Are there any 'everyday' cars without cambelts or with a 'non-interference' engine design?

The thread drifted to: "But are there any pushrod designs left?"

These days there isn't a spanner gap between inner wing and timing cover of a FWD I4. Over 40 years ago BMC/BL got an I6 in the FWD ADO17 2200 "Landcrab" and ADO 71 Princess. ADO17 had a front track width of 1422mm and ADO71 1473mm. Current FWD cars have over 100mm more front track but still have no engine clearance. Passat front track is 1553mm.

Variable phasing gubbins fails on a lot of them. Doesn't damage the engine but it makes some noise.

You don't need a pushrod OHV to have non interference. Non interference OHC engine.

Due to the noise and poor life (less than forever) Rolls-Royce wouldn't countenance a chain on I6 or V8, they had gear cam drive.

Honda had to fit gear drive to V4 DOHC VFR750/800 due to the inverted HiVo chain having serious issues on VR750. Caused by same design issues as Honda CB250/350K4 broke cam in half, CB250/360G5, CJ250/360 snapped end off tensioner blade if revved to 10K (9.5K redline, found 6 in the sump) and CX500 twins sheared tensioner blade bolt. The belt drive Pan-European V4 didn't have these issues as the belt can take the cam drive shock loads. Plastic sprockets can't take the impact loads, not even on I4 and possibly not a 6.

Rolls-Royce had a cam damper on I6. Put another 6 bumps on the cam in addition the 12 that it had for the valves. "cam balancer was incorporated to eliminate rattles of the five gears at the front of the engine (Fig. 13)."

Think you'll find that was only earlier versions of their V8. And a decent chain is likely to last as longs as the cam and followers anyway.

A chain chain last a forever, my previous Saab sold at 280,000 no problemo

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I've corrected your post for you ;-)

The timing chain on any BMC et al 'A' series lump would be lucky to not need replacing before 50k miles. Admittedly that was a lousy design, but a chain nonetheless.

More recently, VW designed a V6 with the cam-chain drive in between the engine and box. The chain would be absolutely shot by 100k, and replacement meant pulling engine and box from the vehicle, then separating them. Additionally, the engine sprocket was machined directly on the crankshaft, and was usually found to be knackered when the chain was being replaced. Older vehicles would be beyond economic repair at that point.

From an engineering POV, a properly designed belt driven camshaft is preferable, and can easily outlast the average life of the vehicle. They only got a bad press because of penny-pinching earlier designs, and the failure of owners to replace them at correct intervals.

Chris

You replaced it because it broke - or just got noisy? I've had lots of A series engined vehicles over the years and never had a failure. Noisy, yes. But usually drowned out by the tappets. ;-)

Plenty of badly designed chain drives around.

The correct interval being the vehicle lifetime? ;-)

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I was referencing 'A' series generally; I used to look after a number of them for others. Never had a failure as in one breaking, but they would idle badly and lack normal power when the chain wore. It was really down to there being no tensioner in the design.

I had a frantic call from a work-colleague once saying his Moggy wasn't running properly, and he was due to go on holiday in a few days time. I collected it, and it was on three cylinders, with terrible top end noise and little power. Popping the rocker cover off revealed the valve clearances had opened due to wear so much that a push-rod had become disengaged! I adjusted all the clearances; the adjusters were near the end of their threads, so the valves could have hardly been opening. I advised him not to use it, but he went on holiday anyway, and said it was the best it had run in ages!

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I did say *can* :-)

Chris

It seems to reason that a steel chain is more durable than a belt made of rubber like material ;-)

cam belts are very much more complicated, even very old V belts have mutiple cores of strong string like stuff, serpentine belts have incredibly fine steel rope inside, cam belts are amazingly tough and they rarely actually break, loss of tension is the usual problem. in the old days loss of teeth due to age and contamination was common (think Pinto lumps) but that doesn't seem to happen now.

Only because you mentioned an Australian design.

At least with the Pinto you could change the belt by the side of road if it broke the reason i know this is i went out to buy a new belt to fit and the old one broke half way home

But think really long term e.g 25 years. Rubber like material seem to deteriorate with age.

I answered the question: "But are there any pushrod designs left?" note the word 'any'

On the road was less common. Pinto ones often went at home, first start of the day when the oil was thick, the extra force needed for the belt driven oil pump took the teeth off the belt at the crank pulley. I have changed the early 2 litre ones with minimal tools at the roadside, later ones needed a puller for the multi belt crank pulley, which was not really a toolbox item. 1600 pintos bent the valves, but at least they were easy and affordable to fix. Most ordinary cars are now not economic to fix if the belt goes.

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Are you sure about that? I thought it was the 2-litre engine that was interference.

My 1.6 Pinto-engined Transit stripped its belt when pulling away at a set of traffic lights when away from home, and a local garage towed it in and replaced the belt all within two hours!

Chris

Definitely sure. I changed literally dozens of failed 2 litres without any bent valves, while 1600s usually bent them. The engine was made with low or high compression, the Transit would have had low compression and more room for valve to piston clearance, hence your one missing. Cortinas (the most common fitting that I had dealings with) had the high compression version and often had bent the valves (usually only a couple) so it may have been a bad luck thing too !

[...]

Ah OK. Understood.

Chris

Ford claim cam belt in oil on Ecotec 1L triple is "for life". I suspect there is a substantial gap between the public's definition of "for life" and Ford's.

Does that mean that like the Zetec 1.25L didn't have O/S bearings they won't be stocking spare cam belts?

IIRC the 1.25 zetec is a Japanese engine (Yamaha iirc), in general it is hard to find and very expensive to get a crank regrind to Japanese oem specs. so probably it was not worth making different thickness crank bearings, just sell a new crank with std bearings, while replacement belts would always be standard size and available for new engines and rebuilds. I used to run a Suzuki Motorcycle main agency, and when the 650/4 engine came out it had a plain bearing crank, we only ever sold one, and that bike had 200k on the engine and was used as a courier bike all its life, so probably the incidence of needing crank regrinds was so low that alternate shells were just a waste of time and money.