You take too much for granted in your build which provokes even more questions.
I verify my cam/crank timing by comparing the rocker arms to the crank's TDC. Here's how:
Look at your firing order:
Since this is a 4-stroke engine, it takes two revolutions to complete a cycle.
1-5-4-2 <--first revolution
6-3-7-8 <--second revolution
That means, when #1 piston is at TDC so is #6. If #6 rocker arms start motion as you rotate the crank in the correct direction, the exhaust comes up first, then the intake starts motion. Right then, when both rockers are dead even (use a straight edge on the rocker arms) they are both slightly open. That means #1 is on its power stroke. STOP right there.
At this point, the crank timing should point right at TDC. The distributor's rotor should point a hair before #1 spark plug tower, which should also be lined-up and pointing at #6 piston.
If your crankshaft timing marks are off, so is your timing chain. This requires, pulling the chain off and doing it over.
Let's assume cam timing is ok. If the distributor rotor is not pointing directly at #1 spark plug tower, your distributor is off a tooth, which makes spark happen between distributor towers. Sometimes the spark 'jumps' to the correct wire and sometimes it jumps to the wrong spark plug. If it is off, re-drop the distributor at the correct gear mesh.
I don't like playing, "what if..." but all I can go by is your answers. We have all made these common mistakes but as you learn more about the mechanics of your engine you will realize, all these settings can be verified before sealing with gaskets. - Dave
- Did you have any machine work done?
- Were the heads or block milled to make them straight?
- What head gasket thickness did you use?
- Did you check 'valve-to-piston' clearance? <--this is important
I verify my cam/crank timing by comparing the rocker arms to the crank's TDC. Here's how:
Look at your firing order:
Since this is a 4-stroke engine, it takes two revolutions to complete a cycle.
1-5-4-2 <--first revolution
6-3-7-8 <--second revolution
That means, when #1 piston is at TDC so is #6. If #6 rocker arms start motion as you rotate the crank in the correct direction, the exhaust comes up first, then the intake starts motion. Right then, when both rockers are dead even (use a straight edge on the rocker arms) they are both slightly open. That means #1 is on its power stroke. STOP right there.
At this point, the crank timing should point right at TDC. The distributor's rotor should point a hair before #1 spark plug tower, which should also be lined-up and pointing at #6 piston.
If your crankshaft timing marks are off, so is your timing chain. This requires, pulling the chain off and doing it over.
Let's assume cam timing is ok. If the distributor rotor is not pointing directly at #1 spark plug tower, your distributor is off a tooth, which makes spark happen between distributor towers. Sometimes the spark 'jumps' to the correct wire and sometimes it jumps to the wrong spark plug. If it is off, re-drop the distributor at the correct gear mesh.
I don't like playing, "what if..." but all I can go by is your answers. We have all made these common mistakes but as you learn more about the mechanics of your engine you will realize, all these settings can be verified before sealing with gaskets. - Dave
Comment