smkn951

Hello everyone,
i recently seized the engine on my 86 944t. i am able to locate a running 85 944na. will the short block work for the 86? what modifications will i need if any.
TIA
Carl

MAGK944

If you swap out the pistons and rods yes everything else is the same on the 85na & 86t short blocks.

nkgosselin

Thats a bummer.

What was the underlying cause of the seize?

odonnell

Early, or late 85? The earlier 85s (although not all 85.1s) have slightly different blocks. I'm wrapping up building an early NA block for my '86 951 and can share my findings if you're in that boat.

smkn951

what about balance shafts?

smkn951

seize may have been due to the walls werevery dry. i was i n haste in putting it back all together.
i made sure all the walls were clean and free of debris upon assembly. didnt lube it nor did i preasurized the oil system to ensure it had oil

smkn951

it looks like #4 piston ring/s broke, wedgededand gouged the wall.

FRporscheman

Aw man, sorry that happened to you.

As others have said, you can use the NA block to build a turbo. But if you want to just use the NA shortblock, yes, you can do that too, just know these 3 things:
1. You'll have 9.5:1 compression, so you'll need good tuning.
2. You'll have cast rods, so you'll need really good tuning.
3. There are some minor mods you'll need to make to the engine, like drilling the upper BS cover for the oil feed to the turbo, etc.

Look for an old post by DanD, something about Yes, you can Turbo an NA or something like that. He uses an NA engine shortblock and said he loved the extra low end power.

odonnell

Is it possible to drill the balance shaft upper cover on an early engine for the oil feed? They're a totally different design than the later engine that had the plug and a bearing cap below the cover. The early engines have the bearing shell seated directly into the cover.

Noahs944

I think late blocks are drilled & tapped for 1 or 2 knock sensors but early, being made from a different casting didn't come with provisions for knock sensor mounting, so you need to be more creative. In my view, it looks like you can drill & tap 1 flat casting in between #3 & 4 cylinder (or is it 1 & 2 ?)-very carefully. Later blocks (1987 944 S n/a) have spots between 1/2 & 3/4 for potentially 2 bosch knock sensors on the intake side of the block because they used 2 on the 16 v engine, whereas the turbo used only 1.

FRporscheman

- The very early design of BS covers, with the separate bearing caps, can still be made to suit a turbo. Porsche sells a bearing cap with an oil feeding hole, a rubber o-ring, and you drill the BS cover. These parts are from the 85.5 turbos from europe, and early 86 turbos here.

- The later design can easily be drilled. If you're lucky, it's drilled from the factory and is plugged with an allen bolt.

- I built my '87 951 engine using an '84 block (and 951 internals), and it had a spot for the single knock sensor.

Here is the thread I was talking about:
https://rennlist.com/forums/944-turb...bo-update.html

smkn951

Thanks everyone. my choices aren't so limited now.
with the earlier 944s, does smaller oil passages hurt the engine much? i'm not tracking the car, just as a daily driver. how do i tell an earlier 944 engine? BTW on my block, there are two ears in which the knock sensor can be mounted, is this an indication that it's not an original 86?
will i be able to just replace the BS cover rather than tap the one i'm getting? are BS cover interchangeable? My BS cover bearings are split.
TIA
Carl

Noahs944

Curious if the pistons were original to the engine (are you aware of block & piston "series 1 & 2...)"? There are matching sets of clearances that need to be respected. I am convinced the series 2 piston that last assembled my series 1 16v block is the reason for mass scouring in the cylinder.


Secondly, the piston rings, were they new or used & if new, did you measure/adjust the ring clearance to each cylinder?

-Just want you to be successful mate.

Noahs944

While on subject, can anyone tell me if the 944 turbo forged pistons come in different series?

V2Rocket

yes but believe most of them were group 1.