Flathead 8ba valve adjusting sequence
- Thread starter mOSkit
- Start date
Scotty's 52 F3
Well-known member
When I worked at a Caterpillar dealership we were trained to adjust all valves with only one crankshaft rotation. Two positions. Applies to all normal 4 stroke engines. I say normal because I don't know if there are any exotic applications out there that do not apply.
TDC of #1 cylinder then one rotation for the rest. The service manual showed which ones but, it was pretty obvious which ones as they had lash.
Just for kicks one day I tried MANY rotations and rechecked each valve adjustment. They were all good.
Scott
TDC of #1 cylinder then one rotation for the rest. The service manual showed which ones but, it was pretty obvious which ones as they had lash.
Just for kicks one day I tried MANY rotations and rechecked each valve adjustment. They were all good.
Scott
Scotty's 52 F3
Well-known member
In the Caterpillar interpretation, they were on the base circle of the cam. Maybe not exactly center but, no lift at all on what is considered base circle. I could always get proper valve adjustment in two spots regardless if a inline 6, V8, V12, V16....
New to flatheads so not familiar with cam profiles.
Scott
New to flatheads so not familiar with cam profiles.
Scott
JSeery
Member Emeritus
I would not adjust the valve clearance this way, but I think it is a fairly common method. As you move away from a stock cam this method becomes more questionable. To me, the lifter should be on the heel of the lobe and that requires the engine to be moved for each valve. But this should only require 2 engine revolutions at most (one revolution of the cam). At each 90 degree rotation of the crankshaft, one intake and one exhaust valve will be in the center of the heel on the camshaft. 8 valve pairs = 7 rotations of the crank of 90 degrees each.
Last edited:
JSeery
Member Emeritus
You want complicated try Rumbleseats methods:
There are two methods I use to adjust the valves during engine re-building.
(1)Degreeing the valves (not the cam). Degreeing the cam using a single exhaust and intake lobe assumes each lobe is EXACTLY the same. I don’t find this to be true in very many cases. Degreeing the valves is by far the most accurate in my opinion. This is done on the engine stand after valves, cam, crank and #1 piston is installed. BTDC is Before Top Dead Center and TDC is Top Dead Center and CW is ClockWise and CCW is CounterClockWise. Bring up #1 piston to exactly TDC.
Make and install a pointer near the crankshaft pulley. Install a degree wheel on the crank pulley. Index the degree wheel so the pointer is exactly pointing at 0 degrees and secure the degree wheel to the crank pulley (a couple of strip magnets work). Be careful to not disturb the degree wheel or pointer from this point on.
Example: Let’s assume a particular cam’s spec for an intake valve to begin opening is 20 degree BTDC. Back off the crank shaft CCW about 30 degrees (BTDC) or so using the crankshaft nut and a long breaker bar. You want to be able to rotate the crankshaft easily and smoothly, so use a long bar or a cheater pipe.
Install a dial indicator on #1 piston’s intake valve. Turn the crank CW (always turn the crank CW (facing the front of the engine) when setting and checking valve clearances) until the degree pointer is 20 degrees BTDC on the degree wheel. This is when the valve should barely begin lifting off its seat. Adjust the adjustable lifter until the valve moves the dial indicator’s needle less than a thousandth of an inch.
Time to check it. Turn the crank CCW several degrees before 20 degrees. Now turn the crank very slowly CW while watching the dial indicator closely. The needle should just barely twitch when the 20 degree BTDC mark on the degree wheel lines up with the pointer. If it doesn’t, re-adjust the lifter and check again. When satisfied, back off (CCW) the crankshaft until you reach the spot where the lifter to valve clearance is the greatest. This is determined by trying various thicknesses of feeler gauges while rocking the crank back and forth several degrees. All that’s left is to measure the clearance between the valve and lifter using a feeler gauge. This is #1 Intake valve’s clearance. Record it for future use as #1 Intake for your records. That valve is done.
Now do all the valves. Don’t forget to record their clearances as you go.for your records. After the first couple of valves, it goes pretty fast. I degree valves in a flathead in a few hours after the initial set up. A real benefit is in the future I need only to re-set the clearances of each valve to the clearances recorded and the valve is degreed. How? I turn the crank so the lifter is the farthest from the valve. Let’s assume a particular valve was degreed at 0.011" clearance. Since valve clearance normally increases, we can use a feeler gauge thicker than 0.011" to determine where the lifter is furthest from the valve. Use the thickest feeler gauge that’ll slide in between the lifter and valve. Say it’s 0.014". With the 0.014" feeler gauge between the lifter and valve, rotate the crank back and forth several degrees until you find the spot the feeler gauge is the loosest. Now adjust this to 0.011" clearance and it’s exactly the same as if you just degreed it! Neat... neat! Degreeing valves always results in an increase in horsepower.
(2) Visual method. This is done before installing the crankshaft. The cam and all valves are installed. Invert the engine so you can see the cam lobes. Rotate the cam and position the exact middle of the lobe’s heel at the lifter. I do this visually. Then invert the engine and adjust the valve clearance according to the cam manufacture’s spec’s. This is done to each valve and requires a lot of block turning.
There are two methods I use to adjust the valves during engine re-building.
(1)Degreeing the valves (not the cam). Degreeing the cam using a single exhaust and intake lobe assumes each lobe is EXACTLY the same. I don’t find this to be true in very many cases. Degreeing the valves is by far the most accurate in my opinion. This is done on the engine stand after valves, cam, crank and #1 piston is installed. BTDC is Before Top Dead Center and TDC is Top Dead Center and CW is ClockWise and CCW is CounterClockWise. Bring up #1 piston to exactly TDC.
Make and install a pointer near the crankshaft pulley. Install a degree wheel on the crank pulley. Index the degree wheel so the pointer is exactly pointing at 0 degrees and secure the degree wheel to the crank pulley (a couple of strip magnets work). Be careful to not disturb the degree wheel or pointer from this point on.
Example: Let’s assume a particular cam’s spec for an intake valve to begin opening is 20 degree BTDC. Back off the crank shaft CCW about 30 degrees (BTDC) or so using the crankshaft nut and a long breaker bar. You want to be able to rotate the crankshaft easily and smoothly, so use a long bar or a cheater pipe.
Install a dial indicator on #1 piston’s intake valve. Turn the crank CW (always turn the crank CW (facing the front of the engine) when setting and checking valve clearances) until the degree pointer is 20 degrees BTDC on the degree wheel. This is when the valve should barely begin lifting off its seat. Adjust the adjustable lifter until the valve moves the dial indicator’s needle less than a thousandth of an inch.
Time to check it. Turn the crank CCW several degrees before 20 degrees. Now turn the crank very slowly CW while watching the dial indicator closely. The needle should just barely twitch when the 20 degree BTDC mark on the degree wheel lines up with the pointer. If it doesn’t, re-adjust the lifter and check again. When satisfied, back off (CCW) the crankshaft until you reach the spot where the lifter to valve clearance is the greatest. This is determined by trying various thicknesses of feeler gauges while rocking the crank back and forth several degrees. All that’s left is to measure the clearance between the valve and lifter using a feeler gauge. This is #1 Intake valve’s clearance. Record it for future use as #1 Intake for your records. That valve is done.
Now do all the valves. Don’t forget to record their clearances as you go.for your records. After the first couple of valves, it goes pretty fast. I degree valves in a flathead in a few hours after the initial set up. A real benefit is in the future I need only to re-set the clearances of each valve to the clearances recorded and the valve is degreed. How? I turn the crank so the lifter is the farthest from the valve. Let’s assume a particular valve was degreed at 0.011" clearance. Since valve clearance normally increases, we can use a feeler gauge thicker than 0.011" to determine where the lifter is furthest from the valve. Use the thickest feeler gauge that’ll slide in between the lifter and valve. Say it’s 0.014". With the 0.014" feeler gauge between the lifter and valve, rotate the crank back and forth several degrees until you find the spot the feeler gauge is the loosest. Now adjust this to 0.011" clearance and it’s exactly the same as if you just degreed it! Neat... neat! Degreeing valves always results in an increase in horsepower.
(2) Visual method. This is done before installing the crankshaft. The cam and all valves are installed. Invert the engine so you can see the cam lobes. Rotate the cam and position the exact middle of the lobe’s heel at the lifter. I do this visually. Then invert the engine and adjust the valve clearance according to the cam manufacture’s spec’s. This is done to each valve and requires a lot of block turning.
flatheadfan
Well-known member
This is the sequence I use:
When you pull of the intake you will find one of the combinations listed on the left. If you find an “a” set opened you use all of the “a” sequencing. If it is a “b” use all the “b” sequencing and so-forth.
Hope this helps. Tom
Sequencing:
Valves Opened - Adjust these
a) 4X -- 1N ---> 3X- 3N- 8N- 6N- 7X- 2X
b) 8X – 5N ---> 1X- 7N- 6N- 7X- 3N- 2X
c) 6X – 4N ---> 5X- 2N- 1X- 7N- 3N- 2X
a) 3X – 8N ---> 1X- 7N- 5X- 2N- 4X- 1N
b) 6N – 7X ---> 5X- 2N- 4X- 1N- 8X- 5N
c) 3N – 2X ---> 4X - 1N- 8X- 5N- 6X- 4N
a) 1X – 7N ---> 8X- 5N- 6X- 4N
b) 5X – 2N ---> 6X- 4N- 3X- 8N
c) 4X – 1N ---> 3X- 8N- 6N- 7X
When you pull of the intake you will find one of the combinations listed on the left. If you find an “a” set opened you use all of the “a” sequencing. If it is a “b” use all the “b” sequencing and so-forth.
Hope this helps. Tom
Sequencing:
Valves Opened - Adjust these
a) 4X -- 1N ---> 3X- 3N- 8N- 6N- 7X- 2X
b) 8X – 5N ---> 1X- 7N- 6N- 7X- 3N- 2X
c) 6X – 4N ---> 5X- 2N- 1X- 7N- 3N- 2X
a) 3X – 8N ---> 1X- 7N- 5X- 2N- 4X- 1N
b) 6N – 7X ---> 5X- 2N- 4X- 1N- 8X- 5N
c) 3N – 2X ---> 4X - 1N- 8X- 5N- 6X- 4N
a) 1X – 7N ---> 8X- 5N- 6X- 4N
b) 5X – 2N ---> 6X- 4N- 3X- 8N
c) 4X – 1N ---> 3X- 8N- 6N- 7X