924Board.org

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

Hey guys and if there are any gals Hey too....

but anyway I'm looking to get some head work done on m 1981 924 turbo. I bought a turbo head off of ebay and well it has little craters in it from detonation. I heard that is nothing since it happens often on turbo heads especially aluminum. I'm also looking for some performance items done on the head like a 3 angle valve job, heavier or double valve springs, possibly bigger valves, the obvious~resurface the head from the detonation, and new valve guides, possibly ported too. Does anyone know how much the typical head rebuild and those thing included would cost? And where can I get it worked on? I live in New York City.

2nd i know the K-26 turbo charger was used on many different cars but they are all different especially the mount. Does anyone know what parts would be okay to use on a 81 K-26 turbo rebuild and what not? I need prices and where can i get a rebuild kit for the turbo.

3rd where can I mount a blow off valve or bypass valve?

Does anyone have a 931 around NYC? I really want to hear it because my car has an exhaust leak from the turbo but besides that it's growling pretty loud when you rev it but it is much faster than the 86 944 i had before. The brakes don't seem to stop too well, I know the previous owner changed the brake master but i'm thinking the brake booster is shot, does anyone know where i can get one and if audi or vw uses the same one with part numbers please?

thanks guys/gals

Peter · Joined: 04 Nov 2002 Posts: 379 Location: New York, NY

Hi Porsche924Turbofied,
Welcome to the Board.
I happen to live in NYC and guess what, I also have a 931.

I had my head rebuilt a few years back at a place called Island Machine Shop (or something close to that name) . I am very happy with their work and once I find their business card I wil post their contact info.
I happen to live in Queens. Where do you live?
I am in the final stages of my 931 repaint, and hope to have it road worthy by the end of the month. You're more than welcome to come over and "hear it." You're also welcome to look at it, touch it, smell it, etc.

Seriously, its good to have another 931 owner in NYC. With Eric in FL, and Vince relocating to FL to be closer to his Int'l Tooth Pick manufacturing business, the 931/924 people in NYC have dried up.

Lizard · Posted: Tue Sep 19, 2006 1:05 am Post subject:

the head already has double valve springs,
with the head, you really dont want to have it shaved as that will up your CR. porting will not make any of a noticable difference on this head,

the turbo if it is needing a rebuild have a shop do it, there are some parts that will need to be replaced which dont come with any "kits" as well the main shaft will want to be balanced and only a shop which specilizes in rebuilding turbos will have that tool.

the regards to the BOF or Bypass valve, the 931 turbo already has one built in to the compressor side of the housing it is a recirculation valve, with the CIS you do not want to dump the air to atmo as it will completely mess up the air fuel mix, and with the turbo already having that in there, why add one?
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3 928s,

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

PM sent on the turbo. I have an extra for you

Post a pic of the "craters" if you can. This is the head that was recently on ebay? I emailed them and they weren't very forthcoming with info...

A 3-angle valve job is always a very good idea. In fact mine only has a single angle cut and I'm thinking of dropping it off at the shop to have it re-cut for a 3-angle job while it's out.

A head rebuild will probably run you around $250 for all the work plus all new valve guides. New valve guide seals come with the 931 head gasket set - just take them to the shop along with the head. Valve guides should be available from ebsracing.com

An exhaust leak around the turbo is likely either a cracked/broken j-pipe and/or a cracked exhaust manifold. Both are common. The j-pipe is still available from auto atlanta (note, this is the one and only thing I would ever buy from them and be sure to put it on a credit card that you can dispute charges if they don't mail it...). The exhaust manifold is costly.

Flush your brake fluid with some fresh and bleed the brakes in the process. A bad vac booster will just make the pedal harder, but the brakes will still work just fine. Does the pedal feel spongy?
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Peter · Joined: 04 Nov 2002 Posts: 379 Location: New York, NY

Here is the info I promised:
Island Automotive Machine Shop
25 Jefry Lane
Hicksville, NY 11801
(516) 942-5699

They pressure tested and rebuilt my 931 head, along with overboring my block and balancing the internals. At the time, they didn't do porting & polishing, that I did on my own with the P&P kit from Standard Abrasives http://www.sa-motorsports.com/diyport.shtm.

You can use any machine shop you feel comfotable with, just tell them you have a VW, SOHC, 2V, 4Cyl aluminum head and you are providing them with (1) the replacment parts (generally only valve guides unless your springs need replacing and they can test them); and (2) the specs from either the factory manuals or the Haynes manual.

BTW, they are a very nice bunch of guys at Island Automotive. Real oldtimes who have seen it all.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Peter · Joined: 04 Nov 2002 Posts: 379 Location: New York, NY

Rasta,
It was fun and very easy. However, the first time you take a grinder to your head

it is a little scary b/c you think you will damage it. But you won't. There is a brief write-up in the 924 Board Tech Section (section 4.1) about head porting. If you follow that and the SA article, you will be in good hands.
Also, I purchased a carbide grinding tip instead of using grinding stones, which made the process much quicker.
Lastly, the SA kit is intended for larger engines, so I had plenty of the sanding drums and buffs left over to use to blueprint my engine.

924guy · Posted: Wed Oct 18, 2006 8:08 am Post subject:

Paul · Posted: Wed Oct 18, 2006 8:41 am Post subject:

The factory shop manual says not to grind the valves, only hand lapping is acceptable.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

NEMESIS · Posted: Wed Oct 18, 2006 9:01 am Post subject:

I picked up an SA kit last year for my race engine build, but have yet to go there with the head.

I did do some work on the carb manifold to port match it to the 931 intake ports. Once you get your feel for it, it goes pretty well.
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82' 931 Platinum <--GTS in progress