4.0 OHV Top Dead Center questions.

[crokarlo]

So to make sure. Because I'm getting tired of redoing the syncro [emoji23] the mark that says 10 degrees is correct right


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[RonD]

A four-stroke engine is what you have, pretty much all car and truck engines are 4-stroke
Gasoline or diesel doesn't matter they are 4-stroke
Many motorcycles and snowmobiles use 2-stroke engines

4 strokes means the piston goes up and down 4 times/strokes, to complete 1 power cycle, not 1 RPM, one power cycle

How it works for #1 cylinder
We start with crank pulley at TDC, #1 piston is at the top of its cylinder
1. Intake stroke, intake valve opens as piston goes DOWN, pulling air and fuel into the cylinder from the intake manifold

2. Compression stroke, piston is at the bottom, intake valve is closed, cylinder is "air tight", piston starts going up compressing the air and fuel mix, which heats it up,
Piston is at the top again, TDC << this is the one you want

Spark plug fires between 10 and 30deg BEFORE this TDC, because it takes 15 to 25 degs before air/fuel fully ignites, the higher the RPM the faster the crank is turning so the earlier the spark plug must fire, best full ignition is at 5-10deg AFTER TDC, when piston has good leverage to push down on the crank adding power.

3. Power stroke, piston is at TDC and on its way down, both valves are closed and air/fuel ignites

4. Exhaust stroke, piston is at the bottom and on its way up, exhaust valve opens and piston pushes out the spent air/fuel mix, the exhaust

Piston is back at the top, TDC, exhaust valve closes and intake valves Opens for start of intake stroke

TDC
Intake stroke
Compression stroke
TDC
Power stroke
Exhaust stroke

4 strokes and TWO TDCs have gone by

Spark and Cam sensor are both timed for #1 compression stroke TDC
Not exhaust stroke TDC

 

[crokarlo]

So should I reinsert the syncro with the engine at compression TDC 10 degrees at the line that is factory there. Not the line that I had to draw correct?


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[crokarlo]

. When I reinstall the syncro. Should the timing needle be pointed at Red circle. Blue circle. Or black circle.


Because I installed the syncro again and lined it up at Black circle. Truck ran a lot better but was still slightly off.


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[crokarlo]

So I'm assuming my timing is 20 degrees off correct? Right now I'm at 10 degrees after TDC and I should be 10 degrees before TDC


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[RonD]

No, the cam synchro is setup using 10deg AFTER TDC
Spark timing and cam sensor timing use 10deg Before TDC

And there is absolutely NO REASON Ford couldn't have used the ALREADY MARKED 10deg Before TDC line, lol.
They made the cam synchro from scratch, so could have set it up to use 10deg Before TDC line or even the TDC line itself.
Why use a line that doesn't even exist??????

I guess we just know that ford engineers have a sense of humor, that or they are Koo-Koo, and I like Rangers so............I pick the former

 

[crokarlo]

I'm very confused here I installed the new cam syncro and used a recently bought and used sensor. I made my own mark on the pulley. And made sure it was on the compression stroke. And installed the syncro using ford tool ect. I started the truck up a few times and it running better but still rough. Under full throttle is bogs down and stutters but only under 20 mph. Before it was under 40. Should I have had aligned it on the line ford provided? Or did it correctly and align it on the line I made. I'm getting a p1340 code now and it's running rough and no acceleration


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[crokarlo]

. So the timing line I should of made ( 33mm ) is the line on the tape correct. If so 33m is at 26 degrees


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[RonD]

No do the same distance as 10deg BTDC it varies by the size of the pulley

 

[crokarlo]

I did... I put it at 10 degrees after with the same distance as 10 degrees before. And it's running rough.


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[crokarlo]

. This is what my buddies Explorer 4.0 ohv book tells me


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[crokarlo]

.

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[crokarlo]

So I just bought the ranger hanyes manual. I have a 1998 4.0 OHV pushrod so I looked up the exact how to on syncro and found this. So according to the book I need to set my engine at TDC 0 compression. Remove the syncro , put the tool on the syncro and stab it in at 0 that's it. No 10 degrees after or before. No 33mm nothing only time that is required is if it's 94-95


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[RonD]

Sounds good

 

[crokarlo]

Sounds good

Thanks Ron! I just set the the engine at exactly top dead. And going to stab in the syncro hopefully this time it works!!


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