AAZ head and MF block questions

[dontdoemyourself]

I’ve done some reading on this subject and am in the process of rebuilding an MF engine out of an 85 Jetta TD to swap into my 82 Vanagon diesel. It used to have an AAZ but I had a runaway situation due to a broken turbine shaft, leading to a prompt blow up. The original MF head has bad cracks between the valves, and I was just going to get a refurbed one.. well.. I found a super cheap AAZ one and it just got here. Looks to be a crappy knockoff. No casting marks, tiny exhaust ports, and so on.. pics included. Would it be a bad idea to run this on a vanagon..? Wasn’t planning to go over 15 psi, I have an AAZ pump, injectors, k24 w/quantum manifold, and plan to do an air/air intercooler. Have boost and egt gauges, oil pressure and temp, and a cool motometer diesel tach. Block is at the machine shop currently, was going to order pistons on Tuesday, so it can be bored. I know the answer is to do an mTDi, I’m just having trouble sourcing an AHU.. or parts car I can afford on top of the pump.. and need to get this van on the road, as another vanagon diesel w/ sunroof project has shown up locally.. help, please, thank you.







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[dontdoemyourself]

also, I have read saurkraut and smokeyeddy's rebuild threads in the FAQ, great reads, I will be doing all bearings, IM shaft included, ARP head studs, new main bolts, rod bolts etc. I guess my real questions are.. with some porting of the exhaust valves, could this head be useable..? Are windage trays good ideas on 50* Vanagon engine swaps? What about external oil coolers? Also, should I pull the cam and swap out mechanical lifters.. ?  cheers, thanks.

[libbydiesel]

Those cracks are larger than I like to see, but did you measure them for the spec listed in the Bentley?  They might be ok. 

The exhaust ports on that new head are almost comically small! 

The concern with the 1.9 head on the 1.6 is that it significantly lowers compression (due to the increased pre-combustion chamber size) so can result in hard cold starts, rough running, and excessive smoke. 

What happened to the AAZ block?  If the block is good enough to be bored over and the crank is still good, you could get oversize ASV pistons and an AHU/1Z head and make an mTDI.  There are other parts needed as well like injectors, pump, fuel lines, but I've built a couple mTDI's using AAZ blocks. 

[libbydiesel]

...and YES, the windage tray is good for the 50° Vanagon install.  I always use one.  I also like to add a thermostatic sandwich plate and run an aux oil to air cooler.  I'm not sure what you mean about the mechanical lifters. 

[fatmobile]

 Yeah, I was kinda shocked when I pulled the cracked AAZ prechambers and saw how large the space behind them was.
 I could shove my finger in there.
 They must have 3 times the area of a 1.6 head.

[libbydiesel]

The prechambers of the 1.5, 1.6 and 1.9 are all proportional to the engine displacement so that they maintain the 23:1 compression ratio.  If memory serves, the added volume of the 1.9 head on a 1.6 will result in ~19:1 compression ratio. 

[dontdoemyourself]

The AAZ block was trashed, had a big hole where the #3 rod bearing cap came off and blew it apart. I still have the crank that could be cut to an oversize rod bearing, thinking of using for a hair ball Frankenstein ABA gasser stroker..

As for the current project.. With the lower compression would it likely need to run some sort of coolant pump block heater for cold starts in these Montana winters. Or would it be futile..?
The exhaust ports are comically small! I will need to buy some porting stuff to take care of that, also will probably leave the intake ports alone... I have some ptsd though.. last time I put a head back together it dropped a valve and blew up.. damnit. Not cool. I’ll take more time next go about

I will definitely run that windage tray, and I have a sandwich style oil/air cooler, definitely going to use as well.

Anyhow, I’ve heard back from the machine shop about my block, it’s ready for a bore, I’m planning on 1st oversize, (.020”) and after that I can get a head gasket, studs, bearings and so on.


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[ORCoaster]

Well if the compression is low... and you stated this:

would it likely need to run some sort of coolant pump block heater for cold starts in these Montana winters. Or would it be futile..?

It would do you well to have heat to the engine overnight, I mean you sleep in a nice warm bed don't you?  The amount of low compression is the question I have for you.  If it is so low, like 360 it may be futile to keep it warm and expect it to fire up in the morning.  Do you know how low it is? 

If you are considering a coolant type heater I understand they are the better between a dip stick type and the coolant type.  VW does have the plug type that goes into the block in place of one of the plugs in the back of the block.  I would venture a guess that you can find them online fairly easily. 

[libbydiesel]

I believe a 1.9 head on a 1.6 shortblock will result in ~80% of the compression pressure of a 1.6 head on a 1.6 block but I am basing that off math rather than having actually done it and measured.  0.80 x 450 = 370

[dontdoemyourself]

Cool, with some new pistons in it it should be right around there. I will do a test once it’s together, and let everyone know for sure. Hoping I can order some pistons today, and to have them here by the end of the week.


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[theman53]

Looks like you have the 85 ish or earlier MF block. I didn't see the 2nd oil drain in your MF head pics. This should just be using the correct head gasket for the solid lifter block and blocking the 2nd oil drain. You may have to put a piece of gasket near the coolant hole by the big oil drain. I did mine many years ago so I forget what all is needed. should be documented in my thread or the franken engine threads/faq if needed.

[dontdoemyourself]

The AAZ head already has a drain plug in there, which I was happy to see. Just need to get it back together so I can measure protrusion and get the right one on order. Project will hopefully be taking a turn here soon, this engine will be ending up back in the 85 Jetta, as I may have today sourced a 1Z for my vanagons future as an mTDi.. fingers still crossed.


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[theman53]

That's what I am saying, your MF head doesn't have the drain, so oil will go on your block, unless you had a hydro block and plugged its return when you used the solid lifter head.

[dontdoemyourself]

Again thanks for the replies! Block should be back from the machine shop in the next few days and I’m going to work on putting it back together.. I’ll post more when things get photo worthy.


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[libbydiesel]

Just to be clear regarding what theman53 was saying, when you go to put a hydro head onto a mechanical lifter block, there is an oil return in the head that lines up with a coolant channel in the block.  BOTH need to be plugged or you will have leakage down the front of your block when you assemble it.