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Darin81T · Joined: 03 Sep 2003 Posts: 124 Location: Vader, WA

Anyone ever read the articles on velocity porting at www.mototuneusa.com?

It's mostly designed for motorcycle heads, but the same concepts apply to bigger engines. Sometimes bigger ports are not the answer...

Read and discuss....

Later,
Darin Flynn

Joes924Racer · Posted: Wed Oct 20, 2004 2:05 pm Post subject:

Thats interesting.. You know I did a radical port and polish job a couple of years ago and stuck a schnieder cam in and it worked nice, with a header and full flow exhaust it was estimated never dynoed to put out about 13-135 hp. You can really tell the difference in performance
with a ported head along with a cam verses a stock head. That head is still around just needs to decked because I threw a water pump belt here this summer. The head didnt warp it just has some nasty ridges between the cyl. it needs to visit the machine shop probly wont cost more than 35 bucks. I have to pull the valves first.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

My924gtc · Joined: 14 Aug 2004 Posts: 1362 Location: 248

Port velocity is the basis for the entire modification from Indi9xx. The theory is all well and good, but the ports are one facet of a full modification.

I also like the idea of larger valves allowing more mixture into the chamber.

I see the ultimate head having a combination of these two theories. We just need to find someone who is willing to flow bench the head and come up with the proper port shape to maximize velocity of the charge. That is all Jon did in the UK, or so he says, but no one thinks they will get their head back from him.

I am going with the Eurorace head, and I may very well take it into another shop near me and have them reshape the ports to creat a venturi and increase the flow rate and try and accelerate the larger charge going into my combustion chamber.

If I am successful I believe I will have created the best possible scenario using the stock head as a base.
_________________
MJ
'81 924 2.0L T
'82 924 2.3L SC/EFI <---online fall '06

Sponsor of the 944 Cup and Super Cup
Sponsor of the "2006 Battle in the Badlands"

Darin81T · Joined: 03 Sep 2003 Posts: 124 Location: Vader, WA

right, I have no experience with modifying 924 heads. I just thought I'd throw a little wood on the fire. I think the main point of that article was that you should always check results on a dyno because the flow rate isn't enough to tell you how the head will really perform.

Anyway, I probably won't be modifying my heads for some time now. I've been throwing money left and right at my 931 to put in a 951 intercooler and a Megasuirt EFI along with fixing all the oil leaks, so I'm kinda broke!

Take er easy,
Darin Flynn