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JR Motorsports Technical Information - Engines

Guide Lines for a JRM Shortblock
Camshaft Degreeing Instructions

1.) Oil System Installation
2.) Harmonic Balance Installation
3.) Cylinder Head Installation
4.) Valve Train Installation
5.) Intake Installation
6.) Distributor Installation
7.) Valve Cover Installation
8.) Water Pump and Pulley Installation
9.) Engine Installation
10.) Starting the Engine and Breaking in the Camshaft

Guide Line for a JRM Shortblock  
1.) Oil System Installation  

Install a new oil pump shaft with a "steel" sleeve on the oil pump. Place oil pump in place and torque the oil pump stud to specifications. Always use an oil pump stud, a stock oil pump stud is not adequate. (figure 1 and 2) Carefully install the pick up tube making sure not to damage the tube while pressing it into the pump. Check the pickup tube to pan clearance. Measure from the oil pan flange on the block with the pan gasket in place, to the bottom of the pick up tube. (figure 3) Next place a straight edge across the oil pan rails where the oil pump will be located. Measure from the bottom of the straight edge to the bottom on the pan (figure 4). This measurement must be greater by 3/8" or .37 of an inch. Adjust the pick up tube until you have the proper 3/8" or .37 inch of clearance. Improper oil pump to pan clearance can cause oil pressure loss, which will cause bearing failure. Before you can install the oil pan you must install the timing cover.
Cam button clearance with the timing must be .005 to .010. Check this by using modeling clay. Adjust the clearance by carefully bending the timing cover. Install both the timing cover and oil pan using a quality gasket sealer. Building a leak-free engine is important, but too much gasket sealer will quickly be washed to the bottom of the oil pan where it can plug the pickup tube (figure 5 and 6). This will cause oil starvation resulting in bearing failure. The oil filer adapter will need to be tapped and plugged with a 1/4 inch pipe plug. This should be done before installing the adaptor on the engine (figure 7).

Figure 4

Figure 5


Figure 1

Figure 2

Figure 3

Figure 6

Figure 7

2.) Harmonic Balance Installation  

If you are using a bonded balancer we recommend marking the inner and out ring with a center punch. These marks give you a reference to see if the outer ring has spun (figure 8). If the outer ring does spin, your timing cannot be set correctly. When installing the balancer, it is very important to use a proper balancer installation tool (figure 9). Do not use the crank center bolt; you can pull the threads out of the crankshaft. NEVER use a hammer on the balancer. Attach the pointer tab. After you have the balancer installed rotate the crankshaft, setting the #1 cylinder on visually as close to top dead center (TDC) as possible. Move the piston down in the bore and attach a TDC stop tool over #1 bore (figure 10) and tighten the bolt stop. Slowly turn the crank clockwise until the piston contacts the stop; note the reading on the balancer. Turn the crank counter clock wise until the piston stops again, and note this reading on the balancer. True TDC lays is exactly half way between these marks you've made on the balancer (use a ruler to find this point). Paint or scribe a new TDC line or move the pointer if needed; adjust the pointer and/or line on the balancer until the mark on the balancer lines up with zero (0) on the timing pointer (figure 11).

Figure 10


Figure 8

Figure 9

Figure 11
3.) Cylinder Head Installation  

Before starting head installation make sure lifters fit the lifer bores properly, lifters should fall under their own weight and spin freely. If you are using heads that have been excessively milled, using a valve bigger than 2.055, or using a valve lift more than .580 lift, use modeling clay to check piston to valve clearance. 060" on intake and .100" on exhaust valve is acceptable (figure 12 and 13). Once you have established that you have the proper valve clearance you're ready to install heads. Make sure both surfaces are clean and dry. Install studs now if you are using studs. Use a Teflon sealant or RTV silicone on studs or bolts. This is necessary to seal head bolts and any other fastener that protrudes into the water jacket. Using a good thread sealer will also lubricate the threads for a uniform torque. Use lube between the cylinder heads, head bold washers also. Make sure you have the right length head bolts; you need at least .500" of thread in the block. Run head bolts or stud nuts down with a speed wrench (figure 14), NEVER use an impact wrench to run bolts of nuts down. Install gaskets making sure gaskets are installed with the proper side up. Torque bolts in three steps using the proper sequence; starting in the center of the head on Chevy small block (figure 15 and 16). Use 30 Ft./Lbs. on the first step, followed with 50 Ft./Lbs., and on the final step use 70 Ft./Lbs., going over bolts twice in the last step.

Figure 14

Figure 16

Figure 12

Figure 13


Figure 15


4.) Valve Train Installation  
Oil the lifter bores with 50 wt. oil. Generously lubricate the cam contact surface (bottom of the lifter) with break-in lube. This applies to either solid or hydraulic. Before installing the lifters, put oil on push rod cup in the lifters. If you are using roller lifters you must soak lifters in clean mineral solvent to remove assembly grease from the roller bearings. Then soak the lifters in oil for at least ten minutes before installation. Now that the lifters are installed you need to determine proper the push rod length. If your head has +.100" longer valve you should start with a +.100" push rod. Mark the rips of the valve on the #1 cylinder with a black mark or a bulling compound. Install push rods and rockers on that cylinder; make sure that #1 cylinder is at top dead center (TDC). Run rocker nuts down until there is no valve lash. Be sure that the push rod is seated in the push rod seat and not hitting the head or guide plate. Rotate the engine for two revolutions. Remove the rockers, check the pattern and adjust push rod length until the pattern is in the center of the valve. If the pattern is in the intake manifold side. of the valve use a longer push rod. If the pattern is on the exhaust side of the valve use a shorter push rod. Make sure at this point the rocker arm is not contacting the valve spring retainer or valve spring. Apply assembly lube to the push rod and guide slots in the head; along with the push rod cups and valve tip contact points. Lube the rocker arm surfaces that contact the valve and push rods. Install the rocker arm applying lubricant to the rocker pivot sockets and the pivot balls (stock Chevy rocker arm) and then set the valve lash.  
5.) Intake Installation  
Before final installation, set the intake on the engine and check the port and intake bolt alignment. Bolt the intake to one head. Check the other head to see if it's parallel with the intake manifold. Use a feeler gauge to check this. If the heads have been milled excessively you may be required to mill the intake manifold flanges or they will be mismatched and not seal properly. Check the space between the manifold and the block rail; you should have clearance of 0.060" to 0.120". If this is correct, glue the gaskets to the heads using and RTV bond adhesive. A bead of 1/8" is sufficient. When bolting on the intake manifold make sure to use the proper length bolts. If the bolts are too long they contact with the push rod or if they are too short they may pull the threads out of the head. Torque intake bolts following the diagram listed on the last page of this manual.
Figure 18
6.) Distributor Installation  
Before installing the distributor you must prime the oil pump. Make sure the oil filter is installed, and oil pan drain plug is tight. With the engine upright pour about 4 qt's of oil into the pan through the distributor hole. this will minimize washing the breaking lube off the camshaft. Next install a special oil pump-priming tool. Connect an oil pressure gauge to the oil galley take off either end of block. Make sure the opposite oil galley take off is plugged with an 1/8" pipe plug. Prime the oil pump using an electric drill turning clockwise for 1-2 minutes. During priming oil may not reach the rocker arms. This might not occur until the distributor is in place and the engine is running. Carefully inspect the distributor gear for excessive wear. If you are using a roller cam you must use a bronze distributor gear. #1 cylinder will need to be at top dead center. Mark the distributor base in line with the #1 post on the distributor cap. With a long screwdriver rotate the oil pump shaft until it's line up with the distributor drive. Lubricate distributor with camshaft lube. Install the distributor. When the distributor engages the helical gear on the camshaft it will turn about 45 degree clockwise. You'll want to start with the distributor about 45 degree counter clock wise from its desired location. Place the distributor in the distributor hole. Wiggle it in place. If the distributor housing doesn't fall in place and sits up about 3/8" you might need to reposition the oil pump shaft until it does. Make sure the distributor doesn't bottom out on the oil pump shaft before settling on the intake manifold by installing the distributor first without a gasket. The distributor should rest on the intake manifold. It's very important to get the distributor installed correctly so the engine will fire and run without excessive cranking time. The distributor should point to the #1 mark on the distributor and the #1 cylinder should be at TDC. (Excessive cranking time can lead to camshaft failure and oil/fuel contamination.)  
7.) Valve Cover Installation  
If you are using steel valve covers be sure to use load spreaders. JRM suggests you use a double cork gasket. Make sure the valve cover clears rocker nuts and stud girdle.  
8.) Water Pump and Pulley Installation  
When installing the water pump and pulleys make sure the water pump does not hit the timing cover. If you're using a cam stop on your water pump be sure that it "just touches" the cover. Too much pressure on the front cover will cause the cam button to wear through the front cover or cause the cam gear to wear on the block. You may check this by putting a piece of paper between the cover and the cam stop; if you can barely pull the paper out without tearing it, the pressure is set correctly. Make sure the pulleys are all aligned properly and the belts are not too tight.  
9.) Engine Installation  
During engine installation make sure the bell housing dowel pins are the correct length. If your race car requires a mid- plate stock dowel pins will need to be replaced with longer ones.
This is also the good time to check the fuel filter and replace if it's needed. If you've had over heating problems, or if your radiator has been used more than one season, it should be replaced. Also make sure your fan shroud fits correctly around the fan blade. Half the fan blade should sit outside the shroud with no more than 1 " of clearance around the blade. This will allow the fan to draw the maximum air through the radiator. Fill the radiator with water. Remove the thermostat housing to let any air locked in the system out. Before bolting on the carburetor, check the power valves, jets, airs bleeds, and replace gas- kits as needed. Make sure the throttle opens completely and closes properly.
Turn the idle screw up and fill the carburetor with fuel before installing on the engine. It is best to start anew engine with a carburetor you are familiar with; one you know is in good condition. Make sure you connect the return spring to the throttle.
10.) Starting the Engine and Breaking in the Camshaft  
First, review the procedure list making sure you have not left out any steps. Re-check to make sure the engine oil pump has been primed. Have your timing light hooked up and have water ready to fill the radiator. Engine should fire within five seconds, or refer to our trouble shooting guide as needed.
As soon as the engine fires make sure you have oil pressure. Set the idle so the engine idles at 2000 RPM. Set your timing correctly and finish filling the radiator with water. Let the engine idle at 2000 RPM for 20 minutes. It's very important not to let the engine idle below 2000 RPM during this break in period. If it does it could cause camshaft problems. Check the fuel pressure and the carburetor float levels. After the 20-minute break in allow the engine to cool completely. Re-torque the cylinder heads, reset the valves, and change the oil and oil filter.
Your new JRM engine is ready for the track. Your first night at the track you should allow the engine to warm up before going on the
track for hot laps. Oil temperature should be 180 degrees. During the first session of hot laps increase the engine RPM slowly for the first few laps. Keep a close eye on your
gauges, oil pressure, water temperature, and fuel pressure. After this hot lap session the
engine is ready to race! Good Luck.
Camshaft Degreeing Instructions  
The purpose of degreeing a camshaft is to ensure that it is phased correctly with the crankshaft. Some factors that may cause improper positioning are:

1. Cam or crank gear marked incorrectly.
2. Incorrectly machined cam or crank gear keyways.
3. Misindexed cam keyway or dowel pin.
4. Improper machining of camshaft or crankshaft.
5. Accumulation of machine tolerances

The important factor to remember is that camshaft position or phasing to the engine is extremely important for the engine to operate at maximum efficiency. Equipment needed to properly “degree” in a camshaft is available at COMP Cams® and is as follows:

1. Degree Wheel
2. A rigid pointer that can be attached to the block.
3. A dial indicator to accurately measure cam lift.

Note: Refer to your spec card for maximum lift and check your dial indicator to be sure it has sufficient range to measure the full cam lift.

4. Either a magnetic or attachable base to affix the dial indicator.
5. A Top Dead Center piston stop.
6. A solid lifter to fit your engine. Engines that have
non-adjustable rocker arms will also require an adjustable pushrod length checker to accommodate
that engine.
7. A means to attach the degree wheel to the crankshaft.

The IntakeCenterline Method  

There are several accepted ways to degree a camshaft. At COMP Cams®, we feel the Intake Centerline Method is the easiest and most accurate. This method of cam degreeing is very practical and indifferent to design characteristics. It simply involves positioning the center, or point of maximum lift, of the #1intake lobe with top Dead Center of the #1 piston. The Intake Centerline Method still requires accuracy to be correct, but it is somewhat more forgiving. Once you have degreed a camshaft using this method, you will be surprised at its ease. We also recommend positioning the dial indicator on the #1 intake retainer because lift measurements will include any deflection that may occur in the pushrod and rocker arm. This makes the degreeing process as accurate as possible in relation to what actually goes on inside the engine.

A "Cam Degreeing Kit" is available, COMP Cams (part# 4796)
Time to Go to Work  
Step 1: The camshaft and timing set have been installed. Make sure that the timing marks on both the cam gear and crank gear are aligned properly per the cam installation instructions. Use chalk or similar marker to better define the marks.

Step 2: For example, we have our cam card and it suggests weinstall the cam on 106 degree intake centerline. Install all the rock-er arm s and pushrods in the engine as normal. On #1 intake lobe, install the solid lifter in place of the hydraulic lifter. If a solid lifter or roller cam is being checked, use that respective lifter. Adjust the #1 intake lash to exactly zero. Do not pre-load the lifter. Next, adjust the #1 exhaust lash to zero. You should be able to turn both pushrods with your fingers easily.

Step 3: Attach your COMP Cams® pointer (part # 4794) to the block. Many people will make a pointer out of somesort of rigid, yet manageable wire. A stiffcoat hanger wire works well (fig. B).

Step 4: Attach the degree wheel to the balancer and install the assembly on the crankshaft. There are several ways to attach the degree wheel to the crankshaft. In our example, the degree wheel is mounted to the balancer. The crank may be rotated from either the front or from the flywheel end. Obviously, if the engine is in the car, you must rotate from the front. Remember, the greater the leverage, the smoother the crank rotation, thus more accuracy. NEVER use the starter to turn the engine while degreeing the cam.

Step 5: Before installing the piston stop, rotate the crankshaft to get the #1 piston in approximate T.D.C. position with both the intake and exhaust valves closed. This can be a rough guess, but it can save you from making a mistake later. Adjust your pointer to zero or T.D.C. on the degree wheel.

Step 6: Turn the crankshaft opposite the engine rotation approximately 15-20 degrees. This will lower the position
enough to allow the T.D.C. stop to be installed in the spark plug hole. Screw in the piston stop until it touches the piston. (fig. C). Continue to turn the engine in the same direction until the piston comes back up and touches the piston stop. Mark the degree wheel with a pen or pencil on the number the pointer is on (fig. D). turn the engine in the other direction, same as engine rotation, until the piston comes back up and touches the piston stop. Make a mark on the number the pointer is on (fig. E).

Figure B

Figure C

Figure D

Figure E

Step 7: Remove the piston stop after marking the two points on your degree wheel. Rotate the crankshaft to the midpoint of the two marks. This point is T.D.C. for cylin-der #1. Without rotating the crankshaft, adjust the degree wheel to read 0 degrees at the pointer (fig. F). You are now ready to locate the intake lobe centerline relative to T.D.C. If you are not absolutely sure that your 0 degree mark is set at T.D.C., repeat this procedure. This step is critical to proper cam align-ment.

Step 8: Attach the dial indicator to the dial indicator mount. Position the dial indicator mount so the tip will contact
the retainer of the #1 intake valve (fig. G). It is important that the indicator plunger be parallel to the valve stem. Any variance in the angle of the indicator will
introduce geometric errors into the lift readings.

Step 9: Rotate the engine in the normal direction of crankshaft rotation until you reach maximum lift. The dial indicator will change direction at the point of maximum lift. At this point, set the dial to zero (fig. H).

Step 10: Back the engine up (opposite normal rotation) until the indicator reads .100”. Turn the engine back in the normal direction of rotation until the dial indicator reads .050” before maximum lift. Record the degree wheel reading.

Step 11: Continue to rotate the engine over in its normal direction of rotation until the indicator goes past zero to .050” on the closing side of maximum lift. Again, record the degree wheel reading.

Figure F

Figure G

Figure H

Step 12: Add the 2 numbers together and divide by 2. That number will be the location of maximum lift of the intake lobe in rela-tion to the crank and piston. This is the intake centerline. For example: The first degree wheel reading was 96 degrees. The second reading was 116 degrees. These 2 numbers (96 +116) added together will be 212. 212 divided by 2 will equal 106. Your actual intake centerline is 106 degrees. Reference back to your cam spec card and we see that the recommended intake centerline for your camshaft is 106 degrees. Everything is where it should be.

In the event that your camshaft did not degree in as per manu-facturer’s specs, it will be necessary to either advance (move ahead) or retard (move back) the cam to meet suggested intake centerline. Depending on the engine application, there are several different suggested methods
for advancing or retarding the camshaft.

One common method is by use of a crank gear with multiple keyways-each one being at a slightly different relationship to the gear teeth. A 2nd method is to use offset bushings that fit on the cam pin and in the cam gear. The offset will advance or retard the cam depending on how the bushing is placed on the cam pin. Another method is by offset keys that fit into the crank gear keyway. A more elaborate system uses an adjustable timing gear. Contact COMP Cams® or your local COMP Cams® dealer for the method best suited to your application.

NOTE: When degreeing a cam, remember to look at the degree wheel as a full 360 degrees no matter how the degree wheel you’re using is marked. Many degree wheels are marked in 90 degree or 180 degree increments. On wheels that are marked in 90 degree increments,

keep in mind that you must continue to count the number of degrees past 90 degrees. Be sure all readings are taken from Top Dead Center. Keep in mind that to advance the cam, you must lower the intake centerline. For example, if our cam has a lobe separation of 110 degrees, the cam is “straight up” when the intake centerline is 110 degrees. Moving the centerline to 106 degrees advances the can 4 degrees. If we change the centerline to 112 degrees, thiswould be 2 degrees retarded.

We at COMP Cams® hope that these instructions will be helpful in making your camshaft installation and degreeing
a successful experience. COMP Cams® produced a video entitled “The Proper Procedure to Install and Degree a Camshaft” (fig. I). This video covers all of the points
discussed here and illustrates many other helpful tips to achieve the maximum performance from your engine. If you wish to order this video, or if you have any other questions concerning your cam change, please call our CAM HELP® technical line at 1-800-999-0853. Our technical special-ists are here to help you 7:00 AM to 8:00 PM (CST) Monday through Friday.

Figure I


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