 Why did my rockers break? 6 cylinder |
|
|
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
|
| David Stowers |
 May 16 2022, 09:32 AM
Post
#1
|
|
Member  Group: Members Posts: 99 Joined: 28-June 12 From: UK Member No.: 14,613 Region Association: None  |
Hi all,
All 3 exhaust rockers broke on one side (4,5,6) when I started my engine for the first rime after cam and rocker re grind. What’s the likely cause here folks? Thank you |
   |
 
|
  |
Replies
| ClayPerrine |
May 18 2022, 11:04 AM
Post
#2
|
|
Life's been good to me so far..... Group: Admin Posts: 16,315 Joined: 11-September 03 From: Hurst, TX. Member No.: 1,143 Region Association: NineFourteenerVille 
|
I have lots of experience with setting the cam timing on 911 engines. I always suggest that you remove ALL the rockers on both sides, then put in just the intake rocker for the side you are currently working on. Once you have it set, then put in the one on the other side and set it.
I always use two digital dial indicators, and once I have them both set, I go back and make about 4 more rotations to verify that the valve clearances are correct and the cams are timed right. Only then do I put the rest of the rockers in the motor. If you do this, and are careful about not forcing the engine to turn when you get resistance, you will not bend any valves. Just my $.02. Clay |
|
|
|
| Jake Raby |
May 18 2022, 08:01 PM
Post
#3
|
|
Engine Surgeon Group: Members Posts: 9,398 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
QUOTE(ClayPerrine @ May 18 2022, 09:04 AM)  I have lots of experience with setting the cam timing on 911 engines. I always suggest that you remove ALL the rockers on both sides, then put in just the intake rocker for the side you are currently working on. Once you have it set, then put in the one on the other side and set it. I always use two digital dial indicators, and once I have them both set, I go back and make about 4 more rotations to verify that the valve clearances are correct and the cams are timed right. Only then do I put the rest of the rockers in the motor. If you do this, and are careful about not forcing the engine to turn when you get resistance, you will not bend any valves. Just my $.02. Clay Same here.. Using the crankshaft position encoder I can check my work on both sides at the same crank position over and over again, back to back. I'd expect the situation the OP has posted has ben some exhaust valves due to timing retardation.. Having things tensioned properly is a key to this. If the tension isn't correct the timing will change during engine operation, Vs what it was set with statically on the bench.. Attached thumbnail(s) 
|
|
|
|
Posts in this topic
David Stowers Why did my rockers break? 6 cylinder May 16 2022, 09:32 AM
Superhawk996 Lots of possibilities. None of them good.
I... May 16 2022, 09:38 AM
David Stowers
Lots of possibilities. None of them good.
I... May 16 2022, 09:42 AM nditiz1 At what point did they break?
Did the cam timing ... May 16 2022, 10:02 AM brant I've been told in the past that some year of T... May 16 2022, 10:52 AM porschetub
I've been told in the past that some year of ... May 16 2022, 07:03 PM rgalla9146 :agree: all of the above.
Consider yourself a... May 16 2022, 04:02 PM mb911 Ugh what a sick feeling. My guess is wrong cam tim... May 16 2022, 04:31 PM euro911
:agree: May 16 2022, 05:04 PM fixer34 Assuming the pistons hit the exhaust valves while ... May 16 2022, 05:44 PM r_towle The valve hit the piston.
Either valve timing or c... May 16 2022, 06:07 PM sixnotfour Bad News, you bumped cast pistons.... May 16 2022, 09:07 PM mepstein cam timed 180 degrees out? It happens. May 16 2022, 09:19 PM sixnotfour
cam timed 180 degrees out? It happens.
:beer2: May 16 2022, 09:44 PM Retroracer Like @FIxer34 suggested, missing or sheared cam ... May 17 2022, 07:18 AM burton73 Cam timing on my 6
This is not so easy and you ... May 17 2022, 10:43 AM sixnotfour Many shops have the tools ,but have done 180 out a... May 17 2022, 08:15 PM Luke M Have you checked the valve to piston clearance ? T... May 18 2022, 08:13 AM |
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:
|
Lo-Fi Version | Time is now: 9th May 2025 - 05:22 PM |
Invision Power Board
v9.1.4 © 2025 IPS, Inc.