924Board.org

[StienbargerR]

Hey Guys,
I'm thinking about building up an engine for my 924. I have really been on the fence about keeping the car, but I decided I will keep it and try to squeeze some more power out of it. After driving a friend's M3, I really want more power.

Here is my idea. it will be based on a 2.0l NA block w/ Euro pistons.

-Skim Block down (to get correct compression)
-Bolt on Turbo Head
-Weber 40 DCOE Carburetors
- Header

I also would like to add a 5 speed transmission at some point.

Are there any problems I will run into doing this? Would timing be affected? Oh, also, if I were to buy a cam, would I be able to use integral's NA cam grinds?

Ryan
_________________
1978 924 NA
-250lb lowering springs, Euro Pistons

[ideola]

Why bother with skimming the block and the unknown of sorting out the 931 head? You'd be better off (IMO) sourcing new custom pistons spec'd to your desired CR from Diamond. You can get the Euro-spec design in essentially any CR you want for ~$160-175 per slug, and that includes any diameter you want (i.e. more displacement) as well as the rings, wrist pins, and retainers.

The 931 in stock form does not flow that much better than an NA head, and since we can now get the big valve setup, you can easily develop the flow needed for better HP with that kit and some porting.

Header's a good idea.

You should have no problem using an Integral cam.
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erstwhile owner of just about every 924 variant ever made

[StienbargerR]

Dan,
I was under the impression that the 931 head was more ideal for performance applications since it had the dish in the head versus the heron style. Is this not so?

As far as the euro race head, are there any estimates of what kind of torque and Hp gains there are? (Im hoping to hear from Chrenan)

Ryan
_________________
1978 924 NA
-250lb lowering springs, Euro Pistons

[ideola]

The 931 head has very marginally better flow than the NA head, nothing that couldn't be surpassed on the NA head with some strategic porting. The big valve head on an NA will significantly outflow a stock 931 head, so given the fact that a 931 head on an NA block is somewhat of an unknown configuration (I don't think there's documentation anywhere), my personal opinion is that you will achieve more results for less money and experimentation going with high comp pistons and the big valve setup. Add a header, and my guestimation is that you'll be in the 150-175 BHP range, depending on the CR you choose. This is based on an ITB car producing ~150 BHP with 9.5:1 CR and headers, with no big valve head and .040" over on the pistons. For your build you could go as high as 10.5:1, and out to 87.5 or 88 mm to develop more displacement and power. Add the head and exhaust to the equation, and I suspect you'd be past the 150 BHP mark.
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erstwhile owner of just about every 924 variant ever made

[924RACR]

What Dan said. I'd rather go with some custom Diamond pistons than hunt down Euro pistons; likely to be cheaper to boot.

Correction though, Dan - the ITB car isn't producing quite that much, more like 140hp tops. Reminds me, we oughtta get it on the dyno one of these days, now that it's running better. Maybe I can convince Merritt to pay for it.

I think there's one big thing you're missing from the equation, and that's a cam. We're not allowed to change it in ITB, but it's the remaining big limitation. I'd spend effort and money on that before I'd waste it on the head or a Weber conversion. So cam, header, and internals - big pistons, and balance, lighten too while you're at it. Overbore isn't quite as significant as CR in generating power, but easy enough to do both while you're at it.

Dan, maybe we need to commission to build him a PUB Racing hot motor.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Martijnus]

I totally agree on the pistons. Skimming the block means your head will sit 'lower' overall, and ofcourse that does influence the cam timing. That's not the real problem though... you can't tension the belt anymore.

I skimmed 1mm off the block, and I had to move the tension roller a few mm in the thermostat housing to compensate for the decreased distance between crank and cam.
You could try to find a belt with one less tooth, but I couldn't find one. (however, there should be a dodge model which uses that..but not available overhere).

It's a much better way to use custom pistons. Baldwin from the board tried to build a 933 engine (in a way)...so NA and raised compression, 931 head etc etc... eventually he sold the car anyway.

If you're going to spend money, why not put on a turbo? it's waaaay more power for the same amount of money.
Ok, maybe it's a bit more expensive, but you can do it fairly cheap

In both cases, you'd need a suitable fuel because the end-compression is higher than stock.

you can easily calculate how much you'd have to skim off the block to compensate for the CR (iirc someone mentioned on this board that the combustion chambers are 21.5cc each). You'd have to raise compression above 10:1 to make it interesting. My 1mm skimming results (in theory) to about 10:1 CR, compared to the 9.3:1 stock. So to compensate for the combustion chambers in the 931 head, you'd have to skim at least 3mm or so... that's really quite a bit! And it doesn't improve the strength of the block if you take off a lot of material. Go too far and you'll end up with an open deck block
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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

[StienbargerR]

Id like to stick with my carbs and euro pistons, as I have both already. Dan, what is the price gonna be for the big valve head? I would rather keep it Naturally aspirated just to keep it a bit more simple.

Thanks,
Ryan
_________________
1978 924 NA
-250lb lowering springs, Euro Pistons

[ideola]

PM sent.
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erstwhile owner of just about every 924 variant ever made

[Vince Ponz]

Ryan
I am happy with my setup euro pistons, mild cam, webbers, msd, free exhaust, 44 suspension, hd shocks, bigger sways with weltmeister in the rear, etc.
I think the real problem with our cars is the number 2 or 3 pistons getting a lack of oil if you rev to 6500 often.
I have tried all types of exhausts including splitting the downpipe for duals and all are okay but save your money for the pistons, cam, etc first.
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"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

[dreamgts]

Well as i am starting a project too im going for-
40 or 45 DCOE webers
11:1 CR Diamond Pistons (87.5mm)
Crower Rods
Bigger Valve head 44mm In 37mm Ex
Race Cam hopefully from Integral (if not from Piper)
Fully balanced Engine

I havnt sourced a Header yet for a RHD model still searching but if yours is a Lhd I sugest you talk to ideola he can source you a good header. Cooling might have to be improved too and brakes definetly. Some good traction tyres set on 15in rims as sugested here by fellow members should do the trick. My 924 is going to be a track/race car based on a DProd body/model or as close as I can get anyway and is being lightened as much as possible, future plans for lightening might include Fibre glass doors and bonnet. Just have to see how fast and quick I want to go and can handle myself basically.

dreamgts
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2 PORSCHE 924 (CURRENT PROJECTS)
2 CLASSIC CORTINAS (FINISHED)
1 CLASSIC FIAT(FINISHED)
1 CLASSIC FIAT 132 2000CC(JUST PURCHASED)
4 SUV'S
2 SEDANS
1 OPEL PANEL VAN
WIFES SUZUKI ALTO

[dreamgts]

Martijnus said--If you're going to spend money, why not put on a turbo? it's waaaay more power for the same amount of money.
Ok, maybe it's a bit more expensive, but you can do it fairly cheap

In my opinion and i know that some might not agree putting a turbo on a 924NA might not be what one wants. For example if I wanted to boost power on a turbo, first thing i would do is buy a 931, In my case i want to get more power out of an NA. Power and speed sometimes is not gained only by BHP increase but by how quick you can get from point A to point B. in my time I have seen small engined cars devastate bigger engines vehicles just because the setup was right, wieght, gear ratios, traction etc all are important to consider. It also depends on what you want to do with the car. If I want to go for a quarter mile run for example with the set up I have in mind i could always squirt the engine with a bit of nitro, Thats power when you realy need it. i have nothing against turbo.s mind you cause i have a future project which involves a turbo. First thing Im gonna do though .... is buy a 931, thats cause I want a boosted 931 and not a turbo 924 na, in my opinion stick to your plans of NA, some guys here will give you loadssssssssss of advise. I know and im sure of it.

dreamgts
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2 PORSCHE 924 (CURRENT PROJECTS)
2 CLASSIC CORTINAS (FINISHED)
1 CLASSIC FIAT(FINISHED)
1 CLASSIC FIAT 132 2000CC(JUST PURCHASED)
4 SUV'S
2 SEDANS
1 OPEL PANEL VAN
WIFES SUZUKI ALTO

[StienbargerR]

Alright,

So as not to start another thread, I'll use my older thread related to some thoughts and questions.

So I've got my header on, next step is the Weber conversion. With the Webers I'm still a little confused about the linkages and fueling.

As far as running the fuel lines, can I use the existing ones that go through the unibody, or should I run new stuff all the way back from the tank? Also, when it comes to a fuel pump, what should I get? do I need a fuel pump regulator?

Also, am I going to need to buy a new throttle cable and a choke cable?

Thanks in advance,
Ryan
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1978 924 NA
-250lb lowering springs, Euro Pistons

[ideola]

Check in with DOCO, he's worked out a lot of the details...but in the meantime, here's my take on those questions:

RE: the fuel lines, you can use what's in the car, no prob.

RE: the fuel pump, you will need a much lower pressure pump, I believe something in the 7-10 psi range, but check with DOCO. You will also want a low pressure fuel regulator.

RE: throttle cable, not sure if you'll need to fab a new cable, but definitely will need to adapt it to a custom bracket for your carbs. Again, check DOCO's thread, I think he's got some pix of how he did this.

How do you like the headers?
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erstwhile owner of just about every 924 variant ever made

[StienbargerR]

Dan,
I actually just started putting it on today. I realized I didn't have nice hardware to install with the header, so Im gonna go pick some stuff up tomorrow to get it on right, but it sure looks great! The nickel-plating was worth it. I had to remove so much stuff to get it on, I ended up refreshing the oil and filter as well. I will try to get pics tomorrow.

Unfortunately, Im going to have to drive it to the exhaust shop with just the header on I always love a loud exhaust......for no more than 3 hours.

Ryan
_________________
1978 924 NA
-250lb lowering springs, Euro Pistons

[Joes924Racer]

Did I hear the word pics... enjoy the drive.. Its gonna be loud.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.