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Author Topic: Piston to cyl clearance  (Read 3783 times)

October 15, 2008, 05:03:15 pm

autoholic

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Piston to cyl clearance
« on: October 15, 2008, 05:03:15 pm »
Just wondering what I should go with for piston to cyl clearance with 1MM over pistons. I am getting started with another block (after the tragic cracked block issue!) and spoke with the local machine shop. They said the clearance should be provided by the piston mfg, and not necessarily the VW spec, I have heard this from others as well. The last block I went with just under  1.5 thou, but just want to get other opinions. I know I do not want them too tight since they do expand alot apparently.
The pistons did not come with any spec, what should I go with?
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Reply #1October 15, 2008, 05:12:52 pm

jtanguay

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Piston to cyl clearance
« Reply #1 on: October 15, 2008, 05:12:52 pm »
i think the clearance is .5mm but best check with the bentley.  the clearance is VW spec.
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Reply #2October 15, 2008, 05:19:43 pm

autoholic

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Piston to cyl clearance
« Reply #2 on: October 15, 2008, 05:19:43 pm »
Yea, I would think just to use the VW spec too, but two different shops told me to go by the piston mfg spec which seems wierd, also they say it will be different since it is 1MM over. Seems like there splitting hairs, but these guys are reputable and build some nasty race motors, crazy sport import stuff.
I'll try to find a spec from the mfg and compare to VW, it would be interesting to see if they are actually different.
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Reply #3October 15, 2008, 05:40:38 pm

dillenger1

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Piston to cyl clearance
« Reply #3 on: October 15, 2008, 05:40:38 pm »
those arent vw diesels :)
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Reply #4October 15, 2008, 09:43:26 pm

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Piston to cyl clearance
« Reply #4 on: October 15, 2008, 09:43:26 pm »
Just went through this hole thing when building my engine. Correct me if I'm wrong but I think the Bentley says, max cylinder to piston clearance is .001 in. , .003 in. is worn out.
Josh
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Reply #5October 15, 2008, 10:05:29 pm

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Piston to cyl clearance
« Reply #5 on: October 15, 2008, 10:05:29 pm »
There ya go. When your machine shop does your boreing, the pistons should be matched to the cylinders. Not every piston is the same size.
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'87 Syncro Transporter Single Cab "Now TDI"
'78 Rabbit..Gas Weekend Racer
'81 Caddy..Diesel 1.6/1.9 TD hybrid 275HP 349TQ "Retired"
'90 MultiVan, 2.5 Suby Swap, Porsche Brakes
'76 Scirocco TD dragster project
'13 Golf R:. Tuned
'98 Puch G320
Reply #6October 16, 2008, 01:27:24 pm

autoholic

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Piston to cyl clearance
« Reply #6 on: October 16, 2008, 01:27:24 pm »
Thanks, I'll bring them all the pistons and go with .0015 clearance, this is what i did last time around and it all looks good after (only) 500 miles. The guy's at the shop really wanted to avoid going too small.
Hopefully I'll have it back in a week or so.
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