Need help about convert 964 crankshaft to 87 930 3.3 engine

[vinyl_tien]

My tech man is working on my 3.3 930 engine, he tear them apart and find out my crankshaft is damage.
Right now I only have 3.2 and 964 crankshaft in hand. I know the 3.2 can work well, but I am thinking use 964's crankshaft.
Can any one tell me If use 964 crankshaft, which should I look after specially?
Need your input!
Many thanks!

[Henry Schmidt]

The main issues are the pistons, front pulley and oil pump clearance.
The rods, and bearing are the same.

Clewett engineering ( info@clewett.com) can make you the pulley.

You can use a 964 , 993 turbo or a GT3 pump. You can also clearance the stock 930 pump but be careful, the housing gets pretty thin after machining.
The pistons are another story. If you have a good piston guy, he can reshape the dome and add valve pockets to make up the difference in pin height.
Properly done, you get more compression and the machine work will lighten the pistons about 5-10 gr. This piston below only needed an intake pocket but two pockets can be added.
New pistons is always an option if you budget allows.

[vinyl_tien]

Thanks a lot, Henry, really appreciate!!!
I do have a 964 oil pump lay in my place. may be it is time to dig it out.
About the piston work, I think my tech man can find man to do it, but is turbo engine need less compression than NA engine? why add compression on it?
Sorry to ask this stupid question.

[Henry Schmidt]

Originally Posted by vinyl_tien

Thanks a lot, Henry, really appreciate!!!
I do have a 964 oil pump lay in my place. may be it is time to dig it out.
About the piston work, I think my tech man can find man to do it, but is turbo engine need less compression than NA engine? why add compression on it?
Sorry to ask this stupid question.

The way we like to build turbo engines is to increase the non turbo (1000-3400rpm) performance and use the boost as an add-on.
By running slightly more compression, bigger ports and nicer cams (I like the SC cam for this application) with a faster spinning turbo, then reducing the boost slightly, you can greatly improve the drivability of 930 engine.

[vinyl_tien]

Hi Henry
Thanks a lot about my question, that really did help.
I had ask a friend, he said i might need new connect rod. But I think I can use original 930 or 964. What do you think about this?
Also after I machining piston, do I have to re-coating the piston? or do any thing?
Thanks!
TIEN

[Jonny042]

Since the stroke increase is only 2.0mm greater than original, 76.4 vs 74.4 is it also possible to use 1.0mm of base gaskets added below the cylinders to make up the difference?

[Henry Schmidt]

Edited to correct "Brain Fart"

By shimming the barrel you lose the benefit of increased compression. Generally beneficial in a turbo if only slight. Too much compression is obviously bad.

The extra.040" also changes the dimensions of the engines. Although .040" is not a lot, you can end up with chain issues, cam to chain box fitment issues and intake fitment issues.

[Jonny042]

Originally Posted by Henry Schmidt

By shimming the barrel you lose the benefit of increased compression. Generally beneficial in a turbo if only slight. Too much compression is obviously bad.

The extra.040" also changes the dimensions of the engines. Although .040" is not a lot, you can end up with chain issues, cam to chain box fitment issues and intake fitment issues.

I would usually think that what you lose is the disadvantage of the piston smacking into the head.... so I see the point of the piston machining a few posts up more clearly, now.

The lack of quench area on these motors astonishes me, but maybe I'll make that the subject of another topic.

[ChrisBennet]

As I recall, the 930 distributor drive gear is different from the 3.2/964 one. The 930 distributor turns CCW, the 3.2 turns CW. It would be an easy thing to miss.

I replaced a trashed a 3.2 crank with a 930 crank once and I remember having to move use the dist. gear from my old 3.2 crank.

[vinyl_tien]

thanks for head up really appreciate !