Went back to the dyno today....
12-28-2006, 02:02 PM
#271
Banned
Thread Starter
Originally Posted by Laust Pedersen
The vintage Bugatti had the block and head cast in one, so no messing with headgaskets, studs, nuts and assembly torque.
The MLS HG is much stiffer than the WFHG, meaning that head-gasket-block separation requires less stretching of the studs and therefore less force (combustion pressure) for the same clamping force (head nut torque).
As Tom was suggesting, I would try to get some information on max allowable head torque and target that. As I recall, I am at about 90 ft-lb with MLS and OEM studs.
Laust
The MLS HG is much stiffer than the WFHG, meaning that head-gasket-block separation requires less stretching of the studs and therefore less force (combustion pressure) for the same clamping force (head nut torque).
As Tom was suggesting, I would try to get some information on max allowable head torque and target that. As I recall, I am at about 90 ft-lb with MLS and OEM studs.
Laust
You are right about the mls
12-28-2006, 03:33 PM
#274
Addict
Rennlist Member
Rennlist Small
Business Sponsor
Rennlist Member
Rennlist Small
Business Sponsor
Originally Posted by special tool
You are right about the mls
The 'theory' is that the aluminum threads are good to approx 110 lb/ft. After that you stand a good chance of ripping the studs out.
ARP and Raceware are extremely similar in strength and appearance.
There is also a theory that over torquing the head will cause an uneven pressure distribution and lead to premature gasket failure…
12-28-2006, 03:49 PM
#275
Banned
Join Date: Feb 2004
Location: In self-imposed exile.
Posts: 14,072
Likes: 0
Received 8 Likes
on
7 Posts
Didn't the GTS use 120 ft-lb? I seem to remember reading that someplace. Granted it was a different head, but it was still aluminum casting with aluminum threads. . .
12-28-2006, 04:00 PM
#276
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Originally Posted by Porsche-O-Phile
Didn't the GTS use 120 ft-lb? I seem to remember reading that someplace. Granted it was a different head, but it was still aluminum casting with aluminum threads. . .
This is a very interesting thread I hope some of the 928 guys are watching (I've sent it to a few). Since any limitations found with the 951 engine can apply to the 928 motor. More so the 16V like mine, but none the less, doesn't hurt to take into account other issues people find.
Keep up the good work ST. Guys like you, Todd, and Louie (and others) are really pushing the limts of what Porsche gave us to play with. There are many high HP cars out there, but very few with open details to share we can all learn from.
I need to print out your dyno sheet for the Supra guys who constantly question why so many of us "bother" with Porsche's!
12-28-2006, 04:37 PM
#277
Banned
Thread Starter
And since I am feeling generous with the info today......
The lift initiates on the compression stroke, NOOOOOOOT the combustion stroke.
This is evidenced by the EXACT correspondance of intake manifold pressure to coolant jacket pressure (yes, I tested in live conditions) and the subsequent RELEASE of pressure on the downstroke.
Don't say I never told ya nothin'.....
The lift initiates on the compression stroke, NOOOOOOOT the combustion stroke.
This is evidenced by the EXACT correspondance of intake manifold pressure to coolant jacket pressure (yes, I tested in live conditions) and the subsequent RELEASE of pressure on the downstroke.
Don't say I never told ya nothin'.....
12-28-2006, 04:43 PM
#278
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Originally Posted by special tool
Don't say I never told ya nothin'.....
Todd has talked about heads lifting, not sure if he has suspected his lifting yet. He is running a custom MLS gasket he embosses himself.
Are the threads in the block stock or have they been rethreaded with something like a heli-coil?
12-28-2006, 05:02 PM
#279
Instructor
Join Date: Oct 2004
Location: Oxfordshire, UK
Posts: 240
Likes: 0
Received 0 Likes
on
0 Posts
Can someone tell my why people are torquing to 90ft lb, is this better than doing the porsche method of 20Nm then 90 degree+ 90 degree. Which is best/more accurate.
according to my convertor 90ft lb is 122Nm, the old porsche method was 20Nm, then 50Nm then 90Nm, so its slightly more clamping force.
according to my convertor 90ft lb is 122Nm, the old porsche method was 20Nm, then 50Nm then 90Nm, so its slightly more clamping force.
12-28-2006, 05:18 PM
#280
Originally Posted by Hacker-Pschorr
Todd has talked about heads lifting, not sure if he has suspected his lifting yet. He is running a custom MLS gasket he embosses himself.
But hasn't Cometic already fixed those leaking issues?
12-28-2006, 05:29 PM
#281
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Originally Posted by BrendanC
But hasn't Cometic already fixed those leaking issues?
12-28-2006, 05:44 PM
#282
Originally Posted by Hacker-Pschorr
Cometic was unable to produce a gasket in his bore size (the embossing portion). So he has them making the three blank pieces, he does the embossing.
12-28-2006, 06:04 PM
#283
Race Director
Originally Posted by ross255
Can someone tell my why people are torquing to 90ft lb, is this better than doing the porsche method of 20Nm then 90 degree+ 90 degree. Which is best/more accurate.
according to my convertor 90ft lb is 122Nm, the old porsche method was 20Nm, then 50Nm then 90Nm, so its slightly more clamping force.
according to my convertor 90ft lb is 122Nm, the old porsche method was 20Nm, then 50Nm then 90Nm, so its slightly more clamping force.
12-28-2006, 06:09 PM
#284
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Originally Posted by BrendanC
I remember now. How is the 427 coming along?
Originally Posted by sweanders
I would rate 32 Nm higher than just slightly.. I'd say that a 35% increase is pretty brutal.
