What cam is this? - Vintage Mustang Forums
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post #1 of 15 (permalink) Old 08-21-2019, 08:50 PM Thread Starter
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What cam is this?

Im trying to figure out just what kind of cam is in the 351W engine in my car. I have no info from the PO so I decided to measure what I could without taking the cam out of the engine. The numbers are accurate as I measured everything at least three times.

Intake Exhaust
Duration (0.050) 231 229
Duration (0.006) 297 281

Max Valve Lift .540 .512

Valve open (0.050) 7BTDC 47BBDC
Valve close (0.050) 44ABDC 2ATDC

Valve open (0.006) 48BTDC 73BBDC
Valve close (0.006) 69ABDC 28ATDC

Lobe Center 71BBDC 72ABDC

Lobe Separation 108.5

First thing I noticed is the intake duration is greater than the exhaust duration. Second, the intake valve lift is higher than the exhaust valve lift. Also, the LSA is quite short at 108.5. Yes, the engine has a very rough idle. It also looks like the grind on the intake and exhaust lobes are not identical or symmetrical.

Is this a racing cam or what is it?

68 coupe, 351W, T5, 3.55

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post #2 of 15 (permalink) Old 08-21-2019, 09:02 PM
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I guess you degreed the cam to get all that info?



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post #3 of 15 (permalink) Old 08-21-2019, 09:25 PM Thread Starter
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I guess you degreed the cam to get all that info?
I did just that.

68 coupe, 351W, T5, 3.55

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post #4 of 15 (permalink) Old 08-21-2019, 09:26 PM
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Possibly a custom ground cam. A narrow LSA, 108.5 is going to produce a strong narrow torque band in the lower RPM. It's not meant as a high RPM grind. I'm thinking around 6k and it'll be done.

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post #5 of 15 (permalink) Old 08-21-2019, 09:34 PM
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I’m gonna guess that you have a comp cams 35-226-3 or something similar.
And you have 1.7 rockers on the intake and 1.6 rockers on the exhaust.

1970 Mustang coupe
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post #6 of 15 (permalink) Old 08-21-2019, 09:37 PM
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THE MIGHTY B...sorry, had too. I have no idea.
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post #7 of 15 (permalink) Old 08-21-2019, 09:48 PM Thread Starter
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Im gonna guess that you have a comp cams 35-226-3 or something similar.
And you have 1.7 rockers on the intake and 1.6 rockers on the exhaust.
All the rockers are 1.6 rollers, verified by Mark II eyeballs.

68 coupe, 351W, T5, 3.55

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post #8 of 15 (permalink) Old 08-22-2019, 12:39 AM
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So two guys named Mark looked at those rockers? Or one, using both eyes at the same time?

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post #9 of 15 (permalink) Old 08-22-2019, 01:46 AM
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Asymetrical cams are where the profile is different on the opening and closing side of the same lobe like yours. You have a dual pattern asymetrical cam where the intake and exhaust lobe profiles are also different. Usually done to compensate for intake or exhaust inefficiency, for example a restrictive exhaust port design, etc.

Last edited by Matter; 08-22-2019 at 01:49 AM.
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post #10 of 15 (permalink) Old 08-22-2019, 06:09 AM
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Quote:
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Asymetrical cams are where the profile is different on the opening and closing side of the same lobe like yours. You have a dual pattern asymetrical cam where the intake and exhaust lobe profiles are also different. Usually done to compensate for intake or exhaust inefficiency, for example a restrictive exhaust port design, etc.
Dual pattern cams are usually made with more lift and duration on the exhaust side.
The only exception I know of are the Comp “thumper” cams where the profile is made specifically to give the engine a really rough sound. And they have more lift and duration on the intake side.

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post #11 of 15 (permalink) Old 08-22-2019, 10:37 AM
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It is a custom cam and similar to a hi po 289 except for the increased lift. It will rev over 6,000 and increase power by 10-15 over a C3OZ ( 289 hi po). It would be considered a street performance improved cam but not a "race" cam. Are there any stampings on the back end of the cam? That could give clues as to the maker.
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post #12 of 15 (permalink) Old 08-22-2019, 01:03 PM
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there are MANY independent cam grinders out there and lots of opinions on what to use for lobes on a specific camshaft. In the mid 60's when the 289 came out 108*s was THE LSA to use. Contrary to what many magazines say , 108*lsa will produce a strong torque curve from 2500-5500 depending on the amount of duration. Ford's famous LeMans cam has a 107*lsa and is the result on MUCH testing in the day by Ford engineers. I counted thirty different "engineering " varieties in the Ford experimental engineering book I have of the same basic cam lobes on development cams for LeMans. That cam DOES have a "peaky" torque curve and not a lot of bottom end torque because of it's mid 250's duration at .050 which also allows it to rev to 8,000.
When choosing a camshaft nowdays , it is really important to consider the airflow of "modern" heads , the amount of cubic inches in the engine and the "realistic" operating range of the engine. Not "every" engine needs a custom cam bu there are "many" that benefit from them.
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post #13 of 15 (permalink) Old 08-22-2019, 08:11 PM Thread Starter
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The cam is in the engine and the engine is in the car so I won't be looking for markings on it anytime soon.

Good information. Thanks. I'm not unhappy with the performance at this point. However, it doesn't like to start when cold.
Hopefully I can get the car on a dyno sometime in the near future.
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post #14 of 15 (permalink) Old 08-22-2019, 09:35 PM
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This is just a guess. Maybe a restrictor plate engine would run this or some racing class with restricted intake manifolds and carbs.


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post #15 of 15 (permalink) Old 08-23-2019, 12:35 PM
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macstang,
Your not far off on your thinking. Years ago , on a "brand X" engine the exhaust airflow was better ( ratio wise) and the engine ( on the dyno) responded to a shorter duration lobe. In other words it was so efficient that it was "over scavenging" during the overlap cycle and hurting power. The shorter exhaust duration lessened the effect. Also in years past , turbocharged engines used that "trick" to create higher exhaust temps and get more boost. Modern turbo cams are the opposite now with 20-30 more degrees of exhaust duration thanks to advancements in sizing of the turbo halves.
Randy

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