 Engine Quiestion..P&C's. |
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| MikeM |
 Apr 26 2011, 05:47 PM
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#1
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Senior Member  Group: Members Posts: 564 Joined: 16-May 10 From: Calgary, Canada Member No.: 11,733 Region Association: Canada  |
Hello all...I was examing bills from previous owners of my car, which is a 1974 2.0 liter 914, LE. It appears that one PO had the pistons and cylinders replaced with bus parts that are 94mm. I don't have the part number here at work but I did some quick searching earlier and it looks like they are indeed bus parts.
Question is...how should this engine be "driveability" wise? What should it feel like? How would it be with proper 914 pistons? Would I notice a difference? Would it be worth changing them? The car has only done about 6000 miles since the pistons were installed. Oh..GA case and working D-jet. Thanks as always... Mike |
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Replies(1 - 7)
| aircooledtechguy |
Apr 26 2011, 06:54 PM
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#2
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The Aircooledtech Guy Group: Members Posts: 1,966 Joined: 8-November 08 From: Anacortes, WA Member No.: 9,730 Region Association: Pacific Northwest |
IMHO, if you can change them yourself and feel comfortable doing it, I would swap them out for a set of 96mm flat-top pistons in a heartbeat. With bus pistons, your compression will be in the low 7s which can make for a very lazy feeling engine that lacks the crispness that higher compression (low to mid 8s) gives.
It's a pretty simple swap over. Just check deck height and CC the chambers of your heads and run the numbers through a compression ratio formula. Bus pistons add about a 15cc dish to lower the CR. . . You don't need or want that in your Porsche. |
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| MikeM |
Apr 26 2011, 08:42 PM
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#3
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Senior Member Group: Members Posts: 564 Joined: 16-May 10 From: Calgary, Canada Member No.: 11,733 Region Association: Canada |
Thanks for that Nate...anyone else?
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| r_towle |
Apr 26 2011, 08:47 PM
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#4
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Custom Member Group: Members Posts: 24,594 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States 
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stock versus what you have (if they are bus pistons) is 10-15 hp difference.
It runs, it starts...drive it like you stole it. If and when you decide you want more power, you are limited to about 25hp increase...which is alot considering you are running less than 100 right now... Will you feel it..yes, for a bit. Its kinda like a computer...a new one seems really fast...for a while. then is just normal. Sure, you can rebuild it, but it may be something to plan out to add some real HP and do a few more things while you are there.. I would not bother to change the pistons and cylinders only in your specific case...but that is just my opinion. Rich |
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| euro911 |
Apr 26 2011, 10:21 PM
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#5
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,851 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California
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I agree ... drive it the way it is, especially when it's just becoming driving season. If you feel compelled to increase your HP, build yourself another engine in your spare time (a nice winter project).
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| McMark |
Apr 27 2011, 12:47 AM
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#6
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
If you can do it yourself, it's worth it. If you have to hire it out, don't bother. Also, be prepared to find head 'issues' if you pull them off.
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| MikeM |
Apr 27 2011, 09:40 AM
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#7
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Senior Member Group: Members Posts: 564 Joined: 16-May 10 From: Calgary, Canada Member No.: 11,733 Region Association: Canada |
Thanks for the replies...Yup, I would expect to find head "issues" if I pull it apart.
I'd be able to take it apart, but might not be able to put it back together!! BTW the part number for the piston and cylinder kit that was installed is 029 198 075. Bus pistons, right? Mike |
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| euro911 |
Apr 27 2011, 10:19 AM
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#8
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,851 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California
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Yes
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