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piston to bore clearance
http://thehaflinger.com/viewtopic.php?f=23&t=3547
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Author:  David bullock [ Sun Jan 21, 2018 2:26 am ]
Post subject:  piston to bore clearance

question to any one out there who has rebuilt one of these things before, i have recived a set of 80.5mm pistons from haflinger technik and have my barrels at the local machine shop and are ready to be bored out. but,, it clearly says in the manual that it should have a piston to bore clearance of 0.05mm, which is the same measurement haflinger technik said,
but this seems very small, and the machine shop said the last set of porsche barrels they did were about 6thou, so can any one tell me what clearance they did?

(i come from the dirt bike world where i have replaced high qulity pistons for wiesco branded ones which expand more than most and lock up at high temperatures)

and she will be driven in 40 degree day quite often.

cheers in advance

Author:  garrycol [ Sun Jan 21, 2018 5:58 am ]
Post subject:  Re: piston to bore clearance

Sorry I cannot help as I have matched VW pistons and barrels.

I would be going with the advice provided in the manual and Haflinger Technik.

Garry

Author:  pureredcordial [ Sun Jan 21, 2018 8:56 pm ]
Post subject:  Re: piston to bore clearance

Sorry no but

From the 1962 Repair Instructions Manual, its says 0.04-0.05mm for 80mm pistons.
and the wear limit is 0.15mm (.006") max

6thou would seeming make them brand new worn out

--matt

<edit - missed you were quoting the manual>

Author:  HaffyHunter [ Sun Jan 28, 2018 4:54 pm ]
Post subject:  Re: piston to bore clearance

David bullock wrote:
question to any one out there who has rebuilt one of these things before, i have recived a set of 80.5mm pistons from haflinger technik and have my barrels at the local machine shop and are ready to be bored out. but,, it clearly says in the manual that it should have a piston to bore clearance of 0.05mm, which is the same measurement haflinger technik said,
but this seems very small, and the machine shop said the last set of porsche barrels they did were about 6thou, so can any one tell me what clearance they did?

(i come from the dirt bike world where i have replaced high qulity pistons for wiesco branded ones which expand more than most and lock up at high temperatures)

and she will be driven in 40 degree day quite often.

cheers in advance


It depends on the piston type you are using. A forged piston (like Wiesco) requires much more clearance as they expand more with heat. If the pistons from Haflinger Technik that you have are original Puch N.O.S. then you should use the manual's recommendation of 0.05mm.

Cheers,
Steve

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