Planet 4x4 - Change your own Camshaft

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Camshaft Change in a GM V8

How to change your camshaft yourself

Looking for a little more power out of your engine? If you’ve already added a set of headers and an intake and still need more, then a camshaft upgrade might be in store for you. I did this mod on a 454, but with the glory of the Chevy engine, it will be almost exactly the same process on a small block. This article should help you change your own Camshaft.

This article assumes that you already somewhat know your way around an engine. It also does not need to be taken literally. There are many different methods and orders to do this. The only real important part is the valve adjustment and the timing setup. If you’ve never pulled a carburetor or changed out a water pump, you might want to get some more experience or a least get a buddy with experience to give you a hand. As it is, two people can make this job go three times as fast. Good luck with it, as for somebody who has never gone this far into an engine; it can be a learning experience.

The camshaft or “bump stick” is often referred to as the “brain “of the engine. It has the say in how high and how long your valves are going to open. This can affect how your engine will run and act. A small cam will add torque but not high horsepower. A very large cam will develop good horsepower but at the sacrifice of low end torque. That is a very general rule but is not set in stone. What cam you decide to buy depends on your 4x4 usage and what modifications you have already made to the engine. If you’re not sure what cam to get, place a call to Competition Cams and they should be able to help you out.

I had just dropped in a nice 454 into my Blazer but was looking for a little more top end. I called up Summit Racing and ordered a Competition Cam Xtreme energy camshaft #CCA-11-242-3. This is a dual grind cam with 224 degrees of duration with .515” of lift on the intake and 230 degrees of duration with .520” of lift on the exhaust. I also ordered a set of lifters and a gasket set and a double roller timing chain set. I also went a picked up a new oil filter and 5 quarts of my favorite oil and a tube of Black Silicone.

Installation was not hard but it was time consuming. I started by disconnecting the battery, unbolting the fan and the fan shroud and removing both. Then drain the radiator and remove the hoses and pull it out to get it out of the way. Now remove all of the engine accessories . These include the alternator and brackets, power steering pump, and the water pump.

If you are running air conditioning, then you will have to pull the pump and also the condenser. You might have to have the system pumped out before you do this to avoid bleeding the Freon into the atmosphere.

Now remove the air cleaner assembly and then the carburetor or TBI and disconnect the hoses and wires (if any), note where they were connected.

With the front and the top of the engine cleaned up now it is time to find Setting the Distributer TDC or Top Dead Center. There are a few ways to go about this but this is how I do it: Find the spark plug wire that runs to the #1 cylinder. #1 is on the driver’s side closest to where the radiator sits or the front of the vehicle. Trace it back to the distributor cap and note where it connects on the cap. Take a marker and make a small mark on the intake manifold for reference. Make another mark on the intake in relation to where the vacuum advance port is pointing to. This will help to establish a baseline for timing when it is all reassembled. Remove the distributor cap and all of the spark plug wires. Now to get TDC, the engine needs to be rotated uSetting the Timing Mark on the Balancerntil the timing mark on the harmonic balancer is lined up to 0 on the timing tab and the rotor on the distributor is close to the #1 spark plug mark that was made earlier. The rotor will turn once for every two turns of the balancer so it possible to have the timing mark lined up and the rotor 180 degrees from the #1 spark plug wire. Put a socket on the bolt in the center of the balancer and rotate it clockwise until both marks are lined up.

With TDC found, remove the distributor and the intake manifold and the valve covers. Using a puller, remove the harmonic balancer and then the tiRemoving the Harmonic Balancerming cover. Don’t forget the two bolts that come up through the bottom of the oil pan into the timing cover. With the timing cover off you will be able to see two gears and a chain. The top gear is larger and connects to the front of the cam. On the top of both gears there should be two round indentations. Take a look here as that is where they need to be when it goes back together.

Move back to the top of the engine and loosen up the rocker arms to the point that they can be twisted out of the way and then you can pull out the push rods. They do not have to go back in any particular order so you do not have to keep track of them. Removing the lifters can be easy or they can be stubborn. To make things easier I like to first remove the cam sprocket and chain. This lets you rotate the cam and push lifters up to where you can grab them. So unbolt the cam sprocket from the cam and pull it and the chain off. Now remove the lifters. You might have to slide a flathead screwdriver under them to get them to move.

Now you are ready to remove the cam but there is still a problem. The cam is too long to slide all of the way out without hitting parts of the core support. On my application I tried to bend parts of it out of the way but I was unable to bend it far enough. In the end I just remove a piece Front of Engine openwith some tin snips and bent a second piece enough that I was able to slide the cam out. Be careful sliding the cam out, you do not want to hurt the bearings so go slow and wiggle it all the way out. It might help to put one of the bolts that held the cam sprocket onto the cam, back on to use as a handle to get the cam started out. Now is an excellent time to replace the timing chain. If you are upgrading from a single chain to a double roller chain, the crank sprocket must be changed. You will need a puller to do this and then use a large socket to tap the new one on.

Before the new cam goes in, all of the mating surfaces of the engine need to be cleaned. I used a combination of a wire wheel on a drill, a scraper, and some fine grit sandpaper. Stuff the lifter valley, ports on the heads, and the opening under the crank sprocket into the oil pan full of paper towels to keep crud out of the engine and go to it. Also clean the intake manifold, timing cover, valve covers, and anything else you would like to clean up. Now would also be a good time to do some painting. This is probably the worst part of the whole job.

Now with all of the cleaning done it is time to put it all back together. Depending on what cam you bought it may or may not have come with cam lube. Mine did and was in a small black packet. If not you can get away with using some type of oil honey. Oil honey is that stuff you can pick up at the auto store that is real thick and is supposed to restore oil pressure and do other amazing things. Before you put the cam in, prelube the whole thing real good, then slide it in. Install the cam sprocket and chain at the same Aligning the Timing gears uptime. You may need to rotate the cam around until the markings on both sprockets are at the top and then bolt it to the cam. Don’t crank on these bolts as they will break. I think spec is around 20 foot pounds or so. Once that is on and lined up, go ahead and drop in the lifters. Dip the bottoms of each one into the lube and slide them in. Put the timing cover back on with new gaskets and sealer. I like to dab the bottom corners with Black Silicone to make sure it stays sealed, and put the harmonic balancer back on. This can be done by beating it to death (not recommended), or using a harmonic balancer install tool. Use the tool; they can be rented for cheap or even free depending on the place. Replace the push rods and set the rocker arms on them. Do not tighten them at this point.

If you ask five different mechanics on how to adjust the lifters, you will get five different answers. None of them are really wrong so you have to pick what works best for you. I am going to tell you what works for me and why and then you can make your own decision. I like to Adjusting the Rocker Armsset them up at this point of the install and have had good luck doing it. The motor should still be at TDC so the lifters on cylinder #1 can be adjusted. Tighten the first rocker arm up until it just puts tension on the pushrod. This can be determined by rotating it between your fingers. You should be able to feel when it starts pressing on the push rod. Now at this point I give the rocker bolts slightly less then ¼ turn tighter. I have seen rebuild manual say to do this from ½ turn to ¾ turns tighter. I do not do this because I always run a high volume oil pump. The higher pressure of oil will pump up the lifters more when the engine is running and amplify your rocker arm settings. I have found that turning ½ turn with a larger lift cam and a high volume oil pump will cause the valves to stay open too long and can backfire through the carburetor. If it turn out that a ¼ turn is to light for you, It is easily fixed later on.

Adjust both rockers for #1 cylinder. Now turn the engine over ¼ of a turn. This can be done by putting a socket back onto the bolt in the center of the harmonic balancer. Look at the timing mark on the balancer in relation to the timing tab to get an idea of where you are. Now adjust both rockers for #8 cylinder. You will do this through two rotations of the engine. This is the order you want to follow: 1-8-4-3-6-5-7-2 or the firing order of the engine. On the last one (#2), the timing mark should be ¼ turn from TDC. Go ahead and turn it back to TDC.

Now that the hard part is over, put everything back on. After the intake manifold has been installed drop in the distributor. Take care that the rotor is pointing back to the mark that you made earlier. It may not drop down in the right spot. The gear on the bottom of the distributor is cut at an angle and the rotor might have to be positioned slightly counter clockwise of the mark before it sets in. If it bottoms out in the correct location but does not set all the way into the manifold, you will have to take a long flat head screwdriver and turn the top of the oil pump rod that is down in the bottom of the hole. The top of the rod has a slot the hooks in the bottom of the distributor and this runs your oil pump. Experimentation should get this into place for you. Line up the vacuum advance with the other mark you made. Hopefully this will get the timing close enough that the engine will start and run decent enough to set it correctly. Install everything else to complete the engine. Leave the air cleaner off for now so that it is not in the way and connect a timing light up.

Now is the moment of truth. Hit the key and hope for the best. If everything is correct the engine should fire up and try to idle. It will take a few seconds for the lifters to initially pump up and you might hear some rattling until they do. If it idles great, check the timing and make adjustments where needed.

It is necessary to break in a new cam. If it is a used cam you do not need to do this. Simply run the engine for a while and then change the oil and you are done. If it is a new cam it needs to be broken in. I do this the same as initial starting of a new engine. I set the engine to run somewhere between 1500 and 2000 rpm and let it go for 15 to 20 minutes. When this is done, change out the oil and you are done.

I noticed a huge difference in engine performance. The thing pulls like a jet and has a very noticeable rough idle which I like. Hopefully you will also get the results that you are looking for.

 Ready to Rip some Butt!

Troubleshooting:

 

Problem: Engine starts but sends flame out of the Carburetor.

Solution: The rockers are too tight. Pull off the valve covers and loosen them all up ¼ turn and then try again.

 

Problem: Engine turns over hard when trying to start and pops through the carburetor

Solution: The timing is set to far advanced. Rotate the distributor counter-clockwise and try again.

 

Problem: The engine starts but only when given lots of throttle and does not want to idle.

Solution: The timing is set to far retarded. Turn the distributor clockwise and try again.

 

Problem: The engine turns over and backfires through the carburetor and pops through the exhaust.

Solution: The distributor may be in 180 degrees off. Pull the distributor and rotate the rotor 180 degrees and drop it back in. If this does not work you must find TDC again and start all over with setting up the Distributor.

 

Problem: Engine runs but the initial rattle of the rockers did not go away.

Solution: Tighten all of the rockers up another ¼ turn and give that a try. The hydraulic effect of the rockers gives you some leeway here.



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