964 engine durability

[rbogh901]

I'm looking at a 964 also. It looks common for these to claim to have rebuilt engines at under 100k miles. The implication is that these M64 engines do not have the longevity of the 3.0 and 3.2. The 200k and 300k mile experiences claimed in the older motors sure speak well for their durability.
It may be that the rebuilds being reported are because of oil leak problems, (89-91 especially), or damage after distributor belt failures, (before venting). What is the consensus on these motors otherwise?

[ischmitz]

I think the 964 share the comon issue of valve guide wear with the older engines. Other than that you are right about a small percentage of the 89 - 91 engines having head to cylinder leaks (mine included) that had to be addressed. And there was the issue with the belts failing before the vent kits became popular.

Another concern on the 964 is the rod bolt diameter. It's 9mm and some say it is a weak link for high-RPM applications. Damage is accumulative and frequently hitting redline can cause the bolts to fail. However, I have not heard about motors here that catastrophically failed.

In general the 964 seems to be a very reliable platform especially after being rebuilt properly with better valve guides and ARP rod bolts. I don't think there are any differences between it and the 3.2. You just have a statistical advantage that produced more high-mileage 3.2 engines by now whereas the 964 engines are younger in comparison. The reason I say that is that you also read a lot more about 3.2 engines being worked on here.

I message board like this will always produce a skewed image of engine reliability. You might want to talk to some of the experienced engine rebuilders to get more objective point of view.

If it was me I would go again for the 964 engine for my early car. I like it for its performance, price point and the fact that is still is a traditional air-cooled engine. With the 993 you get hydraulic lifters and the later 993 have the better intake system. However, from a power point of view I can make almost the same power as the early 993 engines by updating the exhaust.

If your decision is between the 911 Carrera and the 964 Carrera for a complete car there are many more factors that come to mind for the decision. Very different suspension setups, transmission was 915 and changed to G50 later on. More electronics on the 964 that can fail. ABS, airbags, power steering, weight, etc.. I would not make the decision based on the engine alone. Best, test-drive both to "feel" the difference. They are very different cars.

Ingo

[rbogh901]

Yes, absolutely. I see what you are saying. One of the reasons to ask this kind of question is because some of the C2/4 964s are starting to accumulate some significant mileage, pushing 200k but, at the same time, prices are coming down into a very reasonable range.

On another tack, how much did you pay for your motor and what did you have to invest to bring it up to par?

Thanks

[ischmitz]

I got the motor back when the dollar was strong. At around 6k US$ with lots of parts needed for my conversion. I did do a full rebuilt with the help of a friend soon thereafter b/c of the cylinder-to-head leak. We did not split the case but all else was done (heads, valves, new P/C, rod bolts, new cams, etc.) Machine work by one of the best in the industry: Walt @ Competion Engineering. The price was in the 3k range. With that I ended up with a bullet-prove engine and have since put on 25k miles with no trouble.

Othes have bought similar engines at similar price points and did not ever rebuilt. So it all comes down to luck. The seller of the engine agreed to split the cost of the fix since there was some mis-representation involved. So in the end a good deal, still.

ingo

[74threeliter]

Ingo,

I am entering your prevous steps. Looking to pick up a 1991 964 engine with 100K miles and leakdown at or < 12% with one at 10%. There is leaking going on as I have heard these engines referred to as the "exxon valdez" engine(at least those with engine numbers for tiptronic with or after 62M52728). Due to leak I was able to negotiate the price in my favor a bit. My question to you is this:

1) Why did you opt to just do the top end? (I wonder about the durability of the bottom end)
2) Was it difficult to change the rod bolts without splitting the case?
3) Did you do the assembling yourself? How long did it take?
4) How would you rate the 964 engines durability/mpg after your rebuild?

I have a 3.0 and have enjoyed its dependability but now am ready for displacement upgrade.

[930gt-40r]

My old C4 had 175,000 miles on it when I got it (before I swapped the motor for a 930 motor) The engine ran Very strong, but unfortunatly leaked a bunch of oil at the base of the cylinders. Lets put it this way, I destroyed a well modded 2001 mustang GT (gears, intake, exhaust, cams, headers) with the 175,000 mile motor- it was worse than a one legged man in a @ss kicking contest.
Also, it was a wonderful car to dirve around. I live in the northeast and drove the car with bald Pirelli P-zeros through the snow like it was my job. Compared to my 930, the interior is far superior with the heat control and center consol and so on. I will sell my 930 and again have a 964 someday.

[D_P]

My 89 C4 has 175,000 miles and was still running perfectly. Compression was good and car performed well. Once I moved the car to a colder climate the oil leaking from the old style cylinder heads became much worse so I tore the engine down for a rebuild. Inside the engine looked like it was still new and there was very little wear on any of the parts. I would expect if it were not for the oil leaks this engine would have easily gone 250,000 or 300,000 miles.