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Author Topic: Best head to rocker shaft stud  (Read 1434 times)
H67bug
Sr. Member
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Posts: 267



« on: March 07, 2018, 09:25:34 AM »

Hi

What do you recommend? Beetle, over 200 bhp, JPM heads but not JPM rocker shaft. Two bolts.

Have Scat installed now but one sheared so wanted to check what to replace with.

Many Thanks

H
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Neil Davies
Hero Member
*****
Posts: 3200



« Reply #1 on: March 07, 2018, 22:30:08 PM »

I'm interested in this too as I broke one last year. 160bhp or so, Street Eliminator heads. I was just going to replace them with good original German stock ones, as I've never heard of anyone breaking one before!
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2007cc, 48IDFs, street car. 14.45@93 on pump fuel, treads, muffler and fanbelt. October 2017!
ibg
Jr. Member
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Posts: 74


« Reply #2 on: March 07, 2018, 23:01:17 PM »

Berg used to sell them
http://www.geneberg.com/cat.php?cPath=6_199
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bedjo78
Full Member
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Posts: 192


« Reply #3 on: March 08, 2018, 04:12:29 AM »

Pauter studs is super...
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Erlend / bug66
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Posts: 759

SCC Event


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« Reply #4 on: March 08, 2018, 10:17:06 AM »

Pauter studs is super...

I think they are a bit bigger also? Uses a non metric but anyways. I got flanged 12point ARP nuts for mine from Summit. Turbo and large dual valve springs
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10.626 @ 132mph, SCC 2016
10.407 @ 134mph, SCC 2017
Roman
Hero Member
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Posts: 654



« Reply #5 on: March 08, 2018, 15:22:38 PM »

Just a guess here:
They don't shear off. They bend due to a flexing shaft, after a while the material gets exhausted and they break.
I have used Pauter shaft and rockers before with good luck, but now I have the JPM 5-bolt.
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RaptorLou
Newbie
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Posts: 7


« Reply #6 on: March 11, 2018, 15:57:21 PM »

I picked up some at Dave Folts. Limited amount. He sold a bunch to Andy at Majors Motors.

Lou
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Dalland
Jr. Member
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Posts: 58


« Reply #7 on: March 13, 2018, 09:23:05 AM »

Just a guess here:
They don't shear off. They bend due to a flexing shaft, after a while the material gets exhausted and they break.
I have used Pauter shaft and rockers before with good luck, but now I have the JPM 5-bolt.

Or...
Its a fretting problem between det rocker shaft "block" and the stud.
I higher bolt tension could fix that problem, but thats not very safe when the stud is mounted in butter...
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kraftkaefer
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Posts: 64



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« Reply #8 on: March 13, 2018, 12:20:10 PM »

Hello,


i use this one:
https://www.hoffmann-group.com/US/en/hus/Clamping-technology/Clamping-elements/Stud-DIN-6379/p/375380
with this one:
https://www.hoffmann-group.com/US/en/hus/Clamping-technology/Clamping-elements/Collar-nut/p/375390#

Made some heads (kraftkaefer/ Hot Chocolate notch) like in the Pictures 4- M10 -studs and this season 6-studs M8 on A/F Heads in the new kraftkaefer.
Some work to do, but works good  Smiley


Stefan

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www.kraftkaefer.de
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Neil Davies
Hero Member
*****
Posts: 3200



« Reply #9 on: March 13, 2018, 20:33:02 PM »

Just a guess here:
They don't shear off. They bend due to a flexing shaft, after a while the material gets exhausted and they break.
I have used Pauter shaft and rockers before with good luck, but now I have the JPM 5-bolt.

Or...
Its a fretting problem between det rocker shaft "block" and the stud.
I higher bolt tension could fix that problem, but thats not very safe when the stud is mounted in butter...

I wondered about this. My engine is an old one, with various sketchy history going back to the '90's. I had heard about valve springs not liking being kept under pressure for too long, so it's best to take the rockers off. Unfortunately I didn't hear this until I'd had the engine sat in my garage for 6 or 7 years, so I took the heads off and replaced the springs. The engine went in the car, I drove it maybe 65 miles then ran it twice on the strip. Drove it home and it lost power on the motorway and went rattly from the top end.
I had a go-pro in the car for the first run, stuck to the inside of the back window, and the engine note clearly changes when I came of the power at the top of the track. Didn't hear anything on the day, but it just sounds wrong on the video. Second run was quite smoky under power too.  I won't have time to get into the engine until Easter holiday, but I hope it's just frettng caused by the rocker stud not being tightened down properly or something daft like that.
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2007cc, 48IDFs, street car. 14.45@93 on pump fuel, treads, muffler and fanbelt. October 2017!
Dalland
Jr. Member
**
Posts: 58


« Reply #10 on: March 14, 2018, 12:47:17 PM »

Just a guess here:
They don't shear off. They bend due to a flexing shaft, after a while the material gets exhausted and they break.
I have used Pauter shaft and rockers before with good luck, but now I have the JPM 5-bolt.

Or...
Its a fretting problem between det rocker shaft "block" and the stud.
I higher bolt tension could fix that problem, but thats not very safe when the stud is mounted in butter...

I wondered about this. My engine is an old one, with various sketchy history going back to the '90's. I had heard about valve springs not liking being kept under pressure for too long, so it's best to take the rockers off. Unfortunately I didn't hear this until I'd had the engine sat in my garage for 6 or 7 years, so I took the heads off and replaced the springs. The engine went in the car, I drove it maybe 65 miles then ran it twice on the strip. Drove it home and it lost power on the motorway and went rattly from the top end.
I had a go-pro in the car for the first run, stuck to the inside of the back window, and the engine note clearly changes when I came of the power at the top of the track. Didn't hear anything on the day, but it just sounds wrong on the video. Second run was quite smoky under power too.  I won't have time to get into the engine until Easter holiday, but I hope it's just frettng caused by the rocker stud not being tightened down properly or something daft like that.

The problem is quite simple, but the solution is a bit more complicated...
The stud (as all bolting solutions) is a kind of "spring", the "spring" pressure created by torquing the nut was enough for the oem valve springs to clamp the rockershaft to the head hard enough to avoid fretting problems.
But when we upgrade the spring pressure the oem clamping force (torque) may not be strong enough to avoid fretting problems, as far as I know it is not common practice to have a higher torque with the HD studs so that may be something to think about. But I'm afraid that the thread strength in the heads will soon be a problem, maybe it could be fixed with case savers...

I belive that when a stud breaks it's not that it's too weak since the alu threads are much weaker, but that the rocker shaft is moving...
« Last Edit: April 01, 2018, 13:16:25 PM by Dalland » Logged
H67bug
Sr. Member
****
Posts: 267



« Reply #11 on: March 30, 2018, 21:29:28 PM »

Thanks all. Reinstalled new stud- torqued to 15 ft lbs and been ok so far. Will get some miles on once weather drys up. If it goes again will utilise a different suggestion from above.


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