Timing Belt Question

mpertz · Post by **mpertz** » May 10th, 2005, 8:18 am

I have a MX3 GS and the car has been stoped for about 6 months. When I went to start it not long ago it would not start. I changed all the spark plugs and put new gas. The car finally started after a lil work and was idle for about 2 mins till the timing belt snaped. The car was idle and was not moving when the timing belt snaped, is it possible that the valves still bent even though the car was idle??

The car has 270,000 KM on it. I'm not sure if I should just change the engine to a klze insted of tryin to fix it.

If anyone can help me id appriciate it.

bmwm3guy · Post by **bmwm3guy** » May 10th, 2005, 8:26 am

the K8 is a non-interference engine... meaning that the valves will not be affected by a timing belt snap. Just pull the old one off and put a new one on and you're good to go.

T4TURBO · Post by **T4TURBO** » May 10th, 2005, 12:03 pm

is that the case with the klde?

bmwm3guy · Post by **bmwm3guy** » May 10th, 2005, 12:55 pm

yes sir as far as I know all K series motors (I dunno about the KJ) are non interference.

ManoWar · Post by **ManoWar** » May 10th, 2005, 1:00 pm

bmwm3guy wrote:the K8 is a non-interference engine... meaning that the valves will not be affected by a timing belt snap. Just pull the old one off and put a new one on and you're good to go.

You sure someone told me that due to the angle of the pistons it might hit the valves. Also what would happen (if indeed its non interfeering) if it snaps at 5000rpm?

wyldside · Post by **wyldside** » May 10th, 2005, 1:09 pm

At that RPM nothing will be damaged but there will most definitly be one hell of a terrible noise. The engine will emidiately quit since the cams will stop turning therefor no more sparking from the distributor and fuel from the injectors. The ECU would not be getting propper signal either since the distributor is no longer turning. You'd simply come to a rolling stop. It's not something that I would want to experience but that is generally what will happen. Make sure you set the timing correctly when you reinstall that belt.

Rick Johnson · Post by **Rick Johnson** » May 10th, 2005, 1:09 pm

Non-interference means non-interference, it doesn't matter if it snaps at 700 rpm or 7000rpm.

Nd4SpdSe · Post by **Nd4SpdSe** » May 10th, 2005, 1:10 pm

Why would it make a difference? The timming belt is just to syncronise the valves with the strokes of the pistons, so when the belt snaps, they just get out of sync, but nothing hits, besides, he valves are designed to 7000+ RPMs (hence the engine's redline), so nothing will happen, the car will just stall

My sister learned the hard way when her timing belt snaped on her '93 2.3L Prelude, bent 10 valves. My dad and my cousin hook it apart and put it back together, and apparently, my dad said, that where are grooves in the pistons for the valves, i guess the clearance is that small on her engine.

bmwm3guy · Post by **bmwm3guy** » May 10th, 2005, 3:25 pm

Rick Johnson wrote:Non-interference means non-interference, it doesn't matter if it snaps at 700 rpm or 7000rpm.

Snapping it at 7 grand is scary

haha That was my K8's last revolution.

RIP

Post by **Custommx3** » May 10th, 2005, 4:26 pm

did u know that according to the SAE cheets of the K series design, they ran a KL @ a steady 8900 RPM w/ o out any problems (they said with slight modifications but i dont know what the mods were).

Tunes67 · Post by **Tunes67** » May 10th, 2005, 4:29 pm

Probably just a minor adjustment to the valve train to offset valve float at the higher RPMS'.. but thats just speculation.

Tunes67

Gro Harlem · Post by **Gro Harlem** » May 10th, 2005, 5:29 pm

snapping belts is still not good for the engine, but at least you won't have a piston fly into your cylinder head

jschrauwen · Post by **jschrauwen** » May 10th, 2005, 5:42 pm

Tunes67 wrote:Probably just a minor adjustment to the valve train to offset valve float at the higher RPMS'.. but thats just speculation. Tunes67

Stronger return springs you mean.

Had the timing belt on a one year old (dare I say it) MPV jump a bunch of teeth on engine start in the dead of winter and again non-interfearance on that 3.0L V6 = nothing hit or broke.

Rick Johnson · Post by **Rick Johnson** » May 10th, 2005, 5:57 pm

Custommx3 wrote:did u know that according to the SAE cheets of the K series design, they ran a KL @ a steady 8900 RPM w/ o out any problems (they said with slight modifications but i dont know what the mods were).

I don't doubt that at all, and if you think about it, the K8 has even smaller pistons so it should be able to rev even higher...

anyone know how to remove the rev limiter, I'm trying to blow my motor up.... I might as well see what 8000rpms plus nitrous does.

Tunes67 · Post by **Tunes67** » May 10th, 2005, 6:07 pm

Actually John.. there are a number of things that can be done to adjust for and prevent valve float.. Stronger valve springs are indeed one adjustment.. Solid lifters, shims (under the valve spring thus raising the deck height - results in stronger springs), less aggressive cam profiles.. rocker arm / cam follower assemblies (non-mx-3 applications) lots of adjustments can be made to prevent valve float

Sometimes it requires more than just one adjustment as well.. might need a combination of adjustments to get the RPM range you are shooting for. Cheers.

Tunes67