ENGINE: New Camshaft Installation Tips

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ENGINE: New Camshaft Installation Tips

Postby Murphy » Tue Mar 09, 2010 12:51 pm

There has been much discussion about aftermarket cam installation failures that are usually blamed on the cam manufacturer. Not so fast, cam break-in might be more complicated than you think. You don't just install, tune, and go. The break-in procedure of flat tappet cams are critical. This is true for most engines and flat tappet camshafts in general, not just Jeeps.


HERE IS A QUICK RUN DOWN:

* Always use new lifters when installing a new cam.

* Always clean the rust preventative coating from the cam and lifters before installing.

* Always use assembly lube when installing the cam and lifters to prevent dry startup.

* Always add a Zinc additive like ZDDP to the start up oil, or even better use a dedicated racing/break-in oil (high zinc content) for the break-in run, then use a zinc additive with every oil change.

* If you are going to run high pressure valve springs use the weaker OEM springs for your break-in run, then change out the springs.

* When doing the cam break-in run, do not let the engine idle. Keep the RPM's between 2000-3000 and vary the RPM periodically. This is to insure that the cam lobes get fully lubricated. The lobes get lube from splash oil as the crank spins.

* Do at least a full 20 minute run.

* A window box type fan in front of the radiator helps to keep the engine cooler.

* If you notice the exhaust pipes close to the exhaust manifold getting cherry red, increase the timing. This is usually caused by retarded timing or a very bad vacuum leak causing an extremely lean condition.

* It is OK to shut down to fix any problems and then re-start to continue the break-in run.

* If you plan on running ceramic coated or plated headers, do not use them until after you have completed the cam break-in and performed the final timing and any carb adjustments. This is only so that the finish does not get ruined due to any timing errors at the initial start-up.

* Change the oil and the filter immediately after the break-in run.





MISTAKES THAT MAY "FRAG" A FLAT-TAPPET CAMSHAFT AND LIFTERS.


1. Failure to remove all of the rust-preventative coating from cam and lifters with solvent once you get ready to install.

2. Failure to use assembly lube and an additive in new engine oil for camshaft break-in. Each cam grinder may have their own specific product to facilitate cam break-in.

3. Failure to initially adjust the rocker arms properly.

4. Failure to have everything ready for the motor to fire on the first few turns. Fully charged battery, good starter, known-good carburetor with full fuel bowl, Ignition timing set. NO GRINDING ON THE STARTER. NO GRINDING ON THE STARTER. NO GRINDING ON THE STARTER.

5. Failure to prime the oiling system prior to firing the motor. Prime until you get oil out of the top of each and every pushrod. Observe the oil pressure gauge to be sure pressure is registering. Priming will aid lubing the valvetrain at initial startup. It's the last area of the motor to get lubed on dry start.

6. Failure to run the motor at high rpms (2500 or higher, alternating 500/1000 rpm's up and/or down to allow the crank to throw oil in different places at different revs) for the first 40-45 minutes of its life. NO IDLING. NO IDLING. NO IDLING. The motor should not be run at less than 2500 rpm's for a minimum of 40 minutes. If a problem develops, shut the motor down and fix it, then resume break-in. The main source of camshaft lubrication is oil thrown off the crankshaft at speed, drainback from the oil rings and oil vapors circulating in the crankcase. At idle, the crank isn't spinning fast enough to provide sufficient oil splash to the camshaft/lifters for proper break-in protection.



*** The next few are usually not a problem with a mild cam, but it is always good to check anyway. ***

7. Failure to check for valve spring coil bind at max lift. If you cannot tell by eye, verify by inserting a .010- inch feeler gauge between the coils. A .010 space between five coils would give a total of .050 safety margin before stacking solid. If you cannot pass the feeler gauge between the coils, the spring is either coil bound or dangerously close. (Too much valve lift for your springs).

8. Failure to check for retainer to valve guide/seal clearance. 1/16"-1/8" clearance at full valve lift is considered sufficient.

9. Failure to check for piston/valve clearance..... 0.080" on the intake and 0.100" on the exhaust is considered by many to be the minimum clearance acceptable. You will probably find the closest near-miss at the exhaust valve on overlap, when the piston is chasing the exhaust valve back onto its seat.


DISCLAIMER: THE FOLLOWING INFORMATION WAS GLEANED FROM MANY DIFFERENT SOURCES. USE THIS LIST AS A GENERAL GUIDELINE SO THAT YOU REMEMBER TO CHECK ALL THESE THINGS WHEN INSTALLING A NEW FLAT TAPPET CAMSHAFT. DO NOT TAKE EVERYTHING POSTED HERE AS GOSPEL. IF THE MANUFACTURER OF THE CAMSHAFT YOU'RE USING RECOMMENDS PROCEDURES THAT DIFFER FROM WHAT IS SHOWN HERE, USE THE MANUFACTURER'S RECOMMENDATIONS INSTEAD.
Murphy
 

Re: ENGINE: New Camshaft Installation Tips

Postby Elliott » Thu Jan 13, 2011 9:01 pm

Thanks for the info, and something else to add... if you do your own cam bearing install... unlike some motors the cam bearings are smaller at the rear so when installing them in the block you need to stick to the order in the box of bearings or plan to buy another box;)
Elliott
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