SBC rocker arm adjustment
09-04-2013, 10:05 PM
#1
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SBC rocker arm adjustment I would normally adjust them while the engine is running. but it is so far off, its backfiring through the carb and is barly running. I remembered kindve about setting #1 at TDC and adjusting the I and E and then you could adjust several other rockers. heres what I found...
Valve Adjustment The Quick Way:
With the engine OFF and spark plugs removed so that you can rotate the engine with less effort.
1. Get #1 piston to compression TDC, Cam gear at 12 o'clock crank gear at 12 o'clock.
2. Adjust the intake valves on cylinders 1, 2, 5, & 7 by loosening the rocker nut until play is in the pushrod then just take the up and down play in the pushrod and tighten the rocker nut 90 degrees
3. Adjust the exhaust valves on 1, 3, 4, & 8 in the same manner.
4. Rotate crank 360 degrees to get cylinder #6 to compression TDC, Cam gear at 6 o'clock and crank gear at 12 o'clock.
5. Adjust the intake valves on 3, 4, 6, & 8 in mentioned manner
6. Adjust the exhaust valves on 2, 5, 6, & 7
Its step 4 thats confusing me. I assumed that after adjusting #1,, rotating another 360 degrees would be TDC of #8... since it is next in the firing order. Am I wrong about this????
Valve Adjustment The Quick Way:
With the engine OFF and spark plugs removed so that you can rotate the engine with less effort.
1. Get #1 piston to compression TDC, Cam gear at 12 o'clock crank gear at 12 o'clock.
2. Adjust the intake valves on cylinders 1, 2, 5, & 7 by loosening the rocker nut until play is in the pushrod then just take the up and down play in the pushrod and tighten the rocker nut 90 degrees
3. Adjust the exhaust valves on 1, 3, 4, & 8 in the same manner.
4. Rotate crank 360 degrees to get cylinder #6 to compression TDC, Cam gear at 6 o'clock and crank gear at 12 o'clock.
5. Adjust the intake valves on 3, 4, 6, & 8 in mentioned manner
6. Adjust the exhaust valves on 2, 5, 6, & 7
Its step 4 thats confusing me. I assumed that after adjusting #1,, rotating another 360 degrees would be TDC of #8... since it is next in the firing order. Am I wrong about this????
09-09-2013, 12:30 PM
#4
adjusting rockers while the engine is running is a bad idea and risky and almost never a reason you need to do it while running.
you're backfiring and idle problems can be caused by many other things, and if it's having a hard time idling then it most likely is not because the rockers are not adjusted properly. you'd have to really screw up adjusting them to screw things up at idle. my recommendation is do what 87silverbullet said. you just need to know when looking at the valves/rockers which one is intake and which one is exhaust. rotate the engine by hand with spark plugs out, for a given cylinder when the exhaust valve starts to open then you know the intake valve is no where near its lobe so adjust the intake. when the intake valve just starts to close (after having fully popped up) then you adjust the exhaust valve. EO/IC exhaust open / intake closing. when exhaust valve starts to open adjust intake valve. when intake starts to close adjust exhaust valve.
after you take up any play between the pushrod and rocker, which is called zero preload, then i would go at least a 1/2 turn on the rocker nut. The norm for the sbc was 3/4 turn. doing only 1/4 turn is very little preload and will probably give you backfiring at high rpms.
you're backfiring and idle problems can be caused by many other things, and if it's having a hard time idling then it most likely is not because the rockers are not adjusted properly. you'd have to really screw up adjusting them to screw things up at idle. my recommendation is do what 87silverbullet said. you just need to know when looking at the valves/rockers which one is intake and which one is exhaust. rotate the engine by hand with spark plugs out, for a given cylinder when the exhaust valve starts to open then you know the intake valve is no where near its lobe so adjust the intake. when the intake valve just starts to close (after having fully popped up) then you adjust the exhaust valve. EO/IC exhaust open / intake closing. when exhaust valve starts to open adjust intake valve. when intake starts to close adjust exhaust valve.
after you take up any play between the pushrod and rocker, which is called zero preload, then i would go at least a 1/2 turn on the rocker nut. The norm for the sbc was 3/4 turn. doing only 1/4 turn is very little preload and will probably give you backfiring at high rpms.
09-11-2013, 01:16 AM
#5
TDC as described above is right. remember the firing order is as follows 1-8-4-3-6-5-7-2
TDC = 1
rotate (looking from the front of the car clockwise) 90 deg = 8
180 deg = 4
270 deg = 3
360 deg = 6 <<<<<< now at BDC (Bottom Dead Center) one full rotation of the crank
450 deg = 5
540 deg = 7
630 deg = 2
720 deg = back to TDC 1, two full rotations of the crank.
DISCLAIMER
Adjusting the rocker arms in this fashion is ONLY for hydraulic lifter cams
The way 1FMF said to do it is probably the best way to adjust rocker arms, because the lifter is on the base circle of the camshaft where there is no lift at all.
TDC = 1
rotate (looking from the front of the car clockwise) 90 deg = 8
180 deg = 4
270 deg = 3
360 deg = 6 <<<<<< now at BDC (Bottom Dead Center) one full rotation of the crank
450 deg = 5
540 deg = 7
630 deg = 2
720 deg = back to TDC 1, two full rotations of the crank.
DISCLAIMER
Adjusting the rocker arms in this fashion is ONLY for hydraulic lifter cams
The way 1FMF said to do it is probably the best way to adjust rocker arms, because the lifter is on the base circle of the camshaft where there is no lift at all.
