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I have a small problem here.
I took my "compression whistle" and put in into cylinder 1, and after 3 good strong whistle, I took the balance to 0, so I guess I'm TDC.
But look what happened when the timing cover came of, I'm 180 degrees of.
Also.......
1. When is a chain/wheel worn?
2. A hydr. roller cam will come in to the engine (Comp Cams 12-466-8) does the cam need a lock plate, to keep the cam in place?
The "dots" can be in four different positions and cam timing will still be correct. The manuals call for the dots to be in line with the crank dot at the 12 o-clock position and the cam dot at the six o-clock position because that's the most nearly fool proof way to ensure correct phasing between the crank and cam. They could also be correct with the crank at six and the cam at six, the crank at 12 and the cam at 12 (as yours now shows) or the crank at six and the cam at 12. The dots will achieve all of these positions with two turns of the crankshaft since the cam turns at half crank speed. It really only matters when you are installing the distributor to know that the engine is at true TDC.
Yes, you do need a cam button to prevent the camshaft from moving forward when using a roller cam with that block. I believe you are referring to the cam buttons that also serve as a lock plate for the cam bolts. The lock plate itself isn't necessary but, again, the button is. Later SBCs machined for a factory roller cam use a cam retention plate which takes care of the cam walk issue, but that does not apply to your engine.
As to how to tell when they are worn; you are looking for slack in the chain. In a good timing set, there will be very little deflection when you press on the side of the chain. You should also be able to make very slight movements of the crankshaft and see no lag in cam movement.
The "dots" can be in four different positions and cam timing will still be correct. The manuals call for the dots to be in line with the crank dot at the 12 o-clock position and the cam dot at the six o-clock position because that's the most nearly fool proof way to ensure correct phasing between the crank and cam. They could also be correct with the crank at six and the cam at six, the crank at 12 and the cam at 12 (as yours now shows) or the crank at six and the cam at 12. The dots will achieve all of these positions with two turns of the crankshaft since the cam turns at half crank speed. It really only matters when you are installing the distributor to know that the engine is at true TDC.
Yes, you do need a cam button to prevent the camshaft from moving forward when using a roller cam with that block. I believe you are referring to the cam buttons that also serve as a lock plate for the cam bolts. The lock plate itself isn't necessary but, again, the button is. Later SBCs machined for a factory roller cam use a cam retention plate which takes care of the cam walk issue, but that does not apply to your engine.
As to how to tell when they are worn; you are looking for slack in the chain. In a good timing set, there will be very little deflection when you press on the side of the chain. You should also be able to make very slight movements of the crankshaft and see no lag in cam movement.
1. Ok I will turn the cam wheel 6 and the crank to 12 to meet up.
The "dots" can be in four different positions and cam timing will still be correct. The manuals call for the dots to be in line with the crank dot at the 12 o-clock position and the cam dot at the six o-clock position because that's the most nearly fool proof way to ensure correct phasing between the crank and cam. They could also be correct with the crank at six and the cam at six, the crank at 12 and the cam at 12 (as yours now shows) or the crank at six and the cam at 12. The dots will achieve all of these positions with two turns of the crankshaft since the cam turns at half crank speed. It really only matters when you are installing the distributor to know that the engine is at true TDC.
Yes, you do need a cam button to prevent the camshaft from moving forward when using a roller cam with that block. I believe you are referring to the cam buttons that also serve as a lock plate for the cam bolts. The lock plate itself isn't necessary but, again, the button is. Later SBCs machined for a factory roller cam use a cam retention plate which takes care of the cam walk issue, but that does not apply to your engine.
As to how to tell when they are worn; you are looking for slack in the chain. In a good timing set, there will be very little deflection when you press on the side of the chain. You should also be able to make very slight movements of the crankshaft and see no lag in cam movement.
With the crank dot at 6 o-clock, the cam will be at 3 or 9 o-clock, your info is mostly correct though. 1 turn of the crank = 1/2 turn of the cam, so 1/2 turn of the crank is = to 1/4 turn of the cam. Never align with the crank at 6 o'clock, only at 12, cam can be either 6 or 12, TDC compression #1 is cam 12 and crank at 12 o'clock.
It keeps you from being 1 tooth off doing it as stated above I've seen many people miss it by one and the car will run but you'll either have an engine with no torque or an engine that can't rev.
...
2. Can you send me a link for the "lock" needed?
...
You can use the search term "cam button" on any of the online speed shops, like Summit; http://www.summitracing.com/parts/mor-60462 to come up with many purchasing options. But this one includes the lock plate.
Remember the cam shaft rotates at 1/2 the crankshaft rate. Rotate the crank 1 revolution and look at the timing marks...
Marks lined up at 6 and 12 is not tdc (compression) on #1. If you install the distributer thinking you are on tdc she will spit fire, backfire, and belch fire. It's 180* out.
Last edited by Jeff_Keryk; Oct 19, 2014 at 09:43 AM.
From: Las Vegas - Just stop perpetuating myths please.
^^^ What they all said. But sometimes it helps to draw/sketch some pictures of what going on. For ex. the crank turns twice for every full turn of the cam but the distributor turns the same as the cam. So u can plot the cyls that fire every 45 degrees on the dist cap while those cam lobes on the cam will be on the base circle with the vlvs shut. Since the crank has 8 cyls then every 45 degrees of crank rotation 2 cyls have to be at TDC but only one has its vlvs shut ready to fire with the other cyl at TDC has vlvs open in overlap. Firing order is 18436572, so every 45* has 2 cyl at TDC and starting with #1 & #6, then after 45* #8 & #5, then #4 & #7 and finally #3 & #2.
Try drawing this a few times and it should give u a better idea of what is going on with the timing set and timing marks. When timing set marks are at 12 on the cam sprocket and 12 on the crank gear cyl #1 is ready to fire. When marks are at 6 on the cam sprocket and 12 on the crank gear cyl #6 is ready to fire. But both cyls #1 & #6 are at TDC each time.
Thx for your help.
I think know about the TDC ec ec now.
But one thing I don't understand is, how cam a stop button and Lock plate, that you screw in to cam shaft, make sure that the cam shaft doesn't "fall out"
I could understand it, if you screwed the Lock plate into the engine.
Is it because the stop button "press" against the chain cover, and therefore hold the cam in place???
John, "Lock plate" in this sense means the plate that secures the cam bolts (french lock), not to be confused with the lock plate that is used in place of a cam button on blocks that are prepared for that (yours isn't)
You need the cam botton.
How much in tolerance from the button to the chain cover?
And do I need to buy a other chain cover, or can I reinforce the std. 69 cover I have (if yes how)
Timing chain/setup problem
I've seen many people miss it by one and the car will run but you'll either have an engine with no torque or an engine that can't rev.
