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Discussion Starter · #1 ·
Hi,

I'm putting my engine together (351C) & I'm having problems degreeing the cam. Its a hydraulic flat tappet cam. This is what the cam card says;

Valve timing @ .050" lift;
Int. Open 8 ATC
Int. Close 22 ABC
Exh. Open 37 BBC
Exh. Close 13 BTC

Now these are the readings I'm getting;

Int. Open 10 ATC
Int. Close 23 ABC
Exh. Open 35.5 BBC
Exh Close 12 BTC

I've tested, retested & tested some more. I get the same numbers. I've spun this motor so much that I think the rings are seated. So are these numbers normal? I thought that if the cam was off, it would be off the same amount across the board, not different amounts.

Any help would be appreciated.
Thanks!
 

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Hotrodders.com Moderator
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2,783 Posts
cam

They are (95% of the time) always off, unless it's a custom ground cam. Or you get a cam doctor print out with the cam.

The cam cards you get from the "big Name" cam grinders are the numbers for the master cam, not the cam you get in your box. Manufacturing tolerances come into play and allow for a few degrees difference from the card.


You will never see any difference in performance in your engine between what you have now and a "perfect" cam.


Keith
 

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Just stuck
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435 Posts
I agree with K-star and this is just one of the reasons to check ALL cams when you are building an engine. I've had cams come with no card and cams come with cards that were not even for the one in the box. Also have seen mismatched marks on the timing gears, and the list goes on. And I like to stick in the cam after I stick in #1 piston to make life a bit easier then plug in the rest of the pistons after doing the initial degree in. And if you are really bored...check the cam on each cylinder :D That might surprise you. And I highly reccomend custom cams. Off the shelf stuff can get pretty shoddy at times.
 

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WFO
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5,030 Posts
mach1 said:
I thought that if the cam was off, it would be off the same amount across the board, not different amounts.
Check all the lobes, not just one cylinder. As long as the variation is uniform between cylinders, you'll be OK.

If you think you need to adjust the cam timing to make up for any deviation, average the errors and split the difference.
 

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Discussion Starter · #5 ·
Ok guys, I checked the rest of the cylinders & I'm pleased to say that they're pretty consistant with eachother. (Give or take 1/2 a deg.)

So basically it would seem I'm about 1-2 degrees retarded on the intake lobes, and about 1-1.5 degrees advanced on the exhaust lobes. So I guess theres no point in moving it one way or the other, it's pretty much split down the middle as it is.

Thanks to all 3 of you, I really appreciate the advice.

Now I guess it's time to check piston to valve clearance...

Thanks again!
 

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More for Less Racer
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20,952 Posts
Out of your four cam checking points (IVO, IVC, EVO, EVC) the intake valve closing point(IVC) is by far and away the most important. It would be best to set the cam using this correct point than to leave it where it is. The other three are minor in comparison, IVC determines how the engine behaves.
 
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