DeTomaso Mailing List: August 99, Message #335

Ford motorsport makes a timing chain set that has keyways cut with timing
marks at +/- 2,4,6,8 and tdc.  As easy as that

dave "i got one" D

At 11:40 AM 8/8/99 -0400, you wrote:
>Thanks a lot for the explanation, John, but it leads me to another question:
>
>Let's say that I degree my cam and find out that it's a couple of degrees
off. What will I be able to do about it / how can I correct this situation?
I am not aware of any way to advance or retard the camshaft by for example
2 degrees. As far as I understand from your mail, it must be possible to do
so, I just can't figure out how.
>
>Thanks again,
>
>Cristiano Rossi
>thpnma 02869
>
>----- Oprindelig meddelelse ----- 
>Fra: Mary Taphorn <marytaphorn@email.msn.com>
>Til: Multiple recipients of list <detomaso@realbig.com>
>Sendt: 8. august 1999 16:20
>Emne: Re: Degreeing of cam (was Ring Frustration)
>
>
>> Cristiano asks;
>> 
>> 'Can anyone please explain to me why it is a good idea to degree a cam, and
>> what you actually do when degreeing it. Can you do anything else than
seeing
>> at how many degrees (0, +4 or -4) you have installed the cam yourself?'
>> 
>> According to Smokey Yunick - "You must absolutely do it!.The reason is so
>> many things can alter the phasing between the camshaft and the crank. Four
>> mechanical elements in the cam drive affect the camshaft phasing.
>> 
>> 1) The keyway in the crank
>> 2) The keyway in the crankshaft chain sprocket
>> 3) The drivepin  in the nose of the camshaft
>> 4) The drivepin pilot hole in the camshaft chain sprocket
>> 
>> These components are generally manufactured to reasonable tolerances, but
>> there are going to be variations when all these things are bolted
together."
>> 
>> Most of us when rebuilding our engines use a new timing chain, and cam from
>> different manufactures than the crank. It seems reasonably likely there
>> would be some variance.  The last engine I lent a hand on rebuilding was
>> Kirby's, and if my memory serves me correct ( I am sure he'll correct it if
>> I am wrong), he uncovered his assembly was a couple of degrees off which he
>> corrected.
>> 
>> If you don't degree your cam, it may not be worth losing sleep over it as
>> several paragraphs later Yunick almost contradicts himself.
>>     "Modern camshafts are  extremely sophisticated, and if you move the
>> phasing plus or minus four degrees, you generally won't find much change in
>> overall horsepower.  In some instances you may significantly change the
>> torque output- If you advance most cams (Cristiano, this addresses your
>> second question) you will get more midrange torque but you will at the same
>> time ALWAYS lose top-end power- but in general, it isn't going to make a
>> real big difference."
>> 
>> Go figure, he later goes on to talk about the importance of checking the
>> degreeing on every lobe to uncover possible manufacturing variances in the
>> cam.
>> 
>> FWIW, my cam calls for installation 4 degrees advanced.
>> 
>> John T
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