Ever notice how the newer VW diesel headgaskets have some new coolant circulation holes lacking in the old ones?


Take a look at the 1.9l headgasket for example.  In the image above it is on top, and is compared to a 1.6l solid lifter head gasket on bottom.  I am not talking about variations in the coolant flow restrictors, but 8 completely new water jacket passageways in the newer heads, blocks, and headgaskets, which are lacking in the earlier design.  They are on either of side of where adjacent cylinders are closest to one another.

It is speculated that the purpose of these tiny coolant channels is to allow air bubbles that can collect in the water jacket around the top of the block, (where localized high spots seem to be present in the water jacket), to percolate up and through, and to prevent localized hot spots from occurring where the vapor may be trapped.  This "modification" I am told is commonplace on some old american V8 iron.  Might it have value applying it to the early VW blocks and heads?

Well I found (using the VNT Rabbit as the guinea pig...) that retrofitting these extra coolant channels to an earlier block is not a problem.  All that is needed is a simple drilling operation, and use of a later style headgasket incorporating the passageways.

A 1.9lTD headgasket can be used as a template to place the hole positions on the surface of the head and block.  The holes only need be large enough to allow an air bubble to percolate through, and small holes should not significantly effect the metal strength.  The water jacket turned out to be living there, in both the head and the block, about 1/2" past the deck surface for every hole.

[Edit: look down a few posts for pics.]

so how hard is it to use a 1.9 head gasket on a solid lifter engine?

Pics:

Taped off everything during drilling to avoid getting the shavings in sensitive areas...

(that is a brand new head that went on the VNT Rabbit!)

Close up of a hole drilled in the head.  You can see the scribe mark made through the head gasket (used as a template.)  The hole need not be the full size of the head gasket hole, just large enough for air bubbles trapped underneath to percolate through.  You can see compared to the scribe mark how large of a hole I used.


Also drilled holes in the block:


Countersinking the holes after drilling is also a good idea.

Here's what the block looked like all done, ready for the head to be installed...


PS - I had what I believe to be a breakthrough discovery for successfully using the 1.9TD headgasket on a 1.6 solid lifter block! (but that is the topic of another thread.  :wink: )

Looks like I have some drilling to do while rebuilding my TD

And yeah, what is that big hole in the gasket that Mark underlined?

PS - I had what I believe to be a breakthrough discovery for successfully using the 1.9TD headgasket on a 1.6 solid lifter block! (but that is the topic of another thread.  )

details! Im almost at that point!

Aren't the smaller holes referred to as "steam passages" or something like that?  Thought I read that somewhere.

Back in the 80s/90s, Techtonics copied some Oettinger head gaskets that had more coolant openings/larger ones to take some more heat out of the head by the exhaust passages, as the head was getting really hot there on some performance engines.  Something like that anyway.  Been a while.

i know that in the 400 small block chevy motors we called them steam holes mostly because it got so hot between the siamesed cylinders.

Jake,
I have a question.  If one were wanting to ceramic coat the prechamber and cup, piston crowns, and exhaust, intake valves to raise temps and get better burn....would adding this additional cooling to the head serve to pull that away, thereby cancelling the gains realized through coatings?

I could argue, both are useful as you get want you want cool, cooler (head and block) and what you want to stay warm, warmer (combustion chamber).

Not Jake, but I'll throw in my 2 cents worth; I think the mods will be complimentary.

When you're talking about all that heat rejection coating, the goal is more complete combustion, longer prechamber, valve, head, and piston life, as well as containing the heat flow to the turbo for faster spool-up(that can include port/polish & coating of exhaust ports and exhaust manifold passages).

OTOH with the additional cooling of critical areas of the head that Jake's mods could provide, I think that you are mostly going to be dealing with heat that has already gotten past the ceramic barrier and into the head & block.

It seems interesting that, with all the 70s-80s engine failures than VW had(many due to uninformed drivers), quite a few of which were covered by new car warranty, that the factory never put this mod into regular production. I'm assuming that the upgrade is applicable to all the 1.5L and 1.6lL engines.

Hello, Jake?

J.R.
SoCal