924Board.org

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

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1987 951 - M193 Version for Japan

sequential · Joined: 18 Nov 2005 Posts: 500 Location: BANNED

Chrenan,,
On memory from playing with the cis cars 20 plus years ago , the CIS killed any real improvements when trying to modify or improve the engine , it was a big difference when we went to dual carbs,, One exception a friend had purchased a euro GTI scirocco , that we did the head, eurorace cam and pistons and wow , with the euro cis it flew, but ultimately slower than the others with cams and big carbs.
I had eventually gotten my scirocco in the high 14's with this combination on street tires @ 94 mph , ( Daryl Vittone @ techtonics had set a VW water cooled best of 13.2@ 117 mph ) the best for my n/a 924 16.8 @87 mph and guess what that was what a stock 5.0 ran at the time anda stock corvette where doing 15.0 ...emissions where a bitch on the stock cars...

My n/a 924 had , headers , raised CR , 2 .5 inch exhaust , lighten flywheel and low profile 15 inch wheels and tires ( tricked for the time ) bigger throttlebody and 2 deg cam retard for the lower gears. and tweaked CIS..
car ran good, but compared to the lighter scirocco it was a slug , but i loved it on highway trips as the 130 (as indicated , it would pull 6600 rpm in top which i believe was actually 124 mph ) top end came in handy for my friends RX7, 260 ,280 zand early Starions ( 1st year) as i would walked them after 112 mph , even after being reminded it was not a real porsche....
You can run a bigger cam than is recommended on the cis , it will idle like a small block chevy with cams ands but this is taken care of by placing a small hole in the plate to reduce the pulsations at idle.

The roads here in Fl require you to have HP as there are no driving roads with lots of turns , so anything with a power to weight more than 9:1 leaves you not really enjoying yourself when out for a ride . otherwards i would do another small n/a car , but i think it would be a 2L / 914 because of the lighter weight , better driving position and handling......
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928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Thanks for the tips Sequential! I hadn't heard the "hole in the air sensor plate" to work CIS with a hotter cam. That's a neat trick.

If I keep this 924 longer term, I think changing out the CIS is inevitable. Eventually something critical will fail with the fuel distributor, and that will be that. I'm not sure yet whether I would go to carbs or EFI.

For this build I have been documenting, I went pretty basic, a few upgrades, but not too many. I didn't want to go too crazy, screw something up, and then have difficulty figuring out what went wrong. I'm sure there will be problems enough getting everything running again without adding anymore complexity. I am cautious by nature if you can't tell!
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1987 951 - M193 Version for Japan

jurasT · Joined: 24 Nov 2005 Posts: 22 Location: Lodz, Poland

Chrenan, it would be really interesting to see the head (actually valve seats) without valves.
But you probably did not have a reason to take these valves out and take photos

(?)

jurasT · Joined: 24 Nov 2005 Posts: 22 Location: Lodz, Poland

And the next question is

Do you have 7mm or 9mm stems in these valves ?

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Sorry for the slow response, I hardly ever scroll down to the 931 area!

The head came to me fully assembled, so I have no pics of the bare valve seats. I need to dig out the receipt to find out if the valves are 9 or 7 mm stems, I honestly have no idea off the top of my head.
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1987 951 - M193 Version for Japan

Porsche924Turbofied · Joined: 30 Aug 2006 Posts: 5 Location: NYC

Can someone give me a price of getting a 924 turbo head rebuilt? i'm looking minimally get a 3 angle valve job, porting, new valve guides, stronger if not double springs. Does anyone know where to get these BIG valves and does it do anything performance wise on an 81 924 turbo? also Where can i get a 924turbo head worked on. I live in New York City. Does anyone around here have a 931?

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

European motorworks does the Big Valve head:

http://www.europeanmotorworks.com/contact.html

Fully assembled with cam of your choice will cost around $1,100. There is some debate as to whether there is any advantage of a larger valve setup on the 931, which already has a fairly good head design. On the normally aspirated 924 it shows definite performance gains as the stock design of the head is very restrictive, opening it up with machine work and installing larger valves helps.
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1987 951 - M193 Version for Japan

hawkman · Joined: 05 Feb 2004 Posts: 41 Location: Boston, MA

chrenan, did you ever find out what size valve stems those were?
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'81 924 n/a "The Baby" Modified!!!!!
'93 3000GT VR4 "Un-Touchable"

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Woops, forgot to find out. I did look at my documentation from Eurorace and it was nowhere to be seen there. I think if you shoot an email off to them and ask the size used for the 924 big valve head they would know.

I do have a few close-up shots of the stems, but I'm not sure if it helps.

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1987 951 - M193 Version for Japan