OT: timing belts

[jpero at sympatico.ca]

> Yes, I know some small Vauxhall/Opel engines don't run interference.

Chrysler 2.2L and 2.5L (both four inline) aren't interference engine. 
 And runs long timing belt.

> 
> >>  A new timing belt costs a tenner at the most and even on an 
> >> absolutely evil b*st*rd of an engine to work on (step forward, Citroen 
> >> XM 2.5TD, not nearly as nice an engine as the CX 25DTR) it takes at 
> >> worst a couple of hours to fit.  I can do Volvo 2- and 3-series belts 
> >> in about half-an-hour...

A good mechanic can do this on 2.2/2.5 also.  Partially drain 
coolant, you'll see later.  Take both belts (one runs PS, other belt 
runs alternator & water pump) or three if equipped with A/C.  Now 
remove bolts and two nuts (all 10mm) for both upper and lower covers. 
 On earlier 2.2 (before mid 87) external trox socket to remove 
crankshaft pulley bolts (four), later 87 used regular bolts.  Now 
lower cover falls off.  Take a car jack that came with that car and 
piece of wood to protect oil pan, jack up the engine to take load off 
the right side engine mount.  Undo the nut and yoke bolt & nut, 
remove two bolts on the inner fender then remove mount.  Undo the 
bolt on the eccentric tensioner to get it rotated away and lightly 
tighten to keep it there.  Align marks according to the service 
manual, intermediate spocket turns too freely makes this job tricky 
while putting new belt on.   Line up the groove on flywheel to 0 deg 
(TDC), line the cam spocket with arrows evenly with parting line on 
head with small hole uppermost.  Rotate the intermediate spocket that 
it's nick in rim of spocket is pointing to tiny drilled hole in edge 
of the crankshaft spocket.  Tension the belt with weighted tool or 
twist belt longest side almost 90 to check tension.  Manually turn 
over engine 2 turns and recheck alignment and retension belt again.
Reassemble in reverse order.

This what I did on my 1987 caravan 2.2L carb.

> >> As to why we use timing belts, well...  The problem with timing chain 
> >> designs is that the chains wear and go slack.

That's true, it depends on user to do regular oil changes and quality 
of design originally.  For example, mitsubishi 2.6 is very fussy on 
maintaince.  But even with good care the guides are covered with 
nylon wears through then wears through aluminum guide like no 
tomorrow and bam, balance shafts stops rotating that oil pump and 
engine self-destructs with oil pressure loss.  Chain tensioning is 
done with oil pressure. This 2.6 mitsu has two long chains because of 
balance shafts far apart and camshaft is on top of head.

Mitsu currently uses their quirky designs in later engines and more 
involved compared to others unlike Citroen is bit quirky.  V6 3.0L is 
one another quirky engine to work on.  Water pump driven by timing 
belt and to do this job repair, everything on front end of engine has 
to come off and have to replace water pipes to prevent coolant leaks 
because old ones is rusted.

> > I don't know too much about chains used with overhead cams, but on push 
> > rod engines this doesn't happen until many miles are on the vehicle.

Chain is still used on some modern engine with overhead chains even 
some used a short length of chain to turn twin cam, either driven by 
belt or chain.

> Because pushrod engines typically have very short chains.  Compare them 
> with the miles of chain used in Volvo B27 engines (2- and 7-series V6, 
> Renault 30, Delorean)!

I really like push rods for that design, and I really don't see the 
reason that chrsyler engineers (allpar.com has artcles on this) had 
to use belt on 2.2 & 2.5L due to weight issues.  WTF!?
 
> > The only problem I've had with a chain, actually was the top timing 
> > gear, not the chain itself.  It was on my 69 Buick LeSabre.  The top 
> > gear was aluminum with nylon or plastic teeth.  They stripped off, while 
> > on the highway.  This happened in 1995, so the car was about 26 years 
> > old, with 100K miles on it.  I thought the gear design was dumb, but I 
> > assume it was done for sound or vibration purposes.  I know GM may not 
> > rank very high with the Europeans on the list, but it's one of my 
> > favorite cars that I've owned.

Noise reasons that most makers went with nylon coated spockets or 
gears.  Time had progressed that they went back to all metal since 
understanding in making quiet drive trains.

 
> Yeah, as I think I said in another post, the Essex V6 used in old Fords 
> had fibre teeth.  You can replace the gear set with an all-steel one but 
> it's hellish noisy.

Fibre gears is rather durable compared to nylon for their time but 
heat & wear equally destroys the wear resistance on both types 
of composite drive trains. 

> > I did have belt problems once on my 1982 Dodge with a 2.2L engine.  I 
> > got it wet in the snow, since I plowed into a snowbank, with the plastic 
> > cover off.
Tsk tsk... now you know better to keep covers in place, that's the 
major reason.  I had to go to junkyard to get upper cover for mine or 
from dealer's.  Not expensive.

> Argh.  Yes, a lot of engines seem to need a special tool to move the 
> tensioner.

That's true still.   Some are not that special, just make a flat tool 
to tension off the assy belt or put belt back on on chrysler 3.3 & 
3.8L engine, oh yes real old fashioned push rod engines with short 
chain, all metal spockets.  Rather reliable.

> Gordon.

Cheers,

Wizard