8T8T2

Need some help guys. Installing new comp. xe-262 cam on 80 350 L-82. Instructions call for 6 oclock cam gear and 12 oclock crank gear. When I removed timing cover I had 12 /12 oclock with #1 cyl. TDC and dist. hitting at #1 cyl. Talked to comp cams help line and they said to install at 6/12 and this was even after explaining to them my GM manual shows 12/12
Can someone give me some insite on this? This is my first cam install so be gentle.

70PurpleLS7

The 6/12 is the easiest method as far as lining up the marks on the timing chain gears (because they are only - say 3/4" apart). In that postion the engine is set to fire on piston #6 (I think?) - damn where's that firing order when I need it :lol:

After you have the marks aligned at 6/12, you can rotate the engine assembly to 12/12 and you'll be set to fire on #1.



[Modified by 70PurpleLS7, 4:18 PM 1/6/2003]

Larry B.

12 o'clock on the crank and 6 o'clock on the cam will be TDC#6 firing or #1 exhaust.

Smokehouse69

It doesn't make any difference, since the cam turns twice the speed of the crank. 6 cam and 12 crank is the same as 12 crank and 12 cam. The reason they say 6 cam and 12 crank, is that is is easier to verify that the two are lined up.



[Modified by Smokehouse69, 3:26 PM 1/6/2003]

mrvette

Well, it's sorta dependant on the firing order, if you engine is firing on 18436572 it's 12-12, and if it's firing on 7218, 4365 than it's 12-6....

but in reality it's like a flop-flip in electronics....or flip flop....either way.....

but then again....the most significant digit is allways a 1.....

so therefore we fire the 4 corners first, then the center 4 cylinders...
so 12-6 is fine....72184365.....

unless it's the odd day of the month.....

GENE :D :D :D

Jvette73

Smokehouse69, you said the cam turns twice the speed of the crank. Its the other way though. The crank turns two revolutions for every one of the cam. So therefore the crank turns twice the speed of the cam. Im not being pushy. Just pointing it out. Probably just a typo error on yur part anyway.

The marks can be set either way. 6/12 or 12/12. As far as cam timing is concerned it doesnt matter. As stated before, 6/12 would be TDC on #6 cylinder and 12/12 would be TDC on #1 cylinder. So 6/12 or 12/12 is important when droping in the distributor and lining the rotor up to #1 on the cap, but for cam/crank timing it doesnt matter. :cheers:

Big Fish

I installed mine with the marks at 6/12. One thing you need to watch out for: Certain timing sprockets have more than one set of marks. My new sprockets had 3 different marks, each corresponding to a slight alteration in cam timing. I selected the mark my engine shop recommended, can't remember the symbol I used but it supposedly duplicated the "stock" cam timing. Different style symbols were used on the other locations. If you are still running the original timing chain and sprockets, now would probably be a good time to change it if it's seen some miles, just my 2 cents. Good luck with your project. :cheers:

8T8T2

OK lets see if I got this straight. The only reason to go 6/12 oclock is for ease of install but if I do that I should install distributor to line up at #6 plug instead of #1. My firing order is 18436572 and a new gear and timing chain are going in.
My TDC for #1 plug is 12/12 as per chevy shop manual but in comp cams install instructions 6/12 is #1.
What am I missing here?

J75

Install the cam either way that is best for you.Then rotate the engine to #1 comp. stroke and install the distributor to point to #1,set the timing and you are done.

jackson

typical 3-keyway crank gear symbolism

retard = a square or rectangle box
zero (straight up) = a circle
advance = delta (a triangle)

6-12 or 12-12 ... doesn't matter ... cam turns 1/2 speed of crank. What matters is having #1 on tdc COMPRESSION (intake lifter has just dropped) when #1 fires.

Smokehouse69

Jvette, my bad, I had it the other way around and then started thinking about it and changed it. If I hadn't of thought about it.... :D

8T8T2

Guys thanks for the info. After it gets pounded into my head enough it finally takes. Quite often I concentrate on just one point and don't see the whole picture. Ignorance is not bliss--it's just plain frustrating. Thank god for this forum. :blueangel:
Thanks again for the input..