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Engine Specific Info and Questions => IDI Engine => Topic started by: Gnarlodious on August 14, 2018, 02:16:35 pm

Title: Head gasket thickness
Post by: Gnarlodious on August 14, 2018, 02:16:35 pm

I inherited a '78 diesel Rabbit with only 55k on it, so the engine is unsurfaced. What thickness head gasket do I need?

There isn't an existing gasket, someone took it apart years ago and the gasket is gone along with the head bolts. Is there a method to measure which gasket I need?

Title: Re: Head gasket thickness
Post by: libbydiesel on August 14, 2018, 03:28:03 pm

Whether or not the head has been shaved doesn't enter into it.  The thickness of the head gasket is determined by the piston protrusion regardless. 

Do you have a Bentley or Haynes for it?  It lists the various protrusion vs. gasket specs. 

For measuring piston protrusion, clean all the carbon off the piston crown.  Place each piston in turn at TDC.  You can then use a straight edge across the piston inline with the connecting rod and use feeler gauges between the straightedge and block on either side of the piston.  Head gasket is spec'd by the largest measured protrusion.  There are other methods but most alternatives require dial indicator and stand. I have a milled steel block that fits over the cylinder.  I then mount my dial indicator magnetic base to the block, place the desired piston before TDC so it is below the block.  I placed the milled steel over the cylinder, put the dial indicator straight down on top, and zero the indicator.  I then rotate the crank past TDC and take the maximum deflection reading as the protrusion for that piston.

Title: Re: Head gasket thickness
Post by: libbydiesel on August 14, 2018, 03:36:32 pm

Although 55,000 miles is low mileage, the 1.5s are fairly notorious for warping heads, blowing head gaskets, and having the blocks crack around the head bolt threads.  I won't even replace a head gasket on one of them because the odds of it failing are high even if you do everything right.  I would also mention that I have a 1.6TD short block for sale in the classifieds.  It was completely rebuilt 50,000 miles ago with all new German parts (new bearings, oversize pistons, etc...).

Title: Re: Head gasket thickness
Post by: ORCoaster on August 14, 2018, 07:13:21 pm

Try this from the search engine:

http://vwdiesel.net/forum/index.php/topic,6741.0.html