I have the intake off of my 70 454, I think I might have an intake manifold vacume leak. The car runs ok but needs a high idle to keep running and if I cup my hands over the carb it runs better.

While chasing this problem I tried to set the timing but when shooting the mark with a timing light it was nowhere close. So while the intake and valve covers are off Im barring the engine around (plugs out) with my hand on the rockers for #1.

So EX valve opens then closes, then IN valve opens and as it just closes and I can just spin the pushrod how much more should I go to have the piston at TDC? I can see the cam. I think I might have the wrong damper, wrong tab or something but I will put a new mark so I can get a decent setting on the timing.
Thanks

 

The only way to really know where the apex point of the piston travel occurs is to measure the peak movement of the top of the piston. This is easily done with the heads removed from the [short] block; but it can still be done with the heads in place.

Measuring the cam or rockers does not find the TDC point of the crankshaft, as the cam is driven from the crank via gears and chain.

 

And even if the cam and crank were gear-driven, there's still the chance that the cam was not installed straight up, or if it was, that it was ground a few degrees off...

 

The intake valve closes pretty close to BDC, next time the piston comes up is TDC compression. Piston stop is the best tool for the job but just looking in the spark plug hole will tell you if you balancer mark is in the ball park.

 

Ok, so for the ballpark TDC C. 180* from IN valve closed should get me somewhere. I was wondering if there was any upward movement of the piston with the intake valve still open. I have enough of this engine apart the heads are NOT coming off.

 

A tool like this will get you as close to TDC as you can be without removing the heads:

http://www.summitracing.com/parts/ipa-7880

You screw it into the spark plug hole and rotate the engine (sloooowwwwwllllyyyyyy) until you hit the stop. Put a mark on your damper, then slowly rotate the other way until you hit tHe stop again. Mark the damper again and the TDC mark (which I like to highlight with liquid paper) will be right between the two marks.

 

Dial indicator on rocker arm for cylinder #6. when both valves are moving on 6 and both of them stop as the valves are closed, you are at tdc#1 if mechanical timing is correct.

 

The intake valve better be fully closed BEFORE reaching TDC. You do set your timing [re. ignition spark] "advanced" to TDC, don't you???

 

So far I went 180* after #1 IN was closed But Im going to try this and see how close the two marks are. I think problem is the after market timing cover with the wrong timing tab.

 

you are correct going 180 after the #1 intake closed. After the intake valve is closed and the piston sucked all the fuel and air in as it traveled to the bottom of the stroke, the piston is going to travel 180 to top dead center which this is the compression stroke. the piston is going to fire and travel 180 again downwards on the power stroke(at this point we have one complete turn of the crank 360* without the valves moving at all) then 180 back up at which time the piston chases the exhaust valve as it opens(exhaust stroke). My point here is that when both valves are moving on #6, the #1 is around top dead center because the compression and power stroke of 360* and no valve movement is occurring during this time. I made this mistake years ago in my teens and placed my engine 180 out on mechanical timing and almost blew the carb off the intake. I thought that when both valves were moving at the same time and the balancer lined up on the timing tab that it was on TDC but actually was the complete opposite. Just giving my 2 cents which you might already know anyways....