I figure I may as well ask this as I am curious.

I have the B234F 16 Valve engine. I already know that this is an interference engine. Saying that, I was talking with a local Volvo guy one day and I brought up the B234F. What he said about the engine sparked me to ask this question.

He said that the B234F in stock form is "BARELY" an interference engine. He went on to say that it is barely one because the valve to piston collision is VERY minimal, and at the most may cause slightly bent valves and possibly damaged valve seats, unlike many other engines that will simply grenade when a belt snaps (IE broken valves, damaged pistons, cylinder walls, damaged head, etc. (Like what would happen with my Catera.))

My question is, Is this true or is he blowing smoke up my butt? I am just wondering what I am looking forward to in case my belt happens to snap. It shouldn't as it was replaced at 145k exactly one year ago along with the balance shaft belt.

 

Well, barely interference is like a girl barely being pregnant. It costs just as much to replace bent valves as broken valves. The best defense is precisely what you have done...replace the cam and balance belts regularly...then you'll never know!

 

FWIW, I have had two timing belts break on me, both on 4th gen. Honda Civics ('88-'91). The first time, I just replaced the belt and everything was fine. Last time, it apparently bent all the valves (16 of them) virtually no compression on any cylinder. I have the head off now waiting for time to take it to the machine shop. Neither engine "grenaded"; they just stopped running. Maybe that's what he meant by "barely" an interference engine. Swift is right, of course, I just wish the previous owners had taken his advice.

 

Here in the UK the last non-interference engines were the old GM four cylinder around 1.3-16 capacity engines fitted to the old Astras. Most others do involve valve damage if the belt goes. What is also important to look for is replacement of the tensioner, as some GM engines have very poor quality tensioners and if they let go, even with a good belt you get damage. Another hidden issue, is the water pump. Many modern cars (particularly turbo diesels) have the water pump driven by the cambelt. You might as well replace the waterpump at, say the second belt change as many can let go around the 80-120K point. If the water pump bearings go or seize, the belt can be wrecked. I guess you can see that many manufacturers (like BMW) have returned to chains, even though they are more expensive to produce.

 

Preventative maintenance is the key. Cam belt or chain, they both fail today regularly. Here at my shop we see Ford OHC 4.0 V6's, 4.6 and 5.4 V8's with bad chains regularly. Chains don't mean a thing when manufacturers use plastic for the guides and some tensioner pieces.

 

absolutely right on the maintenance...poor oil quality due to non-maintenance or the wrong oil wears the chains rapidly and poor tensioners are a terrible short-cut. I know the some chain replacement jobs (like 24 and 48V engines) have very high labour charges as they are tough jobs