5
votes
Why does this mechanic change the crankshaft mark, during this timing-belt change?
The simple answer to this is that you can make any marks you want on the pulleys before you take the belt off. As long as you put the belt back on with the pulleys in exactly the original position as ...
- 25.5k
4
votes
Is there a risk of igniting the incoming charge with wasted spark systems?
If the inlet valve opens 20 deg before TDC, will fresh mixture be going in or not? As there is still pressure in the cylinder - the exhaust leaving is helping to "draw" the fresh mixture into the ...
- 34.7k
3
votes
When switching off the engine, do the cam and crank shafts always come to rest in an initial state?
No. An engine stops where it stops because it is random when you turn the ignition off, and therefore there is no set place for it to end up at.
- 162k
3
votes
Is there a risk of igniting the incoming charge with wasted spark systems?
The wasted spark will likely be 30 degrees or so before TDC. There would be no fresh fuel charge at this point.
- 294
3
votes
Why don't valvetrains use an idler gear between the cam gears
Bottom line is: It's been done.
Here's one for a small block Chevrolet engine:
Just as you describe, there's an idler gear (well, maybe two) which keeps things in time.
These gears are used mostly ...
- 162k
3
votes
Why is there no valve overlap on 1987 V4 Honda?
In 1987 vehicle manufacturers were struggling to meet the emissions standards
Valve overlap, while a performance gain, is not necessary for an ICE to run properly. Valve overlap will allow un-burned ...
- 33k
3
votes
4 stroke valve timing diagram: if valves are open during TDC, wouldn't they hit the piston?
Question 1: This depends on engine design.
In an interference engine, the valves can collide with the pistons, so you need to design the timing diagram to prevent that.
In non-interference engines, ...
- 4,412
2
votes
Prevention against turning of the camshaft during the tensioner replacing in 1 cylinder 2 valves 4 stroke engine
While I don't have an answer regarding blocking or stopping the cam, You can work around it without too much trouble.
With the chain still in place, You can mark on the crank and cam gear teeth and ...
- 1,646
2
votes
Noisy 4.6L Mustang engine
I know this question is old, but I thought I'd provide some feedback for future.
Cam phasers make noise due to a lack of oil pressure in two cases:
The inner rotating piece connected to the cam ...
- 21
2
votes
Is this valve toast or could I possibly salvage it without tearing into the engine?
I think I'd first be doing a compression test here just to help perhaps rule out an internal engine problem like a burnt valve etc. Assuming pressures are good though... I'd then be considering ...
- 5,067
2
votes
Why don't valvetrains use an idler gear between the cam gears
Short answer: follow the money.
Long answer. Cutting gears and ensuring the mesh correctly is incredibly expensive. You've got to rough form, final form, heat treat then final form again. Then ...
- 6,569
1
vote
How to do a timing job on an engine that only has timing gears
First step is to get number 1 piston at TDC.
Once you have done that then you can engage the camshaft gear with the crank gear using that mark and looking at the camshaft so that you have it in the ...
- 34.7k
1
vote
VW 2.0 TSI jumped time, could the valves be ok?
There may be a position where the chain can slip and there will be no damage, but will it have happened there?
So possibilities:
Use a camera through the plug hole to investigate for contact
You ...
- 34.7k
1
vote
TDC on DOHC but with cams removed
On a 4-stroke engine, when #1 is at TDC, it's at TDC. It doesn't matter at that point if the cam(s) are not connected. Once you align the cam timing mark(s), then you'll set which stroke you are on.
...
- 162k
1
vote
Accepted
Is this valve toast or could I possibly salvage it without tearing into the engine?
Here's what happened to the engine in this case as found when I tore into it:
That roller on that burnt looking rocker arm locked up. It wouldn't turn any more. So it overheated and also dug a lot of ...
- 227
1
vote
Prevention against turning of the camshaft during the tensioner replacing in 1 cylinder 2 valves 4 stroke engine
What I have found with some OHC interference engines is that there are special dealer tools to hold the cam. They usually bolt to the head and have pins that slide into holes on the cam gear. I ...
- 1,318
1
vote
Accepted
Noisy 4.6L Mustang engine
How about substituting one quart of motor oil with Marvel Mystery Oil? You may have a little varnish somewhere on a valve lifter, valve stem, oil pump, etc.
- 2,200
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