924Board.org

bacook · Guest

Will I see a substantial increase in performance in my 924NA simply by swapping the stock head with a ported and polished 931 head? What else needs to change?

924RACR · Posted: Mon Jul 30, 2001 12:23 am Post subject:

Yeah, apparently so. I haven't done it myself, but I've heard from every big name out there that currently does or used to race 924's and it is the way to go. I'd do it on my racecar if it were legal

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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

larso · Guest

It won't work, you lose too much compression while gaining flow.

yada pistons yada.
yada injectors yada
yada spark wires yada

If you ever want to replace the valves on this 931 head on your 924, it now costs 50 dollars per valve rather than the 20 you were paying per valve before.

Just some thoughts to consider.

924 turbo · Guest

You'll also need a turbo intake manifold. The studs are spaced differently.

-nick · Guest

it is absolutely possible and has been done a number of times (ie the 924 DP cars). the benefit is that the 931 head flows better (engines are just pumps). it will require new pistons otherwise you will have very little compression. pistons are available from JE pistons. you'll need patience and a good $1500 clams to get it work right. but a considerable HP increase can be had.

or else you can change to a header and 9.3:1 pistons and have much more power than stock and spend half as much.

-nick

924RACR · Posted: Tue Jul 31, 2001 9:45 am Post subject:

Yeah, but ultimately, with the same setup, the 931 head still has more potential. The question is what your aim is; ultimate performance, or reasonable performance on a budget. For the latter, which I suspect you are after, the header and higher compression pistons are simpler...

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

eturbo924 · Guest

Take a look at a few of the articles on my site. http://www.geocities.com/eturbo924 click on the 924 Power tricks link. The one you want to read I believe is called indian red. It uses a 931 intake and head on a 924 NA block. I talks about all the upgrades he made to have a screaming 924. Cost a lot though.

Eric

daniel · Joined: 18 Jun 2009 Posts: 687 Location: Sydney, Australia

Hey all
Does anyone know if there is another source of the performance upgrades on this site? They seem to have stoped working...

Cheers
Daniel
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Over the top of skyline, total brake failure.... hit the wall at over 200 kp/h at the dipper, so anyone who has to brake for the esses is a pussy.
1977.5 Race Car, CAMS Group S Spec
1989 944 Cabriolet

Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

8 yrs

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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

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

I think he was asking about all the old historic articles that Eric used to have hosted on his site: http://www.geocities.com/eturbo924

The main site is up, but the articles are all 404.
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erstwhile owner of just about every 924 variant ever made

Eturbo924 · Joined: 09 Nov 2002 Posts: 2212 Location: Londonderry NH

I am in the process of reloading them. Unfortunately I lost my disc I had put them all on. So now I have to retype them all into htm files. whoops. Two are back up... the bolt on articles. I will go for Indian Red next. It is a great article.

Funny though... with the cross section that I think are on this site... where some one machined a 924 head to show what all the flow paths are like. I wonder if one went in and welded in some AL and smoothed out the correct spots... if the 924 head would flow better?

It seems there is too much turbulance in areas on purpose. To keep the NA 924 down. Was there not some one in Europe who did this and then went missing because he thoughts people were going to steal his research? I almost got one of these heads way back when .... alas I think it was when I was laid off and could not afford the ship costs. DOU!
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1982 924
1992 968
2003 C4S
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ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

You should try http://www.archive.org/web/web.php. You should be able to plug in your website URL and a historical date, and see what comes up...they may have an archive of those pages that will prevent you from having to retype everything. You might be amazed at what you can retrieve...

...as for the head tricks, yes, absolutely, welding up the floor and changing the angle of the inlet would definitely improve the flow. According to John Brown, he's talked to a couple of old-timers who were doing mods on the 931 head back in the 80s, and that is exactly what they were doing.
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erstwhile owner of just about every 924 variant ever made