Extra!! Extra!! SVX Cam belt survives Arthur!!

[McTaff]

Originally Posted by pylon500

For those that are interested, with most (if not all) Subaru engines, if you lose a cam belt, it does not automatically destroy the engine like most other cars.
It just stops.
Interestingly enough, if your belt jumps a tooth or so, it will actually keep running!
I discovered this in my haste to reassemble my engine and not noticing that my belt had moved THREE teeth on one side, and FOUR on the other, yet it actually started!!

The 'floppy' belt does go away after the engine heats up, but I'm still autious.
I guess I'll have a better idea by the end of the week.

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General info on the subject for people: The SVX has recessed valves, which means even if the exhaust or inlet valves are at 'maximum open' and the belt stops/jumps/is lost, the cylinder head can come up to TDC and still be clear of the valve... even at hotter than normal temps.

Most cars do not have this feature. A slipped or lost cam belt usually resulted with the cylinder head flying up the cylinder at high speed and meeting a set of valves in the open position (trumpet heads down inside the cylinder).

This results in an impact of a stationary body with another with an extremely high inertia and kenetic energy value. This can result in some spectactular (read: catastrophic) engine failures. Bent or broken valves, rocker covers forcibly removed by the shock, damaged cylinder heads or even rarer (even though it is pretty awesome) a broken con-rod exiting the side of the cylinder at high speed. These usually result in total engine replacement, or complete and brutally expensive overhauls.

Another one of the reasons why the boys at FHI get my vote.
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You are right, the engine will still run if you have 'jumped' teeth, but I'd like to know how badly it will run - and if the EMS knows something is up? Or will it refuse to start?

So what exactly happened when you fired it up?

[oab_au]

Originally Posted by McTaff

==============================
General info on the subject for people: The SVX has recessed valves, which means even if the exhaust or inlet valves are at 'maximum open' and the belt stops/jumps/is lost, the cylinder head can come up to TDC and still be clear of the valve... even at hotter than normal temps.

Most cars do not have this feature. A slipped or lost cam belt usually resulted with the cylinder head (I think that would be the piston)flying up the cylinder at high speed and meeting a set of valves in the open position (trumpet heads down inside the cylinder).

This results in an impact of a stationary body with another with an extremely high inertia and kenetic energy value. This can result in some spectactular (read: catastrophic) engine failures. Bent or broken valves, rocker covers forcibly removed by the shock, damaged cylinder heads or even rarer (even though it is pretty awesome) a broken con-rod exiting the side of the cylinder at high speed. These usually result in total engine replacement, or complete and brutally expensive overhauls.

Another one of the reasons why the boys at FHI get my vote.
==============================

You are right, the engine will still run if you have 'jumped' teeth, but I'd like to know how badly it will run - and if the EMS knows something is up? Or will it refuse to start?

So what exactly happened when you fired it up?

(Fixed your post),,,,,Also unlike the WRXs twin cams, the EG33 cams are geared together, so they can't get tangled if the belt breaks.

Harvey.

[McTaff]

Originally Posted by oab_au

(Fixed your post),,,,,Also unlike the WRXs twin cams, the EG33 cams are geared together, so they can't get tangled if the belt breaks.

Harvey.

Thank you!

You are correct. My bad.

[pylon500]

Hey, someone does read my posts!

So what exactly happened when you fired it up?

I don't know if it was relevant, but I had run the SVX up onto some ramps for access so when I went to start it three days later, initially it just fired a couple of times, so I immediately suspected miss timing and shut down.
The next day I got to thinking that maybe it was just starved of fuel from being up at a funny angle, so switched on, pumped the gas a bit, hit start and pumped the gas again and it started and ran.
It was very rough, but oddly enough the CE light did not come on?
This is actually part of another problem, ALL my dash lights have taken to coming on at various times, and at varying intensities, until I hit a bump, then they go out again. Yeah, it's a loose connecter somewhere, but I just haven't had the drive to get to it! I only fixed the pump because I need it to get to work.
I'm hoping to chase up a belt tensioner on Friday as I think mine has died.
I thought at first the engine may have jumped a tooth with the loose belt, but after it warms up, the tensioner seems to come back on line and all goes SVX quite again.
Fingers still crossed for Sunday, hey Jason, will try to have a look for a UHF CB!, my old ones are VHF (around 27 megs)
Arthur.

[McTaff]

Originally Posted by pylon500

Hey, someone does read my posts!

....

It was very rough, but oddly enough the CE light did not come on?

This is actually part of another problem, ALL my dash lights have taken to coming on at various times, and at varying intensities, until I hit a bump, then they go out again. Yeah, it's a loose connecter somewhere, but I just haven't had the drive to get to it! I only fixed the pump because I need it to get to work.

Arthur.

I'm surprised it ran. But I'm curious as to why it didn't flick a warning light on. You'd think it would've worked out something was wrong

As for the lights flashing on - I myself had that problem once. Drove me mad for a year or so, then it just stopped doing it.

Related note: About the time it fixed itself, my cruise control switch began to be a bit indecisive... When I switch the cruise on, the light inside the cruise control switch will light up for a split second, then as I'm letting the buton go, it will switch off again... almost like it doesn't want to switch on. After I hit it a few times, it stays on.

I'm sure this is just a dodgy switch - and both the SVX's do exactly the same thing. So if you work out which connector it is, let us know - and if you are fooling around wih the dash at any time, make sure you clean your cruise control switch up and make sure this don't happen to you. (My main theory is that the switch will travel too far back on it's slider, maybe fooling into thinking it is being pressed twice? Not sure because the light doesn't go off again as it hits the end of its travel... anyway I'll shut up now.)

[pylon500]

cruise control switch began to be a bit indecisive

This is interesting as my cruise control switch does the same thing! although the light in the switch has never worked.
Sometimes I think that the computer gets confused if I select master cruise while driving, but don't de-select before turning off the motor? (I know it's only a momentary switch to promp an action memory in the computer that is then lost when the engine is switched off, but I often get the feeling that there is a kind of decision making process going on in the computers that doesn't always agree with what I want it to do!)
As such I too have to cycle the switch a few times to get cruise control on line.

I had a bit of a wiggle under the dash on Friday, and all the lights went out!
But when I started it on Saturday, they came back on again.
Even as an engineering mechanic, (and should know better) I still find that sometimes my mechanical (and electrical) problems will seem to cure themselves? hums tune to 'Twilight zone' to self...do-de-do-dah, do-de-do-dah....
Is some-one trying to haunt me?
Arthur
By the time you read this, we should have had the drive! and I should be in bed!!(11:40)