considering top end rebuild
 

Hello everyone,

I am at that point in time where I am considering upgrading my performance. I already know what I might like to do in terms of performance but my question is as follows: Do I rebuild the entire engine or just the top end? The performance mods I would like to do are top end add-ons only. Nothing too major(cams, springs). I have heard from various shops that the bottom end is extremely robust and does not need rebuilding unless something is seriously wrong down their. My engine has 134k miles on it, great compression, great oil pressure, and only burns about a quart of oil every 800-1000 depending on how hard I drive. What do you think? http://forums.pelicanparts.com/uploa...1143946069.jpg

hmm why is this pic not loading........ http://forums.pelicanparts.com/uploa...1143946269.jpg

Try downsizing your pic a little. I've heard that helps. Also, are you previewing the pic before you post the message? Maybe it'll show up black on the preview page and save you the frustration of seeing it come up black on the website.

I just had that black wall of death pic on one of my posts.....too many pixels. Used to be it just wouldn't load....

Put in a photo manipulation program or right click, chose "open with" and try the Microsoft program and follow the pull down for resizing....800x600 ish the best.

I just loaded the thing into photo shop and resize it. all set. what is a posting without pics anyway?

Re: considering top end rebuild
 

I think you don't need a top end - are you smoking? 800 to 1000 is still within normal - get down to 500-600 a quart then make it count. And anything with over a 70,000 miles and I would splt the case and replace the bearings et al...

Hmm... I don't know about that. I did a top end on my SC at 136K about 9 years ago, and it's got a 195K on it now and still running great and has decent oil pressure. These bottom ends will go MUCH longer than 70K...

ianc

There is a guy in town who owns the local Porsche garage who put over 300k on his engine before rebuilding it. This includes many track miles as well. When the engine was taken apart, there was hardly any wear to the bottom end of the engine. The bearings and cylinder walls were fantiastic. Although I realise this shop (Carl's place) is very reputable, I am still not sure if I would be better off rebuilding the entire engine or just the top end.

If you have good oil pressure, there's probably no need to. Why replace things before they wear out? I realize there's the 'while you're in there' factor, but you could easily drive this car another 10 years with no trouble.

ianc

ok that's good advice. I will just do the top end. I plan on stretching this job out by working on it only when I have time to. Should be a good project. I really don't think the rings need to be replaced. The compression in this motor is very good, it just needs a bit more go. I drove a Lotus Elise the other day and got a craving for more power. Hate the Lotus Elise, but love the go. Love the Carrera, but hate the lack of go.

Would it be possible to swap the pistons and rings as long as I am in there too? I may decide to put slightly higher compression pistons in as well, but have not decided. JE has some great off the shelf 10:1 pistons for these things for a reasonable amount.

Be careful with compression. The gas is not getting any better and unless you go the twin plug route, you might be better off leaving well enough alone.

The secret of HP is volume. Cams and a chip can give a lot of performance. You might also consider a bigger throttle body. With everything fresh and in perfect tune, you should get real good performance. The right people on a dyno can grab another significant percentage of torque (or flatter curve, as it were) and HP. Don't overlook professional tuning.

where might I obtain a larger throttle body that will bolt onto this manifold? Stock compression in a carrera is 9.4 or 9.6? Cannot remember exactly.

Thats a very beautiful black targa you have there - looks great.

In my very humble opinion (which really is pretty humble!) I wouldn't have thought your engine would even need a top end rebuild given the state of the engine as you describe - the oil consumption and compression etc. I really don't want to state the obvious or anything, but are you sure everything is set up correctly? I've heard that often the throttle adjustment can be out, preventing your throttle opening to its full extent, and that very often this can be the only reason why people aren't 100% satisfied with their cars performance. Might be worth checking?

I am pretty on top of all the mechanicals on my motor. Just installed Magnecors, chip, cat bypass, new o2 sensor, cap/rotor, valve adjust, rear wheel dyno'd to about 19bhp over stock at the flywheel. The car is tip top but, I know it is going to need the top end rebuilt soon, and I just want more power out of the thing.
134k is a lot of miles and I feel as if the car can be better and besides, I like working on engine's almost as much as I enjoy driving. No speeding tickets or idiot drivers trying to race you when building engines.

Yeah... I can understand where you're coming from! I rebuilt my top-end last year, and although its now great to have my car back together I do miss the fun and excitement of doing the rebuild.

Well first of all he's asking for opinion - that's my opinion. Rebuilding an engine is an expensive proposition. MY Mindset was"

1. make it count
2. wait until it really needed it - mine was burning 1 qt per 1,000 - 900 miles - within a year of me driving it hard (DE's and Such)- got down to 400-500 miles per qt.
3. If I'm going to open the engine up (top end job in my case) get some performance out too.

So - I ended up with 3.4 pistons and cylinders - Extrude Honed intake, bored throttle body, performance springs - titanium retainers, 993 ss cams, new bearings, arp rod bolts, and B & B Headers.

Then again, I only dyno'd at 64hp over stock so what do I know.

So 400-500miles/qt is the magic number?

Any indication by SMELL? My 911 is getting downright stinky...

-T

is it smoking a little when warm?
what does it smell like?? unburnt gas or oil burning?