Debrue

Thx for the info I will have to check into headers and exhaust and cat.

Btw whats a CIS?

C4ptainCox

WOT stands for wide open throttle. As the name implies a WOT switch is tripped at near wide open throttle. It just makes the air-fuel mixture richer.

CIS or Continuous Injection System is a fuel injection system that was developed by Bosch and is used in some of the early 928s. It is also known as K-Jetronic.

Since your car is a 4.5 it will either be running on a K-Jetronic or L-Jetronic fuel injection system. The later year 928s all used LH-Jetronic. The easiest way to tell at a glance which system your car is using is to look at the injectors. K-jet injectors each have an individual fuel line coming from a fuel distributor and with l-jet you have two fuel rails each connecting to four injectors above each cylinder bank.

Google is your friend. All of this information could have easily been found by with a couple of quick searches.

danglerb

First get it running 100% in stock form. All 928's share a considerable amount of low end torque with differences "mostly" at higher RPM. If your car has grunt issues, something is likely wrong, unless its an automatic.

ANF

I am contemplating this for my 83 928 S R.O.W. since it dropped a valve destroying a few bits.....
Can the S4 be used as well or just the 85/86 5.0 litre?

Thanks

Adam

James Bailey

The S-4 5.0 block ends up with very low compression......far from ideal unless you plan on boosting it.

Ducman82

what james said.

ANF

Thanks guys, I will keep it to the 85/86 5.0 litre if I do go down that path. Not intending to boost.

Cheers

Adam

slate blue

Hi Adam,

I don't know exactly what your goal is. I will be putting together a number of two valve engines of varying capacities. They will make big power over a standard engine. They also have a lot of reconditioned and new parts. The cylinder heads have had a lot of development. I intend to dyno test the engines also. If you're interested drop me a line.

ANF

I did not really want to re-build/ buy/ fix my engine... that was my ultimate goal
But I do so am looking at the most "economical way! I don't know where you are located, so freight or otherwise may come into it.

slate blue

Mate the freight would be tiny compared to the cost of the engine. Most standard rebuilds in Australia at specialist repairers are $20K (Fitted, two to three days labour included) on average. That is a standard rebuild not run on the dyno etc. Not with ported heads, increased compression and custom manifolds etc. I'm in NSW.

ANF

Ah, you are in Aus
I intend to rebuild it myself, saving a large chunk of that $20k! Unless I can find a good used one that just needs minor things. I don't need or want extra hp, but if it costs the same to do a 5.0 litre hybrid then I will strongly consider it.
Thanks

slate blue

No worries, you can always rebuild yourself but there are lots of areas that most and I am not saying yourself will just cross their fingers and hope things are O.K. Here's a few, is the main bearing tunnel straight? Thats a big one btw, you may need to change clearances on the mains. Have you drilled out the plugs in the crank to clean out years of crud and debris? Have the crank pins been thoroughly checked to ensure they are not worn like an egg? I just had a crank like that. Mic all the rods, my rods were also deflashed and shot peened to make them more reliable and lighter, I had then resized and notched to accept harder rod bearings, not the soft Porsche ones. Deck the block, set a better piston deck height plus it cleans the top block surface up especially if you need to weld the side of the bores because of corrosion. On the crank we repaired, we tested it for straightness and hardness. All the cranks were tested for straightness. The porting costs an extra $2,500 minimum then you add the extras such as bigger valves, Then the valve notches are enlarged on the CNC. Balance entire assembly to 0.1 of gram not the 4 grams Porsche allows. Some of the work requires specialist assembly.

I hope you can now if you didn't already now the difference between an expertly rebuilt engine and a home job. They cost different amounts of money.......

ANF

I take it this is due to the S4 piston shape? So if you put in 85/86 pistons it should all be ok?
Sorry to ask again, just limited supply of engines here in Aus

Thanks
Adam

V2Rocket

S4 head + S3 (85-86 5.0 32v) pistons =~12:1 compression
S3 head + S4 pistons = ~8:1 compression.