gruffalo

I know the hybrid subject has been up a number of times, but here we go again...

I can get my hands on a set of the late (310hp) euro S 16V heads/cams and a 5L shortblock. The problem with mating these items wold be a CR too low. I guess one could machine the block down some to compensate for that. But then the deck height would be too low, or...?

Rumors (Ian to be specific) say that the 944 8v pistons are lower and could perhaps be used with a machined down block. The 944 pistons are 100mm and have cut-outs for two valves, while all the 100mm 928 pistons are for 4 valves.

Is this feasible or should I just try to gather parts to assemble a 4.7L 16v engine instead.

MM

hacker-pschorr

It depends on what 5.0 shortblock you are talking about. The 85/86 lower end will be higher compression than the S4 shortblocks.

checkmate1996

After doing much research on this, I have heard the time/cost/performance is not worth doing. It's better to just have a nice rebuilt 4.7L...

mark kibort

i have one built and barely broken in for you already. Just posted a for sale message on a post today.
basically a brand new engine. just rings, seals, bearings and all the time, is easily worth the cost. Not to mention, its all done and ready to bolt on your heads and intake. Plus, its a true euro 4.7 with the deeper piston cuts. the CCs are near 8cc for the pistons.

mk

mark kibort

what is the deal with the 944 100mm pistons with 2 valve cuts? can they work in a hybrid set up?
That would be an easy way to do the valve cuts on the 100mm pistons, by not having to do it!!

mk

mark kibort

what reseach is this? Not many folks have done this, so i hope my experiences are part of that research. Ive done it 2 times and both times it yeild the same exact results. 290rwhp, a 40hp gain over a standard 4.7 with no other changes.

mk

PS, i made some traces so anyone can attack these valve cuts by themselves with a dremel, or mark the pistons for a machine shop to do the cuts

gruffalo

S4, the early 5L engines are ultra rare over here.

Mark, a 40 hp gain when using an Euro top end, or the US top end?

Are you suggesting the 310 hp 16v would go to approx 350 flywheel hp by adding 300cc?

If that's so, I tink it is worth investigating further.

mm

mark kibort

Take my almost new, 4.7 euro motor. only problem and cost would be shipping.

mk

hacker-pschorr

Stick with the low compression and boost it - you will end up with more HP in the long run that way.

Fabio421

Are these N/A 944 pistons or Turbo 944 pistons?

gruffalo

I don't know. My good friend Ian claims that at least the turbo pistons are somewhat lower, and maybe even the N/A ones too. But this is part of the reason I started this thread... I would like to find out.

Vilhuer

951 piston compression height is some 2mm lower than all 928 pistons except GTS.

We looked into using 951 pistons on S4 block together with S4 heads and intake. In the end friend decided to cut S4 piston tops to lower compression instead partly due to too complex changes needed to join together heads and intake. With 16V intake it would be easier job.

I'm not absolutely sure if NA 944 pistons have same compression height as 951 but its very likely. In any case its possible to leave things as they are and do engine where TDC is 2mm below block deck. I do no like the idea put its proven to work.

gruffalo

Erkka, I was hoping you would join in

Why would your friend wanna use anything but S4 pistons with S4 block AND heads? I didn't get that.

Why don't you like the idea? i'm just curious to find out as much as possible about the subject.

mm

FlyingDog

What are you trying to get out of the engine? Racing? Street car? Just fun with engineering?

IIRC, the 944 deck is lower so all 944 pistons are probably shorter.

mark kibort

2mm deck hight difference is near .080! thats an additional 14ccs of combustion chamber. makes you wonder what the combustion chambers of the 944 look like, if they are much smaller in volume to make up for it.

mk