Valve timing out ???

[beanpole]

Desperate for help now…

My RV8 simply won’t fire up very well at all , when eventually started runs very lumpy on tick over, which has to be fast, and seem to be okay when you rev the engine.

The thing that is worrying me is that the timing has to be WAY out to get to start like this. By way out I mean if you look at the position of the rotor arm when pulley is at TDC , it is halfway between cylinders 1 and 8 !.

Turning the engine over by hand with ignition on.No1 spark plug in the lead and lying on the manifold. The plug sparks at about 50 degrees BTDC !!!

I have reset and checked the static timing several times but have to resort to turning the dizzy (advance), to even get it to try and start.

Could the valve timing be out ???

I just can’t help feeling a bit depressed now, this problem has taken away some of the euphoria of starting the engine.

Steve

;( ;( ;(

[Srv8]

not sure why , or how, but I have read somewhere that the distributor can be put in the wrong way round. that might be the issue - but dont have any technical books to refer too.
you might want to check the valve timing -could be out .. not sure what the firing order is either .. think it starts 1-8 ..
I'm just quessing now ! sorry!

Steve

[Happy Jim]

By way out I mean if you look
>at the position of the rotor arm when pulley is at TDC , it is
>halfway between cylinders 1 and 8 !.


Your not looking at TDC in that position, that's just about 180deg out, (Mine at TDC points to No. 6ish)

I've never had the engine to bits yet, is it possible to put the damper on 180 deg out?

Either way, you need to find True TDC before you start otherwise your never going to win the battle.

Whip the valve cover off, turn engine over by hand until both valves are closed on number 1 cylinder, take No. 1 plug out and drop a welding rod down the hole, stick finger on end of welding rod and rotate engine forward/backwards for highest point (naturally substitute dial gauge for finger if you have one :tu ).

If the degree marks are now on the bottom of the pulley out of sight....oops, but not a problem, scribe a line below the pointer and this is now your TDC mark.

Rgds

Jim

[beanpole]

Battery charged up again, so had another go, started up a bit better but had to pump the pedal after the first ‘catches’ to get all cylinders fired up , so thought must be a bit weak, so opened up the mixture screws a bit. (Weber 500)

Ended up ticking over at about 1000 revs no to bad, jut the odd little splutter. Revs well with a little hesitation if you floor it.

So my thinking is the valve timing cannot be out or I would not get this far, also how the hell can it be running like this and ticking over with the timing so far out ?

I am sure that the pulley timing marks are in the right place, but It would appear they are not.

Well , keep on fiddling and see what happens, at least it will run ..

Steve


:} :}

[beanpole]

Jim,

Have had it running again, still a pig to start, but after pumping the pedal when the first 'catches' start she fires up and will tick over.

So I stopped the engine, ensured No 1 was just starting the compression stroke and laid the plu in its lead on the manifold, carried on turning by hand and watched to see when the plug sparked.

It sparked well before the timing line had even started , if there were marks I would say it would be about 40 degrees BTDC. Yet it runs like this.. strange..

The engine does not seem to be getting hot, temp never goes above 80 oil pres okay etc..

Steve

[SimonP]

Going back to your first post...how about this one?
The distributor body is simply turned round a few degrees too far. You say it fires about 50 deg btdc. Rotor between 1 and 8.
Now, set cyl#1 on comp stroke about 10 deg btdc (or whatever static timing figure is required) on the timing marks.
Mark the distributor body below cyl#1 turret then remove cap.
Turn the distributor body so that the rotor faces this mark.
If you can't get it to line up, repeat the operation with a new mark corresponding to the adjacent turret.
If that now lines up OK, you will have to move your plug leads round a step.

Now listen to the baby purr!!

Simon

[SimonP]

You will also need to re-check the static timing when you've done this, prior to startup. However it will likely be close enough to start straight up anyway.

It does sound like you are a step out with your plug leads. As you move the distributor to correct the timing, it will fire on the wrong cylinder.
That's why it will sort-of run with so much advance.... the spark won't really know where to jump to off the end of the rotor arm, so most of it's energy will be lost before the plugs!

Simon

[beanpole]

Simon,

Youhave obviously pickd up on my limited knowledge and put me on the right track. She now starts up a lot better.

The only problem I had was it did not sound quite right, but thought that was me as I had never heard a V8 close up before. Then the chap next door said, 'hey you are running on 7',(just before he complained about the noise).

Took all the plugs out one by one , and No4 was wet.. Dohh. Sure would explain the lumpy tickoever.

Steve

A lot happier now..

[SimonP]

Hi Steve,
As long as you're happy!

Another little tip which can sometimes prevent unexplained plug fouling, is to use ignition lead separator "combs" - don't cable-tie all the ignition leads together in a bunch.

With modern ignition systems, there can be sufficient energy to induce voltage into closely tied leads (capacitive coupling) and cause backfires or mysterious fouling as the other cylinders fire at the wrong time. It's usually worse in damp or humid weather.

Simon

[osgood]

Contrary Mary

Steve, if the valve timing was out it will spit petrol back out the carb when you try to apply some revs, as the inlet valve is generally open at the wrong time.

You may well have a Range/Land Rover pulley fitted they tell me the timing marks are sometimes in a different location as the woodruff key is in a different position on these applications Eric.