anyone else notice this during a cam swap??
08-21-2005, 11:03 AM
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anyone else notice this during a cam swap?? If you do put your motor at TDC on the compression stroke for the number one cylinder then the cam dot will be at 12 oclock instead of 6 oclock where you think it would be.When you set up a cam dot to dot like you see in the pics on ls1howto.com then the #1 piston is not on its compression stroke.I just found this interesting because i am pretty sure on a convention SBC engine dot to dot(cam dot at 6)the #1 piston is on the compression stroke.
09-02-2005, 10:54 AM
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This is interesting, because I saw this when I did my cam swap and was like 
. I was confused becasue the GM service manual says that when they are dot to dot that the #1 cylinder should be at TDC on compression. Anybody else notice this?
. I was confused becasue the GM service manual says that when they are dot to dot that the #1 cylinder should be at TDC on compression. Anybody else notice this? 
09-02-2005, 02:19 PM
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There are 2 TDC instances for every power cycle: if the power cycle starts at TDC on intake you have
intake - piston travels from TDC to BDC (intake valve open, exhaust closed)
compression - piston travels from BDC to TDC (valves closed)
power (ignition) - piston travels to BDC
exhaust - piston travels to TDC expelling exhaust (exhaust valve open)
This is rudimentary, but you get the picture. 2 TDC instances per power cycle.
intake - piston travels from TDC to BDC (intake valve open, exhaust closed)
compression - piston travels from BDC to TDC (valves closed)
power (ignition) - piston travels to BDC
exhaust - piston travels to TDC expelling exhaust (exhaust valve open)
This is rudimentary, but you get the picture. 2 TDC instances per power cycle.
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09-02-2005, 04:31 PM
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Dot-to-dot is the start of the 4-stroke engine cycle. Compression/firing TDC is 1/2 through the cycle when the cam-mark is at 12 o-clock position.
Technically, as long as cylinder #1 is at TDC you can install the camshaft gear at 6 o-clock OR 12 o-clock, its the same thing since the crankshaft doesn't know where the cam is.
Technically, as long as cylinder #1 is at TDC you can install the camshaft gear at 6 o-clock OR 12 o-clock, its the same thing since the crankshaft doesn't know where the cam is.