Camshaft Offset Key Installation
11-05-2018, 12:53 PM
#46
Hates Family Guy
Rennlist Member
Rennlist Member
Spencer,
In your graph above, how much was shaved on the head? Shaving the head retards the cam timing. I'll do the math later when I have the time.
Also, anyone notice this comment on the Lindsey site?
In your graph above, how much was shaved on the head? Shaving the head retards the cam timing. I'll do the math later when I have the time.
Also, anyone notice this comment on the Lindsey site?
In designing this gear, we measured several factory gears and found the relationship of the gear teeth and key-way to be as much as 2° different from one another. We don't know which is correct, but it just goes to show how far your cam can be off even if your car is completely stock. Then there is the possibility of the same issue on the position of the crank gear key, the crank key and the camslaft key. You really don't know where the cam position actually is. A degree kit and an adjustable gear is the only correct way to know.
11-06-2018, 12:46 AM
#48
Originally Posted by 951and944S
111, you have to maintain the filter, clean and re-oil, yes they flow better and yes they allow production of more power and torque as they are less restrictive.
They become equal to restrictive paper filters when you don't maintain them.
So, closer tolerance engines (?) are ok with more dust and particles....?
The discussion didn't become about SPEC racing but since you mentioned it, a car on track will see 10 X the amount of dirt/dust/debris than a street car.
Have you ever seen the inside of an engine....?
Any engine...?
T
They become equal to restrictive paper filters when you don't maintain them.
So, closer tolerance engines (?) are ok with more dust and particles....?
The discussion didn't become about SPEC racing but since you mentioned it, a car on track will see 10 X the amount of dirt/dust/debris than a street car.
Have you ever seen the inside of an engine....?
Any engine...?
T
11-06-2018, 08:51 AM
#49
Drifting
11-06-2018, 10:31 AM
#50
Racer
Its totally reasonable to have a +/- 1deg tolerance on the keyways for the shaft, cam gear, crank pulley keyway and crank keyway and "that" TDC mark on the flywheel.
Add another deg or so due to timing belt syncing uncertainty to the crankshaft pulley. (You can't perfect sync with a timing belt).
Its conceivable you can have an engine sample that may already be advanced or retarded 2-3 from nominal. Putting a offset key on one of those advanced sample may not get you a good result.
11-06-2018, 10:43 AM
#51
In the world I'm from, when you assemble an engine you always degree the camshaft due to component tolerances, and adjustments are very common. I'm a little surprised there isn't someone here that knows how accurate their camshaft location was the last time they replaced the belts.
11-06-2018, 10:48 AM
#52
Racer
In the world I'm from, when you assemble an engine you always degree the camshaft due to component tolerances, and adjustments are very common. I'm a little surprised there isn't someone here that knows how accurate their camshaft location was the last time they replaced the belts.
Hack: Are you talking about something different?
11-06-2018, 10:49 AM
#53
Drifting
Oh yes, that might be it! The post about burning the cat and poor performance... adding a 4deg offset to an already combined offset due to tolerances could be similar to installing a timing belt 1 tooth off--apparently a 9deg error
I'm thinking of trying the 2deg key... seems like a safe bet and not a pricey experimemt
I'm thinking of trying the 2deg key... seems like a safe bet and not a pricey experimemt
11-06-2018, 11:07 AM
#54
Racer
Oh yes, that might be it! The post about burning the cat and poor performance... adding a 4deg offset to an already combined offset due to tolerances could be similar to installing a timing belt 1 tooth off--apparently a 9deg error
I'm thinking of trying the 2deg key... seems like a safe bet and not a pricey experimemt
I'm thinking of trying the 2deg key... seems like a safe bet and not a pricey experimemt
11-06-2018, 11:34 AM
#55
Nordschleife Master
11-06-2018, 01:13 PM
#57
The only thing you can "degree" on the 944 camshaft is where the keyway is not where the lobes are. There is a tolerance on the alignment between the key and the lob grind. Same goes for the crankshaft keyway, and the gear keyways etc. I can't see how you can be sure that you are aligned any better than 1 or 2 degrees if you just time by the keyway positions.
Hack: Are you talking about something different?
Hack: Are you talking about something different?
I just bought a 944 and I've never had it apart. I am trying to learn from the experts here. I have degreed several cams in the past, though.
11-06-2018, 01:14 PM
#58
Drifting
[QUOTE=MAGK944;15412543]
So I’m curious, how did you degree your 944 camshaft?
Fwiw, the 4deg offset key noticeably improved my na throughout the rev range that matters on a road car.
[QUOTE=MAGK944;15412543]Correctly degreeing a camshaft on a 944 is a pain ...i've done it a few times and it requires a few home made tools to lessen
the deflection on the dial indicator stem , although it gets easier every time ... and that's when an adjustable timing gear comes in handy.
Not too familiar with the timing key on our 2.5 engines but i have offset timing keys on two of my two stroke
snowmobiles and it's pretty effective.
So I’m curious, how did you degree your 944 camshaft?
Fwiw, the 4deg offset key noticeably improved my na throughout the rev range that matters on a road car.
[QUOTE=MAGK944;15412543]
the deflection on the dial indicator stem , although it gets easier every time ... and that's when an adjustable timing gear comes in handy.
Not too familiar with the timing key on our 2.5 engines but i have offset timing keys on two of my two stroke
snowmobiles and it's pretty effective.
