918-S

I have a toasted set of euro heads. What about a set of open chamber US heads, ported with euro valves? I'm sure this has been done and discussed but I couldn't find a topic. Could be cool with a blower...

John Veninger

You would have to install all new valve seats.
Lots of work and $$ to get something less than a good set of EuroS heads.

RicerSchnitzzle

Someone was looking into using larger chevy valves a few weeks ago, search for the thread, you may find what you're looking for.

918-S

I'll do that but really just flying a trial balloon by to see what has been accomplished using US blanks with euro valves.

A Chevy valve may work.

I'm thinking there are a couple of thousand US heads sitting on shelves around the world collecting dust. (at least..) I have three sets myself.

Anyone had problems porting them? is the water jacket any different?

hacker-pschorr

I agree, if you are going to graft in different valves, why stop at EuroS valves? If you want to stick with Porsche, check out the 944 2.7 liter valves. IIRC the intake valves are 2mm larger than EuroS / 951 valves.

mark kibort

dont forget the compression upgrade with the euro heads. just get those and do a simple valve job if it needs it. Or, if you do valves, do really big ones on the US heads.

BC

The Chevy valve change would be your best bet. You, in that 1600 pound car, do not need to worry very much about low-speed torque, so the larger valves would be perfect. Imagine a 5.0L 2V motor with a BIG cam, headers, and proper fueling!

Chevy Valves are cheap, readily available, and good quality. People can cut them to length for you, and cut the proper keep profiles into them. I used Ford Valve Springs when I rebuilt my 2V heads - and recut the valve seats. When you increase the valve size you will really want to increase the spring poundage on the nose and on the close.

918-S

I just picked up my damaged heads from the machine shop. I asked the owner about the cost to install larger seats, valves and springs in a set of US heads. He just rolled his eyes and said... got at least
$ 2000.00!?!?!.... what ever.

So, my thought was to use the euro valves I have in US heads because I have the stuff.

Q) How much will US heads lower the compression?

It's a proven fact that increasing flow makes a better pump.

toofast928

Doing the same on my hybrid 5.0L with USA heads. Got quotes from $1200 to 2000 for installing bigger intake valves only.
So I had the heads ported, the SC should take care of the rest. C/R should land around 9.5:1.
I have an extra set of heads that were port matched to the Euro intake if anyone is interested. _PM me.
Tony

karl ruiter

There is an old issue of VW/Porsche in which the took a stock U.S. car and put euro cams and valves and MSDS headers and got pretty much S performance. But they also ported the hell out of the heads and intake runners.

FlyingDog

Very little. Both heads are ~53cc. The big difference is the pistons (80-83 S ~8cc, 84-86 S ~2cc, US 20+cc).

Disclaimer: Numbers above are from memory and taken from other people's measurements.

Jim bailey - 928 International

That was about 20 years ago .."There is an old issue of VW/Porsche in which the took a stock U.S. car and put euro cams and valves and MSDS headers and got pretty much S performance. But they also ported the hell out of the heads and intake runners." AND Gregg Brown is who did it !!! The very same Greg Brown who builds Mark A. and Joe Fan's race engines and many others . Greg does post on this forum from time to time ...
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mark kibort

There is a difference in the heads for US vs euro. Ive measured it several times and its 53-54ccs for US, and 48 CCs for the euro heads.
I dont think the US 4.7 pistons are 20ccs., but ive never measured them. you are correct on the euro piston numbers though. as a note, the 85 pistons wtih that dish in the middle is around 6ccs. i dont think the US is much more than that, but i could be wrong.

mk