3.2 rebuild vs 3.6?

[gliding_serpent]

Originally Posted by Kemo

if you put in a hotter cam, should we be worried about the rod bolts? I hear all the stories of weak bolts in the 3.2s

I think the dogma is that a rod bolt of unknown history should be replaced as it is a known weak point with terrible consequences. They can be replaced without cracking the bottom end. Another dogma is replace them if your engine is open anyway.

A 964 cam should add 5-6hp above 4.5k according to an expert in the matter if my memory recalls. Probably will not cause much of a change from stock in the stress department.

[ej911]

my best recommendation, (i am nobody), rebuild the 3.2 matching numbers are king. unless you can afford to save the 3.2 and convert to 3.6.

[Reiver]

[QUOTE=gliding_serpent;8481335]The PO did a claimed 4 autocrosses and 2 HPDE's. I changed all fluids and then I did one HPDE. I am thinking over-rev risk.

The oil residue in the lines post engine removal was classic for water in the oil... i.e. not heating the engine up properly. Likely part of why it had so few miles.

PO swore by Rotella T diesel oil (15W40). He was sold on that based on a reputable west coast shop that did a lot of work on PCA race cars and swore by it also. PO only owned it for 6K miles and maybe two oil changes. I used the same oil for 2k miles (changed the oil after getting the car). Good discussion here: Diesel engine oils, good for aircooled Porsche?

Not trying to start an oil war here, but how long do you think it would take bad oil to do this kind of damage?

The Rotella should be good and the broken stud is a classic on a low mileage motor that's not properly brought to temp then sits.
That lobe looks pretty bad for that kind of mileage tho...who knows? As noted improper hardening...I didn't know that to be a common Porsche issue especially at that mileage.
I wouldn't split the cases myself....I've a full top end on a 3.0 euro that had 67k on it (same deal as yours driven little not warmed up ...head studs) when rebuilt and swapped out my US spec for it. I suspect it'll need another head rebuild before the bottom end has any issues.

[TT Oversteer]

You may not want to hear this but.....if the engine is out and apart down to the cylinder head studs I would split the case to inspect. You will then be able to replace the rod bolts correctly with a stretch gauge. It's a good bet your intermediate shaft bearings will be showing copper as most do. If your cams are pitted it may be indicative of hard use, dirty/wrong oil or incorrectly stated mileage. All these things could cause wear in the bottom end. You will also be able to correctly reseal the front pulley seal and number 8 bearing. If you split the case and all is well, you are only out the cost of sealants and a few more hours of labor. The peace of mind will be priceless. Most of the labor involves engine removal/installation and top end disassembly/assembly. I debated splitting my 3.2 case when doing a top overhaul and I was glad I decided to go the full distance. My 100k engine had worn intermediate shaft bearings and gears/chains, and the rod bearings were pretty bad. The mains also showed some wear. This was, I believe, the result of poor maintenance, oil contamination, and neglect. You seem like the type of person who will not be happy with a half assed job. Do it right and enjoy the car for decades to come.

[midnight911]

is 3.6 motor price getting that expensive?
I chose the 3.6 route because rebuilding 3.2...ummm, with 3.4 twin plug high compression was more expensive at the time...circa 2008...

[gliding_serpent]

is 3.6 motor price getting that expensive?

I chose the 3.6 route because rebuilding 3.2...ummm, with 3.4 twin plug high compression was more expensive at the time...circa 2008...

Market for engines is going crazy just like the classic 911 market. If i lived in the us near a big time shop it would be a different story. My quick math says 35k csnadian for a proper used 3.6 install all in (including essential brakes upgrade). Plus labour. The swap alone is more than the price i paid for my car.

[gliding_serpent]

I very much agree with you.

You may not want to hear this but.....if the engine is out and apart down to the cylinder head studs I would split the case to inspect. You will then be able to replace the rod bolts correctly with a stretch gauge. It's a good bet your intermediate shaft bearings will be showing copper as most do. If your cams are pitted it may be indicative of hard use, dirty/wrong oil or incorrectly stated mileage. All these things could cause wear in the bottom end. You will also be able to correctly reseal the front pulley seal and number 8 bearing. If you split the case and all is well, you are only out the cost of sealants and a few more hours of labor. The peace of mind will be priceless. Most of the labor involves engine removal/installation and top end disassembly/assembly. I debated splitting my 3.2 case when doing a top overhaul and I was glad I decided to go the full distance. My 100k engine had worn intermediate shaft bearings and gears/chains, and the rod bearings were pretty bad. The mains also showed some wear. This was, I believe, the result of poor maintenance, oil contamination, and neglect. You seem like the type of person who will not be happy with a half assed job. Do it right and enjoy the car for decades to come.

[Jcslocum]

You are working with a 56K (right?) mile 3.2 here!! Just pull the heads and have them sent out out. for a valve job, replace the studs with new steel ones or a set from Supertec or ARP. This is a known failure and not the end of the world. LOTS has been written about it and many fixes have been documented right here and if you need inspiration, I can find the posts.

I just pulled the full top end off of an '87 3.2 with 100K miles and everything looks like brandy new. I have the rods out for new bolts just as a precaution. This is also a known weakness, and easy to replace. We are replacing the rod bearings because 1 had a polished area where the oil gallery comes out of the crank. The crank measure up perfect and new bearings will be fine.

We are building a 3.4 as a DD for my daughter and expect another 100K out if it before opening the cases.

Doing the top end is kind of easy and new cams are a nice upgrade for your base engine.

[gliding_serpent]

Jcdlocum... I totally agree with you, but the 90's were a bit of a dark ages in my cars documentation a couple of owners ago). Car fax records only start in 2004 or so. I figure is was either in storage, or off the grid (racetrack?).

Signs seem to sugest accelerated wear due to any combo of bad oil, improper warmup, possibly even the jets to lube the cam needing cleaning.

The 915 has had a hard life. The body of the car shows a hard life (red white rub marks on the rubber smile when i got it... You know where those came from...).

The 915 has been opened. 58k and one rebuild already and needing a second. The ring and pinion shows signs of being replaced. I will do a tooth count to see if it is 3.88:1

Something does not add up. Based on how things look when the top end is off, i will have a low threshold to open the bottom.

[safe]

The rod bolts are only weak if you're going to rev it above 6500 for extended periods or have over revved it significantly. I take my stock bottom 3.2 to 6800 on regular basis.
You might not know if it has been over revved in the past, but since it still lives, then probably not, it would have shown...

56k is nothing for the bottom end. If you plan on living above 6500, then go ahead and change the rod bolts, otherwise you can leave it alone.

[Reiver]

If you have major unknowns and suspect some abuse then Id go for the full monty.
The rebuilt 3.0 I picked up had a known history one owner deal so was confident with not splitting.
You won't feel right unless you do from the sound of your posts.

[911pcars]

I concur with jcslocum. While the lower end (main bearings) of 3.2 engines seem to have good longevity (esp. at 58K mi.), the rod bearings don't necessarily follow that path. Easy enough to yank and take a look. Take your cue from the rod bearings as to your next move. At a minimum, I suggest having the rods rebuilt (big/small end, balance) and add the more reassuring ARP con rod fasteners.

And since there's evidence that a cylinder may have bounced around (missing crankcase nut - damn!), I would thoroughly inspect the crankcase spigot(s) and cyl. head(s) for signs of cylinder abuse, then confirm each bank's stack height during fit up (cylinder + cyl. head + cam housing). BTW, the engine internals in the photo don't look particularly clean. May be just the lighting. That typically depends on normal operating conditions and oil change intervals. For example, did the PO install the period-correct, factory race-like air filter delete option? You sure about the documented eng. mileage? Check piston and cylinder wear as well.

Yes, there's no substitute for cubic centimeters. However, you must add the cost of a good or rebuildable 3.6 if you go that route. But then, you might be tempted to continue along that slippery slope.

Sherwood

[Tremelune]

It always depends on your goals for the money. If you rebuild the 3.2 You'll still have a very fun classic to enjoy for another few decades for less money than you can get into another one. For the rebuild/swap price difference, I think you could get a (much faster) E46 M3 on the side.

I have a 3.6 in an M491 coupe. The power is nice, but it still spins the sticky 275 rear tires in a straight line. There have been a few annoying gotchas with the swapped motor, but I knew this would be the case going in. 993 prices are through the roof, and so is the price of parts. The bang/buck is gone.

I have a bone-stock 3.2 coupe. It's wonderful to drive and it's rare that I think "If only I had more power". Damn thing has appreciated like $10k since I bought it with no end in sight. Ride the wave.

[Tremelune]

Which is not to say that the 3.6 isn't particularly wonderful to drive, I just wouldn't build one from a 3.2 anymore.

[gliding_serpent]

As was said, the 3.6 bang/buck is gone. Engine prices have rocketed with the market, making rebuilds the more cost effective option

[JeremyD]

I've done both - and rebuilt both. If I'm spending the money to rebuild an engine - I'll go ahead and do the 3.6. Tough not to like a 3.6 in an earlier car. Creates a nice hooligan machine. (although I have to say that my 3.4 993ss single plug was a screamer of an engine)

[michael lang]

Originally Posted by safe

The rod bolts are only weak if you're going to rev it above 6500 for extended periods or have over revved it significantly. I take my stock bottom 3.2 to 6800 on regular basis.
You might not know if it has been over revved in the past, but since it still lives, then probably not, it would have shown...

56k is nothing for the bottom end. If you plan on living above 6500, then go ahead and change the rod bolts, otherwise you can leave it alone.

That is probably the number one reason why I decided to stop teardown at the heads. My car only has 64,000 and definitely does not live north of 6500. Don't get me wrong, it goes there and I would get everything out of that engine that I could but it didn't live at 6500 and above and I never treated it like a rented mule.

[88coupe]

I recently went through this same issue. My 3.2 has more miles, 114k, and indeed had 2 broken head studs which were discovered 6 months after purchasing the car. I live right near a great porsche shop and that influenced my decision to rebuild the 3.2 with some upgrades. While we were in there I upgraded the head studs, rod bolts, and rod bearings, along with 20/21 cams. The upgrades were of course not necessary, but the added cost at that stage was minimal compared to the piece of mind it gave me.

I'm happy I kept the 3.2 and hope to enjoy it for many miles to come.

Forgot to mention the bottom end, ok actually the middle, was not touched.

[gliding_serpent]

I will add to the 3.2 vs 3.6 debate that goes beyond cost or 3.6 availability:

Bill V's performance graph should be consitered, but at the end of the day, with some light mods, 250hp is quite accessable with a 3.2. The 3.6 964 is 247hp. Now, if you are starting with a 2.2, 2.7, or 3.0, the 3.6 might be an easier choice.

[safe]

Originally Posted by gliding_serpent

...with some light mods, 250hp is quite accessable with a 3.2. The 3.6 964 is 247hp.

I doubt that any 3.6 dynos as low as 247, light mods on a 3.6 and you are pushing 290-300 hp...