 engine is 9.5:1 with 3164cc's

so there is a 42cc difference, and the compression is the same, so i might be 5hp down from the 3.2, or atleast thats what i think.

its already been modified with the 3.2 heads, so its definitely not original. Besides, the original CIS is long gone.