3.2 Top End Rebuild Advice

[1972_911T]

Im about to buy A 1989 3.2 engine for transplant into my 1972t. The engine I am going to buy is currently in its original car showing 140k miles with full porsche service history upto the last 10K. I have seen this engine run and also drove the car with it in. The engine runs well with no unexpected noises and pulls really good. However the owner has expressed concerns about the oil usage and thinks it smokes sometimes when he puts the throttle down. When I look at it when he blipped the throttle a small amount of smoke came out but I wasnt concerned too much about that. The engine oil pressure is about 5bar when the engine speed is up and warm.

After doing some research about the 3.2 engines I have decide it may be best to do the top end while the engine is out, valve guides and reseated etc. What I want to know is if it is worth changing the rings at the same time? In waynes book it says that this can cause excess stress on the pistons if the ring gaps are worn but I was unsure if this was reffering to earlier engines or is this still the same for the 3.2? I know this is a hard question to answer with out the engine stripped for examination but can you noramally get away with changing the rings on the 3.2's without new pistons as well?

Steve

[Jeff Alton]

Do a leak down and compression test. Those rings have 140K on them, plan on replacing them. Rings seem to seat well in cylinders that have been cleaned up with soap and water and a scotchbrite pad. (nikasil) I had a larger thread about that and it should turn up in a search. IF you have alusil cylinders I just had success having them honed with a special Sunnen process on a 3.0 I just rebuilt. There is also a large thread here on re-ringing alusil cyliners. All of this is assumes that the P/C set is within tolerance and not worn beyond spec.

Jeff

[1972_911T]

Ok thanks for that as far as im aware all 3.2's use nikasil's dont they? so if I change the rings and keep original pistons should I have the cylinders honed?

Steve

[garibaldi]

If you only do the top end- meaning just the heads, having them clened up, flttened, replace the guides and seals, rebuild or use new valves and have the seats cut or ground, then you are going to find that the motor is going to use even more oil then previously since the top end is going to be sealing up much more tightly, and it will pull more oil past the worn and tired rings. Everything wore in together before the rebuild, so renewing one part and not the other in this case may cause you to still have an oiling issue.

[JeremyD]

Originally posted by 1972_911T
Ok thanks for that as far as im aware all 3.2's use nikasil's dont they? so if I change the rings and keep original pistons should I have the cylinders honed?

Steve

I think you'll need to measure them first. 140k is alot of miles - if they are in spec - really depends how the other owner did with oil changes and upkeepthen either hone them or one of the home remedies...

The good news is there are lots of options with a top end. you can replace with euro P & C's - bump to a 3.4 - get your existing bored out and go with JE's...

[vichang4]

I agree 100% with garibaldi. A 140K engine that is burning oil probably has many worn parts. And just because it runs good does NOT mean the rings aren't shot. A engine can pull very well with broken rings, it just burns alot of oil. You need to measure the pistons and cylinders and make sure they are still in spec. IF the previous owner was good with the oil changes, they should be. I would change the rings at 140K.
Also, what about the rod bearings? If you've got the engine down to the case you should change the rod bearings and rod bolts. You may want to upgrade to the ARP rod bolts.
What about the main bearings?

[Rot 911]

You won't know what you have without doing at least a compression and leakdown test. And yes you can use LOTS of oil without having worn rings. For example my 3.2 with 133,000 miles was using a quart of oil every 300 miles but was not smoking even on decelleration. Turns out I had some seriously worn valve guides. I decided to do a complete engine rebuild myself. However, turns out that with the exception of the valve guides and valves everything else was way within spec! Course I had already split the cases so I said what the hell and rebuilt the engine anyway.

[1972_911T]

The guy im buying the engine off had compression tested the engine, his figures were all with 6% of each other and averaged around the 199psi mark is this ok for a 3.2?

[JeremyD]

The 6% is good - but it just means that all the parts have worn consistently from cylinder to cylinder.

[1972_911T]

Kurt what was the condition of your valves had just the guides worn badly or did you have to replace some/all your valves as well?

[kühn tune]

I had the same experience as Kurt. Although I wasn't using as much oil, I had to replace all of my exhaust valves.

[JeremyD]

I replaced all my exhaust valves - 6 valves - 57000 miles - 600-700 miles per qt. EBS also said my valve guides were "very worn" and the valve springs were "sprung"

[1972_911T]

Are the replacement valve guides been upgraded or do they still have the same problem as the originals and wear out prematurly? I read somwhere that it was beacuse the valve stem seals were too good initially and didnt allow enough lubrication to the valves!

Steve

[JeremyD]

Steve -the replacements are much better quality.but there are a lot of speculation on why some engines have the problem and some don't.

[Jeff Alton]

I rebuilt a 140 mile 3.2 a few months ago that was using 1 liter every 200 miles. Guides shot, needed one exhuast valve. Just finished a 70 mile 3.0 Guides shot, needed 6 intakes and 1 exhuast. Last spring when I did my 3.2, it had worn guides and did not need any valves it had 120 at the time. You just never know until it is apart!

Jeff

[Rot 911]

Originally posted by 1972_911T
Kurt what was the condition of your valves had just the guides worn badly or did you have to replace some/all your valves as well?

I literally dodged the bullet:



but here is what the cylinders looked like (still have the factory hone marks):

[1972_911T]

Ok I guess im just going to have to bite the bullet and get it stripped. is it possible to asses the bottom end without stripping? I would profer not to split the case if at all possible.

Steve

[Rot 911]

Originally posted by 1972_911T
Ok I guess im just going to have to bite the bullet and get it stripped. is it possible to asses the bottom end without stripping? I would profer not to split the case if at all possible.
Steve

I would first do a leakdown test before I tore into the engine. How much oil was the engine using. Oh and how much does the seller want for the engine?

[1972_911T]

its using about 0.8 of a litre per 1000km no really obvious smoke when warm just a little when you blip the throttle, and hes asking for 2.5k for the engine which seems resonable as breakers in the UK are asking for 4k plus you cannot see them running and dont know that they are any better!

[Bill Verburg]

Originally posted by 1972_911T
Ok I guess im just going to have to bite the bullet and get it stripped. is it possible to asses the bottom end without stripping? I would profer not to split the case if at all possible.

Steve

No, and it's not that much more work, i jave heard several "cought it just in time stories". Do it righttake it to the crank and use the opportunity to update rod bolts, you will sleep better.