Stupid question re TDC
Discussion
Forgive the ignoramous question, but if I turn the engine to 90 degrees before TDC, should all the pistons be the same height (engine is an in-line 4)?!
I presume the easiest way to do this without the aid of any timing marks on the crank pully is to remove the plugs and put say 4 welding rods down the bores and see when they're all the same height?
I presume the easiest way to do this without the aid of any timing marks on the crank pully is to remove the plugs and put say 4 welding rods down the bores and see when they're all the same height?
Sorry, ignore what I posted before. They'll be exactly half way up the bore at 82 degrees after or before TDC but remember in this position two pistons will be 82 degrees BTDC and the other two will be at 82 degrees BBDC which is not where the pistons are half way up the bore. All 4 will be at the same height at 90 degrees BTDC but that position won't be half way up the bore, it'll be somewhat further down than that. Anyway it turns out you weren't the slightest bit interested in any of that.
Edited by Pumaracing on Wednesday 4th November 10:44
Pumaracing said:
No, they'll be at the same height at about 82 degrees before or after TDC although I can't imagine why anyone would want to get them like this other than roughly for the purposes of fitting a cylinder head.
I need to remove the cylinder head on a K series, and I've been told to set the crank to be at 90 degrees before TDC on the #1 piston (which I presume is the piston closest to the crank pulley?) prior to removing the head.fergus said:
Pumaracing said:
No, they'll be at the same height at about 82 degrees before or after TDC although I can't imagine why anyone would want to get them like this other than roughly for the purposes of fitting a cylinder head.
I need to remove the cylinder head on a K series, and I've been told to set the crank to be at 90 degrees before TDC on the #1 piston (which I presume is the piston closest to the crank pulley?) prior to removing the head.fergus said:
Pumaracing said:
No, they'll be at the same height at about 82 degrees before or after TDC although I can't imagine why anyone would want to get them like this other than roughly for the purposes of fitting a cylinder head.
I need to remove the cylinder head on a K series, and I've been told to set the crank to be at 90 degrees before TDC on the #1 piston (which I presume is the piston closest to the crank pulley?) prior to removing the head.Not so stupid a question:
That on most 4 cylinder in line engines is the 'safe' position. Yes, No. 1 cylinder is nearest the Cam/Crank shaft Pulleys ~ the Timing end of the engine.
On the K-series 4 pot, there is an index mark ( a slit ) on the rim of the CRANKshaft Pulley which will be at the 12 O'Clock "safe" position when No.1 piston is at 90 degrees BTDC ( Before Top Dead Centre ). On the K-4 series, it is difficult to see with the engine in the car but, you can reach down and feel with a finger nail for the 'nick' on the CRANKshaft pulley at the top 12 O'Clock postion.
When No. 1 is @ 90 degrees BTDC, all four pistons will, be at the same level, that is mid position halfway up/down the bores. Pistons 1 and 4 on the way up, 2 and 3 on their way down.
With the Crankshaft index at the top 12 O'Clock position, the two CAMshaft pulleys will have their indexes in the "safe" position too. These are the positions for fitting the Timing Belt following cylinder head removal and refitting.
Once the cylinder head is removed NEVER rotate the Crankshaft as that risks disturbing the cylinder liners.
Here's picture I took of friends R25 with the DOHC K-Series showing the location of the CAMshaft pulleys in the "Safe" position used when fitting the timing belt. Hope this helps:~
Note the engraved word EXHAUST on the Exhaust Camshaft Pulley spoke points to the INLET Camshaft Pulley. The word IN on the INLET Camshaft pulley points to the Exhaust Pulley ....
Some folks find the use of a CAMshaft locking tool helps but, it is not essential for the job : about a fiver off Ebay ~ here's one in use :~
thong said:
fergus said:
Pumaracing said:
No, they'll be at the same height at about 82 degrees before or after TDC although I can't imagine why anyone would want to get them like this other than roughly for the purposes of fitting a cylinder head.
I need to remove the cylinder head on a K series, and I've been told to set the crank to be at 90 degrees before TDC on the #1 piston (which I presume is the piston closest to the crank pulley?) prior to removing the head. commonly referred to as the safe position 
MGJohn said:
fergus said:
Pumaracing said:
No, they'll be at the same height at about 82 degrees before or after TDC although I can't imagine why anyone would want to get them like this other than roughly for the purposes of fitting a cylinder head.
I need to remove the cylinder head on a K series, and I've been told to set the crank to be at 90 degrees before TDC on the #1 piston (which I presume is the piston closest to the crank pulley?) prior to removing the head.Not so stupid a question:
That on most 4 cylinder in line engines is the 'safe' position. Yes, No. 1 cylinder is nearest the Cam/Crank shaft Pulleys ~ the Timing end of the engine.
On the K-series 4 pot, there is an index mark ( a slit ) on the rim of the CRANKshaft Pulley which will be at the 12 O'Clock "safe" position when No.1 piston is at 90 degrees BTDC ( Before Top Dead Centre ). On the K-4 series, it is difficult to see with the engine in the car but, you can reach down and feel with a finger nail for the 'nick' on the CRANKshaft pulley at the top 12 O'Clock postion.
When No. 1 is @ 90 degrees BTDC, all four pistons will, be at the same level, that is mid position halfway up/down the bores. Pistons 1 and 4 on the way up, 2 and 3 on their way down.
With the Crankshaft index at the top 12 O'Clock position, the two CAMshaft pulleys will have their indexes in the "safe" position too. These are the positions for fitting the Timing Belt following cylinder head removal and refitting.
Once the cylinder head is removed NEVER rotate the Crankshaft as that risks disturbing the cylinder liners.
Here's picture I took of friends R25 with the DOHC K-Series showing the location of the CAMshaft pulleys in the "Safe" position used when fitting the timing belt. Hope this helps:~
Note the engraved word EXHAUST on the Exhaust Camshaft Pulley spoke points to the INLET Camshaft Pulley. The word IN on the INLET Camshaft pulley points to the Exhaust Pulley ....
Some folks find the use of a CAMshaft locking tool helps but, it is not essential for the job : about a fiver off Ebay ~ here's one in use :~
thanks.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff