Cam pin location question
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Teching In
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Cam pin location question First post! I have searched the internets and come up empty. I have been meaning to join this forum for a while, I've been building a lq4 over the past few months and I'm now at degreeing the cam. I picked up the "how to build an LS engine" book and its been very beneficial! Anyhow, it says to install the crank sprocket (I picked up a summit dual roller with adjustable crank sprocket which is set to 0*) install the cam sprocket with the locating pin to the right. Done and done, problem is, with the pin to the right the intake is just starting to open. the book says (and all things Ive read thus far) on the compression stroke the lifters should be at the base of the lobe. Well when the piston is TDC and the lifter is on the base of the lobe the pin is to the left and the dots are both at 12 o'clock. Am I doing something wrong? I know installing the cam "straight up" is a thing (suprisingly not a lot of info on that) the cam is an elgin 1840P. I'm not moving on till I've got this straightened out! thanks for any help.
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Zackly:
Remember, this is a 4-stroke engine. The crank turns TWICE for each complete engine cycle, the cam turns ONCE.
When the crank dot is at 12:00 and the cam dot is at 6:00, you're at THE OTHER instance of #1 TDC besides firing. At that point, the #1 exh stoke is ending (#1 exh just closing) and the int stroke beginning (int valve just beginning to open). It's also #6 firing.
Turn the crank exactly 1 full turn; the cam will turn ½ turn; at that point both dots will be at 12:00, the engine will be at #1 firing, and #6 will be at the stage described above.
The reason we build em dot-to-dot is because it's easier to see and not mess it up.
Remember, this is a 4-stroke engine. The crank turns TWICE for each complete engine cycle, the cam turns ONCE.
When the crank dot is at 12:00 and the cam dot is at 6:00, you're at THE OTHER instance of #1 TDC besides firing. At that point, the #1 exh stoke is ending (#1 exh just closing) and the int stroke beginning (int valve just beginning to open). It's also #6 firing.
Turn the crank exactly 1 full turn; the cam will turn ½ turn; at that point both dots will be at 12:00, the engine will be at #1 firing, and #6 will be at the stage described above.
The reason we build em dot-to-dot is because it's easier to see and not mess it up.
With No.1 at TDC on the compression stroke the alignment pin on the cam should be at 1:30-2:00 position. The dot on cam gear should be down or at 6:00 position and the dot on the crank gear up at the 12:00 position.
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Teching In
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Ok,I get the cam to crank timing events. The problem is the locating pin when on the compression stroke (both valves closed) is on the left and the dot is up. Dot to dot, the intake is opening, not by much but it is. I'm have issues uploading photos from my phone, I'll try in the 'puter. I honestly think they sent me the wrong cam. It also only opens .253 at the valve. Quite a bit of from .585!
The compression stroke will come after the intake valve has closed. Are you sure that you have No. 1 at TDC of the COMPRESSION STROKE?
If so then the cam and crank dots should be as stated above and the pin on the cam at the 1:30-2:00 position.
If so then the cam and crank dots should be as stated above and the pin on the cam at the 1:30-2:00 position.
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From: Central Cal.
Ok, I get the cam to crank timing events. The problem is the locating pin when on the compression stroke (both valves closed) is on the left and the dot is up. Dot to dot, the intake is opening, not by much but it is. I'm have issues uploading photos from my phone, I'll try in the 'puter. I honestly think they sent me the wrong cam. It also only opens .253 at the valve. Quite a bit of from .585!
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Teching In
Joined: Jun 2020
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Yes! I must apologize! I pretend to know more than I do some times! I never new the only reason to install the gears dot to dot was simply to make life easier. dots up is compression cycle and where I should be to start degreeing the cam. Cam is degreed and all is well! thanks guys.
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Joined: Jun 2016
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From: Central Cal.
Yes! I must apologize! I pretend to know more than I do some times! I never new the only reason to install the gears dot to dot was simply to make life easier. dots up is compression cycle and where I should be to start degreeing the cam. Cam is degreed and all is well! thanks guys.