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degreeing cam
Should I degree my cam? I have a 351W stroked to 393. It has an Edelbrock Performer RPM cam, lifters, and timing chain. My understanding is that this is done to doublecheck for manufacturing errors. Is this right? Am I missing somthing?
Thanks, Pat |
Pat,
Not just manufacturing errors, but assembly errors. Your checking how the cam lobes are acting against the valves reference crankshaft position in degrees. Your looking ofcourse for what the cam is doing against what the grinder says it should do, but also for any over looked offsets between the cam and crank. You'll also see if your timing marks on your damper are accurate or not too. If you have access to the equipment, it's a good test to perform to to give you some piece of mind before you light it off for the first time. You might also want to double check the piston to valve clearance too. - Jim - |
If you are using a major mfg I dont think you'll have any trouble. we used to degree cams when installing them, but of the 150-200 we have done we never found a defect. We use Comp Cams exclusively. I think it is an interesting exercise, but time can be better spent elsewhere.
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Thanks for the replies. I have the machine shop (Jim Green's Performance) preassemble the engine and check the pistons. They did have to cut them a bit to clear the large 2.02 intake valves. I checked the timeing marks on the damper before the heads were installed with a dial indicator. The pointer is right on the money.
--Pat |
Each engine is different. And Murphy has a special place in his little black heart for hot rodders, street rodders and Cobra builders. Why gamble with taking a shortcut, making an assumption that may be invalid. The very thing you should have checked, and didn't, will be the very thing that will make you tear the engine back down again, and make you wish you had checked it in the first place. Ask me how I know.
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Who checks clearances?
If measuring clearances and checking the cams' installed position is something you don't want to do, don't build engines. You must degree the cam to verify that the valves are opening/closing at the right times. You could assume that the cam was ground perfect, that the timing will be the same as marked on the cam card. But how much time and money do you want to bet on it, your whole new motor? This is when you make sure the cam is phased properly to the crankshaft. How far advanced or retarded is it? What's the centerline? 106? 108? don't you know? And yes, cam grinders do make mistakes. We had a couple of cams come out of the box as much as six degrees off. Installed heads up, but measured six degrees retarded. Remember, two degrees of cam advancement/retatard makes a big difference in your powerband. It's all in the details, looking for shortcuts never puts you in in the front.
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If you were running real fast and I throw you a ball.....
Don't miss the catch before it's thrown! Timing is everything, yadeeeyadeeyada. |
Ohh how right JACK21 is!
A decision to pass up a very simple ten minute job just cost me a couple of grand and two months! But what the heck I was in a hurry to get to some kind of Spring Picnic! Made the Picnic but the car didn't! :( DV PS..if you have the ability...degree the cam |
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