Cam install question "cams 101"

[Anonymous]

I am doing my first full rebuild right now. When it comes to the cam I am a little confused. I am reading alot about guys dialing in cams with those wheels etc. I was under the impression that if the #1 cyl is at tdc on the compression stroke and the dots line up on the timing chain sprockets then all was good, just stick in the dizzy pointing to #1 and the car should be close enough to start and then fine tune the timing with a light.

If anyone can share info with me that would be really helpfull. The bottom end rebuild is something that is still new to me....

 

[Anonymous]

Dialing in the cam is to make sure that there wasn't any machining errors. It's not uncommon for the cam to be off a couple of degrees which on a street engine usually wont make much difference. But there are the extreme cases and thats why it's good practice to do this when installing a new cam. I would recomend that you invest in one or borrow one to check the cam timing I have personal experience of the extreme, it's well worth the extra time.

 

[addo]

Until you put that cam in there, the #1 is just at TDC. The cam position determines what part of the cycle it's at.

Before installing it, make sure you have final torques on all the bearings (plastigage them all first, not just one), and have rotated the motor 30-40 times to bed in the rear oil seal.

Determine the balancer is correct by dead stop method - that aligns the degree wheel. Then as Sleeper says, do the cam. Buy a solid lifter (and differing pushrod if necessary) to measure the lift; take your 50 thou open and close points, halve the difference and note it. Measure your lift at TDC and compare that to grinder's spec. Both should match the cam card pretty close - or you could average the discrepancy. And yes, for the time being straight up is the best way to align.

Don't forget a healthy dab of assembly lube to replace what wiped off that first lobe; now is the time to drop all the lifters in (assuming you have attached the oil pan and front cover prior).

NOTE WELL: There is now NO need to rotate the motor again before ignition. As the cam will be on the base circle for intake and exhaust on #1, and you have ensured all your valves are the same assembled height on the head, you can set the other rockers (if adjustable) by measuring the adjuster heights off this pair.

Because you have verified your carb by running it on another car the day before, and tested your ignition off the motor, you only need to prime the oiling, slot in the dizzy and off she goes. People go to all this trouble of priming the oil galleries, and then because parts are unverified or have sat months, they wipe all the pre-lube off the infernal parts cranking and cranking and...

Cheers, Adam.

 

[MustangSix]

I degree my cams because i like to see exactly where the machining process puts everything. When you take into account tiny amounts of core shift, factory maching tolerances, production tolerances for chains and gears, machining tolerances on cams, gears, and keyways, it's possible for a cam to be a few degrees away from the design specification.

Normally, it's a small factor and you could just slap in a cam straight up and it will run fine. But to blueprint to an exact spec or to achieve a particular performance level, you have to go the extra distance and set things up exactly as designed.

In your case, good quality parts and careful assembly will yield good results without going thru the blueprinting process.

 

[Anonymous]

Ok so the term "installing straight up" just means that the dots line up. Or is there more to it?

 

[addo]

Incorrect.

It means that the intake centreline is exactly at the grinder's specified degrees. Your degree wheel tells you if this holds.