924Board.org

Zuffen · Posted: Sun Mar 30, 2003 1:45 pm Post subject:

I would love to see where the spark plug sits on the turbo head.
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Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

Bob, that sent me running to have a look at one of my NA heads.

First thought is that you'd break through the top into the cam chamber (whatever you call that).

Second thought is that you could fill the area before you started.

Third thought is "who cares". You could bore it out like you've shown and then ram a thin-walled aluminium tube into it, blend it in and weld or JB Weld where you've broken through and use JB Weld to fill the area under the new port.

Don't seem to be any coolant channels around the injector apart from the one that's shown.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

78porsche924 · Posted: Sun Mar 30, 2003 4:02 pm Post subject:

Where would u put the injector though, down underneath the intake port maybe? Dunno how hard it would be to do that though. I am seriously thinking about P&P my head now. Ill prolly screw something up though.

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

if you did some radical surgery like Bob suggested or even just filling in the lower lip on the port mouth you'd probably need to make a custom intake manifold or at the least chop and weld the stock one.

That's why the 924 and 931 intake manifolds are not interchangeable.

You could mount the injectors on the intake runners or under the port as you say.

If you do anything that wild do it on a spare head and be prepared to write it off to experience if something goes wrong.

At least 924 heads are more common and cheaper than 931 heads.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

Zuffen · Posted: Sun Mar 30, 2003 11:27 pm Post subject:

I think boring it out and sleeving it is the best idea.

I was thinking that myself, the you just have two areas to seal.

The custom intake is a must period
_________________
Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951

Richard · Joined: 04 Nov 2002 Posts: 617 Location: Pacific N.W.

I know this sounds retarded (which I admit I can be sometimes), but how do you post a picture? I looked through the FAQ and the only mention is an image going to some remote server. Is this really necessary for a picture of a revised port I have on my desktop (apple)?

Twin spark plugs, if that's what you guys are talking about, will probably not do a whole lot of good in this cylinder head. The best results are where the flame front has to travel a long distance, such as around the top of a high compression piston in a hemi head. Still worthy of research though.

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

Richard, have a read of this http://www.924board.org/viewtopic.php?t=1639
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Here are some measurments for those who wanted them. From the dark recesses of my mind, I seem to remember a safety factor for porting of .150" for aluminum and .125" for cast iron. Not sure where I picked up that manutia. Anyway, it leaves plenty of room for some serious porting with a little common sense. I also tried to measure the difference in port size between a 1977 head and a 1979. The ports actually differ quite a bit port to port on the same head so it made it difficult to find a mean measurement. Near as I can tell measuring with snap gauge and a dial caliper, the '77 head intake port is shorter but wider than the '79 head. This makes the '77 port look smaller but the volume is probably close to the same. I don't have the proper tools to CC the heads to tell for sure. Because the '77 port (the sectioned head in the photo) is shorter, it actually has a straiter shot to the valve than the '79 and later. I think if the early heads where fitted with 40mm intake valves, they might flow better than the later heads. Be interesting to find out.

78porsche924 · Posted: Thu Apr 03, 2003 1:05 pm Post subject:

I have a early 78 924. Would i have the larger or smaller valves. I do not know when they changed them.

AznDrgn · Posted: Thu Apr 03, 2003 3:22 pm Post subject:

you should have the larger valves, smaller valves were just the US release 77's
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-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

78porsche924 · Posted: Fri Apr 04, 2003 6:42 am Post subject:

Thanks.

4porsches · Joined: 07 Feb 2003 Posts: 36

Thanks Endwrench! I'm probably going to port and polish my head and wanted to know how clost the water jackets were. I have a 77 model year head that needs a valvejob. I was thinking about trying to put larger valves in it anyway so I guess I definatly will now. I wont have access to a flowbench but I can at least give you guys a set of the pants and I might have it dynoed eventually.

John

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

I am in the process of building a pseudo flow bench at the moment and should be able to tell the difference between the two head styles. I won't be able to give accurate CFM ratings but it should tell me if I am improving or impeding flow with different changes made. With some experimentation, I should be able to make a decent guess at CFM ratings later on. I'll post any data I collect but don't hold your breath. Summer is coming on and I plan to do as much playing as I can get in!

Richard · Joined: 04 Nov 2002 Posts: 617 Location: Pacific N.W.

Hey endwrench, I got some articles on building your own flowbench as I had (have) the same plans. Want to see them? You got my number.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

931 sectioned head photos now available.
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erstwhile owner of just about every 924 variant ever made