George D

My intention in this post is to have a discussion on the merits of sleeving vs not in large (3.0 -3.2) 951 motors.

I am NOT an engineer or a very good wrencher. I have great tools and have done many things to my cars on my own, but I could never make a decent living out of my hobby.

I'm in a position to build a 3.0 + motor for my 89 951. My shop of choice can do either motor for me. Ijust read a horror story about one of our listers with a new 3.1 that required rebuilding after 500 miles! This scares me and am simply looking to see if this was a one of a kind situation, or am I going in the wrong direction with my build using sleeves vs a stock 3.0 block, 2.7 head, and associated parts.

I'm looking for real world experience with those of you who have experience in what I am about to do with my motor. This is an EXPENSIVE project and I don't want to make the wrong decision. A discussion about this would be helpful to me and I hope others on the list.

Thanks for the input.

George

2bridges

I would suggest consultation with Chris White. http://www.944enhancement.com/index.html

He is a builder that has done many any would have the real world results and experience.

DDP

You must remember that there's more then one way to sleeve a motor.

hosrom_951

If you want 3.0+ sleeved or not, you need the 104mm bore block (off the 2.7L NA, or S2/968 block) as the base.

lejams

George, I have an 89 and I am going to build a 3.0 for it. I have decided to use a 3.0 block with new 104.5 bores using Mahle pistons instead of sleeving. Whether you sleeve or not, IMO hosrom is right, the three liter block is the better way to go. Why sleeve if you don't have to? Yes the Mahle 104.5 pistons are few left and expensive....

I will take my 2.5 head and modify for the water jacket and am considering having Lindsey do Stg. III work.

lejams

Tell us more about the 3.1 failure

evil 944t

[QUOTE=lejams] Why sleeve if you don't have to? Yes the Mahle 104.5 pistons are few left and expensive....QUOTE]

Good advise Jim! You can also get away with larger coated pistons in the stock bore. If your concerned with cylinder movement, you can always install a deck plate.

It would be almost to your advantage to get away from the Mahle design and step up into a more modern age piston design. There are lighter pistons out there that are far more affordable.

It would be better to start with a 3.0ltr block. It is far stronger than a 2.5ltr block bored out to except 3+ltr sleeves.

There is nothing wrong with sleeving. It just has to be done right. That goes for both "wet" and "dry" sleeves. I just haven't heard of to many "wet" sleeved motors running so I can't comment.

hosrom_951

But if a bore get's scored on the factory block, all cylinders would need to be bored to the next size, depending on availabilty of pistons.

On sleeved blocks, just that scored/damaged cylinder get's a new sleeve/piston.

Chris White

First – I will pass on making any comments on the 3.1 ‘failure’ for two reasons – one) the final cause has not been documented yet and two) I didn’t build it.
As for failures on sleeved motors (dry or wet) - if you don’t machine and assemble them right they will fail – but this applies to any engine! I feel the sleeved engines are stronger, more dimensionally stable and a hell of a lot more resistant to internal damage than the Alusil engines.
If you use the MID sleeves there is not a lot of difference between the 2.5 and 3.0 blocks. The 3.0 has a slight edge in strength and you can go out to 106mm vs 104mm. But then you have to deal with the different cooling passage – you have to use a 2.7 head or a modified 2.5 head to fit the 3.0 block.
To wrap it up – any engine can fail if not assembled correctly or if the engine management system is off – how many failed alusil engines have we heard off? So lets not make too many blanket assumptions on any process.

lejams

Chris you are absolutely correct to say about any engine that poor assembly, tuning... can cause failure. But the Alusil failures that most of us know all to well, have nothing to do with Alusil in itself, but rather either poor build quality, poor tuning, running excessive boost without proper fuel leading to detonation... Alusil in itself has been time proven and the failures in Alusil blocks are solely our failures. I think it's fair to say that all things being equal in build, tuning, fuel, etc., Alusil works very well and is as reliable compared to any sleeved engine with some rather minor exceptions; sleeves are more damage tolerant but not indestructible, many more piston options are available, and you can bore larger, (none the less, I think I'll be pretty I'll be happy with only 3.0 :-))) Really probably depends on what your goals are. Mine is primarily a street car and little track. Regarding the water passage on 2.5 head on a 3.0, this seems to be a trivial $ fix to accommodate the 3.0 block. I know the deck option is there, but all in all, personally I just feel more comfortable going OEM 3.0 block, Alusil bores with an integrated deck. In some ways maybe this discussion gets to splitting hairs on the advantage and disadvantages. One thing I'm curious about, other than your personal cars, what is the longest mileage MID sleeve engine running out there? Like so many things being done with the 951's, longevity is still an ongoing question which is another reason I opted for the route I'm on. Other than the mods like turbo, injectors, chips, I want to stay as close to OEM as possible and then try not to exceed it's limits. This is what I think happens allot with the 2.5 block.

anders44

all engines blow up.

I've blown both my offshore boats numerous times, my previous car etc.. only one that is stock and reliable was the camry and the dodge

hopefully the 944 won't blowup at least until end of season.

as for tuning, I've owned a few different brands and such, and the 944 world seems stuck in "chip tune" world. that's not a good thing. when changeing injectors, turbo +++ I just don't like the idea.

evil 944t

[QUOTE=anders44]all engines blow up. QUOTE]

Is that a joke? My street car was used pretty hard at times and it went 200k. It could still be going. I'm not sure because I sold it..

Bri Bro

I think the point was that no engine is built so tough that it can't blow up. Offshore racing is a hard test on an engine. I have had several cars go over the 200K mark. But I never raced them.

evil 944t

I agree Off shore motors have a very rough life. I understand but, you can build a motor for 200k+ street miles, a 4 sec run or the 24hrs of Le mans. Pick your poison. When built right and used properly, they should not blow up. Lets keep it apples to apples.. is all I'm saying.

Bri Bro

1+