Timing an engine

[vibrac]

Anyone who has an interest in setting up a Vincent engine and who had used this Forum knows by now about the equal valve opening method of timing a cylinder. Many methods have been explained here but basically you set both valves equally open and the crank at 4 degrees BTDC (4-6 is often quoted)
Now it is said this method will work on any OHC engine. However I am currently rebuilding a 1926 side valve Douglas putting in new valve guides and replacing the worn cast iron pistons with a couple of CB 750 Honda pistons I did track down the timing figures and they are
IO 15 deg BTDC
IC 50 deg ABDC
EO 50 deg BTDC
EC 15 deg ATDC
The overlap is 30 degrees equally spaced over TDC (although the sheet says over lap is 34 degrees?)
so I shall try the equal opening method at TDC since the head and barrel are one piece I can actually see when TDC is reached and I can measure the valve actuators with a height gauge as they rise out of the crankcase so compared to a Vincent it should be easier
I will let you know how it goes

 

[bmetcalf]

Is the sheet overlap at the same lift as your measurement?

Also, I wonder how the cavity beside the bore was machined with the access only from the bore and above the valves? Easy (?) to imagine with a dohc Offenhauser.

 

[Chris Launders]

I have Panhard top ends on a JAP engine, they are OHV with one piece barrel and head and any valve seat work has to be done with a special machine apparently, with the machining head angled at the top.
They are quite a narrow valve angle but you cannot come at them straight on from below.

 

[Keith Martin]

We run our flat tank Nortons using equal lift at TDC or as close as it will get to equal. We favored the intake opening more at TDC if not equal.

 

[oexing]

The Panhard cylinder is most likely same design as aero engine types, head screwed onto the cylinder by a huge male thread on liner/cylinder and female thread in alu or steel head. No gaskets on these I think, just precision machining and torqued down in a jig.
When having maintenance on valve seats in these engines you can only use piloted Neway type seat cutters for some tidying up , else you´d have to unscrew the head - which would be a dramatic action.
SV cylinders with integral head typically got finned "cooling towers" or threaded plugs above the valves so you can machine valve seats through these holes. And yes, equal lift at TDC is quite common and will work on all engines perfectly. Just that the Phils went for a tad more torque at 4 degrees before TDC equal lift, a bit less max power then . Equal lift at TDC is best combination of torque and power, equal lift 4 degrees past TDC will get you max power at high revs but less torque. So you see why I point at going for the equal lift settings and bin all funny numbers of valve timings in old handbooks - which were possibly almost correct when they had all new valve gear in building new engines.

Vic

radial engine cylinders, steel cylinder plus alu heads:

 

[Chris Launders]

The Panhard cylinder is most likely same design as aero engine types, head screwed onto the cylinder by a huge male thread on liner/cylinder and female thread in alu or steel head. No gaskets on these I think, just precision machining and torqued down in a jig.
When having maintenance on valve seats in these engines you can only use piloted Neway type seat cutters for some tidying up , else you´d have to unscrew the head - which would be a dramatic action.
SV cylinders with integral head typically got finned "cooling towers" or threaded plugs above the valves so you can machine valve seats through these holes. And yes, equal lift at TDC is quite common and will work on all engines perfectly. Just that the Phils went for a tad more torque at 4 degrees before TDC equal lift, a bit less max power then . Equal lift at TDC is best combination of torque and power, equal lift 4 degrees past TDC will get you max power at high revs but less torque. So you see why I point at going for the equal lift settings and bin all funny numbers of valve timings in old handbooks - which were possibly almost correct when they had all new valve gear in building new engines.

Vic

radial engine cylinders, steel cylinder plus alu heads:

View attachment 59435

View attachment 59436

The Panhards are one piece aluminium with shrunk in liners, with a step at the bottom of the barrel if I recall so the crankcase helps hold the liner in. They are retained by long studs with nuts roughly where the head/ barrel joint would be, they also feature torsion bar valve springs and unequal length rockers giving increased valve lift.

 

[chankly bore]

The figures cited for the old sidevalves bring to mind one of my favourite quotes: " Valve timing so conservative as to border on the Fascist."

 

[BigEd]

You can spend ages setting the Vincent timing to the published opening and closing figures and then checking and rechecking. When you are happy with it just quickly check for equal lift at 4º before TDC you will almost certainly find it to be OK and wonder why you didn't do that in the first place.

 

[fogrider]

From the timing details Vibrac quotes, I make the inlet valve fully open at 107.5 deg after TDC. It would be interesting to look for that position whilst you're doing it , a report back on that please Vibrac ?
Regards all,
Terry, East Yorks.

 

[vibrac]

Is the sheet overlap at the same lift as your measurement?

Also, I wonder how the cavity beside the bore was machined with the access only from the bore and above the valves? Easy (?) to imagine with a dohc Offenhauser.

you simply cast the head and barrel and cavity in one and put two large cap holes over the top of the valve seats in the cavity (Its a side valve remember ) machine seats (no valve seats straight in the cast iron) and the valve guide locations through the two holes, pop in the valves screw the caps on springs underneath against crankcase
I am waiting for valve springs before I can say when the valves shut but I can do the EO timing without head barrel or valves , strange things side valves