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best bang for buck: cams, CR, or cc's?

I'm getting ready to open up the 3.2 and am beginning
to get parts lists and orders together.

If I open the engine up and find pistons and cylinders are within spec - should I just re ring it and call it good, and move
on to cams? It seems that new pistons and cylinders will
run me around $3k or so - and I may only get 10 to 20
horsepower for that investment.

If I go to 964, GE 20/21, or 993SS cam grind will I see a
substantial performance gain even staying with 3.2 instead
of 3.4 (plan to go to 3.4 if I replace P/C's)

I "NEED" to address the valves - so the valves, springs, cams,
etc. are all part of the "I need to do this" repair. So,
I will go with race springs, cups, retainers, new cams, and
lifters resurfaced.

The P/C's are "while I have it apart" options. But for $3k
and only 10 to 20 HP gain - not sure it is worth the
money.

What do you all think?

I could put the $3k into close ratio gears and possibly
improve acceleration even more dramatically?

Emery
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Old 10-03-2005, 09:21 AM
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if you boil it down to $/hp just about any peformance upgrade on a naturally aspirated porsche engine is hard to stomach.

"There is no replacement for displacement" overall torque levels (the area under the torque curve) is tied more closely to displacement than anything else. This means you gain power down low, up high, and everwhere in between. whether the $3k is worth it to you is another matter. Note that if you have Alusil cylinders, you can't "just re ring it and call it good" without some careful attention, some would say they are not reusable at all. if that is the case, you might as well go to a 3.4. Another possibility is to have your cylinders overbored to 98mm and replated, even if they are Alusil. then you can buy JE pistons and the whole setup costs less than the mahle stuff. Some would question the JEs for an engine intended to go 100k+ miles before another rebuild, depends on your goals. this makes a 3.4 as well.

I wouldn't do a displacement upgrade without doing cams, just because the cams are a good upgrade and not too expensive. 993SS cams might be too radical (talk to camgrinder) but 964 cams are very good. I believe 964 and 20/21 cams are extremely similar. 964 cams don't require new springs, retainers, etc, and I probably would leave those parts stock. of course you do have to get the rockers resurfaced to match the new cams. If you have bad valve guides (is this why you're rebuilding?) you may need to replace valves, but the retainers, springs, etc don't strictly need to be done.

As to the custom gears, this is a good way to look at things (thinking outside the horsepower box). But, you have a problem, because you have a G50 custom gears are pretty expensive. Even with a 915, though, you have to look at your usage. The gears are carefully spaced in both transmissions, so it's hard not to replace most of them. For a street car, you probably still want a high fifth if you do much highway, and a relatively low 1st compared to a race car. This doesn't give you much leeway. Conversely, with a race car gearing can make all the difference, but then you have more flexibility in terms of spacing things closer together without caring about around-town and highway driveability.
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Old 10-03-2005, 09:55 AM
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JE 98mm pistons and rebore and plate your 95mm cylinders to 98 and you have a 3.4 for around 2k. Cams are valve springs and you are still under 3k. Now you will need exhuast to get the most out of it but 993HE and a custom muffler will be under 1k. There are many options.......

Cheers,
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Old 10-03-2005, 10:33 AM
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The 964 profile fits the Carrera cams as a regrind. The other more aggresive cams require a new billet.
The least expensive would be the 964 cams, resurface the rocker arms and a valve job.
The most expensive would be billet cams, resurface the rocker arms , valve spring kit, 3.4 piston and cylinders, cylinder head work, and a Steve Wong chip or aftermarket EFI.
The expensive route does make good HP, but most people who have done it might have been better off with a 3.6 litre conversion.
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Old 10-03-2005, 10:38 AM
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What John said... But then again - there is a piece of mind knowing you have a refreshed engine
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Old 10-03-2005, 12:07 PM
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and I'll add - I think the kicker for me was adding all the other crap. Like I needed 6 new valves - like my springs were shot - like John recommended replacing all my rocker shafts, which I did... oh and my clutch was pretty worn - and the reference sensor and speed reference heat cover was disintergrating. Oh and the one lead cht. New oil pressure sensor, arp rod bolts while you are in there.

The easy stuff is the big hits (like reboring cylinders, new JE pistons - or pelican has the euro 3.2 sets for 1999.00)

Of course, watching that tach winding around makes you forget the money...
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Old 10-03-2005, 12:14 PM
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Your P&C's are probably fine. I would get a Steve W chip for a little HP, get ARP rod bolts for safety and spend the leftover money on track days.
-Chris
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Old 10-03-2005, 01:27 PM
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Thanks for the input folks! I am going to see what's there once I get it apart and I'll use your advice at that point. If it turns out I need to do the P/C's then I likely will go with the JE's but I do not want the 9.5 CR so I will have to search for 9.8's - do not see them listed on reseller websites...

Not sure about pistons - get bored and resurfaced or some nice new ones like LN's! But we'll have to see how it looks.

Does installing the larger diameter MAF really make any real difference other than at WOT?

I'm thinking a NOS tank and a button for WOT might be a cheaper top end power solution - I only need the extra power to pass on the straights at DE's...I'll bet the instructor's eyes would really open if s/he saw me hitting NOS at a DE.
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1988 930 coupe - Silver Metallic
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Old 10-04-2005, 06:07 PM
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Quote:
Originally posted by s5uewf
I'm thinking a NOS tank and a button for WOT might be a cheaper top end power solution - I only need the extra power to pass on the straights at DE's...I'll bet the instructor's eyes would really open if s/he saw me hitting NOS at a DE.
Surprised? Yes, but not in a good way.
If you want to be faster at the track, spend your money on track days. That is really the best bang for your performance buck.
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Old 10-04-2005, 06:59 PM
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Gears, gears, gears,...man,...

Its the biggest bang-for-the-buck for best acceleration, hands down.
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Old 10-05-2005, 12:47 PM
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Quote:
Originally posted by Steve@Rennsport
Its the biggest bang-for-the-buck for best acceleration, hands down.
Is it hard to choose a set for a combined street/track car, tough?

I looked at your website which recommends this gearset:

Quote:
From Rennsport Systems Website
Here is a real nice close-ratio street setup that has been very successful:

1st Gear 11/35 (stock)

2nd Gear 17/31

3rd Gear 21/31

4th Gear 24/27

5th Gear 27/24 or 28/24
I graphed it, and this gearset seems to have a big gap between 1st and 2nd, and a small gap between 2nd and 3rd. I can see where this would be very useful my local tracks (mostly 2nd gear corners with a stock SC, some 3rd), but wouldn't it hurt 1-2 acceleration on the street? I assume this gearset is for an 8:31 R&P, the website doesn't seem to say.

What disadvantages does an SC box with a 7:31 and a higher 5th (like 912E) have compared with this gearset?

Thanks in advance!
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Old 10-05-2005, 01:12 PM
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Andy:

Gear ratio choices are huge.

As you can well imagine, this is not a one-size-fits-all sort of proposition. Gear choices are tailored for each individual's application factoring engine operating range, rear tire diameter, and usage (street/track/racing).

I only offered ONE example of an effective street/track gearstack for the 8:31 equipped 915's.

Remember, one can tolerate a wider split in the bottom gears due to greater overall torque multiplication and much lower aero resistances. At higher speeds, one wants a closer split to enhance acceleration when aero forces grow exponentially higher.

An SC box with a 7:31 would utilize different gearing based on the above parameters.
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Last edited by Steve@Rennsport; 10-05-2005 at 09:56 PM..
Old 10-05-2005, 09:38 PM
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Quote:
Originally posted by Steve@Rennsport
Gear ratio choices are huge.
Thank you for your response, Steve. It took me a little while to get back to this one. I do understand that this is by nature a modification that must absolutely be custom tailored to the use of the car, not a canned answer.

Unfortunately, I think that it is seen as a "Black art" by most, especially for a combined street/track car, because most of us don't have the benefit of having driven a whole bunch of 911s with different gear arrangements.

I will see if I can learn more.
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Old 10-11-2005, 12:24 PM
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Hi Andy:

LOL,..I'm not sure I would characterize gear ratio choices as "Black Art"; its simply an area that requires experience with such activities and the more, the better,.....

Fact is, changing gears is overlooked by the vast majority of people due to lack of experience/knowledge and the fact that close-ratio gears do not sound as romantic or macho as making more HP.

Club & professional racers are the ones that truly appreciate what gears and engine changes do and make the distinction in value. Its merely a statement of Enlightenment.

Once you make the change, you'll understand precisely what I'm talking about,...
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Old 10-11-2005, 01:11 PM
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Quote:
Originally posted by Steve@Rennsport


Fact is, changing gears is overlooked by the vast majority of people due to lack of experience/knowledge and the fact that close-ratio gears do not sound as romantic or macho as making more HP.

Once you make the change, you'll understand precisely what I'm talking about,...
You said it, this is so overlooked, thats the first thing I looked at and changed when I got my 912
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Old 10-11-2005, 02:13 PM
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Steve Weiner, nailed it. GEARS and gears and gears. You can make a vw go like heck on most tracks with the proper gears. Only the wide open (and there are very very few of these) tracks can utilize bokoo hp and speed.
Old 10-11-2005, 10:56 PM
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If you are doing the top end then adding cams into the mix is a no-brainer (I would have thought). The dyno shows that 993SS cams and SSI exhaust made 30fwhp on my euro 3.2.
Old 10-15-2005, 06:50 AM
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Hi,

No one said it yet. Nothing made my 85 come alive like the exhaust. I put a set of ssi heat exchangers on in combination with a chip and really saw a big difference.

Also, not to try to sell things too much here, but I will be selling within the next month a taller first and second gear.

The first gear is a powerhaus II modified and welded mainshaft and second is also taller to give a more even shift spacing.

Thanks

Ed
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Old 10-19-2005, 08:03 AM
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What would be the pro/con between going with 3.2 ROW (higher compression) P/C and the "3.4" P/C?

I see the 3.2 ROW are $1000 cheaper as a set than the
3.4 sets - and I'm wondering if the 3.2 ROW will be
safe with 92 unleaded and will give a power boost
on par with the lower compression 3.4 P/C...

Also - JE Pistons - are they truly durable enough to
replace the Mahle sets (100k + miles, no smoking, etc.)?
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1988 930 coupe - Silver Metallic
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Old 10-20-2005, 05:47 AM
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