Thread: RV8 3.9 Timing Cover on a 4.6

Since I put this up I have got some answers.

1. New camshaft required
2. The spacer has dimensions of ID = 35mm
OD = 45mm
Depth = 18mm

Not sure exactly where the spacer goes - I assume between the pulley and the end of the crank so I assume an 18mm longer pulley bolt is needed but we know what happens when you assume.

3. Need to consider whether to go serpentine belts or V belt. The old 3.9 I have is a serpentine belt.

The other option is not to put the 3.9 timing cover on at all and to use a trigger wheel as the crank sensor and use Megajolt to run the system. The main issue then is to work out top dead centre on the engine as it has no timing marks and the process of working out when the piston is TDC as the crank can move through many degrees of rotation with no noticeable movement of the piston when at the top or the bottom of the stroke.

Cheers

Garry

Originally Posted by 101RRS

Since I put this up I have got some answers.

The main issue then is to work out top dead centre on the engine as it has no timing marks and the process of working out when the piston is TDC as the crank can move through many degrees of rotation with no noticeable movement of the piston when at the top or the bottom of the stroke.

Cheers

Garry

You would have to pull the head to find TDC? Could you use a micrometer onto a piston? Rotate to NEAR TDC and mark the flywheel. Rotate through TDC until the micrometer reads the same again, and mark the flywheel again. TDC is half way between these marks.

In theory you do not need to take the head off.

You can find TDC by making up a tool that screws into No 1 spark plug hole. You turn the crankshaft until the piston is about halfway up the cylinder - this is where crankshaft rotation maximises piston movement.

You then insert the tool into the spark plug hole and screw it in until it is finger tight. Here is my tool (my real one is bigger )
IMG_20190413_121045.jpg

The old spark plug has been drilled out and threaded so the centre piece can be screwed in and out - you can see it has a little plastic on the end to protect the piston crown.

So with the piston in a suitable position about half way up you either screw the centre of the tool down until it touches the piston crown or move the piston a bit. You then mark the crankshaft pulley aligned with a pointer you have already mounted on the engine .

Leaving the tool as is, you then turn the crankshaft counter clockwise (making sure you can do this as some engines you cannot) so the piston goes down past bottom dead centre and then starts moving back up - stop when the piston just touches the the bottom of the tool - there you mark the crankshaft pulley.

Halfway between the two marks (on the TDC side of the crank pulley) is the position of TDC (in theory).

Garry

All RV8s are backward compatible.
A couple of things . Be careful about the gasket that goes between the timing cover and block. In one combination the oil holes are in a different place although they look similar.

Regard s Philip

The 4.6 crank is longer than the 3.9 one, the spacer you need goes in front of the front pulley before you fit the bolt and washer. A cheap spacer can be made from an old bottom timing chain sprocket, just remove the teeth. A serpentine front cover should be an easy fit on the 4.6 but I'm fairly sure there is a dowel on the block face you will have to remove. It's been a while since I did one. You will also need to swap the sump and oil pickup off the 3.9 as they are entirely different on the 4.6. The pickup gallery should be present in the 4.6 block for that purpose. Nothing wrong with a 3.9 serpentine front end but you have to have all the bits as the 4.6 is all different except for the water pump.