[Shop-talk] Volvo Engine Swap

[John Miller]

> Just one data point: I had the timing (I think it was a chain) go out
> in a 1969 Mustang, and it did not trash the entire engine.  We just
> had to replace the chain, and my friend drove it SF to LA later that
> weekend, with no problems.

Depending on the valve configuration, the amount of camshaft lobe lift, 
etc. an engine can be an 'interference' or a 'non-interference' engine. 
  In a 'non-interference' engine a broken cam drive results in the 
engine stopping; in an 'interference' engine it can result in a bunch of 
scrap metal.

Some regard the combination of belt drive and interference valvetrain as 
bad juju, though the real issue here is (a) be conservative about the 
belt replacement interval and (b) replace all the tensioners and guides 
when the thing's opened.  Most call for replacement every 60K-100K miles.

A cam belt change can be trivial or utter hell depending on the car.  On 
an old Audi Fox it could be done in about the time it's taking me to 
type this reply.  But...a year and change ago I did our '02 Audi S6, and 
the first step to changing the cam belt on that car is to remove the 
front of the car - front bumper cap comes off, radiator support unbolts 
and slides out four inches.  Pretty much the first step for doing 
anything around the front of the engine on that car.  Once you've got 
all the cruft out of the way it's not too bad to work on, but it's a 
PITA to get to that point.  On that flavor of Audi the rule of thumb is 
to replace EVERY wear item on the front of the engine - seals, water 
pump, accessory drive belt and tensioner, etc. - when it's opened up, 
because the $150 you save in not doing so will look pretty pound-foolish 
when you end up shelling out another grand in labor (or a full day of 
your own time) pulling the thing apart again to change something later.

Note that most 'cam belt' failures are NOT the belt; the failure is more 
often in one of the tensioners, guides, or idler rollers.  GM has a 
little 54-degree V6 built in the UK that's been used in a couple Saabs, 
a couple Saturns, and the Cadillac Catera (Opel Omega elsewhere.)  It's 
an interference engine and in Europe the belt-change interval spec is 
48K km (30K miles) but when brought to the US GM rolled the dice for 
some reason and kicked the interval up to 60K-100K miles depending on 
the car.  They'd claim they improved the belt guide hardware but 
whatever they did wasn't good enough.

Saab got that engine around '94 in the US, and after a few engine 
failures they settled a class-action by agreeing to pay for 30K mile 
belt changes for the life of the affected cars.

Despite this experience GM *still* stuck a 100K-mile belt change 
requirement on the Catera, and those things blew up right and left at 
80K miles.  Shame, 'cause otherwise it was quite a nice car.

Note that chain cam drive does not mean immunity from failure, many 
chain drive engines suffer significant sprocket or tensioner wear by 
120K or so.   This was the Achilles' heel of the Nissan VH45DE, the 
beautiful V8 used in the '90-95 Infiniti Q45.  You've got to change your 
chain and guide pads every 100K, just like it was a belt-drive engine.

John.