Oversized head gasket

[powermandan]

Hello everybody!

I'm looking to rebuild a 1.9TDI AFN for more power.

My original plan was to bore the block to 81MM ( standard is 79.5) to accept BHW pistons. Which should give me something close to 2.0 litre capacity. Also because it's cheaper for me to get BHW pistons than the first repair size AFN piston.

The stardard head gasket is 81mm, but presumably it spreads when compressed

There doesn't appear an on the shelf gasket for oversize pistons. Which leads me to the question. Do I actually need an oversized head gasket.?

I haven't stripped engine yet, do these pistons come above the deck at TDC?

Thanks in advance . Dan

 

[Mongler98]

Bigger bore trades off lifespan and headgasket issues. Max bore I think is 82mm.....?
Imo put good rods in it and call it good. Not sure on the oversized gaskets though.
What's your power goal?

 

[powermandan]

Hoping for 200Hp at the crank, it's destined for a T4 and turbo placement is an issue as well as gearbox selection. So the current plan is build the engine as strong as I can and hopefully install 02M gearbox on an adapter plate and push for as much as I can. But the journey is a long one. So may just stop at the stout engine build and 160hp at the crank.

Anticipated build of materials:
-Rosten clone H Beam rods
- 10mm pump with 11mm pump head. Currently researching cam plate options
-0.240 injector nozzles
- 81.5mm piston (0.5 oversize BHW)
- head gasket 2.0 petrol ABA (looks like it will fit)
- upgraded clutch/flywheel
- EGT and AFR sensors

Mapping is also an issue as running MSA15 (chip tune) which no one in UK seems interested in mapping.

I have bought all the gear for mapping it and have successfully made small changes to existing map. So there is light at end of that tunnel.

 

[burpod]

i was also interested in 2.0l pistons for my AHU since i was bringing the block to the machine shop anyways. i couldn't figure out the headgasket issue with enough certainty to go for it. however, i feel like an ABA (2.0l gasser) headgasket might work using 2.0L pistons. i'm not positive, but i believe it fits the block possibly with minor modification (to an oil galley?), and googling shows it to be .065", which i believe is very close to a 2 hole AHU head gasket, a brand new one i have hear with my harborfreight micrometer is about .07". i don't remember what the BHW piston height is, but i feel like it's possible, perhaps even relatively easy, to achieve this. if you know the BHW piston height, and your current block piston protrusion, i think the machine shop could deck it to the right height you want to accept BHW pistons with ABA head gasket and retain stock compression ratio.

maybe next block i do, but i didn't feel like spending the time dinking around to increase volume by 5% and just went with 80mm .5over pistons.

i also wouldn't get smaller than .260 nozzles. i have .260 now in my AHU with 17/22 now, but after a timing belt slip i'm rebuilding also with chinese forged rods and asv pistons, ported head and 1856 vnt.

 

[Mozambiquer]

Couldn't you use a BHW head gasket?

 

[powermandan]

They seem quite different to AFN/AHU gasket.

Can you upload photos to this forum?

 

[powermandan]

i also wouldn't get smaller than .260 nozzles. i have .260 now in my AHU with 17/22 now, but after a timing belt slip i'm rebuilding also with chinese forged rods and asv pistons, ported head and 1856 vnt.

What pump config are you running? I have spent hours researching what to go for. Still no further forward. It seems you have to become an expert in multiple fields to be able to make any progress!

DE143 cam plate seems like popular choice with 11mm head as far a I can see

Also what HP are you getting ?

I have ordered a petrol head gasket to see how it fits. Not too worried about thickness as you can you can mix and match MLS layers to get a range of thicknesses

 

[Mozambiquer]

They seem quite different to AFN/AHU gasket.

Can you upload photos to this forum?

I'm not 100% sure, but to me that would be the logical first thought. I believe it's similar to the ALH, and I was thinking that the ahu is pretty much the same head gasket pattern at the ALH, but I don't know that for sure.

 

[TDIMeister]

So the current plan is build the engine as strong as I can and hopefully install 02M gearbox on an adapter plate and push for as much as I can. .

...
-Rosten clone H Beam rods

Use the whole BHW/BGW block and use the stock gasket that comes on it. The crank journals are larger than AFN and the rods are beefier for more strength. The cost of aftermarket rods pay for the block at a breaker yard.

 

[powermandan]

I take it BHW is a PD engine. If so they don't fit well in T4's presumably non of the standard engine mounts fit. So would have to fabricate even more.

 

[TDIMeister]

Many of the engine mount holes in the BGW/BHW already exist to transfer AHU bracket counterparts over. The most difficult aspects of the swap would be the crankshaft position sensor gear wheel, drilling and tapping what few holes aren't there (detailed instructions can be found by searching around here - albeit to adapt to an ALH, but will be similar) and employing a suitable oil pan for the inclination of the engine position. The bellhousing to mate to the 02M should be a direct bolt-on. While you're at it you could upgrade to a newer computer used in the ALH or ASV.

 

[powermandan]

Thank you for your insight, I will see how I get on with the hunt for a gasket. I'm fairly sure I will be ok so will probably take the well trodden path of AFN in a T4 and potentially the not so well trodden path of 02M gearbox.

Im sure what you are saying can be done. However I don't know of anyone who has achieved it with a T4 and I've been on a dedicated forum for quite some time. So that gives me some conserns.

Also I have a spare AFN and ABL motors sat on a pallet ready to be combined. All ready to build up to replace the existing AHU which I am quite familiar with .

 

[burpod]

i don't know anything really about mixing pump internals, i just am using a regular 11mm alh pump. the alh style gear makes it easier for setting timing rather than futzing with injector lines. i only have a general idea as to what hp/tq i was making with the old setup - stock block and head, .260 injectors, 17/22 28psi max boost (26psi actual requested but always goes over), mk4 lift pump... it was enough to make my ~300ft-lb rated valeo clutch slip. i put in an sbc 3 daily (400 ft-lbs) and hoping that is strong enough for the new setup - 32psi, 1856, ported head + stage3 cam, rods + asv pistons

 

[Cannedheat]

I'm curious if this engine ever got build and which head gasket was ultimately used, I am in the same predicament. I have 81.5MM BHW pistons which are going into a bored ALH. I do understand a BHW head gasket will work, but I have also come across other info which suggests that the head gaskets should be at least 0.7mm larger than the cylinder bore

 

[powermandan]

Never got built. Just went the standard route of PD150 pistons and forged rods.

I made enquiry with cosmetic to see if they could help with a gaslet. They were talking big money.

If you really wanted to do it. I think you would be able to turn a small chamfer on the top of the new pistons to clear the head gasket.

Edit. I see you are using an ALH. It's a different situation to mine

 

[bn_]

ELRING 150.791 working fine here (ALH 81.5mm). Thats a 2-hole 2.0 TDI gasket, probably BHW, too.