M96 3.4 Engines

[Lightning]

I am in the process of looking at a 3.4L conversion for an '01S. I'm sticking to '99 to '01 Carrera engines because I want to retain the stock Motronic 7.2 ECU (this is for a modified street car which is frequently driven on the track, and will also have to pass smog).

I'm currently looking at a '99 engine with 35k and an '01 engine with 65k and was wondering if the sages of cyberspace might weigh in on such a choice. (I've already decided that either way, the engine will get a 997 RMS, an IMS upgrade, an X-51 oil pan, and an Accusump, as the car sees at least 1.2g's in cornering and braking).

[mikefocke]

just posted the first draft of an article on engine swaps done in collaboration with someone who had done what must be a half a dozen in his car. Might find some thoughts there.
http://forums.pelicanparts.com/boxster-cayman-forum/

[Franco]

Hi, thanks for the draft.

How can the owners of 1997 Boxsters find out if their cars have reprogrammable
DME,s before investing in an engine and whats the cost associated with having to change the DME. if it can't be re-programmed.

Thanks

[BYprodriver]

I am rebuilding my 2000 3.2 to make 3.6 & pass smog check as soon as it is complete sometime next month. Also have a 2001 3.2 to do the same 3.6 build with.

[Cloudsurfer]

Of the two, I would clearly choose the 01 over a 99. By then, it seems that the factory had the casting process better controlled, so the chances of a D-Chunk failure should be lessened, and by 01, the issues of the sagging bearing carrier causing pragmatic RMS leaks should have been resolved.

A replacement RMS seal (use the 997 part, and install the seal to the newer spec, deeper depth) and IMS upgrade (especially on the 01, as it is likely single row) are very wise.

[Lightning]

So we think the changes from '99 to '01 are more important than the extra 30k miles the '01 engine has on it? Or is it that the '99, with only 35k, might not have shown all of its flaws?

p.s. Thanks for the link to Wayne's project page. I've poured over that, as well as Todd's old pdf file. I know the '99 would need a newer e-Gas throttle body, and maybe a newer oil pump if it's missing the Boxster's 4th engine mount boss...

[Cloudsurfer]

Originally Posted by Lightning

So we think the changes from '99 to '01 are more important than the extra 30k miles the '01 engine has on it? Or is it that the '99, with only 35k, might not have shown all of its flaws?

p.s. Thanks for the link to Wayne's project page. I've poured over that, as well as Todd's old pdf file. I know the '99 would need a newer e-Gas throttle body, and maybe a newer oil pump if it's missing the Boxster's 4th engine mount boss...

The 99 will have the "better" dual-row IMS bearing, which you really don't care about since you've said you'll be upgrading it. The 99 is, however, rather more prone to sagging bearing carrier (which causes the dreaded RMS leak that cannot be fixed) as well as D-chunk failures (though pretty much any of the 3.4 or 3.6 engines can do this, as they have the thinnest liners of any of the M96/97 engines- the 3.6, if you aren't aware, is just a stroked 3.4).

What is interesting, however, is that many of these motors, when torn down with mileage on them, begin to show signs of bore distortion as they become out of round ("stretched" in the thrust plane). While the degree to which the bores become out of round depends upon a myriad of factors (such as how hard the engine was driven, for one), it is reasonable to assume that the higher the mileage the greater the chance of this happening is. In this aspect, the 01 you are looking at is at a disadvantage.



I wouldn't worry too much about the lack of the 4th mounting boss.