slate blue

When we CCed the early S heads we got 52 cc. The later ones with the bigger valves and relieving around the valves was about 53 cc. I'm sure it wouldn't take much to fit the bigger valves and hog out the ports a little and your heads will flow what the Euro S does. Remember that the later heads don't have that little cut out in the centre of the chamber. So without the hogging out the chamber is probably smaller than the 52 cc of the earlier head.

Ian928

Thank you for confirming my measurement of 53cc for the Euro S heads!

I am a little puzzled about your comment about "Early S" heads? I guess you mean early Euro heads?

slate blue

You are correct, the early S head is the head that came on the K Jet cars.

Herr-Kuhn

Hacker, I have cc values for the 81 heads at home somewhere. By my measurements it came out to 8.1:1 on CR, this was stock. I'll see if I can find the numbers. I use clay to fill the voids, then water displacement method in a graduated cylinder...re-shape the clay to fit as it can't be compressed. 1ml=1cc. Just cc'd a 4.7 Euro with this method...9.75:1 was the result. 10:1 is that spec. I believe Porsche plans for the heads being shaved once and thus not exceeding CR when complete. If you shave a head this could easily mean .25 or more on cr.

Ian928

Can you post your numbers for heads and pistons for that one? I calculated my Euro S to 9,3:1, that was with these numbers:

Head: 52,5
Piston: 8,7
Clearance volume: 0,56 (Used Tony's number from a S4 - there may be some error there?)
Head gasket volume: 8,9

Carl Fausett

When I do headwork on the 16v Euro heads, they start out at about 48cc (like Kibort says). Then, after we unshroud the intake and exhaust valves a bit, we match them up to all be 52cc.

Here are some pictures, and there are more pictures here:
http://www.928motorsports.com/services/headwork.html

slate blue

The're the early S heads, we got 52 cc when we did mine, well the race shop that does my work did anyway. We shaved a 1 mm off to bump the comp. Can't remember all the figures but I do remember that we were aiming at 12 to 1. My block has positive deck height also, need to consider that too. I think it was positive to the tune of 0.25 mm. It will be interesting to get a cranking pressure on that one.

Herr-Kuhn

Right off my excel spreadsheet.

4.7 Liter 928 Euro Compression Calculations

Stroke, cm 7.89
Bore, cm 9.7
Volume bore and stroke 582.7605285

Head gasket bore, cm 9.9
Head gasket thickness, crushed, cm 0.112
Volume head gasket 8.6170392


Swept total volume calculations
Vbore (calculated), cm^2 582.7605285
Vhead gasket (calculated), cm^2 8.6170392
Vvalve relief (clay/H20 displacement), cm^2 8
Vcylinder head (clay/ H20 displacement), cm^2 50
Vtotal swept volume, cm^2 649.3775677


Clearance volume calculations
Vhead gasket (calculated), cm^2 8.6170392
Vvalve relief (clay/H20 displacement), cm^2 8
Vcylinder head (clay/ H20 displacement), cm^2 50
Vtotal clearance volume, cm^2 66.6170392

Compression Ratio, Stock 9.747919984


Swept total volume calculations
Vbore (calculated), cm^2 582.7605285
Vhead gasket (calculated), cm^2 8.6170392
Vvalve relief (clay/H20 displacement), cm^2 8
Vcylinder head (clay/ H20 displacement), cm^2 50
Add 15 cc "dish" to piston 15
Vtotal swept volume, cm^2 664.3775677


Clearance volume calculations
Vhead gasket (calculated), cm^2 8.6170392
Vvalve relief (clay/H20 displacement), cm^2 8
Vcylinder head (clay/ H20 displacement), cm^2 50
Add 15 cc "dish" to piston 15
Vtotal clearance cm^2 81.6170392

Compression Ratio, New Pistons 8.140182175 Suitable for turbocharged !!!

Herr-Kuhn

As with any method, there will always be error in measurement. This isn't an exact science. For my needs the above method identifies what is required to drop to a more suitable level for force feeding. Of course, anything past one decimal on the results should be considered "not significant".

Ian928

So you are saying for sure there is two different "S" heads? Did they change the head at the same time as they changed the piston cutouts?

Ian

Ian928

To me they look exactly as mine, of course it is very hard to see a 10% difference in volume. Here are a picture of my chamber: http://www.flickr.com/photos/2196736...7594052999722/

By the way, you say you are unshrouding the valves, what do you do? I can see no differnce around the valves compared to mine. (If this is a "trade secret" please don't respond...)

slate blue

Yes there are K Jet heads and L jet heads, the one pictured are K jet heads.

hacker-pschorr

Now for the $million$ question. Will Euro S (L-jet) heads bolt onto a stock 79 using 79 cams? Or will I need to yank the motor and modify the pistons?

Since this thread was started I found a set of Euro S heads. I'm staying with the 79 cams.

mark kibort

so you have to think about this one carefully. I measured the euro valve cut outs on the euro block 4.7L and they were a shade over the intake valve size of 45mm (like 1mm larger) when i measured the US 4.5 and 4.7 pistons, the cut outs were a shade over the valve size of 43mm (by 1mm) so, if you need valve reliefs, the euro valves will not fit in the US piston valve reliefs . however, what i did prove is that you can use the euro 83 cams on the US heads and the deeper push , doesnt hit the pistons valve relief bottoms. (probably not your choice here)

so, you have two choice. pull the heads, and tape off the engine openings and grind away at the pistons. you certainly dont need to pull the pistons to do a 2mm larger valve relief diameter . (only 1mm on the half moon greater )

Mk

mark kibort

all euro heads are the same. im puzzled how you saw (or anyone has seen) 52mm on a euro. the euros are noticably shallower, and they CC out to 48mm. my part euro had 82 cams, heads , and 84 intake. it cc'ed out to 48mm. if you go through the ratios, 52cc on the heads would put it near 9:1. in fact, it works out to 10:1. the 84 onward euro heads are also 48mm. now, with the much more shallow piston cuts (2cc vs 8cc) you can see that it goes up to over 10.5:1 ignoring the piston being flush with the surface or not.

I think the shop that cc'ed your euro heads at 52cc , made a mistake, or didnt tape it off . heck, i remember trying to put 52ccs in the euro with water and it totally flowed over .

go to the compression calculator and plug in the values. its pretty easy.

I think we are all using about 1mm .039 for the head gasket.

Mark



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