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Premium Member
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Discussion Starter #1
Time for a valve adjustment, several K-miles after a head rebuild. I noticed that, with the crank pulley at "P", the exhaust cam lines up with the marks on the front bearing cap. However, the intake cam is behind it (retarded) as much as 3 - 5 crankshaft degrees. This is a 502 series motor, #13655 , but the cams are inscribed "101-06 FO76". First, are these cams from a different motor? And, is the retardation of the intake cam sufficient that I should address it? The motor runs pretty well, but with some persistent fluffing just off idle.
 

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Richard Jemison
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7,377 Posts
Cam

Has to be 10106 03200 00. Thats the only Alfa cam starting with those numbers.

Check the cam cap mark position. The factory specified 104.5 int and 106.5 exh.
These cams were poor performers at low RPM. Probably a better driver at about 108 intake LC.
 

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Premium Member
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Discussion Starter #3
1600 Camshaftf

True, those are the numbers cast in to the camshafts. But where the A and S are, the area has been polished and someone used a scriber to inscribe the 101-06 FO 76. D'you suppose those numbers are meaningful, as in someone reground them or something?
 

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Richard Jemison
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7,377 Posts
Cams

Who knows??

Measure the lift. Stock cam lift is 9mm (.354) that is lobe lift (nose to base minus BC measurement. The stock BC is 1.085 (27.6mm)
If they have been reground the BC will be smaller.
 

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Discussion Starter #5
1600 Cam Timing

Yikes, Richard, I'm really grateful for your advice on this issue, but I'm lost. In your earlier post you quoted some numbers for the intake and exhaust cams (" 104.5 int and 106.5 exh.. . . about 108 intake LC"). To what do these numbers refer? Also, in your later reply you refer to a BC number (" . . . BC measurement. The stock BC is 1.085 (27.6mm"). What is BC? I'd sure appreciate knowing how this all works. Thanks!
 

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Somewhere on the BB either Richard or someone else has a discussion obout camshaft anatomy that illustrates these points. It may be an old discussion that was in a Centerline catalog with a cutout for lobe center markings on front cam caps. Unlike BB which is bullitin board, BC is, in fact base circle, the non pointy part of a cam lobe. With Alfa's, and most other engines, the original design geometry establishes a BC diameter. With a reground cam, for more lift, the BC may be cut smaller.
Numbers other than factory cast in place numbers on a cam may indicate the cam has been altered. Alfa themselves used some cam cores for other applications, grinding off the raised numbers and stamping new numbers. However, the factory renumbered cam numbers are known, and your re-number is not, so there is no way to tell who ground it.
For a cam profile, to find out what it really is, and how it should be used, you could spend many hours with a degree wheel on an engine, with two or four dial indicators, as we did in the 1960's. This is a time-eating procedure with few "OH Golly!" moments of enlightenment. Today, the cam is sent out to a good cam cutter with computer profiling equiptment, (WebCam) and you get back 2 (or more) profiles that STILL tell you nothing (No "OH Golly!" moment) UNLESS you are a cam designer like Richard. Even then, with his knowledge and experience in cam design, it is more than likely he will tell you your cam is junk, as it is worn out, or has a useless profile.
In conclusion, you are better off starting with a cam with known performance characteristics, in as close to un-used condition as possible.
This is from my own experience, degreeing odd cams for many years the old way. I don't do that too often anymore.
 

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6,808 Posts
Somewhere on the BB either Richard or someone else has a discussion obout camshaft anatomy that illustrates these points. It may be an old discussion that was in a Centerline catalog with a cutout for lobe center markings on front cam caps. Unlike BB which is bullitin board, BC is, in fact base circle, the non pointy part of a cam lobe. With Alfa's, and most other engines, the original design geometry establishes a BC diameter. With a reground cam, for more lift, the BC may be cut smaller.
Numbers other than factory cast in place numbers on a cam may indicate the cam has been altered. Alfa themselves used some cam cores for other applications, grinding off the raised numbers and stamping new numbers. However, the factory renumbered cam numbers are known, and your re-number is not, so there is no way to tell who ground it.
For a cam profile, to find out what it really is, and how it should be used, you could spend many hours with a degree wheel on an engine, with two or four dial indicators, as we did in the 1960's. This is a time-eating procedure with few "OH Golly!" moments of enlightenment. Today, the cam is sent out to a good cam cutter with computer profiling equiptment, (WebCam) and you get back 2 (or more) profiles that STILL tell you nothing (No "OH Golly!" moment) UNLESS you are a cam designer like Richard. Even then, with his knowledge and experience in cam design, it is more than likely he will tell you your cam is junk, as it is worn out, or has a useless profile.
In conclusion, you are better off starting with a cam with known performance characteristics, in as close to un-used condition as possible.
This is from my own experience, degreeing odd cams for many years the old way. I don't do that too often anymore.
Amen to that !!
 

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Premium Member
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Discussion Starter #8
Thanks all, but as I've driven the car with these cams for close to 30 years, I think I'll stick with them, and not care too much about their particular characteristics. I thought that maybe there would be something knowable from the numbers scribed on them, but I drive the car too much too want to spend weeks bent over that little thing with multiple dial indicators, and Spring is coming to the Intermountain West and . . .

you know.

Thanks again!
 
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