Thread: Another Cam Suggestion

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Another of the problems I see constantly is that most fellows have no idea how to adjust the lifters once they are finalizing the motor build. I wrote this for another forum, but will paste and copy it over here for you and others to see....I wrote it so that an idiot could understand it, because I'm pretty sure there will be some idiots reading it.....

ADJUSTING VALVES AND TIMING THE MOTOR INITIALLY AFTER A REBUILD, SMALL BLOCK CHEVY / BIG BLOCK CHEVY. Remove spark plugs. Remove valve covers. Remove distributor. Standing at the front of the motor, at the water pump and looking toward the rear of the motor, #1 cylinder will be on your right, the first one, just behind the radiator. The next one to the rear will be #3, then #5, then #7 will be the last one on the driver's side, next to the firewall. Looking on the other side of the motor, the passenger side, the front cylinder will be #2, the next one to the rear will be #4, then #6, then #8 all the way to the rear against the firewall. Do whatever you have to do to get this all fixed in your mind. If you have to make a diagram on a large piece of paper and sit it against the carburetor, then do it. The importance of knowing which cylinder is which cannot be over-stated.

Also, knowing which way the crankshaft turns and which way the distributor rotor turns cannot be over-stated. As you are standing at the water pump, the crankshaft turns clockwise, the same way the hands on an analog watch or clock turn.

If you were to climb up on top of the motor from the front and look directly down on the distributor with the cap off, you would see the rotor turning clockwise also. See this cute little animation.....
http://www.boxwrench.net/specs/chevy_sb.htm

With a socket and long bar with a ratchet attached to the bolt head that holds the harmonic damper onto the front of the crankshaft, turn the crank clockwise while a friend holds his thumb over the #1 spark plug hole. Using the starter for this operation WILL NOT WORK. When your friend feels air pressure beginning to build under his thumb, that means that both valves are closed and the piston is coming up on the compression stroke of #1 cylinder. Watch the harmonic damper and you will see the notch that is cut into the outer ring of the damper come up to the top. When that notch is at the top, STOP. You are now at approximately top dead center on #1 cylinder. It doesn't have to be EXACTLY at top dead center to adjust the valves.

Make a mark on the harmonic damper ring so that you can reference this TDC position again later. Either use a yellow crayon like they use in the service department of a tire store or a piece of tape placed at that position or whatever your mind can come up with. Make the mark at the top of the harmonic damper inertia ring. We are going to refer to this position as NORTH, because if you got down on your knees and looked at the harmonic damper from straight on, like you were looking straight through the centerline of the crank, this would be the NORTH position.

Loosen both adjusting nuts on both rockers on #1 cylinder until the rockers are loose on the studs. Have your friend hold his finger on the tip of one of them so that he is pinching the rocker arm down onto the tip of the valve, holding it tightly. Now, you grasp the pushrod for the rocker he is holding down and jiggle the pushrod up and down while using a socket wrench to slowly tighten down the rocker arm adjusting nut until all the slack is removed and you cannot move the pushrod up or down any longer. Be delicate here. This is not a strong-armed operation. You are simply taking all the slack out of the pushrod and getting the rocker adjusting nut very slightly tightened down against the trunnion of the rocker arm. Now, make 1/8 turn more on the adjusting nut.....1/8 turn.....45 degrees......OK, that valve is done. Now, move over to the other valve on #1 cylinder and repeat the operation.

You may have heard that you can rotate the pushrod with your thumb and forefinger until the pushrod gets tight and use that for adjusting the valves. While that may work for someone who builds motors day in and day out for a living, it WILL NOT WORK for someone like you who has no way of knowing how much resistance he should be feeling for. Jiggling the pushrod up and down is BULLETPROOF and can be done successfully by even a first-time builder.

Now, you have both valves adjusted on #1 cylinder. With the socket and ratchet on the harmonic damper retaining bolt head at the crank, turn the crankshaft 1/4 turn clockwise. That will mean that the mark you made on the damper ring will move clockwise from NORTH to EAST.....STOP. Make another mark on the damper ring at the straight-up position. Now, you will have a mark at EAST and a mark at NORTH.

You have moved the crank 90 degrees and into the next cylinder's firing range. There are 720 degrees in a full cycle to fire all 8 cylinders, so turning the crank 90 degrees at a time will allow us to adjust the valves on all 8 cylinders with just 2 full turns of the crank. If you knew that a small block Chevy's firing order is 1-8-4-3-6-5-7-2, then you would know that it is now #8 cylinder's turn to fire. Go to #8 and loosen both adjusting nuts, just like you did on #1. Have your buddy hold the rocker down against the valve stem while you jiggle the pushrod up and down to remove all play, all the while slowly turning the adjusting nut to remove the play. When all the play is removed, tighten the nut another 1/8 turn. Move on to the other valve on #8 and do the same.

Now, you have adjusted the valves on cylinders 1 and 8. Put the socket on the crank nut and turn the crank 1/4 turn to the right (clockwise, just like before). Place a mark at the top of the inertia ring like you did last time. This mark will be at NORTH. The mark you had at EAST will move to SOUTH and the one you had at NORTH will move to EAST. Following the firing order, we will now go to cylinder #4 and adjust both valves. Then we will move the crank 1/4 turn and make another mark and do cylinder #3. Then we will move another 1/4 turn (the crank has marks for each 1/4 turn now) and do cylinder #6. Then we will move the crank another 1/4 turn and do cylinder #5. Then we will move the crank another 1/4 turn and do cylinder #7. Then we will turn the crank another 1/4 turn and do cylinder #2. Then we will turn the crank another 1/4 turn and be back to firing on #1, where we will stab the distributor into the motor and install the retaining clamp and bolt. We will leave it a little loose so we can rotate the distributor housing. You may have to use a long screwdriver to line up the slot in the distributor driveshaft as you look down into the hole where the distributor goes.

As if we were standing on the motor and looking down on it, we will want to point the rotor tab at #1 cylinder, approximately 5:30 O'Clock if you look at a clock face. The rotor will move as you drop the distributor into position, because of the way the gears are cut. Pull the distributor out and rotate the rotor at another position to get the rotor to point at #1 cylinder when you drop it in. Position the distributor housing so that you can twist it both ways without the vacuum advance can hitting on the intake manifold or firewall of the car. Replace valve covers. Replace spark plugs. Using your longest spark plug wire, plug it into the 5:30 position on the cap, coinciding with the tab on the rotor at 5:30 and run the other end of the wire to #1 spark plug. The longest wires will be for #1 and #2. The next longest wires will be for #3 and #4. Next longest for #5 and #6. The shortest wires will be for #7 and #8. Going around the cap in a clockwise manner, the next hole in the cap will take the wire for #8 spark plug, then #4, then #3, then #6, then #5, then #7, then #2.

Now, depending on where the timing tab is on your motor (there were 3 different positions used), you might have to rotate the distributor housing a little one way or the other to get the motor to fire off, but unless I miss my guess, SHE WILL FIRE OFF. Have a timing light affixed to the #1 spark plug wire, adjust timing and lock the distributor down.

A little more info about the different timing positions. Like I said, there are 3 different ones. There is a 12:00 Noon position, a 2:00 O'Clock position and a 2:30 O'Clock position. Through the years, the timing tabs and front covers get mixed up on these motors, so you really should find top dead center and use the proper mark on your harmonic damper to line up with the timing tab on your front cover.
If you can follow these instructions, the valves will be adjusted properly and the motor will be ignition timed.

Decided to go ahead and run a DynoSim before going to bed.
RPM HP TQ
1500 103 360
2000 148 390
2500 185 395
3000 235 411
3500 285 430
4000 325 426
4500 353 412
5000 365 381
5500 321 306
Peak volumetric efficiency 87.7% @4000
Peak BMEP 181.2 @3500
This is a street motor, not a race motor. It exhibits excellent torque right off idle to pull a heavy vehicle off the mark smartly using the stock torque converter and tall rear gear and will do it on junk pump gas. If you are using a 3.89 gear and a 2200 stall converter, this motor should rip your head off in 1st gear, that is if you can hook it up!

TechInspector has a lot of good advice. If you decide against a roller cam, just make sure you add the appropriate zinc additives (EOS or other such products) to your oil and break it in properly. New oil formulations are not good for flat tappet cams. And IMO, the XE-274 is a little big for a 350 if you want to have a street-friendly driver.

Tech is very knowledgeable on this subject. I built a 383 based on his recipe and it screams. I used the comp hyd roller 286 magnum(230/230 @ .050)
I have built many engines and one thing that I have discovered is that from the very beginning, you must really think long and hard about what really you intend for the car. Are you really going to put 10,000miles on it? does it have ac and other power accessories?
As far as sound is concerned, I agree with tech. Hyd (flat tappet or roller) will never sound like the solid roller that I just put in a recent 427 ford build( 254@ .050) NEVER.
It is not necessarily the camshaft itself that is the culpit for poor driveability (aside from low vacuum) It's the things that complement the camshaft requirements ie...high compression, high stall, lowgears ect...
Comp created those thumper cams specifically for sound. I have put them on the desktop dyno and they inferior to other cams from a performance stand point.
I probably will never install another flat tappet again. After the last wipeout, too $$$
I like the sound of solid rollers as you can hear the valvetrain components clearly. Plus, solid rollers separate the fairweather corvette dorks from real muscle car enthusiasts!!!!!

I have a question about the valve adjustment. Techinspector1, you said to adjust the rocker arms 1/8 turn after all the slack is removed from the valvetrain(zero lash). I have always adjususted 1/2 turn except when using Competition Cams Pro Magnumroller lifters. The Pro Magnum is basicaly a race lifter. The rest of the Comp Cam line is 1/2 turn after zero lash. G.M. recommends 3/4 to 1 turn after zero lash. I'm just a little concerned why you would say to adjust the valves 1/8 turn without knowing which lifters are going into the engine.

Originally Posted by techinspector1

Loosen both adjusting nuts on both rockers on #1 cylinder until the rockers are loose on the studs. Have your friend hold his finger on the tip of one of them so that he is pinching the rocker arm down onto the tip of the valve, holding it tightly. Now, you grasp the pushrod for the rocker he is holding down and jiggle the pushrod up and down while using a socket wrench to slowly tighten down the rocker arm adjusting nut until all the slack is removed and you cannot move the pushrod up or down any longer. Be delicate here. This is not a strong-armed operation. You are simply taking all the slack out of the pushrod and getting the rocker adjusting nut very slightly tightened down against the trunnion of the rocker arm. Now, make 1/8 turn more on the adjusting nut.....1/8 turn.....45 degrees......OK, that valve is done. Now, move over to the other valve on #1 cylinder and repeat the operation.
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It was brought to my attention on another forum that there are some lifters that want only 1/8 turn. This is only the static adjustment anyway, just to get you in the ballpark to crank the motor and for the cam run-in. You are expected to do a hot lash after break-in and can set the preload anywhere you think is right. I have read lately that some fellows are using 1 1/2 turns after the slack is removed.