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Joey
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Location: Nova Scotia - Canada
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 Posted: Tue Jan 26, 2010 4:30 pm Post subject: Wrist pin to rod bushing fit |
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I just got my connecting rods (1200cc) back from the machine shop. They replaced the bushings and honed them to size - .0004-.0008" clearance. The pins seem way too lose to me, they easily fall right through and have a slight wiiggle. Shouldn't they be a slight push fit. I have no real way to measure them so how can I convince them they screwed up?
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Joey
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keifernet
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| Posted: Tue Jan 26, 2010 4:54 pm Post subject: Re: Wrist pin to rod bushing fit |
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| Joey wrote: |
| I just got my connecting rods (1200cc) back from the machine shop. They replaced the bushings and honed them to size - .0004-.0008" clearance. The pins seem way too lose to me, they easily fall right through and have a slight wiiggle. Shouldn't they be a slight push fit. I have no real way to measure them so how can I convince them they screwed up? |
Did you give them the pins you were using or did they ream them to a "spec" out of an old manual? Many of the "aftermarket" Piston and cylinder kits these days have wrist pins that don't match old German specs and many of the "better" VW machine shops will ask you what your using and ream to what you have if tell them. I'd say your too loose... need to not rock and be a slight hand/stiffer fit but not a "press fit" no.... |
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Joey
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| Posted: Tue Jan 26, 2010 5:00 pm Post subject: |
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Yes, I gave them the pins along with the specs. I'm re-using the old P&C. The pins are in great shape, .7870" across the pin.
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Joey
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keifernet
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| Posted: Tue Jan 26, 2010 5:42 pm Post subject: |
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well was it local machine shop? I would say send the rods back and have them put new wrist pin bushings in and re ream them... it's not like it's expensive mistake on the shops end... but sure would be on yours.
wrist pin bushings probably cost them 2 bucks each if that.... and time to re press and ream them right... they owe you, you paid them already....  |
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djkeev
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Joey
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| Posted: Tue Jan 26, 2010 6:57 pm Post subject: |
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Yes, it was a local machine shop. $16 a rod. I'm going to go back and talk to them tomorrow. Problem is I can't find any 40hp bushings locally. CIP has them but it'll cost $24 to get them shipped here.  I doubt they'll pay for that.
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Joey
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Joey
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| Posted: Fri Jan 29, 2010 4:04 am Post subject: |
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I took the rods back to the machine shop and they checked them @ room temp and they said the clearance between the pins and bushings are between .0005-.0006". They say it's within the specs I gave them so they won't do them over.
Should the pins be a 'push fit' oiled or not oiled?
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Joey
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keifernet
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| Posted: Fri Jan 29, 2010 9:18 am Post subject: |
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| Joey wrote: |
I took the rods back to the machine shop and they checked them @ room temp and they said the clearance between the pins and bushings are between .0005-.0006". They say it's within the specs I gave them so they won't do them over.
Should the pins be a 'push fit' oiled or not oiled? |
Well do you have to push them through? Or do they just drop/slide through on their own weight if you turn the rod sideways and set the pin in them they just pass right through.... if so that's too sloppy.
It should take some effort but not be so tight that you can't push them through with your thumb and fingers. And for rebushed there should be NO ROCK. There are "acceptable wear limit" specs that things can still be used if you want to, the Bentley and others cleary have those specifications but if your installing NEW/rebuit rods then I am with you... the spec should be correct.
Sounds to me like the machine shop in not familiar with VW rods? or? do they do much VW work? |
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drscope
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| Posted: Fri Jan 29, 2010 9:18 am Post subject: |
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They should tap in pretty easy with a hammer, but you shouldn't be able to push them in with your fingers oiled or not oiled unless you are big and green or have a big S on the front of your suit.
This is one thing you don't want loose enough to hammer itself to pieces. At 3,000 rpm, the piston has to change direction 50 times a second.
Where did you get the specs you gave them? And have you measured them for yourself, or are you going off their measurement?
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Joey
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| Posted: Fri Jan 29, 2010 9:30 am Post subject: |
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A hammer? I think you are talking about pin to piston clearance (I hope). I'm talking about pin to rod bushing clearance.
I don't have nothing to accurately measure them. Maybe I'll take them to another machine shop to get them to double check them
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Joey
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Joey
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| Posted: Fri Jan 29, 2010 9:36 am Post subject: |
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| keifernet wrote: |
| Well do you have to push them through? Or do they just drop/slide through on their own weight if you turn the rod sideways and set the pin in them they just pass right through.... if so that's too sloppy. |
On their side, the pin easily falls through with no oil. With oil it take a second or two to fall through and there is still rock.
| keifernet wrote: |
| Sounds to me like the machine shop in not familiar with VW rods? or? do they do much VW work? |
They've done them before but don't do them on a regular basis.
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Joey
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Joey
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| Posted: Fri Jan 29, 2010 11:28 am Post subject: |
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I just got my wrist pins and bushings measured, they are all:
Pin - .7871"
Bushing - .7879" (one bushing was .7877")
That's .0008" clearance which is at the end of the wear limit. (.0004-.0008")
Why would the machine shop hone them that close to the wear limit?
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Joey
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keifernet
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| Posted: Fri Jan 29, 2010 11:34 am Post subject: |
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| Joey wrote: |
I just got my wrist pins and bushings measured, they are all:
Pin - .7871"
Bushing - .7879" (one bushing was .7877")
That's .0008" clearance which is at the end of the wear limit. (.0004-.0008")
Why would the machine shop hone them that close to the wear limit? |
I like germansupplyscott's answer in the thread you dug up in that forum.
http://www.thesamba.com/vw/forum/viewtopic.php?t=361585
I think they don't know what they are doing, don't care or both.
You might consider getting these from Chadd.... and then having them re done at another shop if they won't work with you.
http://www.thesamba.com/vw/classifieds/detail.php?id=902961 |
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