Mark:

Not sure what your picture is showing me. Need an arrow or something. At any rate, .050" is plenty for anything spinning on the bottom end.

greg brown

 

Greg,
sorry, didnt get a chance to put the arrow on the grinded off spot on the crank.
what if its about .020", that enough? the place right below the center main bearing is where the later crank stuck as we were test assembling the engine. (little shiney area) I guess the clearances on the older crank vs newer cranks are different. Newer cranks have the bigger rod oiling holes.

Thanks for the responses.

Mk

 

Mark:

.020" is a bit close for my tastes, especially considering it is a radial clearance that will be influenced by the wearing of the thrust bearing. I use a minimum of .040" for things that spin....slightly more for a radial clearance. There is no reason that you can't remove the material from the block, where your shiney area is...nothing is going to happen bad right there. You could undercut this area quite a bit without hurting anything.

Is that a narrow thrust bearing on a wide thrust bearing crank???

greg

 

Thanks Greg!

so, Ill get out some feeler gauge and make sure i end up in the .040" range .

as far as the thrust bearing, we are just using the stock bearings for the older blocks. ( '82 euro and US are the same ). I dont know what the actual year of this crank is, but 928intl said that it was the same as the '84 type, which had those larger oiling holes you can see on the rod bearing area.

when i did a thrust bearing movement measurement, it seemed to be in spec. I do remember when building the 85 block up a long time ago, that it had a different single piece front main bearing. maybe those cranks used a wider thrust bearing to match a maybe wider thrust bearing area on the crank???

I know you should be working on Mark A's new engine, but thanks for taking the time to chat about Scots proposed 5 liter bored out 4.5 liter block and ??? crank with stock bearings.

mk

 

Was looking for squiter info and noticed this. Must have missed your comment when thread was new. Also GTS rods are exact same size as others. Its pistons which have lower compression height and they make total crank-rod-piston combination same as on others when crank stroke increases.

Also all 944 and 968 rods are same lenght. Only difference is they have 2mm wider big end. 944 S2 and 968 pistons have even smaller compression height than GTS pistons to counter longer throw crank.

 

I have a GT engine complete minus computers, but includes wiring harness for $4000, oilpan to intake manifold and everything in between

 

We've got a short block from an '89 car in the shop here, ~75K miles. We decided to sell the '89 motor in parts.