James Bailey

Correct ANY ABRASIVE will ruin the alusil surface and sadly happens all to often when someone decides to use a bottle brush hone. Then when reassembled and started the pistons will QUICKLY sieze......
The surface is polished with special honing paste and a felt padded hone which cuts back the aluminum but leaves the silicone standing proud. Reynolds 390 as I recall is the USA version of the Mahle alloy and was used on the Chevy Vega which caused the Chevy guys all kinds of problems when they tried to rebuild them like they did an old small Chevy.

Rob Edwards

Just run the block through the parts washer, rinse with water, blow it completely dry with compressed air, then wipe the bores with some ATF on a paper towel. Now it's ready to be bore-gauged to get a sense of what condition it's in.

What tolerance group number is stamped on your pistons? Like so, up on top of the crowns:

atb

If you do deglaze you would use a honing tool mounted with felt pads and silicon paste.
But since you're not going to do anything to the cylinders, you don't have to worry about it .

LT Texan

Have you looked at the engine identification stamp on you current engine?

You say it's not an S4 but how do you know?

I hope you don't expect to use this shortblock to replace your current engine because it has an oil pan leak.

Do you really want to "rebuild" this shortblock?

1989porsche928

the motor in the car does not have an s4 bottom end, i looked up the number that was stamped on it i think it was like an 86 bottom end. yes i want to rebuild the block

Mrmerlin

dont go near the bores with anything other than some acetone or brake cleaner and rag,
then coat with oil when assembling.

your bores are ready to be assembled

mark kibort

why not just measure the crank play, and if good, just re ring the pistons and rebearing the rod bearings and put it back together. I don't think anyone here has ever seen a main bearing fail beore, so if its not a blown engine, or an engine that has gone through something terrible, just rebuild it the short cut way. if you do split the block, make sure you have the manual to make sure you do what is needed to make sure you have perfect alignment. using the oil pump , etc. and the right sealant. (and have cleaned the surfaces perfectly before hand.)

edit.... well, we were too late. you split the block. just got caught up. I would use only simple green on the cleaning of the block. nothing harsh on the cylinder bores. they should be fine. even a few small scratches are ok. post pictures here so we can see. boring and oversized pistons would be a huge expense compared to the cost of a replacement block. just redoing the paste process will remove most all scratches if they are minor.

have fun!

1989porsche928

it probably would be a good precaution to buy a can of AN-30 and a felt hone , the engine i am building came off of ebay

LT Texan

What problem are you trying to solve with this new shortblock?

1989porsche928

Lt texan i want to rebuild it and eventually put it in my car. after i clean the rods and pistons tommorow im going to start the measuring of everything.

Rob Edwards

What part of "don't touch the bores" do you not 'get'?

Hilton

Post pictures - the engine number is on a plinth under where the upper radiator hose comes out of the coolant bridge.

It should start with M28/xx 81 x xxxxxx

That is the most meaningful number.

If your engine definitely, by the engine number (not by any other stampings on the block), has an 85/86 block, then all bets are off as to what your car actually has in it -it could be a lightly modified S3 bottom end, it could be a stroker, it could be S4 crank/pistons in an S3 block.

As for polishing the bores with the correct alusil paste - there are old threads here about people doing it - I say have at it (easy for me, its not my engine).

The important part is not to use anything rougher than a felt pad in there.. no scothbrite, no stones, no nothing.

James Bailey

If you read the workshop manual and the description of the process of boring then honing with the felt pads and paste it is pretty obvious that they are removing material enlarging the bore to the finished size and surface texture. That said if you start "polishing" it you might just make it oversized and that would be a bad thing.

mark kibort

again, I wouldn't even touch the bores. certainly, if its your first time, I wouldn't even attempt to "freshen up" the bores with the paste and felt pads. Ive build a bunch of these and the one or two that needed it, I let the pros do it. guys that know this engine block or other blocks like the 928. again, if there is a scratch that is really deep, then start to worry and think about ways to fix it. if its just little scratches, forget about it, its probably fine and the most important thing is just assembling it without damaging it. (re-ring, rebearing, etc, check bearing clearances with plastisine, etc) are you going to reuse the main bearings? this is not uncommon, as they are a little pricey these days, but ive had great success with stock Glycol bearings for all the motors ive built.

Don Carter

I don't want to hijack the thread, but have a couple of related questions. I'm doing the same block split right now on an 89 TBF block to sell to Carl for a table. I'm stuck on two things. I have all the bolts out and the cradle is mostly separated from the upper block accept the spot closest to the starter mount. Maybe a stuck locator pin? A bolt I can't see? (It's sitting flywheel down right now). I've hit it pretty hard with a chisel.

Also, I don't seem to have a tool to get the rod end cap bolts off. Anyone know the size and type of socket needed? and if it's available at local auto parts stores. It's rare I run into a tool I don't have these days...