When #1 cylinder is TDC on compression stroke, which of the other valves are depressed. it takes 720 degrees for all eight to fire so its tricky to figure out which valves are depressed. My firing order is 18436572
Well, 360 degrees divided by 8. That where I'd start. With a degree wheel you should be able to plot that out with pen and paper to get an answer open and close on #1. Intake and exhaust. Then do the others. Now if your trying to adjust valves, say that and you'll get a different answer.
1 and 8 should be closed, both fully in the process of compression stroke. Intake of 4 will be just about closed, intake of 3 should be fully open, 6 just starting to open. 5 exhaust should be just about closed, 7 exhaust open and 2 exhaust just beginning to open.
I am getting different results then above. I believe I am TDC because when I start passing it (clockwise) the #1 intake starts to open meaning the explosion already happened. The difference is my intake 4 is open and my exhaust 5 is open. Not all of my lifters are not pumped up so its hard to tell because the engine is assembled.
If # 1 intake is starting open, that’s the beginning of the intake stroke. The next rotation will be compression and at TDC (well a bit before) the spark ignites. That’s the TDC you want to look for
Oh, go to YouTube and search for “4 cycle valve events/timing “. Edit: I mentioned YouTube because I found a nice animated video for a friend wh thought his valve timing may be off. He wasn’t understanding what I was trying to get across on the phone.
Negative. This is the beginning of the explosion, as you put it, process. When the piston comes back up will be compression and ignition. Good luck figuring the rest out.
Thats what i meant when i said i passed it. On the tdc cycle when the intake opened up, the next 360 around is combustion and thats where my valves did not match what phila said.
I got confused by what Phil was saying, so didn’t reply to it. Only one piston is at TDC at full compression at a time. Are you adjusting valves or?
Chances are that the intake valve should just begin opening before TDC. and the exhaust would close the last little bit shortly after you pass TDC. Lynn
Is this for the L82 engine you have mentioned here before ??? If so, the firing order for a L82 is 1-8-7-2-6-5-4-3........ EDIT: This is for the later 5.3 litre L82 engine designation. The early L82 Corvette 350ci engines have the standard sbc firing order of 1-8-4-3-6-5-7-2. See post #23. Sorry guys.......
Twenty8 is the man. I screwed up. Iam an old mopar guy 18436572 but yes the l82 is different. So do the cams interchange. What if someone put a cam from a l98 into a l82 block. The firing order would change. Nice adjusting chart, what is the typ gauge thickness?
If you are going by the timing chain...number one TDC compression stroke, is when both the cam and crank gear dots are at the top. Gene.
Wish I could use the sprocket dots but the timing cover is on. Is the above chart for adjustments based on 1-8-7-2-6-5-4-3.
Yes. FYI, having the two dots next to each other is not on a compression stroke even though the piston is at tdc.
The chart that Johnny Gee posted in post 7 is the primary one I have seen for SBC. On top compression both valves will always be closed or should be. Ideally you would figure out with the heads off and a degree wheel on the crank. I'm thinking that the crank turns 90 degrees to bring the next cylinder on top compresson though. Meaning have #1 on top compresson, adjust the valves, rotate the crank 1/4 turn (90 degrees) and adjust the next one in the firing order, rotate it another quarter turn and do the next. All the while watching the action of the rockers or valves as the intake should be finishing closing.
Which L82 do you have? Seems that I gave you the firing order for the later engine....... The early '73 to '80 engine may have had the same firing order as the standard 350ci. (1-8-4-3-6-5-7-2) GM 5.3 Liter V8 EcoTec3 L82 Engine The L82 is a 5.3 liter, eight-cylinder engine from General Motors used in pickup trucks. Featuring an OverHead Valve (OHV), or “push-rod” design” in a “V” configuration, the L82 is part of GM’s Gen V Small Block engine architecture that’s known in trucks and SUVs as EcoTec3. The L82 is essentially the same engine as the 5.3L V8 L84 with Dynamic Fuel Management, but instead of being equipped with Dynamic Fuel Management, the L82 features Active Fuel Management. The L82 is somewhat of a direct successor to the GM L83 engine, and was first launched in the fourth-generation 2019 Chevy Silverado 1500 and fourth-generation 2019 GMC Sierra 1500. To clarify, the L82 designation was also used for a performance variant of the 350 cubic-inch V8 produced from 1973 to 1980. This particular L82 was used to power the Chevrolet Corvette as well as the Chevrolet Camaro.
What do you mean by "depressed"? With a 90 deg crankshaft cylinder #6 is 360 deg from #1 [both pistons will be a TDC] #1 should be at TDC compression and #6 at TDC with valve overlap [Exhaust closing and Intake opening]
Depressed means the rocker is pushed down and the valve is open. So its 90 degrees because 720/8=90 right? I was using 360. But what is really tough and causing me an issue is #1 exhaust lifter is leaked out and has pushrod play through 720 degrees. If both the #1 valves were working I would not be posting this. The priming rod and starting it with the distributor in only yields about half the rockers wet but since the #2 rockers are wet that tells me the galley is full of oil. So what I do know is when the mark is at TDC and I start to turn it clockwise the #1 intake opens and when I bring the mark around 360 its closed. That tells me that it was going on a down stroke sucking in fuel and going back for the compression but someone here posted thats wrong. I dont see how it could be.
I guess here is an easy way to check. If my lifters are working on #6 and the rockers are loose its on compression which means #1 is not and if I rotate it another 360 #1 will be on compression,
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