The V8 Owners Forum -

With paraffin leaking at that tiny rate I would have expected more than enough compression to start an engine - for 0-10 PSI in all cylinders, for one reason or another the valves would have to be open when the pistons came up on compression.

I can only think of two reasons that the valves would be that open to have zero compression - The lifters and the camshaft. I would double check the camshaft timing and then inspect the lifters and the preload.

Wondering about pre-load, since all the valve gear was new, we slackened a rocker shaft until there was obvious clearance with the valves closed.
Made not a scrap of difference to the compression reading.

The RV8 is an interference engine. If the valve timing is wrong, there is a very real chance of valves hitting pistons.

With the paraffin test, a tiny leak would be one that only appeared overnight.
But I've always been told there should be no leak at all. If a liquid like paraffin can flow easy, gas under pressure even more so.

I think that as ive got to this stage of stripping the engine down, I will knock off the front timing cover and check for my own peace of mind that ive got the timing gears aligned correctly... then re-assemble.

Or - is there another way of checking that the camshaft lobes are pointing at the correct cylinder,without having to remove the front timing cover?...


If not , is there a "lazy" way of removing the front timing cover without dropping the sump? -

I think that as ive got to this stage of stripping the engine down, I will knock off the front timing cover and check for my own peace of mind that ive got the timing gears aligned correctly... then re-assemble.

Or - is there another way of checking that the camshaft lobes are pointing at the correct cylinder,without having to remove the front timing cover?...


If not , is there a "lazy" way of removing the front timing cover without dropping the sump? -

I think that as ive got to this stage of stripping the engine down, I will knock off the front timing cover and check for my own peace of mind that ive got the timing gears aligned correctly... then re-assemble.

Or - is there another way of checking that the camshaft lobes are pointing at the correct cylinder,without having to remove the front timing cover?...


If not , is there a "lazy" way of removing the front timing cover without dropping the sump? -

I think that as ive got to this stage of stripping the engine down, I will knock off the front timing cover and check for my own peace of mind that ive got the timing gears aligned correctly... then re-assemble.

Or - is there another way of checking that the camshaft lobes are pointing at the correct cylinder,without having to remove the front timing cover?...


If not , is there a "lazy" way of removing the front timing cover without dropping the sump? -

I think that as ive got to this stage of stripping the engine down, I will knock off the front timing cover and check for my own peace of mind that ive got the timing gears aligned correctly... then re-assemble.

Or - is there another way of checking that the camshaft lobes are pointing at the correct cylinder,without having to remove the front timing cover?...


If not , is there a "lazy" way of removing the front timing cover without dropping the sump? -

When you did the compression test I presume you had throttle held wide open?

If not it cannot suck any air in to compress

And will give an artificially low reading

Ian

Ian Anderson wrote:When you did the compression test I presume you had throttle held wide open?

If not it cannot suck any air in to compress

And will give an artificially low reading

Ian

10psi rather than about 160?

10psi or 10 bar?

10bar = approx 140psi with throttle closed about right

Ian

Says 'psi' Every time mentioned. Near zero on the gauge. Off the end of the red bit.

Bigger

I thought I was onto something!

Ian

UPDATE - But i need a little more help i'm afraid!

Ive got the heads back from the machine shop and they are ready to fit. the guy who carried out the works said that they needed doing and all 16 now seat well!

When inspecting the pistons carefully, there seemed to be the faintest linear marks (5mm) on most of the new piston crowns,where i assume the pistons may have partially touched the edge of the valves - perhaps where they were not seated properly. Its either that, or my timing gear/camshaft is out and causing the pistons to hit the valves!! - which i am 99% confident that all marked were correctly aligned!

see here:


http://s12.postimg.org/6j84r93kt/IMG_3178.jpg[/img]

http://s21.postimg.org/h5gwaiop3/IMG_3179.jpg[/img]

http://s15.postimg.org/jd4kisx4b/IMG_3181.jpg[/img]


My thoughts here are that surely if something was out of kilter, then more damage would have been caused to the piston crown/valves/pushrods, simply by spinning over engine on the starter? the marks literally looks like a small pencil marks.

You only need the valves to hit by a few thou to cause damage & this is probably the reason they weren't seated.

I would say you were lucky the lifters weren't pumped up properly.

Here is another image with the areas highlighted, just incase its not apparent from the previous images..

[img]
http://s14.postimg.org/f3dc981ch/MARKED_PISTONS.jpg[/img]