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Question cylinder head question

I have an '87 924S I just bought with 88,000 miles. I understand the compression ratio is lower on the pre '88 cars. Is this a deference in the cylinder head? The car needs to have the belts done. Is this the perfect time to make 10hp? I have an engine from an '88 with 110k on it.

JRW
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Old 09-30-2003, 01:47 PM
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The higher compression is different pistons...
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Current: '86 951 Sunroof Delete - '89 951 - '83 944 Spec - '08 Cayenne Turbo
Past: '88 924S Track - '86 944 16v - '87 951 - '87 951 - '88 951S - '08 Cayman S - '87 944 Track - '93 968
Old 09-30-2003, 04:01 PM
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Actually the early 944's have a very slightly higher compression ratio than the later 944's.

BUT!

The later 944's have a longer duration on the exhaust timing!

This adds a few more ponys to the corral.

Don't know if it's the pistons or the heads or both.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 09-30-2003, 04:30 PM
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Quote:
The later 944's have a longer duration on the exhaust timing!
In reference to the cam, I assume? So some early pistons in a later engine would yield an HP gain?
Old 09-30-2003, 04:44 PM
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Hmmm.... IF that is the difference AND the pistons don't hit anything different on the head.

I would just use the later cam on an early engine.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 09-30-2003, 04:47 PM
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I was hoping it would be easy. Maybe I will call my local shop and ask if any of them have an opinion on the matter. Does anyone know ware I can get some concrete facts?

JRW
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Old 09-30-2003, 05:09 PM
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You just did.
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 09-30-2003, 05:13 PM
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The SoCal knows the way, young Padawin, he is strong in the Force. Believe him you should.
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Old 09-30-2003, 05:37 PM
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Thanks for the info. I have a whole '88 parts car minus body what parts should I put on the 924S. The two best ideas I have are the rear sway bar and the rear wheels because I hear the 924S's aren't as wide. I also read in Grassroots the DME has diffrent mapping or something.

JRW
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Old 09-30-2003, 07:31 PM
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And about the compression ratio I thought the early model had 9.?/1 compression and the late model had 10.2/1 compression.
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Old 09-30-2003, 07:33 PM
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http://www.pelicanparts.com/944/tech_specs/944_model.htm


8 valve engines

2479 cc
83 through 86 9.1 : 1 = 150 HP at 5500 rpm

87 and 88 are 10.2 : 1 = 158 HP at 5900 rpm

2688 cc
89 10.9 : 1 = 162 HP at 5800 rpm
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Hugh - So Cal 83 944 Driver Person
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When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
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Old 09-30-2003, 07:50 PM
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DME 83 through early 85

DME 85.5 to 87 models.

88 and 89 DME are different from each other and the earlier two changes.

Check out www.frwilk.com

What year is the 924S?
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 09-30-2003, 07:54 PM
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1987 924S with 88k miles, phone dials, no rear sway bar. And thanks for answering my questions so quick.
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1987 924S White
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1971 914 Red
-doesn't see road much-
Old 09-30-2003, 08:03 PM
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What is wrong with the 88?

Personally I would put a sway bar on the 924S and just drive it.

If the engine dies then put the 88 engine and DME in it. Might have to change the DME wire harness but possibly not.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 09-30-2003, 08:09 PM
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Your right thats why my 914 is in pieces and not being driven. And that website looks like it will be very helpfull.

JRW
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1971 914 Red
-doesn't see road much-
Old 09-30-2003, 08:14 PM
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1986 9.7:1
1987 9.7:1
1988 10.2:1
Not a big diffrence in compression but these are the numbers from pelican parts.

JRW
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Old 09-30-2003, 08:34 PM
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head questions, cam stuff.

hp figures aren't what they are cracked up to be, what is the torque values between those engines! thats what realy counts.

as for cam towers and clearances, total lift and duration are important factors. if you have exsessive duration in the exhaust lobe you increase the scavenging effect of having the exhaust open at the same time the intake is coming alive. I beleive the exhaust does not come near the piston at top dead center to acheive this it would have to be a zero interfearance profile. I know the intake valves will hit, I've seen photo's of broken belt victims. does anyone know if the exhaust valve gets in the way of the piston?
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Old 10-01-2003, 05:00 AM
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Both times my timing belt let go I bought the four exhaust valves but only one or two of the intakes.
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Hugh - So Cal 83 944 Driver Person
NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts and/or cam chain and tensioner?
New Users please add your car's year and model to your signature line!
Never break more than you fix!
Old 10-01-2003, 09:59 AM
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Quote:
Originally posted by SoCal Driver
You just did.


Trust the man; he knows what he's talking about!!

I have a question......a later cam would help MY car some,, eh? I really don't care about HP, what I REALLY want is torque. I have some, but more is what I want........if a cam will do that, then I got a job for my buddy!
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Last edited by daveimme; 10-01-2003 at 11:25 AM..
Old 10-01-2003, 11:23 AM
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