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Questions about 3.2 rebuild vs. 3.4
Happy Thanksgiving!
I purchased an 87 3.2 Carrera about 6 months ago with 95k miles and so-so paint for a fair price. Was going to slowly fix a few issues (sunroof and A/C, etc) myself. Well, took it int to be checked recently after a solid PPI and no noticeable issues driving and found that it has broken head studs (they couldn't tell till they opened the valve covers for an adjustment), worn pistons, etc. This is a reputable shop in the Dayton OH area that was recommended by multiple local PCA members, so I have no reason to doubt the veracity. Right now looking at about 20k in repairs. So.... The question: do I put it back to stock for about 20k. Got to 3.4L displacement with new pistons, etc and a new tune for an extra 3k Upgrade to more of a racing cam for an extra 2k (including tune). Or do both for about 4 k more? I am both interested in bang for buck (as in, will I notice the difference) and resale. This is not a "collectors quality/garage queen" car. Any advice? FYI, my purchase price was fair for a car in decent drivers condition. Even keeping it stock probably puts me under water 10k. Look forward to your comments |
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You could always keep the motor and put a 3.6 in it. If not I would do the 3.4 and make it as fast as you can afford. My 2 cents.
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It wasn't a solid PPI if they didn't check the head studs.
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Finding a good 3.6 now is not as easy as it was just a few years ago. Most will need some attention and possibly even a complete rebuild if not right away, then soon. Factor in the extra goodies required to do the swap and it's not the relative power-cost bargain it once was. Don't get me wrong, if you have the cash to do a rebuild on a 3.6 you could have a very hot ride. It's something I would do if I had the resources. |
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I faced the same questions some years ago and went the 3.4 route. It has been a great decision and am so glad I did it. Went with Mahle Max Moritz-style pistons, and Web 2.0/21 cams, plus a list of other items. Power is noticeably better. The slippery slope is there, however, so get to decide how much is enough.
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I agree with Lyle O and also vote for the simple single plug 3.4 setup -- use 3.4 Mahle Motorsports P&Cs (e.g. https://lnengineering.com/products/mahle-motorsports-c-p-sets/porsche-911-carrera-32l-to-34l-1984-1989-motronic-inj-mahle-cylinder-and-piston-set.html) which are the "max moritz" style and work well with a single plug setup. You should end up with a noticeable torque/hp bump with a (relatively) minimal additional expenditure.
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If it were me, I'd probably complete the investigation. I'd pull the valve covers and see for myself whether the barrel nuts are still there. I'd guess your mechanic is being truthful, but that's what I'd do.
A diagnosis of worn pistons is significantly more curious, particularly at 95K miles. At about 200K miles, I replaced my head studs and the most wear I could find on the worst cylinder was .0015". This amount of wear is best termed "miniscule." If your mechanic says your pistons or cylinders are worn, I'd ask for the data. Compression and leakdown test. On a leakdown test, you can listen at various places (assuming there is leakage) and get more information about where the air is going. If I were you, then before I start planning on fixing something, I'd first learn all I can about the problem you are trying to fix. Respectfully. |
Crap, I posted something earlier and didn't comment on the OP's question...
If it was me and confident a rebuild was necessary, and being the engine would be already completely torn down, I'd absolutely go for the displacement increase. However, I'd think hard about 3.5 litres instead of 3.4, which really isn't 3.4 but rather about 3.36. A 3.5 is actually just over 3.5 litres. And I'd twin plug. If staying with single plug, I'd stick with the 3.4. As for cams, that's really an area I'd look to pros to help navigate. A cam can change the personality of an engine completely. And it is affected by the displacement. You might get a real torque monster or a high strung "race" cam that makes loads of power, but way high in the rev range that's only really useful on a track. I like the Webcam 20/21 for a mid 3 litre engine from what I've read, but I know there are others that might meet my needs even more. That's really a personal choice. If your builder is talking about a "racing cam", maybe try to nail down what exactly that means. Because you're already in this far perhaps talk with Sal Carcellar about his MAF conversion and injectors. I understand he's seeing really positive results. A thread about that and a displacement increase is here: http://forums.pelicanparts.com/porsche-911-technical-forum/904111-cams-3-2-engine.html. Good luck! |
I'd agree with much of Kevin's advice, and I can report enjoying very much the torquiness of the 20/21 cams. I'd disagree that head studs, or even pistons, necessitates a complete teardown. If you will do a complete teardown, then my advice is to make sure everything is spec'd and balanced. Rod reconditioning, wrist pins, blah blah. This really is a slippery slope. Twin plug is spendy, AFAIK.
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Bore and plate the cylinders, use a CP or JE piston and its closer to 2k, not 3K. As you are using the stock intake, any suitable cam profile (964, 993SS, DCXX etc) can be reground on your stock cams. Plan on 500 including shipping to/from your grinder. Rebuild rockers arms adds to that. Steve Wong (911chips) Eprom for your ECU to match. We have built many of these motors and they make for a fun motor with very little added expense.
Remember, if your P/C set is out of spec, you need to spend that money anyways. It is the same dollars at that point to move to a 3.4. :) Cheers |
I just went through this exercise on my new to me 1988 911 Cab.
155k mi time for valve job. Which lead to new P&Cs, and what the heck, while not needed i decided to go all the way and do bottom end too. Then, the real slippery slope started. Revisit P&C, head work, twin plug, euro or us spec, 3.4 or 3.5, cams etc... Because it a cab being built as a DD as much as I was stoked to go all in to do a hot rod I decided to stay with the 3.2 US Spec Mahle and single plugs. Everything balanced of course and some cool head work, and Steve Wong chip with a no cat tune. If this was a Sunday driver coupe this build would be much different. It is a slippery slope once you go off script. Fun but a different direction and lots and lots of decision points once started. Enjoy. |
Thanks all for the advice. I am in no way experienced enough to question the mechanic. The best I can do is say that they are well respected and highly recommended.
To clarify, the mechanic said the pistons put in the car can either be the kind that can be reground and still used (maybe Mahle?) or the kind that can't. I, of course, have the kind that can't. So, he is not saying they and the rod bearings are completely shot, just that there is evidence of wear, and if we are this far, it may be better to address it now then put it back together and redo lots of this work in a few years. If I was going to sell it in the next few years, he said you could certainly not address the bottom end. Seems silly to wait if Im going to keep it though. Keep the advice coming. I am leaning toward the upgrade to 3.4 |
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Random data points:
- As someone mentioned, a 3.6 will need a top end at least and you’ll want to tear it down far enough to fix all the leaks that are somewhat common with this motor. - if you’re replacing the cylinders anyway, the 3.4 is not much more. Don’t expect much more horsepower though. It’s a 6% increase in displacement. - If you are thinking of going with a 3.4 twin plug you can bump up the compression and get a nice bump in horsepower. I’ve done this. At the end of the day though, you are trying to duplicate something the factory did and you don’t get the knock sensing and engineering that a factory motor has. If your building it for fun, the 3.4 twin plug is a fun project. If your not, look at the HP/$ of each and decide. |
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