Degreeing the cam---Can it be this far out?

[Alabama65stang]

After two years of rough idle, low vacuum, poor gas mileage, and oil consumption, I have pulled the head and bought the tools to degree the cam. Upon checking my existing setup, I find the cam is at 96 degrees. CompCams recommends 106 for this cam. Is it very unusual for one to be this far out with a stock gear set? The gear set was from NAPA with the engine rebuild kit. I've now got the adjustable set and plan to install it with the cam at 104 degrees (only 2 degrees advanced, right??) What do you think I can expect as far as the performance issues listed above? Is there any way the cam being advanced this far could affect blow-by and cause my oil consupmtion problems? (don't want to pull those pistons if I don't have to) Any input would be appreciated!!!

 

[addo]

I think 11° is the record for cam timing inaccuracy; that makes you second placegetter.

For oil consumption, examine the bores' surface finish, and for the most fouled plug maybe check that cylinder extra closely. You can do an old school feeler gauge "pull test" with the rings off the piston, and also check end-gaps.

Regards, Adam.

 

[rbohm]

8) sounds like you have a tolerance stack problem. comp cams usually grinds their cams 5 degrees advanced to allow for timing chain stretch, but when you factor in the tolerance allowances for the gear set, you can find yourself just about where you are now. that is the reason you should always degree a cam. that said however, it is rare that cams are that far out in real life.

as for the oil consumption, after you check what addo suggested, also check the valve guides and valve seals.

 

[Gene Fiore]

Years ago when I built my first 250 motor I installed a Sig Erson cam and attempted to degree the cam, never having done one before. Well, I had no one to help and I was getting readings that seemed so far off that I just assumed I was doing something wrong and gave up. So I just lined up the timing marks and installed the cam straight up. Everything seemed fine until I took the car out to the drags and it ran no quicker than when it was running the stock cam. Wow, was I disappointed to say the least! I figured something must not be right with the cam, so I took it to a professional shop and had them degree the cam with the motor still in the car. Indeed it was so far retarded that they had to bump the timing chain one tooth which over advanced it and then had to retard it with an offset keyway just to get it about 4 degees advanced. What a difference it made at the drags! So I guess what I am saying is it is possible for your camshaft to be that far off. Good luck.

 

[MustangSix]

What I've observed is that it's almost always the timing set and not the cam itself. I've found as much as 8 degrees difference between timing sets and I could see where 10 or 11 degrees error might occur. The replacements are not as accurately made as the originals, it seems, so your findings could be correct, depending on the set you used. The adjustable set should cure the problem.

 

[wsa111]

Alabama65stang, your comp cam has a 110 degree lobe center, you need to degree to the intake lobe center to 106 degrees to be 4 degree's advanced which is recommended by comp cams & works best.

Comp cams are normally pretty close. Clay Smith cams sold by Mike at classic inlines are also very close & the same with crane.

Always degree your camshaft to be sure. William

 

[mugsy]

If I remember correctly, my cam was about 10 degrees too advanced. Luckily I had one of Mike's adjustable timing sets. It was my first time degreeing a cam, so I might have done it wrong too. I did get the same numbers the three times I tried degreeing the intake centerline. Glad to knwo that others have had the same issue as me...

tanx,
Mugsy 8)