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Number order of pistons

Posted: Wed May 25, 2016 11:45 am
by Leyland
This may seem a daft question but I just cannot remember.
Is number 1 piston the radiator end or the bulkhead end please.

I ask because I know on old Jaguar engines no 6 piston is the radiator end!
Many thanks

Re: Number order of pistons

Posted: Wed May 25, 2016 11:46 am
by les
1 = rad end.

Re: Number order of pistons

Posted: Wed May 25, 2016 1:40 pm
by oliver90owner
Nothing to do with the rad, per se. Convention is drive to the engine 'brain' - the camshaft. No1 was always at that end of the engine, as were any rod cap markings, whether it were mains caps numbering, or rod markings which would denote the camshaft side of the engine as well as the hole/bearing number.

The adoption of overhead cams and transverse engines has somewhat muddied the waters, but the convention should hold true for almost all older engine designs.

RAB

Re: Number order of pistons

Posted: Wed May 25, 2016 3:14 pm
by les
I made the assumption the vehicle was a Minor.

Re: Number order of pistons

Posted: Wed May 25, 2016 4:24 pm
by philthehill
Not withstanding the timing gears / chain / bevel gears at the rear of the block or even in the middle of the block :wink:

Re: Number order of pistons

Posted: Wed May 25, 2016 8:50 pm
by bmcecosse
Does it really matter which is #1 ?? The engine rotates clockwise as we look at it from the timing chain end .

Re: Number order of pistons

Posted: Wed May 25, 2016 10:21 pm
by Leyland
It is a minor I am referring to. I ask because setting distributor drive and eventually timing, the manual says set piston 1 or 4 at TDC. So being a minor engine is no1 piston the radiator end please.
Thanks

Re: Number order of pistons

Posted: Wed May 25, 2016 11:00 pm
by bmcecosse
It can be either! But most of us would assume it is at the front.....yes - at the radiator. And unless there is something terribly wrong - both 1 and 4 will be at TDC at the same time...... Of course - what you really want is for #1 to be on the firing stroke... Put a straw down the spark plug hole and turn the engine till it reaches the high point - then look at the valves - both valves on #1 should be closed .

Re: Number order of pistons

Posted: Thu May 26, 2016 12:00 am
by Leyland
Thanks bmcecosse, that is really helpful.