924Board.org

Octane · Last edited by Octane on Tue Aug 11, 2009 9:35 pm; edited 3 times in total

Here's what I have so far... I am currently daily-driving a '77 924 N/A that I am going to transform into a track car over the winter. Might race it a little bit, but mostly for track days. I currently race a Formula Vee as well.

I know there's not a ton you can do for these, but I want a little bit more on somewhat of a budget...

- MSDS Header http://www.msdsinc.com/exhaust_1.htm

- Custom Free-Flowing Exhaust

- Stage 2 (or 3?) Integral Camshaft...how do these compare to Web Cams? They seem to be a good company and reasonably priced. ($350 vs. $546) http://www.integralcams.com/924.htm

-PURCHASED European high compression pistons and rods

-NO LONGER NEEDED Big bore throttle body (Either Audi 5000 or etc.) + ported manifold

-PURCHASED Solex carb and manifold setup.

Otherwise, I'm not sure...

What am I missing here? What else can be done while the engine is apart relatively inexpensively? Of course I will be installing new main bearings, gaskets (931 head gasket?), seals, etc. Just want it to have a little more.
_________________
- Brendan
1977 Porsche 924

Rich H · Posted: Mon Jul 13, 2009 11:23 pm Post subject:

I take it you don't want my Euro Spec pistons then?

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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Octane · Posted: Mon Jul 13, 2009 11:30 pm Post subject:

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

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

Stay away from Paeco. They don't know anything specific about these cars, the info on their website is garbage and not specific to the 924, they don't do very much of their own work most of it is outsourced, they are very costly, and their service and response time leaves a LOT to be desired.

Here is my obligatory RECOMMENDED READING pointer.

But to surface a very important point, you really need to decide if you're just going to do track days (I assume you mean driver's ed events?) or if you want to do AutoCrossing, Porsche club racing, or SCCA / NASA type competitive racing, you need to determine that now, as your decision will have a significant impact on what is permissible in terms of engine mods.

Regarding a stroker, there are two primary paths to go: one is to weld and offset grind the crank, then use stock rods (well, sort of...more below) and custom pistons with the pin offset for the CR you want. The other option is stock crank with a longer VW rod and again a custom piston with the pin offset for the CR you want. Neither is a cheap alternative, you're looking at a minimum of $2500 either way. For the crank regrind approach, you will either need to grind clearance on the block for stock rods, or you will need to get custom rods like the Crowers that Tom Cooper and I have. If you want to go the VW route, talk to Jorge at European Motorworks in Cali. They haven't done one in quite a while, but they had a kit at one point using VW rods and flattop pistons. All of this will be moot if you want to race competitively as I don't believe any of those classes allow stroking.

Personally, I would recommend that you buy Rich's Euro-spec pistons and rebuild the lower end pretty much as stock Euro-spec and leave it at that. Focus your spend on the top end. Integral Cams are GREAT and seem to be highly regarded here. Definite improvements available in the head with some serious porting and larger valves, go with Jorge's "big valve" head. A header and better exhaust won't hurt, but only after you've addressed the top end.

If you really want to build a stroker, and you want to go the offset grind approach + Crower rods, I can help you with that. But it's not cheap.

The other obvious thing to consider would be Engine Management, but again, that depends on your decision regarding race class. Again, strongly recommend that you read the entire Performance Upgrades thread that I linked to above, and develop a plan.
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erstwhile owner of just about every 924 variant ever made

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

OK, something doesn't jive when you say you're considering a $2200 stroker from Paeco, but $250 is too much to spend on Euro pistons

Buy the Euro pistons. It's the best bang for the buck on the bottom end you will be able to find.

One other thing I forgot to answer from your OP. The Luminition ignition applies to cars with points, which I believe your car has. You can get them elsewhere besides Paeco and I suggest that you do. More importantly, as I noted before, you really shouldn't consider any engine build until you first settle on a strategy for Engine Management. You may wish or need to stay with stock ignition and CIS fuel injetion, in which case, replacing the points is probably a good thing. However, if you're not constrained to CIS, some sort of conversion to a modern EFI would also help you eke out the last drop of performance possible.
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erstwhile owner of just about every 924 variant ever made

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

You can stick with CIS if you did the build I did. If you increase displacement you cannot stick with CIS, you'll need to move to carbs or EFI. Ditching CIS is a good idea though, there are a lot of restrictions in the intake tract due to CIS, you'll almost always see a gain in performance and throttle response from carbs or EFI.
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1987 951 - M193 Version for Japan

Octane · Posted: Tue Jul 14, 2009 5:40 am Post subject:

I'm not trying to sound cheap about the euro pistons, I know they are worth it and I have no problem paying that. I'm just looking for the best value, so before I go replacing pistons, etc. etc. etc. I wanted to see if the stroker kit would make that much of a difference. It wouldn't make sense to buy euro pistons then upgrade to the stroker kit later. My friend in the UK is trying to find me a set as well. I just got this car less than two weeks ago so I don't know a whole lot about it as of yet. Do I need the euro rods too or are they the same? In either case I'll probably pick up the ones Rich has then. Where can I find rings, circlips, gaskets etc.? I will also need main bearings, which I will probably buy from Idolea.

Chrenan, can you tell me more about the big valve head? Where can I get one and how much does it cost? It only makes sense to replace the head as well. Does it come with a camshaft? If not, which one would be best from Integral cams? I'm thinking I will do the big valve head, euro pistons and rods, MSDS header and the Audi 5000 throttle body. Some more compression and better flow in and out. What else could I do while it's all apart?

I am compiling parts for this over the next few months. The engine will get pulled and rebuilt over the winter with the high performance stuff. I am also concerned that once I get the engine open it might be rebuilt already (bored over) and I won't be able to use the euro pistons... but I guess I can always sell them. Any other advice would be great, thanks.
_________________
- Brendan
1977 Porsche 924

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

Octane · Posted: Tue Jul 14, 2009 6:33 am Post subject:

Alright, I just bought Rich's euro pistons...
_________________
- Brendan
1977 Porsche 924

!tom · Posted: Tue Jul 14, 2009 6:40 am Post subject:

I believe the '77 has a slightly different head than the '77.5 model, in that the valves are bigger in the 77.5 and later cars.

If you're doing head work like Chrenan had done, you'll have bigger valves than came stock on any year, but I would expect a performance increase if you just swapped your head for a 77.5 or later one, due to the bigger valves.

Unless you've got a '77.5 instead of a '77.
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78 924 NA
5-lug

Min · Posted: Tue Jul 14, 2009 6:57 am Post subject:

Your decisions for engine management will also govern what kind of camshaft you can use. Some cam grinds don't play nice with CIS. Insure you get something that will work with your combination.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

Min · Posted: Tue Jul 14, 2009 6:59 am Post subject:

And remember whatever you do, details are important, Last motor I put together I polished the pistons and comubstion chambers to a mirror finish.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

Octane · Posted: Tue Jul 14, 2009 7:17 am Post subject:

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

Biggest bang for the buck on the low end is definitely Euro pistons. Stroker costs $$$ and there isn't much information available to determine the benefits of the stroker alone. All of the historical examples we have are shrouded in mystery and misinformation, and neither Tom nor I have completed our builds yet. For a relatively "budget" build, the highest compression pistons you can get plus a EMW big valve head should have very nice results.

An intermediate path between an all out stroker and the above might be some custom high compression pistons (figure in the $500-$800 range), and a reworked 931 head. This is essentially what the D-Prods did, but unfortunately, you'll be on your own path to discovery as to making it all work. It will probably require carbs or EFI, as well as a custom exhaust header. So not cheap either.
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erstwhile owner of just about every 924 variant ever made