head gasket thickness

I have an AFN with a blown head gasket. I pressure tested the system and I have coolant weeping out of the head gasket just below the injectors. The coolant bottle was getting pressurised by compression gases but there's no oil in the coolant or coolant in the oil.

I also have a donor AFN engine with a good head. So I'm going to buy a new head gasket, new bolts and use the donor head.

My question relates to head gasket thickness. I understand the thicker ones are to compensate for material removed from the head during skimming/decking. If I am to use a good original cylinder head I presume I'm supposed to use the thinnest gasket?

Now, while I'm replacing all this stuff, is there any advantage to using a thicker gasket than normal? It will lower compression ratio but I'm using a bigger turbo/injectors/pump head already so is there any performance benefit to using a thicker gasket, lowering the compression ratio to maybe allow more boost?

I'm competent enough to do the work myself but the theory behind the performance aspect is an area I'm just learning about. Any advice appreciated.

Thickness is chosen by the measurement of the protrusion of the pistons.

About performance, check this:

http://forums.tdiclub.com/showthread.php?t=13714

Ditto, gasket thickness is chosen based on piston protrusion at the block by using a lift gauge.

If you're going to the effort of taking the cylinder head off the other engine you really ought to have it serviced at the machine shop. Rule of thumb is to have the head checked and leveled every time it's removed from a block since the act of torquing the head properly can warp it slightly. Also, depending on miles on the replacement head you might want to have a valve job or at least to valve stem seals and maybe even some exhaust valve guides too.

If your not decking the block then gasket thickness should remain the same but it's always good to check piston protrusion anyway.

The link that k_pt provided is a good discussion about what happens to performance when you alter gasket thickness.

Steve

thanks for the input guys. I've read through that thread linked and I've decided use the standard thickness head gasket but to remove the tips from the glow plugs or remove them altogether and fit blanking plugs. They're currently fitted but the whole glow plug loom has been removed so they're not doing anything anyway. That will lower CR a little bit without altering the volume of the squish area.

Steve, good point about freshening up the donor head before fitting. I'll look into it.

There is a tab on the head gasket right next to the IP. It will have an oval hole and possibly 3 other holes. Count the holes and buy the same sized gasket that was put in.
The thickness has nothing to do with the head, and everything to do with the deck height of the block.
Unless you deck the block, keep the gasket the same hole (1, 2, 3, or 4)

When you get your head (I suggest you keep yours and have it worked) you need to make sure its FLAT. It’s fairly easy to check with a true strait edge and a set of feeler gauges. (Pro tip) get a straight edge metal ruler, and put some 200 grit sand paper up against a mirror or window and sand it flat to grantee your strait edge is true, now feel around on the head and make sure it is.
You can send your head to franko6 if you want to know it’s done right.
If you keep your head and have it machined, you need to make sure that the valves have no play in them or within tolerance. Do not swap lifters around or the cam, cam and lifters stay as a pair.
Turbo engines rarely have an oil to water cross contamination on a head gasket failure, it’s usually due to boost levels and the compression gasses making it past the gasket and lifting the head. It’s a typical issue with AHU and ALH TDI's

trevorbrady said:

thanks for the input guys. I've read through that thread linked and I've decided use the standard thickness head gasket but to remove the tips from the glow plugs or remove them altogether and fit blanking plugs. They're currently fitted but the whole glow plug loom has been removed so they're not doing anything anyway. That will lower CR a little bit without altering the volume of the squish area.
Steve, good point about freshening up the donor head before fitting. I'll look into it.

Click to expand...

there is no standard size, count the holes on the tab.

Thanks mongler.

Since I'm here asking questions and you guys are being so helpful...

I have 0.280 nozzles, 12mm pump head, GT1749vb turbo. So far just on the factory map. Once i have the head gasket issue solved I'll be getting it dyno'd and remapped to get the best out of the parts.

What's a good max boost to go for? I'd like this car to be reliable and fun to drive. It's a 1983 mk1 Jetta so a relatively light car.

well, maybe someone can chime in here, i have get to get my hands into an AFN, but i assume there virtually the same as the AHU. they look the same! So i would have someone confirm the headgasket hole sizing for the AFN.
Im assuming you did this as a swap!, thats fun. pictures would be nice.

Yeah all my work. I'll post pics later.

AFN is almost identical to AHU. 110bhp vs 90bhp from the factory though.

The problem in lowering compression ratio by using a thicker headgasket is getting air pockets outside the piston bowl, that do get the injector spray.

The way to go is work on the piston bowls.

You need to count the holes. Always put in a gasket with the same number of holes. Gaskets are the same for 1Z/ AFN/..
Good example here:
http://rosten-performance.com/produ...sel/1-9tdi-headgasket-afn-option-1-2-3-notch/

lisab4 said:

You need to count the holes. Always put in a gasket with the same number of holes. Gaskets are the same for 1Z/ AFN/..
Good example here:
http://rosten-performance.com/produ...sel/1-9tdi-headgasket-afn-option-1-2-3-notch/

Click to expand...

thats what i thought. i didnt know what differences are on the AFN vs AHU, my hunch is that its a 10mm IP vs the 9 the AHU has.

yah, the AFN has a 10mm pump head to start with. I have a 12mm head fitted now. Pics soon...

in no particular order...
ebay GT1749VB turbo core


Gibonta 0.280 nozzles


ebay 12mm pump head


PD130 inlet manifold. The EGR body is still there as it gives me somewhere to fit the MAP sensor but it's been totally gutted and machined smooth inside and out.

ebay intercooler & pipe kit



G60 flywheel
VR6 clutch
02A CTN (mk3 Golf TDI) gearbox
02J shift tower
9N Polo shifter
custom (DIY) engine & gearbox mounts
T4 Eurovan clutch master cylinder
mk4 Golf FBW acc pedal
mk4 Golf TDI engine bay loom and ECU
custom (DIY) 2.5" exhaust from turbo to tailpipe

I drag raced it for a while but really, FWD is a handicap and I never saved up the money to invest in a LSD for the 02A so I've given up on racing and it's going back on the road.


still on the stock mk4 ALH map from the mk4 ECU I used so it needs to be dyno'd and mapped properly but it pulls strong in all gears.

What’s up with the coiled line, before the IP? Is that head and rotor Bosch?

Mongler98 said:

my hunch is that its a 10mm IP vs the 9 the AHU has.

Click to expand...

AHU and 1Z both have 10mm pumps.

-Todd

ToddA1 said:

What’s up with the coiled line, before the IP?

Click to expand...

that's aluminium piping, I made that coil and fitted it to the return hose from the pump to the tank. It's an experiment in fuel cooling. I read somewhere that the larger piston in the pump head leads to the fuel heating up dramatically. It's not very scientific as I didn't test fuel temps before or after the pump upgrade nor did I test fuel temps before or after my DIY fuel-cooler to see if it works. The plan was to duct an air supply to it or find a nice spot behind the grille to fit it but TBH, I haven't gotten round to that yet.

ToddA1 said:

Is that head and rotor Bosch?

Click to expand...

nope, some unknown brand/unbranded part from an ebay vendor in Germany.

Probably Chinese in origin but who knows?

Without fins, I’m curious how effective just the AL coil could be. I considered running a small transmission cooler, for the project car.

-Todd

Yeah you're probably right. A proper cooler would be better.

A cooler goes After the fuel from the ip, putting this before only will help cool a little bit vs lots of cooling because of slower flow from the fuel return to tank. Take a note from stealth TDI scotts build on this one.
Also hope you cleaned out your ebay pipes, ran a microfiber cloth soaked in acetone and it took out LOTS of metal that would have hurt things.
Also i meant to say 10 vs 11, not 9 vs 10. its been a while!

The diy cooler experiment is on the line from the pump to the tank.

The eBay intercooler and pipes have been fitted a couple of years now. They're well cleaned out at this stage!!

where is the fuel filter?

there's an in line Fram diesel filter on the rhs chassis leg, out oof shot.

trevorbrady said:

there's an in line Fram diesel filter on the rhs chassis leg, out oof shot.

Click to expand...

i am interested, you got a part number or a link?

trevorbrady said:

https://www.ebay.co.uk/itm/Fram-P10...=item3d6fab980d:g:bPsAAOSwH4dbavPX:rk:23:pf:0

Click to expand...

lol, total going to try this out.