Cam Synchro/ TDC/ Rebuild Question

[KRH1326]

Hey Guys,

I know, maybe this should have been posted elsewhere, but the folks that I want to ask are here, not there.

In the proccess of rebuilding the 3.0 v-6 vulcan in my 1999 Ford Ranger. Pistons, crank, cam, lifters, cyl heads, timing gears and chain, timing cover and oil pan are installed.

Going for the new cam synchro at this point.

Crank and cam are still in the 'just installed' position. They have not been rolled, the keyways and marks are still lined up.

0 (tdc) is right on the mark to the right of the crank position sensor.

Is this my TDC on exhaust or intake stroke? Is this the position that I want to install the synchro??

I am asking when the timing set is freshly installed, and the timing marks are all lined up, what stroke would the crank be in? I'm trying to figure out, in the factory, when they put these together, the timing marks are aligned. When they drop in the synchro, does it go with the timing set marks still aligned, or do they roll the crank once.

Yes, I could postpone synchro install until intake, rods and rockers go in, to roll it over to check the for suck or blow at the plug hole, but I am famous, or infamous, for setting distributers 180 out, so I wanted to try to head this off at the pass.

Thanks for any input.

 

[Bondo]

Re: Cam Synchro/ TDC/ Rebuild Question

Ayuh,.... Donno 'bout yer Ford pickup motor...

Generally speakin',... The cam to crankshaft timing is Irrevelant to Igntion timing in most motors...

 

[KRH1326]

Re: Cam Synchro/ TDC/ Rebuild Question

WOW, THE GUY that I was targetting, hit right off the bat.

There is no distributor in this rig. It was replaced with a cam synchro. It must be installed while the #1 is at TDC after compression stroke.

So I am asking what stroke the crank is in when the timing gear marks are lined up, as oppossed to one crank revolution, where the crank mark is back in the up postion, but the cam mark is also up.

One has to be in intake and one in exhaust.

 

[Bt Doctur]

Re: Cam Synchro/ TDC/ Rebuild Question

#1 has to be at TDC compression stroke first.turn the motor watching #1 intake lifter rise and fall, continue turning untill piston it TDC

 

[Don S]

Re: Cam Synchro/ TDC/ Rebuild Question

Crank and cam are still in the 'just installed' position. They have not been rolled, the keyways and marks are still lined up.

Not sure about your particular engine, but every engine I have rebuilt, when the marks are lined up you are not on the compression stroke. You would need to turn the engine 1 complete revolution to be on the compression stroke.
To verify, rock the crankshaft back and forth about 20? either side of 0. If the lifters on #1 cylinder move, you are on the exhaust stroke.
If they do not move, you are on the compression (firing) stroke.

 

[KRH1326]

Re: Cam Synchro/ TDC/ Rebuild Question

OK so I get what you are saying. I am just trying to get it crystal clear before I screw it up.

Which drawing represents TDC on compression stroke.

 

[Don S]

Re: Cam Synchro/ TDC/ Rebuild Question

Like I said before, you need to check it by checking the valves/lifters. Your engine may be different than any I have rebuilt so there is no way to tell what the lifters are doing by looking at the marks on the crank and cam gears. Those marks are for timing the cam to the crank only, nothing else.

 

[Glastron_V210]

Re: Cam Synchro/ TDC/ Rebuild Question

So, if I read this right, you`re using a cam trigger and edis perhaps? Some type of distributorless right?

Without the crank hooked up to the cam there is no #1 comp, or exhaust there is just #1 tdc. You're going to establish whether it's intake or exhaust by the relationship when you hook them up.

Ok, this is how I would do it:

Hook the cam and crank together the way you figure you should.

Do just like Don says, but I like to use the screwdriver method as well. You can do this yourself, but it's easier if you have a partner rotate the engine for you.

First, pull the #1 plug. Hell, pull them all to make it easier. To find compression stroke, stick your thumb over the plug hole. As your partner rotates the crank you should get a buildup of pressure when the piston travels up on compression. If this doesn't happen the cam is in the wrong phase somehow. Now, grab a CLEAN screwdriver and insert it a small amount past the spark plug hole and tilt it down. as your partner rotates the engien slowly, you'll feel the piston make contact with your screwdriver and tilt it up. Where it stops coming up is TDC compression.
Repeat it a couple of times to nail it down as precisely as possible. There will be a spot where the piston will stop moving up or down...this is the sweet spot. Make sure you are rotating the engine in the correct direction (CW probably). If you go backwards, go backwards 1/4 turn, then go forwards again.

After you know where this is, make sure it all makes sense. Mark tdc, and on the other side of the crank pulley, 180 deg out, mark approximate bottom dead center. At tdc comp you should have no valves open. As you head towards bdc the exhaust valve should open, then stay open until after tdc exhaust. The intake valve will open before tdc exhaust (the intake and exhaust 'overlap')and close after bdc intake.

If this matches up there is a 99% chance you did it right!


Chay