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944 / 931 ... which is cheaper?
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friskynibbles  
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PostPosted: Wed May 01, 2002 11:22 am    Post subject: Reply with quote

my 931 might need new pistons, sleaves plus all the regular stuff you replace when you rebuild. i talked to a guy who works on porsches in my area and he said i'd be looking at 1200-1500 dollars for a new piston set and at that price he said it would be a wise choice to switch to the 944. he said it has more horsepower and is cheaper to maintain. true? false? the opinions in this forum seem to be pro-931. i'd like to keep my 931 but i'm not rich.

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John H  
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PostPosted: Wed May 01, 2002 11:46 am    Post subject: Reply with quote

Have aloka roudn at the other threads but to put it simply - it's cheaper to rebuilt your 931 than swap ina 944.
If your mechanic can do the swap for less than the dollars you mentioned then get him to do it. Make sure he gives you a firm price to do everything needed to do the swap.
The 944 while a newer motor is higher on maintenance cost than a 931 (thats my opinion). it doesn't put out a smuch hp as a 931 (mine's a GT so I get 200 + hp). Personally I woudl stick to the 931 but then I biased towards the old motors


[ This Message was edited by: John H on 2002-05-01 10:48 ]
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Rick MacLaren  
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PostPosted: Wed May 01, 2002 11:54 am    Post subject: Reply with quote

Your mechanic guy said: "it has more horsepower and is cheaper to maintain"

False. He's wrong on both counts.

For the US/CANADA market:

The 944 NA was circa 140 HP.
The 931 stock was 150 HP.

Reliability and inexpensive parts? Look at it this way: One is a true Porsche engine, the other is the engine from an Audi truck. Which is gonna be more reliable and inexpensive?

Your mechanic guy said: "1200-1500 dollars for a new piston set and at that price he said it would be a wise choice to switch to the 944"

It probably would be cheaper to take the bus too, but his reply is certainly not a 'good' answer to the question "What do I do now?". First, he's way overcharging for the stock pistons. Second, you can rebuild your engine with used pistons and rebore it with new rings for less than $1200.

I'd look around for options. One is pistons. You can get them a lot cheaper than that.

A friend of mine is rebuilding his 944 engine himself.

Did you know they have to coat the block in a special (and $$$expensive$$$) solution before any engine reassembly can occur? Did you know you have to adjust your belt tension with a tool that costs $650 CDN? And how many belts are there to break? How many valves? If it's an 8 valve you're in luck, but 16?

Pistons? You'd better count on $1600 CDN for 944 pistons (stock) for non Mahle pistons. Mine were original Mahle, overbored, rings, pins, circlips, and upped the compression for the same price.

Why a 944? I'd buy a 944 for any of these reasons:

- good aftermarket supply
- more Porsche credibility
- more P mechanics willing to work on them
- good documentation

Why not a 944?

- Hydraulic tappets versus mechanical
- Try busting a belt in a 944 and watch your wallet disappear
- 400 to 600 lbs heavier
- more expensive parts. Check Automotion. Any set of randomly chosen 5 944 parts will cost more than the same parts for a 931.
- must pass emissions tests, whereas a 931 does not. You want to spend money? Get a 944 emissions tested. Just buy one stock cat and muffler and you're into 'second mortgage' zone.

Up to you. Depends on what's important. But if price and reliability were issues, I'd stick to the 931. I'd go for the 944 if I were thinking of upgrading to a 944 Turbo in the future.


[ This Message was edited by: Rick MacLaren on 2002-05-01 10:58 ]
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dvarholy  
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PostPosted: Wed May 01, 2002 4:10 pm    Post subject: Reply with quote

was $1200 the cost of the pistons, or the whole job? A few years ago, I priced Mahle (stock) 931 pistons at Automotion. They were about $600 or so with the rings. Here are a few price comparisons on 931 vs 944 parts:
water pump: 931 $35 / 944 $150
timing belt(s): 931 $11 / 944 $45
ignition wires: 931 $75 / 944 $150

many internal engine parts are double the price of a 931. Don't buy a reman 944 water pump. Many mechanics won't even guarantee them. Also< if the pump hasen't been updated to the new (951) type that will need to be done. And then there are the leak problems with the water to oil cooler used on the 944.

I would keep the 931 (just my opinion)
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friskynibbles  
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PostPosted: Thu May 02, 2002 3:13 am    Post subject: Reply with quote

if i wasn't clear, that information came from a man in my area who has a bunch of porsches, not my mechanic (who knows almost nothing about porsches).
so the consensus is to keep the 931.
the estimated price for the pistons was 1200-1500; that was JUST for the purchase of those parts. i can't find any catalogues or anything around here. nobody knows about my car! the only place i had any luck was midas (they found the exhaust on their computer) and napa (brakes). where can i get a good parts catalogue?

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friskynibbles  
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PostPosted: Thu May 02, 2002 3:59 am    Post subject: Reply with quote

ebs lists pistons:
924 Turbo - JE piston set $625
would those be any good? can anyone recommend some?

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teo  



Joined: 07 Sep 2001
Posts: 637
Location: Hungary, Europe

PostPosted: Thu May 02, 2002 4:00 am    Post subject: Reply with quote

Hey guys,

are we talking about US$ or CDN$?

I feel like it's a little bit mixed in here.
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friskynibbles  
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PostPosted: Thu May 02, 2002 4:29 am    Post subject: Reply with quote

all my quotes were canadian EXCEPT the ebsracing quote which i presume is american.

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Rick MacLaren  
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PostPosted: Thu May 02, 2002 5:51 am    Post subject: Reply with quote

Your problem is parts supply and getting people who KNOW the car.

EBS has good pistons for your '81 fairly cheap. But why not just put used pistons in there and save your pennies?

I put new pistons in my car and in retrospect I regret doing so. Used pistons will work quite nicely thank you and don't require a large layout of cash. I've heard guys say "Oh they become oblong" but I've never seen it and neither has my engine builder. Used 931 pistons will work fine.

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friskynibbles  
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PostPosted: Thu May 02, 2002 6:10 am    Post subject: Reply with quote

i never considered using used pistons in it because i didn't know i even could.
hmm...

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numbers  
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PostPosted: Thu May 02, 2002 8:20 am    Post subject: Reply with quote

What is wrong with the pistons you have?
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friskynibbles  
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PostPosted: Thu May 02, 2002 9:52 am    Post subject: Reply with quote

the guy i got the car from says he thinks one of them is busted and who knows what else is wrong too.

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Rick MacLaren  
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PostPosted: Thu May 02, 2002 12:04 pm    Post subject: Reply with quote

You can really only 'know' by seeing it. But some mechanics can have an ear for it. Make no mistake, a busted piston would make a heckuva loud scary rattle - ya hear it and you just know you're reamed.

My piston had a 2.5 cm x 1 cm piece broken off, banging up against the head. Came on all at once. But was preceded by a lot of rattling in the head area, probably caused by a piece of piston ring. A 'clatter sound'.

Anyways, can you (i.e., are you willing yet to...)crack open the head and have a looksie?


[ This Message was edited by: Rick MacLaren on 2002-05-02 11:08 ]
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gohim  
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PostPosted: Thu May 02, 2002 1:42 pm    Post subject: Reply with quote

Replacement 931 and 944 pistons are about the same price on the aftermarket ($600-$800 a set).

Machining a 944 block is tougher than doing a 924 block because of the materials the blocks are made of. The 944 block requires a special slurry to be applied, and honed so that the silicone crystals in the alloy are exposed. The silicone crystals are what the pistons ride on in a 944 block. The cylinder bores are not coated, the pistons are plated with iron.

Early US 944 engines are rated at 150hp, like the 931, the hp was increased in later models. The 931 was uprated from 143 to 154, and the 944 was uprated from 150 to 160.

The biggest advantage of the 944 engine is the flat torque curve. Unlike the 931 which must scream to produce torque, the 944 engine produces most of it's rated torque over almost all of it's usable rpm range.

Scheduled 944 maintenance is much higher than a 931. The 944 engines are all interference engines, meaning that broken or bent valves are usually the result of the loss of the timing belt, any rollers or pulleys under the timing cover, the loss of the balance shaft belt, or seizure of the water pump bearing.

Every 10K miles, a 944 engines timing and balance shaft belts must be inspected and retensioned. Every three years, or 30K miles the same belts ($20-$50) must be replace. When the belts are replaced, it is a good idea to replace the water pump ($100-$200), rollers and pulleys ($125), and front engine oil seals ($75).

Early 79-80 931 engines are Non- Interference Engines, but the later (81-later) 931 engines are Interference Engines, with same problem that 944 engines have, if the belt breaks, so do the valves.

The high cost replacement item in the 931 is the turbo. A replacement rebuilt turbo is $500-$1000, and may last 15K-50K miles, depending on the driver. The cost of the gaskets and seals to replace the turbo is another $100-$200.

The labor time to replace a turbo, or service the timing and balance shaft belts on a 944 engine appear to be about the same at 8-12 hours.
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Cbass  
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PostPosted: Thu May 02, 2002 5:41 pm    Post subject: Reply with quote

It all depends where you want to go with the car. If you want absolute performance, find a 924S with a bad motor and swap in a 951 engine.

If you want good performance, but reliability and cheap parts, rebuild your 931.
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