[Jack_K]

When installing the timing gears and chain on a SBC, I have always thought that the mark on the cam gear should be at the bottom for TDC on #1 cylinder. My 1980 Service Manual shows the mark should be on the top of the cam gear for TDC #1 and on the bottom for TDC #6.

Have I been wrong all these years? Yes, the last time I built engines was in the 70's and 80's. I have a great memory, it's just really short.

Jack

 

[Skandolis]

you're not wrong, with the timing marks pointed at each other(dot to notch) check number one piston, it will be up top and both valves closed, remember your cam turns once for every two turns of the crank

 

[Jack_K]

you're not wrong, with the timing marks pointed at each other(dot to notch) check number one piston, it will be up top and both valves closed, remember your cam turns once for every two turns of the crank

You mean the service manual is wrong? And my Chilton's manual?

 

[Jack_K]

I just looked in an old Chilton's (1984) I also have. It shows SBC V8s have the mark at the bottom of the cam gear up to 1979. From 1980 on it shows #1 TDC at the top.

I'd think the camshaft itself would determine which way.

 

[Skandolis]

if you turn the crank one full turn, the mark on top of cam gear moves to the bottom, but the number one piston is still at tdc just the cam is 180 degrees out from what it was, different timing gears could be marked differently, but i have never ran into that problem.the firing order did not change up to present, 18436572 has been standard sbc, i probably should look at the manuals a little more often, but i build at least one sbc a month and have never had a problem timing them dot to dash. as even with the number one on top when you assemble the chain, you still are timing the distributer to number one on a compression stroke, so basicly the books are both right, (it's the same thing just looked at from two different angles) pistons one and six are up top at the same time, one is on a compression stroke while the other is not

 

[JJLT1]

what he said,,
there both right,, your ether TDC on the compression stroke or,,TDC on the exhaust stroke..:texas:

 

[hotrodelco]

what he said

When the dots are lined up next to each other, (I.E. the cam dot is at the bottom, and the crank dot is at the top)you are at top dead center(compression) on # 6 cylinder. If you are building an engine, and the distributor is not in the engine, put the timing cover on and turn the crank one revolution, and now you can point the rotor to the #1 spot on the cap or just point it at #6 with out turning it.
:beer: