marc abrams

Your probably right. I'll wait a bit longer to check.

Humboldtgrin

It should, it has more power. Also is the Chrysler an interference engine? I don't think it is. That would be a MAJOR factor!!!!

odonnell

Out of curiosity, how does power play into timing belt life? Yeah the crank can exert more force on the belt, but even a 5hp motor could probably strip teeth on a belt under the right conditions. I asked RL about timing belt stress a few months ago and these are the replies.

JustinL

I think the hype is overblown. IMHO most broken belts are due to another primary factor like a seized roller, improper installation or being mistensioned.

Humboldtgrin

The right conditions being an old belt? Or sucked in a spark plug? The resistance in the valve train also plays affect. It all added up. Big four cylinder engine, lots of crank torque and valve train resistance adds to lessening the life of a timing belt. And on a interference engine that cost a LOT, it worth changing out frequently. It's like pulling the timing belt teeth one way it's whole life cycle. After a while the teeth don't play anymore. That's not even mentioning oil leaks that can saturate the timing belt that the 944 seem to have because some people don't change out the front sleeves with the seals.

Jay Wellwood

Heat in the area also plays an important factor as well I think in belt longevity.

Humboldtgrin

On start up and sitting at curb idle is where it puts most of the stress on the belt on a four cylinder. Along with all the other mentions. In the end just change your belt on these 944 cars at three years or 45k. Also I have an 87 DOHC 944 and the intake cam started to seize to the head creating to much resistance for the chain, it broke and bent intake valves, but the belt was fine because it was new. So there's always mechanical issues on these cars to look at as well, as mentioned the rollers could be seized also creating major issues. Or water pump seized. But if all is working fine the biggest factor is its a four cylinder engine and at idle and start up it puts a lot of load on the belt due to the RPM difference at idle constantly wearing at the belt. A v6 or v8 won't see that RPM change like the four cylinder will so they will have much less stress after start up.

porscharu

You could clarify by saying inline four cylinder. EJ255/257 subaru engines are boxer fours, interference, and four cam gears (VVT) with a 100k mile timing belt interval.

Butters944

I agree its overhyped mainly on the tension specs. From what I've seen, the belts are pretty lenient on tension as long as they're meeting about a 90* twist. I think people often overtighten because they seem relatively loose when theyre at correct tension. Loose enough that one could slip the belt off and on the cam sprocket by hand (tried this recently) without de-tensioning.

V2Rocket

Butters...
you should not be able to pull the belt off the gear if it is at the right tension.
it should be very stuck on there until the tensioner is fully relaxed...
the timing belt should just barely be able to twist 90* by finger strength, the balance belt 180*.

Humboldtgrin

Key word: DOHC and 30 years better belt design= less stress on the belt because weaker valve spring pressure and smaller valves and different engine design and less aggressive cam. A 968 is every 60k miles, I'm sure the 944S and S2 could get away with 60k also. I'm thinking Porsche has a little more confidence with the less valve spring pressure and smaller multiple valves. If you have a SOHC and use and aggressive cam with bigger valves and 160# springs making the RPM's more erratic at idle that would put more stress on the belt, I would change it more often then.

marc abrams

I think it's all perception. When a 944 newbe comes along and he's told to "change the belts because 944s are known to break belts and bend vavles" l think a better to praise would be "as with all interference engine's you should do the belts and roller's every 3 year's or 45000 miles". I believe that's it's the timing belt issue that keeps the 944 from reaching the status it deserves.

marc abrams

I don't know if that DOHC theory hold's water. The roller cam probably has done alot to extend belt replacement frequency.

Humboldtgrin

When a newbie comes along he's told to change his fuel lines and read Clarks garage web page.

odurandina

the number of death cards drawn is truly damning.....

to date, we've had over 1600 timing belt failures separate from 800+ complete engine failures. here on the forums...

also: 22,000+++ no starts usually leading to junked 944s.

go back 6 years and look at the avatars.

yep, they're all dead sir.

nobody gives up their 944s unless you pry them from their cold dead hands. RTFM

look on the bright side.....

you can still blast Stevie's pretty voice over the stereo paid for with help from blowing off the scheduled re-tension.......

www.youtube.com/watch?v=U_aYibUx1B8