What valves are open at TDC?

[Drewster]

Just to double check, if my Buick 231 motor is at TDC, the #2 Intake and #6 Exhaust valves are open. Right?
Andrew

 

[BlackBandit]

Depends on which stroke you're on. Are you talking with the number one piston at TDC on it's compression stroke?

 

[Drewster]

I am refering to the TDC for #1 piston at the begining of the 4 stroke cycle.
Where the cam and crank timing marks are closest to each other.

I havent heard reference to other TDCs.

I want to make sure i am not 180º out before I install my cam sensor.

 

[novaderrik]

at TDC on the compression stroke of the #1 cylinder, both valves will be closed. the intake vavle will close as the piston comes up towards TDC.
just turn the motor over clockwise as you look at it from the front and watch for thei ntake vavle to close, then line of the timing mark on the balancer.

 

[Drewster]

Which cylinders are intaking or exhausting when cylinder #1 is at TDC after its exhaust stroke?

Right now I belive I am at TDC and 2I and 6E valves are open. If valves on#3 and #5 should be open, then I need to rotate 180º before setting my cam sensor.

I would like to get confirmation that 2I and 6E valves should be open at #1 TDC (after exhaust)

 

[JDEstill]

This I can say for sure (it's one way I've verified proper TDC for setting the cam sensor in the past) - if either #1 valve is moving when you are turning the engine over to get to 25deg ATDC, then you are at the wrong TDC - crank the engine over another 360deg to get to the right one. Neither #1 valve will be moving when you are at the proper TDC. I used to look down through the oil fill hole in the valve cover to watch the valve springs compress - if I could see it compress, I knew I was at the wrong one.

Now onto your particular question - I believe the #2 intake is open and the #6 exhaust are open at the wrong TDC - both #1 valves should also be open at this time. 5I and 3E are the ones that should be wide open when you are at the correct TDC.

Don't forget, you don't want the engine right at TDC when you set the cam sensor - you want it 25deg ATDC.

John

 

[whitehot1]

post #5 in this thread may help you.

http://www.turbobuick.com/forums/general-turbo-buick-tech/237224-preload-w-tds.html

 

[excobraguy]

Take out your #1 spark plug, place your fingertip on the spark plug hole, rotate the engine and you can feel when it is coming up on it's compression stroke as it will push the air out.

 

[kenny]

Take out your #1 spark plug, place your fingertip on the spark plug hole, rotate the engine and you can feel when it is coming up on it's compression stroke as it will push the air out.

.

 

[Drewster]

thanks for answering I was not aware the cam sensor is set on the compression stroke.
I bolted up the front cover and pan 3 months ago and lost track of the TDC.

Is the Crank / Cam timing marks set at #1 TDC on compression or exhaust?

 

[excobraguy]

Vortex Turbo Buick Performance

It's under tech pictures/instructions cam sensor install

 

[excobraguy]

Cam Sensor Installation and Adjustment



Two Notes:

1) The cam sensor has nothing to do with ignition timing. That is controlled by the chip. It locates cylinder #6 so that both injector pulse and ignition spark will be on the correct cylinders. Rotating it like a distributor does not affect actual spark timing. It is either right, or it is wrong.

2) If you have bought the Casper's replacement cap with the led in the top. Use the instructions that came with it instead of the below.

This method is proposed by Chuck Leeper of Cody Motorsports. It uses the Caspers Cam sensor tool rather than a volt meter but the technique is valid for either.

Take a piece of masking tape and make two marks 1.45" apart.
Go to the harmonic balancer and position one mark on the top dead center notch with the other mark positioned counterclockwise from the first. This corresponds to 25 degrees ATDC. Make a mark on the balancer at this point.
Turn the crankshaft on clockwise until this mark lines up with the pointer. Note, it is important that the crank is on Top Dead Center and then 25 degrees past TDC. Remember that the cam turns at half the speed of the crankshaft and merely turning the crank until the point lines up with the pointer only assures you a 50% chance of being correctly on the 25 deg TDC mark. TDC is found when the notch on the balancer lines up with the timing pointer on the cover and both valves on cylinder # 1 are closed. In order to not have to pull the valve cover, I remove the spark plug and start turning the crank clockwise until I feel a puff of air come out the plug hole. This will be the compression stroke and I then continue turning the crank until I reach the 25 ATDC point. If you don't get this right, you will not like the way it runs as it will be spraying fuel 180 degs out of phase.
Take the camshaft positioning sensor and turn the gear until the dot on the gear is aimed toward the passenger fender when the the wires on the cap are pointed toward the driver's side headlight.
Install the sensor into its hole. It helps to lube the O-ring a bit so the sensor will slide into place. Note that as the sensor is inserted, the gear on the bottom will mesh with the gear on the cam and then the end of the sensor drive must line up with the end of the oil pump drive shaft. If the shaft and the sensor drive don't line up correctly, the sensor will not go all the way down. If you felt the two gears mesh, just bump the engine over while gently holding the sensor down. When the sensor turns enough to line up with the drive shaft, it will drop down into place.
Install the hold down leaving the sensor just loose enough to rotate when you turn it with your hand.
Using the Casper's cam sensor tool, plug it into the cam sensor harness.
Turn the cam sensor clockwise until the LED on the tool goes out, then turn the sensor counterclockwise until the LED comes back on. I suggest turning the sensor about 1/8" to 1/4" further CCW from this point before tightening the hold down clamp. The LED should still be lit, however.


If you don't have Casper's tool, Here is a method of adjustment using your volt meter. Also, at the bottom of the page will be a picture from the factory manual on using a voltmeter.
For an in depth discussion of the cam sensor function, go Here.



The following pictures were provided courtesy of Chuck Leeper, Cody MotorSports.



This picture shows the cam sensor drive and cap assembled with the Cam Tool plugged in. This one is from ATR.



Dot goes toward the passenger side fender when inserting drive assembly. Remember, engine must be sitting at 25 degs ATDC!



Window will be pointing toward the drivers side fender when inserting drive.



Top view of drive assembly. The wheel must be pinned into place so that it cannot rotate versus the drive gear. If the wheel moves, it will screw up the fuel timing and the car may not start, or, it will run very badly.

Voltmeter procedure from the shop manual below.

 

[Drewster]

Nice site!

I was wondering how you typed so fast! Saved to favorites!

 

[excobraguy]

I have a whole host of Buick favorites on my yahoo.......!