OK, I OH my engine and It wouldn't start, I screwed up the cam degreeing operation. I set # 1 cylinder to TDC and both valves closed. I removed the timing cover and noticed my timing marks were off. I aligned the crank/cam dots and I think it is on time now. My question is, after #1 TDC cylinder begins to go down, #1 intake valve begins to open. Is that correct? I thought #1 exhaust valve begins to open.

 

Intake valve goes first!Because the cycle just begining on the first cylinder.

 

OK, I thought so because I have the #1 cylinder TDC with the timing crank gear pointing up and the timing chain off. I line up the timing cam gear and continue rotating to see the entire operation and #1 Intake valve always opens up after #1 TDC cycle. Thanks.

 

If the intake valve starts opening first, I think you are 180 out on timing. Cylinder six should be firing at that point.

 

Why would six fire next if the firing order is 1-8-4-3-6-5-7-2? I have the timing chain off so the crank is not moving, only the cam, lifters and pushrods.

 

The ignition timing mark will line every revolution but the cylinders fire every other revolution on a 4 cycle engine.
When the marks are lined up on the gears #6 is in firing position and #1 is starting the intake stroke.
That is if I'm not mistaken.

 

Charlie is correct.

 

I think I know your problem:

You lined up the dots on the gears to face each other while the rotor was pointing at #1. So the cam gear marking was at 6 o'clock and the crank gear was at 12 o'clock. That is wrong. That is actually #6 TDC.

BOTH gear marks must be at 12 o'clock when the #1 cylinder is at TDC.


it can really screw with your brain because there are essentially 2 TDCs for every complete cycle of one cylinder. The TDC that we speak of when degreeing a cam is always the point at which the spark plug fires, which is the combustion stroke. In that stroke, both valves are closed and the first to open will be the exhaust valve as the poison gets very near the bottom of the cylinder and begins to come up.

The next stroke upward is referred to as the overlap, as the exhaust and intake valves are both open for just a little bit at the top of the stroke. the exhaust valve being open just a bit helps pull the charge into the cylinder thru the intake valve at a higher velocity. Thats called scavenging, it uses the low pressure caused by the back side of the exhaust pulse wave to pull fresh air into the cylinder.

The overlap is where you run into piston-to-valve clearance issues on camshafts.

 

Im really confused now, I have OH my truck twice and didnt have this problem.

OK, tell me if this is correct. Both sprockets marks are aligned together, crank sprocket at twelve and cam sprocket and six o'clock. Piston cylinder #1 at TDC. Distributor rotor pointing to # 1 spark plug wire. Is this the correct installation?

 

If the intake valve on number 1 starts opening when you turn the crank, point the distributor at number 6 instead.