Here is the latest reader question, along with my reply!
Mike asks: My question is, do you know why V6s have timing belts that require changing and V8s have timing chains that do not require change?
My reply: IIRC, the first American production engine to use a timing belt was actually a six! This was Pontiac’s overhead cam Sprint six, used in the late 1960s in cars like the Firebird. The advantage of the belt is light weight and low cost – this is probably why so many of the early Japanese and other import cars also had engines with timing belts. The problem with belts, of course, is that they generally require regular maintenance (replacement) at certain specific mileage intervals while timing chains usually last the life of the engine.
Interestingly, timing chains are making a comeback – and being used in small (four cylinder) engines made by import brands. I suspect the reason for this has to do with the timing belt’s replacement cost issues and also longevity/reliability issues. Cam/valve timing is emissions (and economy) critical and these are Very Big Deals these days, for every car company.
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Eric:
“…while timing chains usually last the life of the engine.”
Yaaa, not on a VW. VW has nothing but problems with timing chains. VR6’s of all sizes are lucky to get 120k before a replacement is necessary, I’ve seen them go at 75k. 5 cylinder VW’s have issues as well, same with early chain driven direct injected 4 cylinder turbos. VW/Audi likes to put the chains on the transmission side of the engine, so ya, you have to pull the trans to do the job, some Audi’s require complete drive-train removal to replace. I’d rather have a timing belt any day.
Here’s some Audi pics.
https://www.google.com/search?q=audi+timing+chains&client=firefox-b&tbm=isch&source=iu&ictx=1&fir=QdOSK0uCkawI1M%253A%252CiSNDPKz4ayYMwM%252C_&usg=__nNKqnOZJQAH44dvKCj0BCgv28jU%3D&sa=X&ved=0ahUKEwiWioHo2NvZAhVDwlQKHfatCtQQ9QEIYzAE#imgrc=QdOSK0uCkawI1M:
Hi Adam,
Hat tip for the advisory on the VW/Audi timing chains! I’m looking forward to lots of fun as these new DI (and variable cam/valve timing) engines age…