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This motor is surely a basket case and if you can bring it back from the dead all well and good. I was about to post something on your motor's condition within my own thread pertaining to corrosion.
You mentioned that the motor had been using green coolant- this an old technology coolant but ironically, in terms of preventing corrosion I suspect it is still the best corrosion protective coolant there is. The downside is the coolant life span. To help analyse what has happeend here it would be useful if you can advise anything about the motor's history and specifically that of the coolant deployed. It would also be useful if you can post a couple of photos showing the head condition and the head gasket that came out- on both sides.
Regarding the block- the green coolant is based on silicates and phosphates. The Americans supported this format probably because it looked after their cast iron blocks very well. The silicates look after the aluminium alloy very well. The problem with the phosphate package is not its functionality rather it is the water used to dilute it. Use anything other than distilled water [or quivalent] you get scale formation everywhere [including your radiator core which is probably buggered as a consequence]. To get rid of the scale soak it in white vinegar overnight. You could also try brushing it on as an intial trial to see how it fares. Another approach is to make a thick paste using baking soda and brush the stuff on- again a trial run on one of those bad patches at the top of the cylinder would not go amiss. I cautioned earlier about using dip baths as they invariably contain caustic soda and as Dr Bob also mentioned, not good for aluminium blocks in totality never mind the bores.
Regarding the corrosion hot spots this is more problemmatical. The first thing you have to do is find out how deep the rabbit hole goes. There is at least one divet that penetrates to the line of the fire ring and quite possibly a couple more. You need to clean these out using your dremel and a burring tool to see just how deep the rabbit hole goes. Regarding recovery there are two approaches- full recovery involving welding or a halfway house approach wherein you try to seal off the damage and stop further rot. The block metallurgy complicats things a little given the alusil material involved but there are rods available specifically designed to weld alusil so it most certainly is doable but you need a top notch welder who knows his onions to do the job. Even so, welding creates what is known as "undercut" at the joint between old and new deposition which basically means you would have to skim the block to recover the flat surface. Other approaches are based on the premise that there is enough residual structural strength to support the stresses of use and thus aim to seal off the damaged site- aka a patch repair. This is what you would be doing using HT2000 rods. If one went down that road one would have to use an old asbestos tile segment to dam the fill material, that or something a bit more technologically up to date HSE wise or so I suspect. The easiest approach is to use Belzona 1511- their higher temperature expoy repair. I have used this to great effect on pump casing repairs- get the prep right and it works really well- not cheap but good value considering what you are trying to recover. The downside is that the site will lose a little of its heat transfer capability but nothing the system cannot handle I would suggest.
Regarding the head studs- if they are not corroded I would leave well alone and use new nuts on the rebuild.
This has become a very common sight in older 928 engines...especially ones that have sat with coolant in them.
As the years pass, we are going to have to repair more and more of these engines that have this kind of damage.
If that's the best/only 4.7 you can find, you need to use it, right?
I had a very similar problem with a 928 engine, which we needed to use, because of the serial number. We welded the top of the cylinder (Involved process) and then surfaced the top deck of the block.
Turned out perfect. Cylinder was still round and did not need to be bored.
I had an engine with a divot right near the fire ring, which we welded and then surfaced the deck.
Greg,
Can you tell me how the top of the cylinder was welded ?
What products did yo uuse to weld ? Tig ? Which type of alu wire in the TIG ?
I am asking this because I want to weld my engine but the amount of silicium might be a problem.
I'm not sure how pricey it is to ship an engine to Australia, but given the level of work involved I would seriously consider waiting until November and picking up a used 4.7 from 928 INTL. The 4.7 engine itself is pretty cheap, especially when they run their half-off sale at Thanksgiving. A used short block is only $750, which drops to $375 the day after Thanksgiving. Just a thought.
I'm not sure how pricey it is to ship an engine to Australia, but given the level of work involved I would seriously consider waiting until November and picking up a used 4.7 from 928 INTL. The 4.7 engine itself is pretty cheap, especially when they run their half-off sale at Thanksgiving. A used short block is only $750, which drops to $375 the day after Thanksgiving. Just a thought.
Now that is an interesting thought. I just need to make sure that it is the correct block : it needs to be a euro block M28.11, M28.12, M28.21 or M28.22
Those 4 blocks have 97mm pistons. The only difference between first 2 and last 2 is the ignition. Last 2 blocks are from 84 till 86 with ECU ignition while my engine M28.12 is CIS Kjet
I would say go ahead and try the repairs you have in mind. If it works...great! if not you're not out much.
It would be fun to play with to see what happens.
Now that is an interesting thought. I just need to make sure that it is the correct block : it needs to be a euro block M28.11, M28.12, M28.21 or M28.22
Those 4 blocks have 97mm pistons. The only difference between first 2 and last 2 is the ignition. Last 2 blocks are from 84 till 86 with ECU ignition while my engine M28.12 is CIS Kjet
Ah - you'd have to check with Tom and see what he has in stock. The Euro block could be more.
I had a catastrophic failure in my 84 US-model 4.7 a few years ago (overheating, engine seized, my fault for not catching a leaking coolant hose in time) and bought one from them during their Thanksgiving sale. Luckily my failure was in October so I didn't have to wait long to order it half price. It was definitely the most affordable way to go for me. Its been running well now for about 3 or 4 years since that swap.
Ah - you'd have to check with Tom and see what he has in stock. The Euro block could be more.
I had a catastrophic failure in my 84 US-model 4.7 a few years ago (overheating, engine seized, my fault for not catching a leaking coolant hose in time) and bought one from them during their Thanksgiving sale. Luckily my failure was in October so I didn't have to wait long to order it half price. It was definitely the most affordable way to go for me. Its been running well now for about 3 or 4 years since that swap.
Hard to see in the webshop whether these are L-jet US engines (only year is mentioned 80-82 & 83-84)
Prices here in europe are quite expensive : about $3000 for a used engine with exchange of your own engine. And I only need the base block.
What exactly is the difference between a short & long block ?
...
What exactly is the difference between a short & long block ?
Cylinder heads. If you can refurb your heads locally, do that as you'll save on the cost difference and on shipping. With the short block, you get to look at the condition of the bores and cooling jackets prior to shipping. Long block, used, means you don't see those until it arrives and you tear it down.
Cylinder heads. If you can refurb your heads locally, do that as you'll save on the cost difference and on shipping. With the short block, you get to look at the condition of the bores and cooling jackets prior to shipping. Long block, used, means you don't see those until it arrives and you tear it down.
Then the short block will be my option. I indeed need to make sure the bores are OK (no deep scratches), and preferrably no oversized pistons.
Not an easy task to find the proper short block. Very often in Europe the blocks that you can find are damaged.
When I was in search for a new engine 6 years ago (engine in my 928S was end of life and was not the 4.7L 300HP but the 4.5 240HP), I had to search for almost 2 years before I could find one on a scrapyard of twenty 928 Porsches.
Only one of the 20 engines was OK (I checked them all via endscopic camera).
So that will leave me with not much options....unless I can find a very good local welder that can weld aluminium engines...
Don't rely on the online shop for inventory. Just email Tom at 928 INTL. it seems to just have a subset of what they have in stock.
They will get back to you very quickly and may even be able to provide you with some details about the specific short block you're looking for. They are VERY knowledgeable and helpful.
The car came from a junk yard, so history is completely unknown. All I know if when I pulled it a bunch of green coolant came out. I know it's been sitting for years. Could be 5 years, could be 10. Some guys had it in a crash repair shop for years and eventually got sick of looking at it.
Here are the heads and head gaskets
First head First head gasket side one Head gasket other side Other head Other head gasket side one Other head gasket other side.
It's pretty stupid in OZ. You would NOT believe what I've been quoted for a 16v engine that's been sitting in a shed for 10 years. Completely and utterly out of the question.
$300-400 USD for a short from the USA is an ok deal, even with the exchange rate meaning it's about $650 AUD. Shipping would be a killer though.
The alternative is either re-power with a LS/LT or 1UZFE, or ditch the whole thing and get a sweet twin turbo BMW ride or something and call it a day.
05-14-2020, 04:00 AM
