GerritD

Dear 928 enthousiasts ,

is it possible to swap my current engine (M28.12) 4.7L 300hp,
with a more recent engine of the 1984 model : (M28.22) 4.7L 310hp ?

But I would like to keep :
* 1 single distributor (instead of 2 double distributor from '84 model)
* mechanical injectors (instead of the electrical ones from '84 model)
* K jetronic (instead of LH jetronic from '84 model)
* 1 Bosch ECU unit ( instead of the 2 ECU units from '84 model)

So I just want to change the basic block with the cilinders because it would cost me more to overhaul my current engine than swapping with a good used 16V engine.

kr
Gerrit

The Forgotten On

You should be able to, the intakes bolt right up, you will just have to retard the timing a bit for the increase compression ratio of the S2 engine.

They are literally the same block with higher compression heads and pistons along with better cams.

The S2 ignition system does give you a lot more mid range torque though...

GlenL

Really?! It's just higher compression pistons from what I know.

Bolt up the parts you want to keep and you'll be fine. And don't skimp on the octane.

GerritD

that's what thought, but I was not sure. Perhaps the silent blocks(dampers) of the engine
are also different..And higher compression ofcourse demands higher octane..

The Forgotten On

K jet S has 10.0:1 compression LH jet S2 has 10.4:1 compression. Just thought I should clarify a bit.

Engine mounts might be different, but I think S cars all had hydraulic mounts, not sure though. A used lower cross brace is pretty inexpensive from an 83+ parts car.

GlenL

No matter. The blocks are all the same. Just bolt up what is already in there.

GerritD

Thank you all for your expertise on this matter.

danglerb

I agree with whats been said, except chances are good the 84 block should be refreshed with a minimum of new seals and head gaskets with a good inspection of the head and valve guides.

Intake system off the 84 and your heads and cams from the 80 should be easy to sell at a good price.

What is wrong with the 80 engine?

mark kibort

having done quite a few of these , in all sorts of configurations. 4.5, 4.7, 5 liter etc.
the blocks are the same. heads are near the same. CIS is very differnet than the LH jet, so the injection system is completely differnet. However if all you want is the better cams and higher compression pistons, then just swap out the long block and call it a day, because thats all you want anyway. However, if i were you, why not just put in a 5 liter bottom end? all you need to do is notch the pistons? that would be a huge improvement. going something like 260rwhp to near 300wrhp. I wouldnt worry about the timing and certainly not enough change to worry about having to use race gas. you are stilll SO far under the potential of this engine, its not even funny. you will be in the 275rwhp range when done.

mark kibort

so, get a used 5 liter block. re-ring and bearing it , cut the pistons. (about $600 ) OR, if its a decent block, just do the rod bearings and pistons cuts and re-ring. that way, its an easy rebuild.
then, just bolt all the old stuff back on. find some euro 84 cams if you really want to get fancy, but they are very close to the 80 euro cams. (just more duration, same lift).

GerritD

That is what I was planning to do : new seals and gaskets together with overhaul waterpump.
My engine has loss of compression on cilinder 8 : 4bar instead of 8.5
I did a compression check (leak down) and it is the piston itself, probably worn segment ring or worn on cilinder surface (nikasil worn)
And this is quite expensive to overhaul : about $2000 only for setting a new layer of nikasil on all cilinders. Other cilinders had a compression loss of 15 to 20%, so I need to renew all cilinders if I want to do it properly.
Together with renewal of piston segment rings ,bearings,gaskets and seals it would cost me $6000 to $7000 dollar, the work not included and keeping the old pistons. If I need to replace pistons and valves, it would cost me nearly $10000 dollar.

Parts here in Europa are quite expensive for the Porsche 928.

GerritD

Here in Europe the good old CIS (Kjetronic) 4.7L engine has 300hp , that's what I am aiming to achieve.
The 4.7l LH engine of the '84 model has 310hp, so there is not much difference.
The 5l engine has 320hp.

Hilton

Hi Gerrit, send the user "Hopwood" a PM - he has an early '80 car with exactly the mod you're proposing done on it - i.e. K-jet but with 4.7L block/cams from '84 928S2. He's in England.

Richard S

Keep in mind that the early 84 Euro engines used pistons left over from 83 Euro engines. So early 84 engines probably have lower compression than later 84 engines.

Rich.

GerritD

That's new to me...how can you recognize early or later 84 engines,
from what VIN number?

Difference in valves or pistons' shape?