Why aren't more cars fitted with non-interference engines?

[Twincam16]

Chains can do serious damage if they break. IIRC the Porsche 928's V8 is a non-interference engine, but its timing chains, if they break, can whirl around smashing the timing gear to pieces, resulting in a big bill regardless of whether or not the valves have hit the pistons.

[Dracoro]

kambites said:

mmm-five said:

Yes, a tensioner failure will let the chain jump a tooth and can cause engine damage - that's why you'd check the tensioner & tensioner rails every 20,000 miles or so to ensure they're still up to the job, or get them replaced. If you don't then I've got no sympathy when it fails. Even if you spend the £100 every 3-5 years to replace it as a precaution it's surely worth it. I've only needed one tensioner in 8 years as the diaphragm was leaking.

My (belt) tensioner failures were both newish tensioners. I had the Corrado's belts done and about 4k miles later the tensioner went. Had it (and the belt) replaced again and it went again. Dodgy batch of components maybe? Dunno. Neither time did any damage, just made the engine sound like a diesel.

I assume you don't have a VR6 tho as that has timing chain.

[kambites]

Dracoro said:

I assume you don't have a VR6 tho as that has timing chain.

Correct, it was a 1.8 16v. Same engine as the Mk2 Golf GTi I believe.

My MGB has a timing chain which is still going strong after about 160k miles though.

Edited by kambites on Monday 16th June 09:52

[thinfourth2]

Munter said:

kambites said:

herewego said:

Pistons don't have to be flat on top. I would have thought a designer could cut a bit away for the valve and add a bit elsewhere to maintain the volume.

I believe that pistons are generally designed to rotate in their bores to make sure that they wear evenly so you'd have to make any cut-out symetrical.

rotating pistons! I think not.

Actually you do get rotating pistons


http://www.marinediesels.info/4_stroke_engine_part...

[kambites]

thinfourth2 said:

Actually you do get rotating pistons


http://www.marinediesels.info/4_stroke_engine_part...

Woohoo, my stupidity was quite so stupid after all!

[kambites]

Just realised that my engine has valve cut-outs in the piston face too.

[thinfourth2]

kambites said:

thinfourth2 said:

Actually you do get rotating pistons


http://www.marinediesels.info/4_stroke_engine_part...

Woohoo, my stupidity was quite so stupid after all!

Well in car engines it was only slightly stupid

But i shall quote the above for the enjoyment of others

[Mr Whippy]

I've had an engine with a chain go, and an engine with a belt go.

Both break.

What you want is a gear train

Or push rods, if they snap the valves should come fully closed.

All in though, the costs vs the benefits just don't weigh up. Belts are great, just maintain them

Dave

[funwithrevs]

Switch to jet engine power?

Then we can all pretend we are Batman.