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How Large can the Piston Bore size wear too..
by
Peter
on 19 Jan, 2010 12:46
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when measureing the difference taken from the very top of the piston bore (just below the deck) and comparing that to the measurement taken at the top of the piston stroke (just before the worn cylinder ridge)..I have about a .005th difference..would this be too large for useing the "stock" pistons with new rings..or would an "over size" piston be needed here..in a perfect world re-boring is the only way...but practically..would the older pistons and new rings work OK..anybody have experience with this..the last time I did this on another diesel it was a no-brainer..only .001 diff
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#1
by
Doug
on 19 Jan, 2010 17:57
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My 1.6 had a .004" wear difference between the top and bottom of the bores. I elected to go with the original pistons as they were still in good shape as well as the ring land wear was within spec. The new rings seated fine and as expected with more service have continued to reduce in oil consumption. Boring and pistons would have set me back somewhere close to another thousand. If you want a general driver admitting that you are not building a new engine then you might get away with it. Replace the big end bearings though while you are in there as it is very cheap insurance.
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#2
by
burn_your_money
on 19 Jan, 2010 20:13
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I only have a mk3 bentley with me and it states that a maximum allowable deviation from nominal diameter cylinder bore is 0.08mm (0.0031 in)
I think you would be better off measuring at the base of the stroke rather then measuring the ridge.
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#3
by
maxfax
on 19 Jan, 2010 20:16
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Not meaning to thread jack, (but I am anyhow
) What are you folks paying to have a block bored now days??
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#4
by
rs899
on 20 Jan, 2010 04:38
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I think the machine shop down my street wants $125 to bore four holes. That's not bad, but the bill always seems to creep up whenever you deal with any machine shop....
Rick
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#5
by
maxfax
on 20 Jan, 2010 18:21
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The fellow I use charges about $25 per hole, but there is a charge for tanking the block and for magnafluxing.
That's generally what I have been paying as well... It does seem to get cheaper the more cylinders I have bored though.. My Vw was $100 (plus tank and mag).. Yet the 351 Ford was $150 (plus tank and mag) I guess since the machinery was already setup they cut a break... My 2 cycle Harley golf cart was almost $50, but it's rather small and delicate...
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#6
by
truckinwagen
on 20 Jan, 2010 18:43
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you guys are super lucky, the local shop here wants $500 to tank and bore a four cylinder, hell just the hot tank is $80.
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#7
by
Dakotakid
on 20 Jan, 2010 21:27
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I think I would be "importing" a block from somewhere else. Why is labor so much up there.....the high cost of polar bear repellant
?
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#8
by
truckinwagen
on 20 Jan, 2010 21:31
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well, they have us over a barrel, there is only one shop that really does engine machining.
the lack of competition drives the price of allot of things up quite a bit.
there are of course a few places that charge reasonable rates, but most of the automotive work up here is expensive.
-Owen
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#9
by
maxfax
on 21 Jan, 2010 02:19
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We really only have one machine shop in this area, but with a few drag strips and several dirt tracks around they make the real money from building race engines.. When I drop off my VW stuff I make sure to tell them that I'm not building a race engine and get a cheaper rate..
Well, okay so I don;t have to tell them, they know....