14 replies to this topic

[IainNeon91]

Hello everyone, 

 

My engine is near completion but I'm having a meltdown trying to get my head around whether my engine is set up correctly...

 

This is how my engine looks at TDC 

 

No 1 piston at TDC

 

 

Timing marks lined up

 

 

Valves 1 and 2 are fully closed

 

 

And my rotor arm is point at about 2 o'clock

 

 

Does this seem right to you??

 

I've read that my engine should look like this but when I turn the engine over, the first valve that should open is number 1 exhaust??

 

But when I turn the engine through its cycle to get number 1 valve to start to open, my engine isn't at TDC...

 

I'm really confused

 

Any help would be great!

 

Iain.

 

[jime17]

Would the exhaust valve not start to open when the piston was at the bottom of its stroke?

[Stu1961]

Do both rocker arms move when you try and rock them? If so the piston is at the top of it's compression stroke. The next part of the cycle is the piston will move down (Ignition Stroke) both valves will still be closed only when the piston reach's bottom dead centre will the exhaust valve begin to open.

So you are correct but when the exhaust valve opens you will be at approximately BDC not TDC. Hope that makes sense anyone correct me if I am wrong or confirm that I have got that right.

[KernowCooper]

The exhaust valve will open before the piston reaches BDC even with standard cams.

[Stu1961]

Note I said aproximately

[Island Mini]

Is just your intake valve open on cylinder 4? Assume it is...

 

(is it cyl 4 working off memory?? if not which ever other piston is at TDC)

[IainNeon91]

Thanks for the comments. 

 

The other piston is cylinder 4, yes. I will have to check if the inlet valve is open tomorrow. 

[Stu1961]

Yes No4 will also be at TDC (At the top of its exhaust stroke) and both rocker arms will be rocking (In contact with their respective valve stems), exhaust will be almost closed and inlet beginning to open.

Edited by Stu1961, 30 April 2014 - 10:16 PM.

[Stiggytoo]

Unless you've fitted the timing chain/sprockets in the wrong orientation, there's no reason for concern.

[IainNeon91]

Unless you've fitted the timing chain/sprockets in the wrong orientation, there's no reason for concern.

What do you mean by this?? 

[KernowCooper]

Means the cam timing on the sprockets is not done correctly

[IainNeon91]

Well I followed the guide in the Vizard book, got the dots lined up on the sprockets put them on, then checked the timing and it came out at 106.5 degrees (i have a 266 cam), so i didn't bother putting a offset woodruff key in... 

 

The crankshaft woodruff key was at 12 o'clock and the camshaft woodruff key was at 2 o'clock when i put the sprockets on... Which it says they should be in the haynes.

Edited by IainNeon91, 30 April 2014 - 11:09 PM.

[KernowCooper]

Then with your setting then your timed ready to start.

[Stu.]

It all looks set correctly to me (for ignition timing). At tdc with No1 on compression both valves are closed. Not sure what you mean when you talk about the exhaust valve opening and the timing marks move from tdc. They will won't they, the crank and cam shafts have to rotate through the cycle to move the valves at the correct time. Can you expand on this concern a little?

[Leonrjohnson]

When you rotate the crank, both #1 and #4 pistons are parallel and will be at TDC together. When they are both at TDC, one of these cylinders will be on the firing stroke, while the other one has just finished its exhaust stroke and beginning its intake stroke. So when #4 rockers are both rocking at TDC, #4 has just finished its exhaust stroke and beginning its intake stroke. At this point, #1 cylinder is on its firing stroke and the TDC timing mark should line up. This is the point when the rotor should be pointing at #1 Plug wire, and the points should be opening at 10 degrees Before TDC(whatever your engine spec is). Ideally the rotor should be at the 1 oclock position. If not, then the distributor drive has been fitted in the wrong spot. It can be pulled out and fitted in situ, but make sure a bolt is screwed into the centre of the spindle so you can grab it. It can fall into the gearbox! Be careful.