Cam timing
03-01-2016, 07:39 PM
#1
Rennlist Member
Thread Starter
Cam timing
I am fixing some oil leaks, in particular a leak from cam shaft/ chain housing seal. Just out of curiosity I figured, may as well check the cam timing before I take it all apart.
So here is what I found. Left bank i.e cyl 1-2-3 the timing was 0.77 mm, and the right bank 4-5-6 it is 0.44 mm, that is some seriously retarded cams. According to my info the timing should be 1.16 - 1.36 mm, and I understand that most people set it at 1.25 mm.
My question is, could running this much retarded cam timing have caused any damage to the engine, and how does that affect the performance of the engine.
When I first bought the car back in 2007, I knew it needed cylinder head rebuilds, which was done in July 2007, so the engine has been running like that for around 25000 KM.
So here is what I found. Left bank i.e cyl 1-2-3 the timing was 0.77 mm, and the right bank 4-5-6 it is 0.44 mm, that is some seriously retarded cams. According to my info the timing should be 1.16 - 1.36 mm, and I understand that most people set it at 1.25 mm.
My question is, could running this much retarded cam timing have caused any damage to the engine, and how does that affect the performance of the engine.
When I first bought the car back in 2007, I knew it needed cylinder head rebuilds, which was done in July 2007, so the engine has been running like that for around 25000 KM.
03-02-2016, 05:10 AM
#2
RL Technical Advisor
Steen,
No damage, but certainly those values result in less upper RPM performance. I would recommend setting them at 1.25mm and get them as close to each other as possible.
No damage, but certainly those values result in less upper RPM performance. I would recommend setting them at 1.25mm and get them as close to each other as possible.
03-02-2016, 10:24 AM
#3
Steen, I am curious if you felt the car was down on power noticeably and How much of an effect
there will be with correct valve timing. I have experimented with timing on engines I've built but
never to the degree! you have. 964 grinds are fairly mild since much overlap isnt well tolerated
by the air flow meter so some deviation really doesnt have much effect. I think though that perhaps
Steve was having a "moment" when he wrote that retarded would reduce top end power. As a
rule you retard for top end and advance for lower RPM use.
there will be with correct valve timing. I have experimented with timing on engines I've built but
never to the degree! you have. 964 grinds are fairly mild since much overlap isnt well tolerated
by the air flow meter so some deviation really doesnt have much effect. I think though that perhaps
Steve was having a "moment" when he wrote that retarded would reduce top end power. As a
rule you retard for top end and advance for lower RPM use.
03-02-2016, 10:39 AM
#4
Rennlist Member
Thread Starter
Thanks Steve, I always appreciate your input, good to know the extreme retarded timing haven't done any damage. I will set both cams as close as possible to 1.25 mm.
prschmn, I can't comment on the performance with that amount of retard, cause back in 2007, I only just received the car and it went straight to the mechanic for a top end rebuild, so basically thats how its been all the time I have owned it. I will however report back when i get it on the road in April, and give you a seat of the pants impression.
prschmn, I can't comment on the performance with that amount of retard, cause back in 2007, I only just received the car and it went straight to the mechanic for a top end rebuild, so basically thats how its been all the time I have owned it. I will however report back when i get it on the road in April, and give you a seat of the pants impression.
03-03-2016, 04:10 AM
#6
Three Wheelin'
Apologies for hopping onto your thread Steen,
Does anybody have a picture of the tool used to remove/refit the camshaft sprocket? Is a special tool even required?
I'll be checking and adjusting mine soon and want to ensure I have the tools required to remove it before I start.
Does anybody have a picture of the tool used to remove/refit the camshaft sprocket? Is a special tool even required?
I'll be checking and adjusting mine soon and want to ensure I have the tools required to remove it before I start.
03-03-2016, 06:20 AM
#7
Instructor
Trending Topics
03-03-2016, 08:09 AM
#9
Three Wheelin'
I think(?) the crows foot is only needed on the earlier 911 engines. With the 964 you use the tool shown above to hold the sprocket whilst removing the bolt with a 19mm(?) socket. Someone who has actually done it will hopefully chime in...
03-03-2016, 02:20 PM
#11
Burning Brakes
I want to do this process as well just to know I can ... I have small oil leak right behind the driver side chain box and can not view up through that area from under side 
. Assume can not undo TC cover box with chain on cam. Will check existing factory settings just to learn and would expect to be very close to 1.25mm.... Hope you chaps will post a thread on you methods and experience 
. Assume can not undo TC cover box with chain on cam. Will check existing factory settings just to learn and would expect to be very close to 1.25mm.... Hope you chaps will post a thread on you methods and experience
03-03-2016, 02:22 PM
#12
Ah ha! that will teach me for watching build videos from the wrong year!
Good advice, I shall be doing mine in the summer I expect.
I do know about the spark plug to remove the timing pin lol.
Good advice, I shall be doing mine in the summer I expect.
I do know about the spark plug to remove the timing pin lol.
03-03-2016, 08:28 PM
#13
Instructor
FWIW- I used the Steve Stomski tool below, actually bought 2 of them one for each side so I could see both cams as i rotated the crank. worked out pretty good, left 1.26 and right 1.28 was as close to 1.25 as I could get.
http://www.stomskiracing.com/product...timing-fixture
http://www.stomskiracing.com/product...timing-fixture
03-04-2016, 05:17 AM
#14
Three Wheelin'
I've got one of those to. Looking forward to the simplicity of using it. Finding secure enough mounts/positions for a dial gauge for these kind of things is normally half the battle!
