Timing a Peacock VW

Dave Unwin · Post by **Dave Unwin** » Sun Dec 11, 2011 12:11 pm

Hi All, does anyone have any good info/data/ tips re timing a belt-driven Peacock VW?
Cheers, Dave

Noel Howard · Post by **Noel Howard** » Wed Dec 14, 2011 1:08 pm

Dave, the method I use for my VP-1 1835 engine is as follows. Firstly you need to set the crankshaft to top centre of number one cylinder with both valves closed. Viewing the engine from the propeller end, number one cylinder is on the left side at the back. You need to position the crankshaft accurately. You should put a rod into the sparking plug hole of number one cylinder to detect accurately the TDC point. Ideally use a dial micrometer, but if that isn't available use a pencil (long enough not to drop into the cylinder) and find the highest point of the piston. Take your time over doing this until you have got it dead right.

Mark the prop driving hub with a spot of typists correction fluid (eg Typex or Snowpake) in line with the joint between the halves of the crankcase.

Next you need to calculate the point at which the magneto points should open as a distance on the propeller driving flange. This should correspond to 27 deg. before top centre. The calculation is -

X = pi.D.27/360 where D is the diameter of the prop flange in whatever units you want to use and X is the distance measured on the periphery of the flange in the same units. This formula boils down to X = 0.236 x D
So if D is 5 inches (as on my engine) then X works out at 1.18 inches (say 1.2").

You should measure this distance to the right of the TDC mark and put another mark on the flange. This is the point at which the magneto contacts should open. Turn the crankshaft back until this point lines up with the crank case joint line.

You then need to set the mags so that the rotor arms of both mags point to number one plug lead and carefully rotate the magnetos so that the points are just beginning to open at this crankshaft position. The belts need to be set for this.

Check that the plug leads are in the correct firing order 1 4 3 2

It is easier to do this than it is to describe it. Don't over advance the engine as the propeller will kick back when you try to hand swing it. You can buy various magneto timing devices from LAS or simply use a piece of thin paper (cigarette paper is ideal) between the contacts to detect when they begin to open.

Best of luck,
Noel.

Noel Howard · Post by **Noel Howard** » Fri Dec 16, 2011 11:20 pm

Oops! I wrote that number 1 cylinder was on the left hand side, it isn't, it's on the right.
Noel.

Brian Hope · Post by **Brian Hope** » Sat Dec 17, 2011 8:44 am

If you don’t have a dial gauge and fittings to mount it in the plug hole, a better way to find TDC than a pencil is to take an old plug, knock the centre out – ceramic etc, until you are left with just the a hollow plug body. Put a piece of studding into it that sticks out what was the electrode end a couple of inches and have a nut both ends of the plug body to hold it tight – 6mm studding will do, the bottom nut needs to be small enough dia to allow the plug to screw into the head.
Now, making sure the piston is somewhere near the bottom of the stroke, screw the plug into the cylinder and then turn the crank until the piston comes up hard against the end of the rod. Mark the prop hub in line with the case joint ‘line’. Turn the crank back the other way until the piston up against the rod again. Mark another line. TDC will be a position exactly in between those marks, and BDC will be exactly between those marks on the other side of the hub circumference. Using a pencil is OK but very close to TDC the piston moves a very small amount in relation to the crank and it is easy to be out by a few degrees.

rogcal · Post by **rogcal** » Sat Dec 17, 2011 5:23 pm

All very good advice so far but before going to the trouble of seeking TDC via the above methods, it may be an idea to check that the prop hub has not already been marked with TDC and 25/26/27 degrees BTC.

I tried 28 degrees BTC one and broke the trailing edge of the prop on my hand when it viciously kicked back.

Personally I prefer 26 degrees and keeping my hand intact.

Dave Unwin · Post by **Dave Unwin** » Mon Dec 19, 2011 12:01 am

Thanks all - have been away from computer. Very grateful for all your advice, hope to get Biffo back in the air soon!
Cheers, Dave