There are tensioners - rubber rings. However, most tensioners only take up the slack on the non driven side, so ain't going to do anything as regards valve timing drift with chain wear. Or more importantly ignition timing if the dizzy is driven off the cam.
But I've never had one where there was any noticeable performance fall off through chain wear, if the ignition timing was correct. Sure it hadn't jumped a tooth?
Not so. The belt is reinforced. Might be possible to use a textile with less stretch than steel.
The 'O' ring that fitted in a groove around the sprocket was there to try to quieten the chain noise; it didn't really help to tension a chain as it wore, and in any case was not fitted to all engines.
It wasn't the case that poor performance was caused by a drift in ignition timing because you could just re-time it to compensate. The problem was that the timing jumped around as the camshaft wasn't driven consistently. You could actually see the effect if you tried to set the timing with a strobe; the marks would be jumping around all over the place.
The 'S' engine had a duplex chain, which lasted much longer before it caused a problem. Later 'A Plus' engines finally had a tensioner fitted.
Dead sure! I would doubt that an 'A' series would even run in that eventuality as they didn't run too well when all was correct!
Chris
Here is the mostly 'complete' answer:
Will it be like Vauxhall's "lifetime" (100k or change of owner) warranty?
Ford didn't sell a 1.25 Zetec crank, they sold a short engine. You could buy pistons, rods and big end bearing separately but not a crank without a block.
It was a cast iron KENT block, Ford were too cheap to build a new line. Yamaha stiffened the poor thing up so it could take the power the Yamaha head made by bolting a die cast aluminium sump to it and a bearing girdle was used. To make an engine run smooth requires a tight control on main bearing clearance. They had 20 different thickness of bearing shells to get the main bearing clearance due to the utter inability of the knackered 50 year old Ford production line to hold tolerance when boring the main bearing housings in the block. Then Ford made claims that due to using lasers to gauge the thing they couldn't be re-ground as it must not be disassembled. But having lasered it they had to disassemble it to put the crank in.
My Nissan CA has 5 bearings for OEM assembly. When regrinding the crank the under size bearing bore has to be measured with bearings installed in the block and caps and girdle torqued correctly. Then the crank is ground to a size that gives the required clearance.
Clearance = 0.021mm - 0.048mm. (wear limit 0.1mm) Tolerance 0.027mm.
Main journal 52.951mm - 52.975mm Tolerance 0.024mm.
Standard bearing thickness tolerance 0.004mm x 5 grades. Total range 0.02mm.
Under size -0.25mm, thickness 1.947mm-1.960mm. Tolerance 0.013mm.
I don't know the housing sizes in the block but that is made to a tolerance as well. The required clearance tolerance is much less than crank and shell thickness and adding tolerance of housing will increase the tolerance range.
Simply wading in grinding the crank 0.25mm under size is a route to scrap. If the machine shop doesn't ask for the block, bearing caps and new bearing shells they don't know what they are doing and may as well be a bunch of monkeys with a grinding machine. Pick up your crank and RUN AWAY!
Same goes for a rebore. There are 5 grades of OEM piston and bore,
0.01mm steps for a total bore tolerance of 0.05mm. Grade "A" 83.00mm - 83.01mm bore takes a 82.975mm - 82.985mm piston. That gives clearance of 0.015 to 0.035mm. Which is what the rebore has to match as well. So again just wading in with a boring machine to +0.5mm on the 83mm nominal won't deliver the right piston fit. The piston has to be measured and the bore sized +/-0.1mm to give the correct clearance.It's not new Japanese rocket science. Rover used selective fit for 3.5 V8 pistons. Didn't need lasers, they air gauged the bore and pistons to grade them.
replying to Mrcheerful, Fredbair wrote: Fiat punto have non interference engines I was told from the year 2000 to the facelift change
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