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Engine Specific Info and Questions => IDI Engine => Topic started by: ein bora on April 04, 2011, 09:47:15 am

Title: Piston Protrusion Measurement
Post by: ein bora on April 04, 2011, 09:47:15 am

I have read on here enough to know that I need to measure the piston's protrusion before assuming what head gasket to get. This has been frustrating as every time I take a measurement I seem to get a different reading. I've cleaned both the deck and the pistons, but I do believe the quality of my dial gauge or my technique maybe an issue.
However - on the majority I am getting a reading of 77 mm. The old gasket is a two notch, so does this match up correctly??
I do have a brand new one notch and I was hoping to use it, but it seems thicker than the two notch.
Which has left me totally confused. ???
Also stamped on the pistons is 1.9 UD and 79.48 DN, anybody know what all that means.

Any help appreciated. Thanks in advance.

Title: Re: Piston Protrusion Measurement
Post by: R.O.R-2.0 on April 04, 2011, 09:50:39 am

Quote from: ein bora on April 04, 2011, 09:47:15 am

I have read on here enough to know that I need to measure the piston's protrusion before assuming what head gasket to get. This has been frustrating as every time I take a measurement I seem to get a different reading. I've cleaned both the deck and the pistons, but I do believe the quality of my dial gauge or my technique maybe an issue.
However - on the majority I am getting a reading of 77 mm. The old gasket is a two notch, so does this match up correctly??
I do have a brand new one notch and I was hoping to use it, but it seems thicker than the two notch.
Which has left me totally confused. ???
Also stamped on the pistons is 1.9 UD and 79.48 DN, anybody know what all that means.

Any help appreciated. Thanks in advance.

so this is an AAZ/1.9 block?

i just throw a ruler over the pistons, on edge, and use a feeler gauge to check protrusion.. and i use the highest reading..

1.6 has a 77.48mm bore, 1.9 has a 79.48mm bore..

Title: Re: Piston Protrusion Measurement
Post by: ein bora on April 04, 2011, 10:45:27 am

Quote

so this is an AAZ/1.9 block?

Yup - sorry 1.9

Title: Re: Piston Protrusion Measurement
Post by: 745 turbogreasel on April 04, 2011, 11:29:23 am

If you get different heights between pistons, a rod is probably bent.

Title: Re: Piston Protrusion Measurement
Post by: ein bora on April 04, 2011, 01:57:16 pm

Thanks guys. Much appreciated.
And no nothing is bent, engine worked fine. Just starting my passat gas to 1.9 idi conversion and this motor came out of my doner car. I have the cam, I have the vnt turbo, I have the cooler, I have the ported and polished head, I have the giles pump, so want everything else to be just so.

Title: Re: Piston Protrusion Measurement
Post by: blackdogvan on April 04, 2011, 09:39:41 pm

When you say the 1 notch is thicker than the 2 notch are you comparing the new 1n to a used (crushed) 2n?

Title: Re: Piston Protrusion Measurement
Post by: ein bora on April 05, 2011, 07:02:25 am

Quote from: blackdogvan on April 04, 2011, 09:39:41 pm

When you say the 1 notch is thicker than the 2 notch are you comparing the new 1n to a used (crushed) 2n?

 :-[ Yes - but I have since mended my ways.

Title: Re: Piston Protrusion Measurement
Post by: 745 turbogreasel on April 05, 2011, 11:13:18 am

Quote from: ein bora on April 04, 2011, 01:57:16 pm

And no nothing is bent, engine worked fine. Just starting my passat gas to 1.9 idi conversion and this motor came out of my doner car.

And you know that car never had a valve  crash or  headgasket hydrolock?
A little bend in a rod  won't affect engine feel till one day...