Studs?
Senior Member
Joined: Oct 2001
Posts: 10,906
From: Peoria, AZ
Originally Posted by GMON' post='811836' date='Apr 3 2006, 05:11 PM
Dowelling is not meant to prevent twisting.
Its to add more support to the combustion chamber which just happens to be the rotor housing. The whole side of the housing can deflect during a bad burn. This pushes the cumbustion chamber away from the rotor. Since the tension bolts are not machine fit there is enough room for the housing to deflect about 10mm which is enough to cause serious problems. After this happens the housing is back in the shape it had and the only evidence is a crack at the stock dowels and/or some scoring on the plates and housings by the water seals.
Studs that act as dowels both add support to the combustion chamber while adding resistance to twisting.
Maybe twisting isn't the best word, a more general term like "moving" should be used.
There is movement between the housings/irons no doubt, now to what extend/what exactly causes this I don't know. In agreement with what you said; you can see a "chaffing" or "etching" on the rotor housings near the water jacket areas, same thing you see on on some piston engines. Usually just seen on race engines that have been overheated, or improperly torqued; being too loose for each circumstance.
Senior Member
Joined: Oct 2001
Posts: 10,906
From: Peoria, AZ
Originally Posted by GMON' post='811839' date='Apr 3 2006, 05:37 PM
I see no benifit in the tension bolts not streatching.
A)The engine expands when it warms up and the bolts should streatch a little.
They are designed to do this, as the engine warms up its held toguther tighter.
B)Bolts that dont streatch would not allow for this expansion and would hold the
engine toguther much tighter than stock. I am sure you can think of a few clearences
that this would be detremental to?
As for breaking. Well, we all know how much of a problem those are.
I mean damm, I can get those stupid stock bolts to stop breaking.
As for vibration, Such a major casue of rotary breakdown. Anyone that has ever played a string
istrument knows how to fix this one. Mute it with a bit of silicone. Also, when you make them a macine
fit, dowel or bolt they are not going to vibrate.
Its not a stretch or don't stretch situation, its to what extent they are allow to stretch. How much stretch is determined by how much torque is applied; with the relativly low amount of torque applied the studs are being allowed to stretch, to account for different expansion rates.
Clearances are not the issue with limiting the engines expansion, there is something else that happens first, and its only a problem once the engine cools down...
I've never personally seen a tension bolt break, but that doesn't mean it doesn't happen. I spoke with a shop owner at the PRI show who strictly builds high revving race engines, and he told me it was not uncommon to see the tension bolts break from vibration.
On a side note, don't forgot the stock bolts when torqued are twsiting. Ovetime they untwist, and inconsitent torque levels result.
Vibration and resonance still play a factor even if something is machine fit.
Senior Member
Joined: Aug 2004
Posts: 426
Originally Posted by GMON' post='811836' date='Apr 3 2006, 02:11 PM
Since the tension bolts are not machine fit there is enough room for the housing to deflect about 10mm which is enough to cause serious problems.
10...one-zero mm?
Senior Member
Joined: Oct 2001
Posts: 10,906
From: Peoria, AZ
Originally Posted by GMON' post='811839' date='Apr 3 2006, 04:37 PM
As for breaking. Well, we all know how much of a problem those are.
I mean damm, I can get those stupid stock bolts to stop breaking.
As for vibration, Such a major casue of rotary breakdown. Anyone that has ever played a string
istrument knows how to fix this one. Mute it with a bit of silicone. Also, when you make them a macine
fit, dowel or bolt they are not going to vibrate.
http://www.rx7club.com/showthread.php?t=559062
Senior Member
Joined: Mar 2002
Posts: 126
The studs we use are not really a "tight" fit either and they are the same exact size Guru sells. You have some play .008 oversize on the hole. We have ran them on a few motors here and I like them. I just hate the build/teardown when/if needed. I have had NO vibration issues. As for ARP some of their stuff is good for most apps. I know their stuff wasn't not sufficient for what I needed for my mains on the GTS motor.
-S-
-S-
Junior Member
Joined: Jul 2004
Posts: 14
From: Bundaberg, Queensland, Australia.
If the Guru stud kit uses a 1/2 UNF thread then the tightening torque is exactly the same as stock. The helix angle of both threads are the same so the torque should be also.
Chris
Chris
Senior Member
Joined: Oct 2003
Posts: 1,420
From: Boston Ma.
https://www.nopistons.com/forums/index
Scroll down some on that page, Some info on torque specs and some other stuff.
Scroll down some on that page, Some info on torque specs and some other stuff.
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