Engine block compatibility

xupkid2 · 11-21-2006, 06:57 AM

Wondering if anyone knows if a 1987 Turbo block will work for a 1987 NA rebuild. Found out that I need to replace my block and found a turbo block for $200 in my area. I know the stroke, bore and displacement are all the same but wasn't totally sure it was compatible. I also assume the turbo block has the bolts for the timing belt tensioner but will make sure before I pick it up. Any help would be appreciated.

xupkid2 · 11-21-2006, 06:57 AM

Sorry forgot to include that this was for a 944.

bleu951 · bleu951's Garage

Blocks are the same.

hpaulb · 11-21-2006, 09:59 AM

Typically the compression ratio is different from a Turbo to NA. Better check on that stroke.

legion · 11-21-2006, 10:03 AM

From what I understand, the difference in compression ratios between Turbo and NAs is acheived by different pistons (the turbo pistons are bowl-shaped). I believe they used the same length connecting rods and a similar crank. (I think the parts are identical in shape but differ in method of manufacture.)

Razorback1980 · Razorback1980's Garage

I'm not sure, but I'm guessing you will be using the pistons and crank from your old block if possible? So, if you are just concerned about the block, they should be the same.

xupkid2 · 11-21-2006, 11:34 AM

I will be using the same pistons, connecting rods and crank from my NA. The compression ration is lower on a turbo so as long as the blocks are identical I am going to snag this block and dive into the fun of tearing the thing apart again.

If anyone knows any other little secrets such as no honing please let me know cause I dont want to do this one more time.

Thanks for all your help
Brian

Zero10 · 11-21-2006, 07:31 PM

Okay, from the story I have read, check your pistons before you re-use them in a new block. There should be a coating on the piston skirts, if you have scrubbed it off altogether then you could be in for some more trouble in the future.
You will find that turbo blocks take a lot more abuse than N/A blocks and usually show much more wear. Don't go by cylinder appearance only, always have it measured.

svandamme · svandamme's Garage

weren't there differences in types of cylinder wall coating throughout the years / models

eg Nikasil vs Alusil?

i've been told that early NA's were Nikasil, but later NA's were Alusil for cost savings...

dunno but Turbo's , but i would assume that the Turbo's might have the Nikasil treatment again , to cope with higher loads ?

Porsche-O-Phile · Porsche-O-Phile's Garage

Block is the same. Heads and pistons are different (as has been said).

You'll need to plug the oil supply port on the upper balance shaft housing (normally feeds the turbocharger) though.

Or just keep all the turbo stuff if the guy still has it.

And lose the auto-tensioner. Those things are a pain in the ass.

rudidelange · 11-24-2006, 05:01 AM

No honing, special method of honing if the sleeves are rebored, then special method of honing.
These blocks have silica carbide embedded in them which makes tham hard wearing and they last longer.

Porsche-O-Phile · Porsche-O-Phile's Garage

You probably won't be able to simply transplant one set of pistons into the other block - you'll need to measure the bores and select pistons of the appropriate tolerance group.

Or just avoid the whole mess, have the thing Darton sleeved and make a 3.0L out of it. . .