Diesel Engines Cyl Head re-fitting

From VW T25(T3)-Tech
Jump to navigationJump to search

Head Gaskets

Simon Baxter: There are 3 thicknesses.

GSF only sell the thickest, the 3 notch.

VW sell them, but they are back ordered from Germany, and very expensive.

I'm slowly building up a stock of gaskets and I'm expecting the next delivery from Elring in the next day or so, but I am now away on holiday till the 11th of August.

I have on order 1, 2 and 3 notch head gaskets so the job can be done properly. (Did you know you have to measure the piston projection from the block to determind what gasket to use?)

.66-.86mm 1 Notch (1.4mm thick)

.87-.90mm 2 Notch (1.5mm thick)

.91-1.02mm 3 Notch (1.6mm thick)

Isn't it funny that Elring don't stock and never have stocked anything other than the 3 notch gasket. The idea of the different thickness gaskets is that you make sure the pistons don't touch the head and you get the best compression. Basically, you use the thinnest gasket you can get away with so you maintain good combustion pressures. Just out of shear laziness most garages either replace what was on, i.e. 2 notch comes off, 2 notch goes back on or just put a 3 notch gasket on.

Great for clearance, not so great for compression pressures.

If you are replacing a gasket there is a fancy VW special tool specially for the job but it isn't the cheapest item (I have bought one because I do a few of them, and it will pay for itself in time) but you can get away with a DTI and a magnetic stand. Make sure you test all the cylinders as they can differ. It is common practice when an engine is reconditioned to "deck" the block, meaning the top face is machined flat much the same way as a cylinder head is skimmed, so the piston protrusion, or projection in VW speak is a must in my eyes.

Cylinder-head bolts

These are 'stretch' bolts, torqued up in two stages then 'set' using a given angular rotation (Torque 1, torque 2, 90 degrees, 90 degrees usually)


HarryMann: Some useful tips here, from General Tools and Techniques - Thread-chaser

Head-studs diesel 01.jpg

Andy Simpson: The bottom bolt in the picture is cut-off and slotted - two of these are useful for locating the head on engines that are fitted on the slant, such as the VW T25 diesels - stops head sliding off the gasket while fitting in situ. (Make sure you don't screw them in too far, so that you can't get them back out)

Other things