How do you know when each cyl is at TDC

[prayers1 153]

I have double valve springs. The outer springs are only installed to break in the motor. Now that it's broken in, I need to pull off the spring and install the inner springs. I need to do this when each cylinder is at TDC. How do you know when each cylinder is at TDC.

[THE EVIL TW1N 12]

I have double valve springs. The outer springs are only installed to break in the motor. Now that it's broken in, I need to pull off the spring and install the inner springs. I need to do this when each cylinder is at TDC. How do you know when each cylinder is at TDC.

You can look at the valves. For each cylinder, when the exhaust valve is beginning to open, the intake valve is at the base of the cam circle. When the intake valve is beginning to close, the exhaust valve will be at thee base of the cam circle.

 

Unless you are trying to do them both at the same time, then you would need to know exact TDC.

[prayers1 153]

Yes, I need to do the both at the same time. When I compress the cylinder with air, I want the cylinder volume to be as small as possible in case by accident I get an air leak and a valve drops.

 

I have one of the push button starters, I can stick a finger by the spark plug hole and feel when the cylinder is at TDC. I was thinking there was a better way. Maybe some sort of measurement on the harmonic balancer or something else.

[THE EVIL TW1N 12]

Yes, I need to do the both at the same time. When I compress the cylinder with air, I want the cylinder volume to be as small as possible in case by accident I get an air leak and a valve drops.

 

I have one of the push button starters, I can stick a finger by the spark plug hole and feel when the cylinder is at TDC. I was thinking there was a better way. Maybe some sort of measurement on the harmonic balancer or something else.

Oh I see, that makes sense. I don't know of any markings at all that would indicate TDC for any of the other cylinders. I guess we'll have to wait for a better answer.

[det0326 179]

Yes, I need to do the both at the same time. When I compress the cylinder with air, I want the cylinder volume to be as small as possible in case by accident I get an air leak and a valve drops.

 

I have one of the push button starters, I can stick a finger by the spark plug hole and feel when the cylinder is at TDC. I was thinking there was a better way. Maybe some sort of measurement on the harmonic balancer or something else.

 

First of all let me say I may not even know what I am talking about. But if you have the harmonic balancer on top dead center of number 1 cylinder the next cylinder in the firing order would be a quarter turn or 90* to top dead center. I get this by it takes 2 revolutions of the crank to complete one cycle of all 8 cylinders so 360 equals one turn of crank and 360 times 2 equals 720 divided by 8 equals 90. Does this make any sense are am I crazy?

 

Dave

[THE EVIL TW1N 12]

First of all let me say I may not even know what I am talking about. But if you have the harmonic balancer on top dead center of number 1 cylinder the next cylinder in the firing order would be a quarter turn or 90* to top dead center. I get this by it takes 2 revolutions of the crank to complete one cycle of all 8 cylinders so 360 equals one turn of crank and 360 times 2 equals 720 divided by 8 equals 90. Does this make any sense are am I crazy?

 

Dave

This is the only way I know of, but it may not be at the accuracy the OP is looking for. Maybe putting a mark or some tape on the crank pulley before doing the 90* spins.

[det0326 179]

This is the only way I know of, but it may not be at the accuracy the OP is looking for. Maybe putting a mark or some tape on the crank pulley before doing the 90* spins.

 

Yea or maybe some white paint with a tiny brush and turn the crank with a pull handle and socket with the bolt on the harmonic balancer. This may be more accurate than trying to position it with the starter.

Dave

[LoneWolf2U 136]

:closedeyes:...Mmmm..... Well Dave are you crazy? I don't know you so its up to you to fess up.

 

But Yes you are correct in your thought of 90* turn on the crank.

I have my lower pulley marked at tdc,90,180 and 270 just for the purpose of setting my valve lash on my solid lifter cam.

Starting with tdc on #1 I can set both intake and exhaust valve lash.

A simple turn with a 1/2in drive ratchet on the crank bolt to the next mark on the pulley and move on the next set of valves in the firing order till done.

It is written up in the Ford manual under valve lash settings an will work for hyd lifters too.

[prayers1 153]

So, you are saying every 1/4 turn is the next cylinder on TDC and does this go by firing order 13726548.

 

Remember, I not adjusting valves. I only want to bring each cylinder on TDC to change the valve springs.

Edited June 18, 2014 by prayers1

[DocWok 30]

All of replies above are correct.

There is another way instead of having your piston on exact TDC and using compressed air to hold the valves up while you change your springs.

As you are changing your springs I assume you will remove your rocker gear, so you could remove your spark plugs and feed some flexible rope through the spark plug hole, about 2 foot will do it, and then just rotate your engine by hand until the piston forces the rope up against your valves, when you have finished changing the springs just rotate the engine backwards a bit and remove the rope, I find this easier than using the compressed air method, plus there is zero chance of the valves falling down into the cylinder.

[prayers1 153]

How do you know when the piston forces the rope up against the valve.

 

What size rope are you using and is it nylon.

[72Pstroke 10]

If you put the piston at top dead center and apply air to the cylinder, the air pressure will cause the engine to turn over.

You will need to come up with a way to keep the crankshaft from turning if you are going to use air pressure at top dead center.

Tim

[det0326 179]

So, you are saying every 1/4 turn is the next cylinder on TDC and does this go by firing order 13726548.

 

Remember, I not adjusting valves. I only want to bring each cylinder on TDC to change the valve springs.

 

Yes the next top dead center cylinder would be the next one in your firing order. Doesn't matter about whether your setting valve lash or not this method would put the next piston in your firing order on top dead center and would be as accurate as you are at putting the marks on your harmonic balancer. But as 72Pstroke said compressed air will have the tendency to drive the piston back down if you don't lock the crank in some way.

Messing with valve springs/stem locks with heads still on the block is risky business one wrong move and break the air seal its all over but the crying. never used the rope trick but it sounds as though it maybe safer as long as you don't leave any rope in the cylinder.

Dave

 

PS I assume you already know but if using the 1/4 turn method make sure you turn the crank in the correct engine rotation.

Edited June 18, 2014 by det0326

[DocWok 30]

Using the rope method is easy enough, just use any flexible rope say 5/16" or 3/8" in diameter, it's not critical.

While the piston is down the bore a bit push in the rope then continue winding the engine over by hand.

You will feel the resistance when the piston squeezes the rope against the valves because you wont be able to turn the engine any further, so stop there and change your springs.

Just don't go overboard and try and break the nut off the front of your crankshaft when you compress the rope !

[prayers1 153]

I like the rope method.

 

I was just confussed on how to tell when the next cylinder in the firing order is coming up. The Cleveland head is so big and with the Sanderson headers I can't look into the spark plug hole to see if the cylinder is up.

 

So, here's my plan w/ the 3/8 nylon rope, about 3ft long.

I'm gonna start at the #1 Cyl. just before it reaches TDC on the balancer I'm gonna put in the rope, as I continuie to turn the crank, I should feel some resistence before TDC, this will tell me that the rope is now sandwiched in the cyl.

 

After I replace the springs on Cyl. #1, I'm gonna back off from TDC and pull the rope out.

 

Next, bring the balance to TDC, then turn a 1/4 turn and that should be TDC for the next cyl w/in the firing order. Back off on that mark , put in the rope and repeat as above for all 8 cylinders.

 

Sound Good?????????

[det0326 179]

I like the rope method.

 

I was just confussed on how to tell when the next cylinder in the firing order is coming up. The Cleveland head is so big and with the Sanderson headers I can't look into the spark plug hole to see if the cylinder is up.

 

So, here's my plan w/ the 3/8 nylon rope, about 3ft long.

I'm gonna start at the #1 Cyl. just before it reaches TDC on the balancer I'm gonna put in the rope, as I continuie to turn the crank, I should feel some resistence before TDC, this will tell me that the rope is now sandwiched in the cyl.

 

After I replace the springs on Cyl. #1, I'm gonna back off from TDC and pull the rope out.

 

Next, bring the balance to TDC, then turn a 1/4 turn and that should be TDC for the next cyl w/in the firing order. Back off on that mark , put in the rope and repeat as above for all 8 cylinders.

 

Sound Good?????????

 

once you pull the rope out of Cyl 1 and move back to top dead center mark for no. 1 the next cyl in the firing order should be down for enough to install the rope then move a 1/4 turn to you feel the resistance again. Want be necessary to turn 1/4 turn then back off. Will save some turning steps.

And doing it this way both valves would be closed and no danger of a valve closing on the rope (if possible that it could) because as the piston is coming up to top dead center would be the compression stroke and both vales closed but right before compression stroke would be intake stroke meaning the intake valve is open.

dave

[DocWok 30]

If you have your rocker gear disconnected none of the valves on any cylinder will be opening or closing.

Just have all your spark plugs out so it's easy to turn, you can do any cylinder you like.

When you have finished changing all your valve springs, reinstall your rocker gear and then reset your valve clearances.

[Rcodenewf 44]

I agree with DocWok as i just did this awhile back on my 75 f150 390. Rope works well. As he stated just bump it up close to tdc...feed in the rope and then continue by hand. Pull off the rockers first to allow the valves to close. You can change both springs on one cylinder at at time that way. Then turn the crank in the opposite direction a bit and pull the rope out and onto the next cylinder.

 

I'd leave the rocker installation until last when all valve springs have been installed.

 

Hope this helps.

 

John