drscottsmith

Well - I have continued working on the teardown of the 951 engine and have some updated photos below and some serious questions that I need advice on (Maybe I am overreacting)...my comments below the pics as usual.


Here is what was lurking behind the Oil Cooler body.

And the water pump...apparently coolant or water was left in here for all too long.

I pulled the cam tower and was relieved to see no gunk at all, so I thought that pointed to oil cooler o-ring failure instead of head. Perhaps all the gunk was confined to the water passages?

Looking down into the head pre-removal...looks pretty clean in there.

Then I pulled the head and found this. I was able to vacuum a good bit of the scale, etc. up. The white powdery stuff in Cyl 4 was almost top to bottom in the water jacket. The gasket itself lifted off in one piece but has some issues.

After I got some of the scale and residue out with the shop vac. Pretty deep down in the jacket though.

Looking from front to back across the bores. A little skeptical on the vertical marks - from what I understand that is bad.

So here is where the advice comes in. I believe I have two options: 1) continue pulling this engine apart and take the block to a machine shop and have the cylinders bored and wet sleeved. Option 2 would be to find a replacement block. With option 1 I know I would reuse everything (balance shafts, pistons, crank, etc.).

For option 1: Can I reuse everything with a different block? My understanding is I can use a N/A 944 block as this is a 1986 model. As long as I use the same crankshaft and balance shafts everything is ok?

FWIW this is the farthest into a 4 cycle engine I have been - so I am reading and learning as I go. Going farther is fine but we will have more questions (many more)!

Thanks for the input.

T&T Racing

Post photo the cylinder head with the combustion chamber showing. The cylinder wall apparent scratch marks, are they smooth or can you catch a fingernail on it?
The heavy scale deposits and sludge on the water side indicates improper coolant mixture used, not Porsche specified.Can all the scale be removed with cleaning? If not, the scale through thermal expansion and contraction can flake off and end up in the radiator core or the cooling circuit for the turbo.
I would contact Mike at Lindsey Racing to evaluate your options

drscottsmith

Hey T and T -

Some answers to your questions -

I can feel the scratches when running my fingernail across them (on both 2 and 3).

attached some photos of the block side of head.

some of the scaling came off simply with shop vac. Will have to try some additional cleaning to see if it will come off via chemicals, etc.

if I am going to have that block sleeved, I was assuming (probably incorrectly) that part of that process would be an acid-type cleaning that would get everything off of it. If that block is no good I obviously don’t really want to spend any more time cleaning parts I can’t use on a different block.

thanks for your input so far!

wildcat077

If it was me , i would start fresh with another solid clean block ... the cost of sleeving your current block and not knowing if chunks of rust
are going to detach themselves down the road is a risky thought.Just refacing that head is probably going to remove close to .030 or more.
That engine is a boat anchor,Tom is correct about the flaking, don't waste your time.
For what it's worth , balance shafts are engine specific , or rather the covers are ... but i wouldn't mix and match balance shafts or covers.

There are a lot of people on these forums who have good engines for sale for $500.00 or so dollars , Lart,Plyhammer,Dimi, etc ...

Cheers
Phil

tempest411

The corrosion can be cleaned out pretty effectively. There aren't many hidden places on the block that aren't well exposed when it's stripped. I'd sleeve or plate the block. You'll end up with a far better foundation for a new engine than using a used engine. There are too many people out there throwing these things away like there's an endless supply!

T&T Racing

Thank you for the cylinder head photos. I am not sure how an aluminum block is cleaned. I would send your photos to Mike at Lindsey Racing to evaluate and provide options for block and head.

My 944 block work for cylinder wall Nikasili to original finish, block deck skim, block prep, new studs, and shipping was about $2K. I did discover that some of the stud threads in the block were not chased clean after Nikasil process. Purchased a extension tap for $170 to chase four or five.

T&T Racing

My opinion on the scale is that the coolant was a mixture of hard water and phosphate-based antifreeze leading to precipitation of the calcium on the hot surfaces and corrosion from a pH issue.
From Chevron,
Diverse technologies have been developed to protect engines from corrosion. In Europe, problems with hard water minerals forced coolant technologies to be phosphate-free. Calcium and magnesium, minerals found in hard water, react with phosphate inhibitors to form calcium or magnesium phosphate, which typically leads to scale formation on hot engine surfaces. This could lead to loss of heat transfer or corrosion under the scale.

AnthonyGS

Take it to a good machine shop and have it hot tanked and cleaned (the block and bare head). Then perform a thorough inspection and then decide. Hot tanking will remove all the gunk and sludge and get you down to bare metal easily.

T&T Racing

Need to evaluate this, spending $$ and then finding out the block and or head are toast. Need an 944 machine shop to evaluate and recommended options/risks

AnthonyGS

This is exactly what I hate about the internet.... poor advice.

This engine needs to be cleaned so it can be evaluated. That’s why it needs to be hot tanked.

If you want to cheap out, buy used and roll the dice.

drscottsmith

Thanks all for the feedback. I am going to weight everything out and try to figure out the best path forward. Will update this thread moving forward! Please feel free to continue to weigh in.

drscottsmith

I should add a couple more points to this thread as I am positive it makes a difference...

1) I plan to get this car back to a reasonable condition - not a concours example
2) This will be a strictly street driven car - no track use at all

Thank you all again!

T&T Racing

My statement said evaluate as is before deciding. The machine shop might say, I cannot evaluate until the block and head are cleaned or the machine shop might say the block and/or head is toast, so no cleaning needs to be done.

Your statement and qualifying phrases said do the cleaning first as if you are the "expert."

V2Rocket

long flat screwdriver and a lot of scraping should get most of the rust chunks off the cylinder barrels, loose enough to vacuum up.
block is probably OK, but that head i think will be toast.

AnthonyGS

I’m not having this pointless internet qualification discussion.

I am positive you need to get this block and head stripped, cleaned and then take a lot of micrometer measurements before deciding. If you can’t it for yourself find someone that can.

Or you can just burn through money guessing.

If all of that is too complex, buy a refurbished longblock from a reputable Porsche shop. Or you can go used and roll the dice.

No one can evaluate this block and head until they are bare and clean, their proclaimed expertise is irrelevant until this happens.

Finding a good machine shop with a nice caustic hot tank = easy button for clean.

This thread is a pretty good example of why I stopped working on cars for money and only do my own junk for fun.