Camshaft timing - valve lift question. Rebuild Continues...
01-09-2013, 06:18 PM
#1
Burning Brakes
Thread Starter
Camshaft timing - valve lift question. Rebuild Continues...
I finally figured out my camshaft sprockets are parallel and within spec. Time to move on to funner things, timing. I am using the back-dating technique with the 964 style sprockets and pin.
I have read here/elsewhere various numbers for setting the valve lift, any where from .8mm to 1.36mm. Two numbers I see a lot are 1mm and 1.26mm. I would hate to ruin my new SW heads and pistons but also would like to improve upon Porsche's factory setting which is somewhere around .8mm.
Opinions?
I have read here/elsewhere various numbers for setting the valve lift, any where from .8mm to 1.36mm. Two numbers I see a lot are 1mm and 1.26mm. I would hate to ruin my new SW heads and pistons but also would like to improve upon Porsche's factory setting which is somewhere around .8mm.
Opinions?
Last edited by Vorsicht; 01-09-2013 at 07:12 PM.
01-09-2013, 06:43 PM
#2
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There is no published specs from Porsche because they expect you to use their $$ tools.
After some investigation, I used 1.0mm, but it can easily be 1.1mm. 1.0mm was recommended to my by Gerry Woods during his engine rebuilding course. If you used an higher number, it will move your torque/hp peaks lower (since you are advancing your cams) and change the feel of the car (more torque lower is great for the city), but you are getting the valve deeper and closer to the piston. I really liked the feel of my car at 1.0mm. I also checked the piston/valve clearances to confirm no touching, and just to be totally ****, and there was lots of clearance.
cheers,
Mike
After some investigation, I used 1.0mm, but it can easily be 1.1mm. 1.0mm was recommended to my by Gerry Woods during his engine rebuilding course. If you used an higher number, it will move your torque/hp peaks lower (since you are advancing your cams) and change the feel of the car (more torque lower is great for the city), but you are getting the valve deeper and closer to the piston. I really liked the feel of my car at 1.0mm. I also checked the piston/valve clearances to confirm no touching, and just to be totally ****, and there was lots of clearance.
cheers,
Mike
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Gjbacci (11-18-2020)
01-09-2013, 06:52 PM
#3
There is no published specs from Porsche because they expect you to use their $$ tools.
After some investigation, I used 1.0mm, but it can easily be 1.1mm. 1.0mm was recommended to my by Gerry Woods during his engine rebuilding course. If you used an higher number, it will move your torque/hp peaks lower (since you are advancing your cams) and change the feel of the car (more torque lower is great for the city), but you are getting the valve deeper and closer to the piston. I really liked the feel of my car at 1.0mm. I also checked the piston/valve clearances to confirm no touching, and just to be totally ****, and there was lots of clearance.
cheers,
Mike
After some investigation, I used 1.0mm, but it can easily be 1.1mm. 1.0mm was recommended to my by Gerry Woods during his engine rebuilding course. If you used an higher number, it will move your torque/hp peaks lower (since you are advancing your cams) and change the feel of the car (more torque lower is great for the city), but you are getting the valve deeper and closer to the piston. I really liked the feel of my car at 1.0mm. I also checked the piston/valve clearances to confirm no touching, and just to be totally ****, and there was lots of clearance.
cheers,
Mike
01-09-2013, 06:59 PM
#4
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Thanks Bill!
For Andial cams or the stock cams? I measured the engine before I took it apart as a point of reference, and it got 0.65mm. I know 1.0mm worked for me, and the feel of the engine was great - here is the dyno run for the car, totally stock with no ECU upgrades.
If I was to use 1.8mm, I would really check clearances, but that is just me. It's quite far from what I found from the stock settings before taking the engine apart.
Cheers,
Mike
For Andial cams or the stock cams? I measured the engine before I took it apart as a point of reference, and it got 0.65mm. I know 1.0mm worked for me, and the feel of the engine was great - here is the dyno run for the car, totally stock with no ECU upgrades.
If I was to use 1.8mm, I would really check clearances, but that is just me. It's quite far from what I found from the stock settings before taking the engine apart.
Cheers,
Mike
01-09-2013, 07:12 PM
#5
Thanks Bill!
For Andial cams or the stock cams? I measured the engine before I took it apart as a point of reference, and it got 0.65mm. I know 1.0mm worked for me, and the feel of the engine was great - here is the dyno run for the car, totally stock with no ECU upgrades.
If I was to use 1.8mm, I would really check clearances, but that is just me. It's quite far from what I found from the stock settings before taking the engine apart.
Cheers,
Mike
For Andial cams or the stock cams? I measured the engine before I took it apart as a point of reference, and it got 0.65mm. I know 1.0mm worked for me, and the feel of the engine was great - here is the dyno run for the car, totally stock with no ECU upgrades.
If I was to use 1.8mm, I would really check clearances, but that is just me. It's quite far from what I found from the stock settings before taking the engine apart.
Cheers,
Mike
the Supercup cams were 2.0mm
964 was 1.26mm
01-09-2013, 07:15 PM
#6
Burning Brakes
Thread Starter
I also checked the piston/valve clearances to confirm no touching, and just to be totally ****, and there was lots of clearance
01-09-2013, 07:21 PM
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The factory specification books show figures for valve lift at 1mm lift (with zero clearance) of the intake and exhaust valve opening and closing points . If you fit a degree wheel to the crankshaft and set the intake & exhaust valve lift as accurately as you can to these figures you will be able to deduce the required valve lift at TDC. That said, 1mm is pretty darn close for the stock 993 camshafts.....
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01-09-2013, 07:26 PM
#8
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Thanks Colin!
As for measuring technique, using a stock mechanical rocker and dialing it down until it contacted the piston, and measuring the differences. Tedious but its; good to do.
A lot of information is in Wayne Dempsey's book "how to rebuild and modify Porsche 911 Engines 1965 - 1989". Our engines are an evolution of the engines in this book, so you can use the techniques. It documented way better than i can do here on pages 171 - 174
The basic premise is to measure the distance between the valves and the pistons for the entire profile of the cam set to the timing you landed on. Their must be clearance obviously. It also makes sure that, if you heads have been machined, that you have not reduced the clearances too much. you will need to do both the left and right sides.
What I did is work though the cam lobe pressing a valve in 5 degree increments, i measured the valve clearance by stopping at a spot, and dialling down the old-style valve (which you will need to grind to make fit) until the valve is against the piston, and count the number of turns of the rocker foot (1 mm per turn). Measure, move the crank 5 degrees, and then measure again. You should have measurements on both sides of the camshaft lobe for both the exhaust and intake valves, both sides.
A rule of thumb is to allow 1.5mm clearance for intake and 2mm clearance for exhaust.
cheers,
mike
As for measuring technique, using a stock mechanical rocker and dialing it down until it contacted the piston, and measuring the differences. Tedious but its; good to do.
A lot of information is in Wayne Dempsey's book "how to rebuild and modify Porsche 911 Engines 1965 - 1989". Our engines are an evolution of the engines in this book, so you can use the techniques. It documented way better than i can do here on pages 171 - 174
The basic premise is to measure the distance between the valves and the pistons for the entire profile of the cam set to the timing you landed on. Their must be clearance obviously. It also makes sure that, if you heads have been machined, that you have not reduced the clearances too much. you will need to do both the left and right sides.
What I did is work though the cam lobe pressing a valve in 5 degree increments, i measured the valve clearance by stopping at a spot, and dialling down the old-style valve (which you will need to grind to make fit) until the valve is against the piston, and count the number of turns of the rocker foot (1 mm per turn). Measure, move the crank 5 degrees, and then measure again. You should have measurements on both sides of the camshaft lobe for both the exhaust and intake valves, both sides.
A rule of thumb is to allow 1.5mm clearance for intake and 2mm clearance for exhaust.
cheers,
mike
01-09-2013, 08:45 PM
#9
Burning Brakes
Thread Starter
Thanks Colin!
As for measuring technique, using a stock mechanical rocker and dialing it down until it contacted the piston, and measuring the differences. Tedious but its; good to do.
A lot of information is in Wayne Dempsey's book "how to rebuild and modify Porsche 911 Engines 1965 - 1989". Our engines are an evolution of the engines in this book, so you can use the techniques. It documented way better than i can do here on pages 171 - 174
The basic premise is to measure the distance between the valves and the pistons for the entire profile of the cam set to the timing you landed on. Their must be clearance obviously. It also makes sure that, if you heads have been machined, that you have not reduced the clearances too much. you will need to do both the left and right sides.
What I did is work though the cam lobe pressing a valve in 5 degree increments, i measured the valve clearance by stopping at a spot, and dialling down the old-style valve (which you will need to grind to make fit) until the valve is against the piston, and count the number of turns of the rocker foot (1 mm per turn). Measure, move the crank 5 degrees, and then measure again. You should have measurements on both sides of the camshaft lobe for both the exhaust and intake valves, both sides.
A rule of thumb is to allow 1.5mm clearance for intake and 2mm clearance for exhaust.
cheers,
mike
As for measuring technique, using a stock mechanical rocker and dialing it down until it contacted the piston, and measuring the differences. Tedious but its; good to do.
A lot of information is in Wayne Dempsey's book "how to rebuild and modify Porsche 911 Engines 1965 - 1989". Our engines are an evolution of the engines in this book, so you can use the techniques. It documented way better than i can do here on pages 171 - 174
The basic premise is to measure the distance between the valves and the pistons for the entire profile of the cam set to the timing you landed on. Their must be clearance obviously. It also makes sure that, if you heads have been machined, that you have not reduced the clearances too much. you will need to do both the left and right sides.
What I did is work though the cam lobe pressing a valve in 5 degree increments, i measured the valve clearance by stopping at a spot, and dialling down the old-style valve (which you will need to grind to make fit) until the valve is against the piston, and count the number of turns of the rocker foot (1 mm per turn). Measure, move the crank 5 degrees, and then measure again. You should have measurements on both sides of the camshaft lobe for both the exhaust and intake valves, both sides.
A rule of thumb is to allow 1.5mm clearance for intake and 2mm clearance for exhaust.
cheers,
mike
11-11-2020, 01:22 AM
#14
Hi, sorry I had to enter into here. I want to do some sealing work on 993 can, 96.. in manual it says if we use Porsche tools than we do not need to adjust timing much, it will be all perfect.. ?
There is no information I could find in manual about how to adjust valve clearance, can someone please share any knowledge here ?
Thanks..
There is no information I could find in manual about how to adjust valve clearance, can someone please share any knowledge here ?
Thanks..
11-11-2020, 07:55 AM
#15
Race Car
The 993 uses hydraulic lifters and therefore you do not set valve clearance. When using the Porsche spec'd timing tools, there is no need to adjust valuable clearances.
However, if setting the cam timing using conventional method with a degree wheel as noted earlier in the thread, you will need to use a mechanical rocket from earlier 964 set at 0.1mm or 0.004" valve clearance on the intake valve when setting the valve lift to +1.1mm at TDC.
However, if setting the cam timing using conventional method with a degree wheel as noted earlier in the thread, you will need to use a mechanical rocket from earlier 964 set at 0.1mm or 0.004" valve clearance on the intake valve when setting the valve lift to +1.1mm at TDC.
Last edited by 95_993; 11-11-2020 at 08:51 AM.
