Lets talk about valve size - 16V's
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From: Helsinki, Finland
4.5L valves are obviously small meaning 43/38mm. US '83-84 uses same valves. Also intake chamber. US '83-84 spider legs are same as US '80-82. These all point to US model 16V S using small valves.
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From: Southern Alberta, Canada
I read the spec books to reference engine differences by number and global location:
Was their emmisions reasons at the time where the North American engines were of lower tuned state than ROW? or was Porsche just using up parts?
Was their emmisions reasons at the time where the North American engines were of lower tuned state than ROW? or was Porsche just using up parts?
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From: saratoga, ca
Hey, havent we talked about this before??
euro heads are 48cc combusion chamber
USheads ALL US HEADS, are 54ccs
euro S heads with big valves are 45/40mm intake to exhaust
US heads all the way back to 79 are 43/38mm valves (corrected from 37mm)
euro intake and exhuast ports are larger as well.
Here is a data point left off. the euro heads have a port at the rear of the cylinders that ports to all the exhaust ports. the US heads, 80-84, all have the same LOOKING port, but it connects all the intake ports. on the US its used for extra fuel for the cold start circuit, where on the euro that same port actually connects to the exhuast ports on the euro so you dont want to be feeding raw fuel into the exhaust port!!!
so, you have to do a little tricky mod to feed the cold start to the intake manifold through one of the existing ports. otherwise, you have a hard starter.
Mk
euro heads are 48cc combusion chamber
USheads ALL US HEADS, are 54ccs
euro S heads with big valves are 45/40mm intake to exhaust
US heads all the way back to 79 are 43/38mm valves (corrected from 37mm)
euro intake and exhuast ports are larger as well.
Here is a data point left off. the euro heads have a port at the rear of the cylinders that ports to all the exhaust ports. the US heads, 80-84, all have the same LOOKING port, but it connects all the intake ports. on the US its used for extra fuel for the cold start circuit, where on the euro that same port actually connects to the exhuast ports on the euro so you dont want to be feeding raw fuel into the exhaust port!!!
so, you have to do a little tricky mod to feed the cold start to the intake manifold through one of the existing ports. otherwise, you have a hard starter.
Mk
Originally Posted by Hacker-Pschorr
Damn it - I've seen that chart before, couldn't find it 
So what is so special about the EuroS heads that people ask so much freeking money for when they have the same "big valves" as the US 83-84 heads?
A friend of mine has a set of 83-84 heads he will not need. So I could have bolted those onto my 81 two years ago when I replaced my head gaskets. Now I'm pissed, after spending all that money rebuilding my 81 heads when I had a set of "big valve" heads right at my fingertips. I never even thought to compare the valve sizes of the two. Then again the million dollar question, how much is 2mm really worth?
The 89 2.7 liter 944 head has 47mm intake valves. Hardly a worthwile upgrade for what those heads are worth.
Is the combustion area the same on the 83-84 US heads and the 84-85 EuroS heads?
So what is so special about the EuroS heads that people ask so much freeking money for when they have the same "big valves" as the US 83-84 heads?
A friend of mine has a set of 83-84 heads he will not need. So I could have bolted those onto my 81 two years ago when I replaced my head gaskets. Now I'm pissed, after spending all that money rebuilding my 81 heads when I had a set of "big valve" heads right at my fingertips. I never even thought to compare the valve sizes of the two. Then again the million dollar question, how much is 2mm really worth?
The 89 2.7 liter 944 head has 47mm intake valves. Hardly a worthwile upgrade for what those heads are worth.
Is the combustion area the same on the 83-84 US heads and the 84-85 EuroS heads?
Last edited by mark kibort; Feb 11, 2007 at 03:24 PM.
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From: Southern Alberta, Canada
Originally Posted by mark kibort
Hey, havent we talked about this before??
I re-read the spec book "928 '81 - '82 models/928S '80 - '84 models" published 31/12/84 which does not reference the combustion chamber vols. for the different engine size or which global application.
From the '83 Service Information book:
Erik, do have the answers to your questions.............its snowing and -11C so lots of time to look at the books.
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From: saratoga, ca
Its not listed, nor is the piston volumes, but ive measured them many times.
i actaully have a set of US 82 heads right now, and scots will be off in a week if you want picture confirmation. 48cc euro vs 54cc US. piston volume 2cc euro 85, 8cc euro 80-83, 6cc[ US 4valve 85, 8cc US 4 valve with 2 valve cuts
Mk
QUOTE=the flyin' scotsman]Some of us haven't
I re-read the spec book "928 '81 - '82 models/928S '80 - '84 models" published 31/12/84 which does not reference the combustion chamber vols. for the different engine size or which global application.
.[/QUOTE]
i actaully have a set of US 82 heads right now, and scots will be off in a week if you want picture confirmation. 48cc euro vs 54cc US. piston volume 2cc euro 85, 8cc euro 80-83, 6cc[ US 4valve 85, 8cc US 4 valve with 2 valve cuts
Mk
QUOTE=the flyin' scotsman]Some of us haven't
I re-read the spec book "928 '81 - '82 models/928S '80 - '84 models" published 31/12/84 which does not reference the combustion chamber vols. for the different engine size or which global application.
.
[/QUOTE]
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From: Southern Alberta, Canada
Erik may want pics.............I had enough fun playing with 2 stroke combustion chambers, crankcase vols, tuning carbs and playing with expansion chamber shapes and sizes; BTDT ain't going back..........c'est fini.
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From: Orange, Cal
How it was described to me is that the Euro head is "already" ported and has room for more porting that the US head has metal for. The reason to use the Euro head is that its cheaper and easier than paying to have the valves changed to larger ones and porting the head, but if you are thinking of larger than Euro valves to start with, maybe the US head is good to work from?
That said I remember somebody in the south east that has three CIS, early US I assume, motors they are trying to get rid of, maybe there is gold in the piles of aluminum, in terms of heads and cams and cranks.
That said I remember somebody in the south east that has three CIS, early US I assume, motors they are trying to get rid of, maybe there is gold in the piles of aluminum, in terms of heads and cams and cranks.
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From: Orange, Cal
I know nothing of the details of porting, but those look like round holes, wouldn't it be fairly easy to make them larger round holes?
Easiest place to host picts is right here, just become a full member.
Second choice is, http://www.imagehosting.com/index.php totally easy, no signup, browse, upload, and copy the link.
Easiest place to host picts is right here, just become a full member.
Second choice is, http://www.imagehosting.com/index.php totally easy, no signup, browse, upload, and copy the link.
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From: Up Nort
Wow, first time I've seen a side by side of the combustion chambers.
Has anyone measured the valve spacing? Meaning the distance between the center of each valve? Yes I realize they are (should be) the same, just curious.
Has anyone measured the valve spacing? Meaning the distance between the center of each valve? Yes I realize they are (should be) the same, just curious.