TDC is determined by the position of the crank, not the cam. The camshaft timing will be off if the dot in not in the right place. If, as seems to be the consensus, you are off by one tooth,; when your crank is at TDC the valve timing will not quite be where is it supposed to be, I think retarded here. The car will still run, but not well for a stock engine. Heavy duty racers play with retarding and advancing the cam timing depending on what results they want.
A few timing gear questions
- Thread starter kursed30
- Start date
I replaced my two piece cam gear several years ago and apparently got it right. If I recall the crank gear tooth was marked on the back side of the gear - does not make sense. Then the installation was oriented to the keyway on the front side. It did come out slightly left or right of the keyway, don't recall which. I have no way of knowing who or where that mark was made. Several years doesn't help the memory.
John
John
TDC can be a few degrees left or right on the crank position. Watch the piston while moving the crank left and right and you won't see any movement from TDC. You can still be 1 tooth off when viewing TDC through the spark plug hole.
John
johnneilson
Well-known member
The key in the crank is in-line with the rod journal. Cam timing mark is not at TDC, it is to align with the camshaft. Key should be pointing toward the cam centerline.
The gears are helical, the correct timing mark will be to one side of the keyway, but if you follow that tooth, it will cross over the center of the key about halfway across the gear face.
Now as to advancing or retarding the cam, as mentioned it will run, but not at full potential.
As to racers, yes cam timing gets altered, usually to compensate for something or correct a custom cam.
J
The gears are helical, the correct timing mark will be to one side of the keyway, but if you follow that tooth, it will cross over the center of the key about halfway across the gear face.
Now as to advancing or retarding the cam, as mentioned it will run, but not at full potential.
As to racers, yes cam timing gets altered, usually to compensate for something or correct a custom cam.
J
Tom Wesenberg
Well-known member
The cam gear mark should fall in line with the right side of the keyway in your picture.
Your's right now is on the left side as you face the picture.
The cam gear should have a mark. Look behind the oil slinger.
Wonder if someone installed the crank gear backwards, as the mark should face the front.
https://www.fordbarn.com/forum/showthread.php?t=287570&highlight=picture+timing+gear+tom+wesenberg
See the link I just posted. Reply 9 is my picture showing the correct timing marks.
Your's right now is on the left side as you face the picture.
The cam gear should have a mark. Look behind the oil slinger.
Wonder if someone installed the crank gear backwards, as the mark should face the front.
https://www.fordbarn.com/forum/showthread.php?t=287570&highlight=picture+timing+gear+tom+wesenberg
See the link I just posted. Reply 9 is my picture showing the correct timing marks.
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Patrick L.
Well-known member
It does appear you are off a tooth. Being off a tooth changes the valve timing, it'll either advance it or retard it depending. Changing valve timing can be a good thing if done a couple degrees, but, not by a whole tooth.
Advanced valve timing gives more low end and retarded more high end power.
Tom, I found the mark or marks where you described on two engines so I don't think the gear was put on backwards (if it can be). The mark is hard to spot between the slinger and gear. Hence the reason to install in relation to the crank gear key way.
John
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Patrick L.
Well-known member
Its not too hard a job, but, it has to done. Practice makes perfect. [ smiley face]
Dan McEachern
Senior Member
Ruth and John are correct- you were 1 tooth retarded. Just FYI, the centerline of the gear tooth at a point halfway from the front and rear of the gear aligns with the centerline of the crank key. Being a left hand helix, the tooth starting on the right hand side of the keyway is the one with the timing mark.
Has any one else found a marked tooth on the front of the crank gear behind the oil slinger or is mine a mechanics made mark? I can just barely see it with a flash light. Les Andrews book shows this on page 1-138 paragraph 5. I think the drawing is slightly wrong but the narrative is correct.
John
John
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See post #13.
By jove, I think you've got it!!
I think the keyway should be to the left (in your picture) of the cam gear mark.
The diagram in post #13 is off by one tooth, check the dot in relation to the key way. Compare that to post #9 in the thread titled "Timing Gear" - the dots are obvious with the slinger removed. The crank gear mark is hard to see with the slinger installed but it is there. Forget the key way as a reference and find the crank gear dot! Save yourself a lot of mental gymnastics trying to mesh the gears in relation to the key way. It is a lot of work if you get it wrong.
John
Dave in MN
Well-known member
I agree that you now have it correct based on the last photo. (Entry #31)
See attached gears. 25 teeth on the steel gear makes it easy to mark the centerline through the hole/crankshaft. See where the line passes at the key on the front surface for future reference. The marked tooth is clearly clockwise of the keyway.
Good Day!
Attachments
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