Outback H6 Aluminum Crankshaft

In my humble opinion, the timing chain is a good thing.

I have never in my life heard of an AL crankshaft in *any* internal combustion engine. I would have to seriously doubt the veracity of this data. Find me a link.

There's really nothing wrong with either one. I'd just give a chain a slight preference over a belt because the chain does not have a changeout schedule.

As the the crankshaft, I'm guessing they meant crankcase.

Aluminum crank pulley maybe? but then, not with a timing *chain*... Which, by the way isn't infallible either. Plus, it adds mass, sort of like a flywheel. Isn't that why they put a timing *belt* into the Lamborghini Diablo?

florian

Not just that, but it adds to engine noise as well. True, chains are not indestructible. The Nissan Sentra 4cyl. models have a chain that goes out around 100k. My mechanic said labor for timing chain on that model is 13 hours. Motor swap is only 7.........

Henry

Aluminum crankshaft? Not saying it's not possible, but I've never seen or heard of one. Sounds like a recipe for short life if true. Cranks experience a lot of flex, and aluminum's not the best material for that type of app. Aluminum "crankcase" as someone suggested sounds more like it.

On timing chains--properly designed and lubricated, chains should be much longer lived than belts. Poorly designed (particularly in the lubrication department) they'll fail early like the Nissan example. BTW,

100k on a chain is absolutely criminal in my book--they should be good for double that or more. Sounds like a lube problem?

Subaru's timing belt life has always seemed a bit short to me, but my first experience with timing belts, on the first water-cooled VWs, might have spoiled me. ISTR seeing something about steel cord in the original VW belts. I only know there wasn't a recommended change interval in the book at the time, and I got 190k miles on one of mine. Even if I had to change a belt, it was only a 30 minute job, not the exercise my Subie belts are. My guess is Subie went with a chain on the H6 cuz of the longevity issue?

Rick

Well, I hadn't either; I have misread the specs at

which say aluminumcrankcase not crankshaft. My apologies, I'll double check next time. Gregg

I'm just speculating here.

If you look at the front of the H6, you can see that they were able to shave at least an inch, maybe 2 off of the overall length of the engine by going to a chain. I suspect that this was a *big deal* to get the engine to fit. They would have probably had to use a wider belt to handle the load of 2 extra cylinders. I suspect that when they looked at the big picture of shortening the engine, removing the scheduled replacement and loosing 4 potentially leaky camshaft seals the chain started to look pretty good.

Well, in defense of Subaru there are models with shall we say whimpier timing belts. My brother has a '96 Hyundai and the change interval on those is 60,000 miles mandatory. They can break within 10,000 or so of that limit and bend the valves from here to never. I looked at one once that needed and engine because of that very issue. I called a dealer service department to see what was involved and he gave me the rundown on it.

So, 105k on a Subie looks better to me. In fact, my dad just got a '95 Impreza with 150k and no belt change yet. I plan on doing that one this weekend.

Henry

The H-6 uses TWO chains, slightly offset. Passenger side driven directly by the crank, Driver's side from an idler pulley driven from the passenger side chain.

To some of the other posts I'll add this:

1 - The chain definitely was a factor in reducing the length of the engine. 2 - The chains are designed to last the life of the engine, given that proper engine oil maintenance happens. 3 - Their are 59 (!) bolts of four different lengths that attach the front chain cover to the rear. It indeed would be a big job to replace the chains. Of more concern would be any water pump/oil pump maintenance that might need to occur. Though it looks as if only the RH chain would need to be loosened (?) to get the pump out, I would dread removing all of those bolts and getting them back in the right spots. 4 - There are oil ports that spray engine oil directly on each chain to ensure it receives the proper lubrication. 5 - The LH chain has 148 links, the RH 134. 6 - The oil pump is driven from the RH chain, as is the water pump 7 - I don't know how the noise will work out in the long run, but I know the cases were designed to minimize chain noise. I haven't notices any difference from the belt driving cams. 8 - Overall, I would not feel very comfortable doing a chain replacement... I've had no problems doing belt replacements. I'm counting on the long life, and believe that will be the case as with all-things-Subaru. John

I hope the water pump doesn't leak into the oil if it fails. That's an awful lot of labor should one of the pumps fail. Has anyone actually had a water pump fail on a Subaru? I am going to replace mine when I do my timing belt.

Henry

replacement...

Henry, You are right; I guess it would be possible to get water into the oil... not good. I have never had a water pump go out (a PS pump, but not water pump). However, I did replace one when I had the opportunity during a timing belt change. John

Develop a slight leak? Yes. Outright fail (bearing seizure, impeller lets go with fan digging into radiator type stuff)? No.

Rick