Is it possible to install a camshaft "upside-down"
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Joined: Aug 2007
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From: Johnson City, Tennessee
Is it possible to install a camshaft "upside-down" If you install the LS1 cam "dot-to-dot" is it possible that the cam could be installed 180 degrees out of phase in relation (crank spins 2x for every 1x of the cam) to the crank thus causing the engine to think that the exaust stroke were the compression stroke or vise-versa?
Thread Starter
Teching In
Joined: Aug 2007
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From: Johnson City, Tennessee
I'm definatly overcomplicating a simple issue. Here is the thing. I think I pulled the stock cam out with crank-gear dot "up" and camshaft dot "up" as well. Then I reinstalled the camshaft "dot-to-dot" (crank dot up and cam dot down) then I decided it would be a good idea to make sure I didn't curse my self so I'm doing some follow up. How does the engine know when to pulse the injectors and the spark?
If you installed the cam "dot-to-dot" it's correct. The cam rotates at half the crank speed, which is why you turn the crank 90 degrees to install valvesprings, the cam only rotates 45 degrees. 
There are cam/crankshaft position sensors that allow the PCM to "know" where the two shafts are and control spark and injector pulsing.
There are cam/crankshaft position sensors that allow the PCM to "know" where the two shafts are and control spark and injector pulsing.
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From: Texas and Qatar
Originally Posted by Mike94ZLT1
YES, you can install the cam so it is off. If the dot on the cam gear is UP, and the dot on the crank gear is UP, it is 180 degrees off and will not run.
On a side note, when both timing dots are at straight up at 12 o' clock, that is the number 1 cylinder's firing position, perfect place to check preload and/or leakdown, when the dots are together that is cylinder 6's firing position, and cylinder 1's start of intake stroke and usually still in overlap (both intake and exhaust valves slightly open).
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Originally Posted by Mike94ZLT1
YES, you can install the cam so it is off. If the dot on the cam gear is UP, and the dot on the crank gear is UP, it is 180 degrees off and will not run.
Also, like already said, if both dots were up you would just be at No 1 TDC on the other stroke.
Originally Posted by -Joseph-
No, thats exactly the same thing as lining it up dot-to-dot. Now if the crank dot was anywhere other than the 12 o' clock and the cam gear is still at 12 or 6, then you have problems. If you line up a cam dot-to-dot and then rotate the crankshaft one turn you'll see that both dots will be at the 12 o' clock position. Its a 2-1 ratio gear so cam spins half as fast as the crankshaft, meaning 1/2 cam revolution per 1 crank revolution, or 1 complete cam rev. per 2 crank rev. for the complete 4-stroke cycle.
On a side note, when both timing dots are at straight up at 12 o' clock, that is the number 1 cylinder's firing position, perfect place to check preload and/or leakdown, when the dots are together that is cylinder 6's firing position, and cylinder 1's start of intake stroke and usually still in overlap (both intake and exhaust valves slightly open).
On a side note, when both timing dots are at straight up at 12 o' clock, that is the number 1 cylinder's firing position, perfect place to check preload and/or leakdown, when the dots are together that is cylinder 6's firing position, and cylinder 1's start of intake stroke and usually still in overlap (both intake and exhaust valves slightly open).
You cannot be off when it comes to this. If one is down and the other is down. up and up. dot to dot. doesnt matter. With the crank positioning sensor designating which cylinder to fire when it doesnt matter. Back is the day is was possible but only required rotating the distributor 180 degrees to put the ignition on the right stoke.
my 2 cents make sure its at top dead center and dot to dot because i put a cam in my camaro and it was at 6 tdc and not 1 tdc lined up dot to dot and it never ran till i pulled the motor and reinstalled the cam
That was kind of my thought as well. The proper way is by making sure piston number 1 is at TDC. Then line up dot to dot. Just follow the proper steps and you want have a problem.
So I hope I'm not breaking any rules by reviving an 11 year old thread but I was doing some DD and ran across this thread. I finished rebuilding my LS6 about 4 months ago and was chasing an electrical issue for a large portion of the time sense then. Finally got that resolved and now I'm running into a problem that the engine will not start and it is acting like their is a timing issue when you try and turn it over.
I've checked the Crankshaft and camshaft sensor connections and even replaced them both but still have the same symptoms. A friend suggested to look into this so my question to this group is the same as discussed in this thread. If I lined everything up at dot to dot but had #6 at TDC would I run into this issue?
I've checked the Crankshaft and camshaft sensor connections and even replaced them both but still have the same symptoms. A friend suggested to look into this so my question to this group is the same as discussed in this thread. If I lined everything up at dot to dot but had #6 at TDC would I run into this issue?
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From: Central Cal.
No. When aligned dot to dot, the crank and cam are in specified, fixed positions. The sensors see only that. It's a foolproof setup, timing-wise. Back in the day, with distributors, it was easy to get it "180 out", as it was called. BUT if the front timing cover were off and the cam position was known, even that could not have happened.
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From: PDX-OR-USA
I have gotten cams, cam sprockets and crankshaft cam sprockets that were marked incorrectly. Had to use a degree wheel to sort it.. Sometimes you get the Friday of 4:59 PM part and sometimes you get the Monday morning I drank too much all weekend parts.. LOL
When you ask a question and some people say yes and others say no you should be able to figure out that you don't know the REAL question you want to ask OR how to ask it Some people figured this out as I did and gave you mocking answers as I often do You need to study 4 stroke theory some more so you know how it works then ask your question Before the chain is installed there are NO STROKES The cam and crank don't even know each other exist The crank is the heart and the cam is the brains When you MARRY the cam to the crank with the chain they have 4 babies the very day they get married Their names are Intake, Compression, Combustion and Exhaust They are born in a specific order and they must maintain this order and relationship to the crank for the engine to work correctly I believe I know what question you want to ask, but you need to study more so you can ask the correct question which leads to the answer you want