Timing question(s)

[Insanejughead]

Ah, that does suck a bit. However, you're still good because as long as you line up that indentation on the backing plate to the crack (where the triangle should be), you'll be close enough for correct timing.

For each notch that the belt is off (roughly 3/8"), it'll change your timing by 10 degrees, which is VERY noticeable when you're final checking your timing.

For future cases, you can look for a new plastic timing belt cover and replace yours.

 

[zekew64]

For future cases, you can look for a new plastic timing belt cover and replace yours.[/QUOTE]

First, +1 on the tooth adjustment.

However, some additional info:

The timing spec on a 2.3 is 10 degrees BTDC (Before Top Dead Center). What this means is, the crankshaft pulley needs to be at the "10" mark on the cover in order to be correctly timed, NOT top dead center (all the way at the top of the piston stroke). Otherwise, the exhaust valve won't have started to open, expelling the exhaust gas to let in more air/fuel. In essence, when you put gas under pressure, the pressure will go to where the containment is weakest--usually through a valve seat or rings. This is bad juju, and if you leave it at TDC, you'll probably have to replace your motor within a couple of years, due to extreme premature wear. The motor will also run like shit, by the way, as well as sounding like it's backfiring under normal running conditions. Bottom line, the motor will sound like it's really sick, when in fact, it just needs to be tuned properly.

First, line the crank pulley at 12:00, the cam pulley at 5:00, and put the oil pulley mark (it's the spoke of the sprocket that is different) in line with the cam.

Now, after you do this, put the belt on per the normal procedure. Rotate the crankshaft with a breaker bar and proper size socket two times, listening for valve-to-piston contact, doing this with the cover on (this is important). Rotate the engine two more times, this time stopping at 10 degrees BTDC.

Next, take the cover back off, being careful not to move the crankshaft pulley. Disengage the tensioner, pulling the belt off of the camshaft sprocket ONLY, in order to finish the rotation of the sprocket to the 5:00 position (one tooth position forward in the rotation).

Put the cover back on, and rotate the engine two more times (I know, this can be annoying, lol); if no contact is felt or heard, then you have successfully timed your motor correctly.

I say all of this because I have done this myself, when I installed another motor in my truck last year, due to the previous motor throwing a bearing, and not having the proper tools to replace all the bearings in the block.

Good luck.

 

[one1]

Thank you I will look into that tomorrow (but do keep in mind my 97 engine is different from even the 95 spec, much less your 92 spec), but I put it all on tdc earlier and it is really smooth so far. Also, my truck has flow master on it so it always backfires lol. I haven't spent enough time with it to tell you anything at this moment I just fired it up and went around the block and it was fab.

Upate: went around the block again and it was REALLY smooth and runs like a new truck. I think TDC suits this truck fine, but I will continue to monitor it over the next few days. I appreciate all the info and now I understand my truck properly. I don't use haynes manuals or chiltons, I prefer to learn without the book unless it is something that I need torque specs on then I look them up. It's easier for me to learn hands on without the book because once I have done it I'll remember it. If I read the book I always have to go back to the book to read it again. Anywho all is happy at the moment and it really is smooth as silk with everything at TDC. I'm pleased Anything else I'll update as it arises.

Many thanks to jug for the continued info

Here's the payoff, short video of it's first few seconds of life today.

http://www.youtube.com/watch?v=nWgp5I5pZPc

The flowmaster has a choppy sound, it's idling smooth as silk.

 

[4b316]

It is designed to be set at TDC not BTC.It is not a interference motor so you never will hear valve to piston contact.The crack in your cover is just about perfect for lining up.As long as it is running fine now,line up the other two marks and put a paint mark on it till you get a new cover if you want.

 

[Insanejughead]

The timing spec on a 2.3 is 10 degrees BTDC (Before Top Dead Center). What this means is, the crankshaft pulley needs to be at the "10" mark on the cover in order to be correctly timed, NOT top dead center (all the way at the top of the piston stroke). Otherwise, the exhaust valve won't have started to open, expelling the exhaust gas to let in more air/fuel. In essence, when you put gas under pressure, the pressure will go to where the containment is weakest--usually through a valve seat or rings. This is bad juju, and if you leave it at TDC, you'll probably have to replace your motor within a couple of years, due to extreme premature wear. The motor will also run like shit, by the way, as well as sounding like it's backfiring under normal running conditions. Bottom line, the motor will sound like it's really sick, when in fact, it just needs to be tuned properly.

No. This isn't good to read for people searching for this in the future, nor does it make much sense at all.

The engine's base ignition spark happens at 10 degrees BTDC, but when aligning the pulleys and sprockets of the crank, cam, and aux/oil shaft, they have to be ON THE MARKS at TDC.

The crankshaft position sensor (or distributor pick up coil/TFI) takes care of making sure that ignition timing and spark happens exactly when needed, but it depends upon the timing belt being situated exactly at TDC.

Another thing, what you said about the exhaust gases being under pressure doesn't even make sense once you think about it. How much pressure is the fresh air/fuel mixture under RIGHT at combustion? A LOT! The pressure of the exhaust gases right before the exhaust valve opens up is negligible compared to the pressure of the entire compression stroke.


Also, it's a non-interference head, so valves will never touch pistons, no matter how off the cam is set. Thanks for restating that, 4b.

One1, it sounds like a purring kitten! Glad it's running top notch!

 

[one1]

Fruits of my labor...... a full detail to go with a new top end

 

[zekew64]

Insanejughead:

I said what I did because your point only deals with fresh air/fuel, NOT both the air/fuel AND the exhaust gas. Basically, it's a law of physics that when you put more gas in a given area, and then compress it, if the containment area can't stand the pressure, something will fatigue or buckle. And in a motor, that can lead to catastrophic failure.

And before you say that the EGR system also puts in additional exhaust gas to reburn it, that amount is a fraction of what remains in the cylinder after the primary combustion. If the valves don't open when they need to, that gas then gets put under pressure with the new air/fuel. Why do you think on high-mileage engines the compression rings go before the oil rings? Because over time, that compression, if it is correct, still wears out the rings. And if there is more pressure than what an engine is built to handle, than logic dictates that something--usually a valve seat or a part of the system where fatigue is the greatest--will break and let go.

 

[Insanejughead]

Zekew64, you still don't make sense. I'm going to handle this as respectfully as possible.

This argument started off of a disagreement of whether or not the timing belt alignment is set to be at TDC or 10* BTDC because of exhaust gasses and their affect on the cylinder head. Is that right? If so, that 5* of CAMshaft rotation isn't going to matter to the life of the valves and the possibility of catastrophic failure.


10* of crank rotation with the exhaust valves still closed isn't going to affect the valve seats, either. They don't even begin to open until after the piston is beginning to travel back up in the cylinder, anyway.



1st stroke = Piston goes down, intake valve opens, fresh air/fuel is drawn in.
2nd stroke = Intake valve closes, piston goes up, compression happens, ignition + combustion
3rd stroke = Piston travels down, valves stay closed, this is the "power" stroke.
4th stroke = Piston begins to rise, exhaust valve opens, exhaust gas expelled.

Usually, cams are ground so that the intake valve opens right as the exhaust valve finishes closing anyway. This is overlap, more aggressive cams have lots of this, but factory cams don't.


If you still want to argue this point, then you need to take it up with someone who designed the camshafts and engineered the engine.