Jussi

I have original 3.6Ltr 107mm diameter TT engine case and I want machine in new 3.8Ltr set which are for 109mm diameter case.
Does anobody knows what are exact dimension for that enlarging process?

Do we have to enlarge it like 109.04 mm at the beginning and after 8 mm spigot make it larger like 109.60 mm to end? Are the dimensions right or what they shoud be?

And is that larger dimension even needed or can we just bore engine case to 109.xx mm from start to end?

Thanks!
- Juha

JJayB

Juha
I'd call several engine builders who have actually built 3.8's. Andial or Protomotive would know.

Jimmy

Kevin

Send it to a machine shop that does this work on a daily schedule. If you mis-machine the case you will be sick to see the price of a new one. DHL or FedEx the case if you don't have anyone local that knows what to do. There is a step at the bottom of the spigot and you should cut a ring in the bore similar to what Porsche did. If you don't locate it correctly (depth of kurf cut for oring) you will break through onto the backside of the stud hole.. From memory I believe that it's 2 and 5 that you have to worry about.

Jussi

I have 3.8L cylinder set from LN Engineering and those don't have any spigots.
The sleeves are in same diameter from start to end. See pictures (left orig. right nickies):


I asked machining advice from that shop and they answered:
"The case would need to be opened up to 109.00mm or alternatively just
make sure there at least .0032" clearance on diameter between the
cylinder skirt and the opening in the case."

So, can we enlarge case with just that one dimension, 109.00mm?
How about sealing, are gasket enough between case and cylinder or should I use Curil T or Curil K2?
Thanks for your help!

Regards
Juha

m42racer

Usually when fitting these larger Cylinders, an O ring groove is also machined in the Case as there is very little room left for a good seal on the face.

This operation requires CNC work I think. This shortens the list of who can or who will do this work. Call Neil @ Performance Developments 949 646 7461. They do this kind of work for many shops all the time as they have all the CNC machines in house. Probably a 1 day turnaround for you.

Good luck.

Kevin

Juha, you missed what I wrote about sealing. M42 has also just told you again.

When increasing the bore especially in a turbocharged engine you need to oring the spigot bore in the case.. The turbulance in the case will blow buy the little oring that sits in the groove of the liner.. Do some research as to what Porsche did with the RS case..

As far as your original question, measure your liners and add the clearance. I'd ask them to recheck that number that they gave you.. That's diiferent from my specs..

Kevin

With the photo that shows your case, I'd knock out the oil galley plugs and re-clean the galley. You have boat-tailed your case that means that you have metal that is blow arounf your case. Even if you have plugged the holes.. It just takes a small burr to ruin your work.

Jussi

What do you think about enlarging engine case to 109.04mm from start to end?
That 109.04 is diameter from 3.8 RSR engine case, is that right?
Now when I have cylinder which sleeve is in same diameter from start to end, why should I use two different dimension, like in original.
Is there enough room to machine o-ring groove to case?
RSR o-ring groove needs 115,2mm diameter.. I think there isn't enough material for that or am I wrong?
And thanks Kevin from that cleaning tip! But how to remove those oil gallet plugs?

Kevin

Juhu, I going to be posting my finished cases.. One has the large bore machining and RS oring. I will show you the plugs to remove. Basically you drill a hole in the plug and screw in a threaded bolt and use a slide hammer to pull them out.

m42racer

js 911,
Your worrying about something you need not. There are shops out there that do this type of work everyday for many of the engine builders on this forum. I gave you a contact. They know what to do exactly and can supply the correct O ring you will need. The wrong type of O ring and assembly will be a nightmare. The O ring will dictate the size of the finshed bore.

Do yourself a favor and stop worrying and call those who do this type of work.

Jussi

In Finland, where I live, aren't so many experienced Porsche machinist. Here are only three (3) Porsche 993TT cars, and mine in one
So I have to get good instruction from somewhere and then go to the CNC machining mill which does aluminium boring.
I have got the RSR machining drawing but I'm still thinking that is there really enough material for 115.2 mm o-ring groove in 993TT engine case?
Kevin: What kind of dimensions you used in that large bore RS oring version?
Thanks!

racing97

If you get no response you can PM me and I can send you a CAD file or best I can fax you a print in case you can't open the file.

regards

Jussi

Could you give me measurements for that machining(bore and oring groove)? You can send it also by email or PM.. Thanks!

racing97: I sent PM to you.