Thread: Vacuum Advance

A rangie in low range revving at full song is gonna drink like that uncle no one talks about...

What do you expect hahaha

Hold the throttle open to around 2000rpm and then test for vacuum with your finger. The vacuum advance isn't supposed to come on at idle. The throttle blade passes the port as it opens and gives vacuum. Sometimes those ports block with carbon, you can easily poke it out with a scrap of MIG wire or a small drill bit. Make sure the throttle blade isn't under the port as you do this or you'll break the drill bit.

Oh and I hope you've set the advance at idle with a timing light to around 8-10 degrees BTDC, this helps economy a bit. Mind you a RRC will never get anything approaching "economy" unless you have the torque converter locked in 4th at a steady 80 km/h on the bitumen. Off road, forget it.

I have set the timing at idle to 9 DBTDC. This also got rid of the dead spot at 2000 RPM on GAS.

I was aware the vacuum advance on the distributor is only meant to come it at higher revs than idle i just wanted to test the vacuum diaphragm on the distributor. And it was seem it works. I did also test for vacuum at higher revs but with no success.

I've tried to clear the dizzy vac port before with small wire but it hit something solid. I did do this with the throttle shut though. And i have seen a plate under this port when i pull the plenum off last time.

So to clarify - in order to clean this port i need to open the throttle before poking wire done the hole? Will i be able to push the tips of the wire into the centre of the plenum or will something stop it from going that far?

I'm not chasing great economy but was not convinced the engine was running right.

It does mean however the RRC doesn't drive far enough before it needs to refuel as i need to drive 200kms before i get to the bush. This is 60 litres of gas gone. Then i need to refuel with gas and makes sure petrol tank is full. I use one tank per day of 4WDing which is between 60-70kms.
Then i switch to gas to drive home again. So this equates to approx 460kms using 2 tanks of gas and 1 tank of petrol for 1 days 4WDing.

Therefore if I cannot do something about fuel range the Rangie will be up for sale. Apart from the fuel usage it is a GREAT TRUCK keeps up with every 80 series, 100 series and GQ or GU patrol I've ever gone 4WDing with.

Thank you all. After all this discussion i was able to get vacuum out of the port for the dizzy.

I ended up putting a short 2" bit a vacuum hose on the vacuum port for the dizzy. I didn't have any carby cleaner or engine degreaser so i used WD40 (yet another use )and filedl up the hose with it, at first nothing happened so i forced the WD40 down the hole with the air compressor. Some went everywhere else but it was a controlled exercise. After doing this twice i noticed the engine revs drop so i put the air compressor away and just filled the vac hose with WD40 the engine revs picked up until the WD40 was gone. I did this about 6 times and afterwards i could feel the vacuum with my finger over the port.

Once this was done i reset the timing as i read in the land rover manual how to do this properly. I was only 2 degrees out before but now i've done it at about 600RPM with the vac hose for the dizzy disconnected. The timing is now 10 DBTDC.

I went for a drive afterwards and I've worked out in normal driving conditions. I get a combined fuel economy of approx 20lt / 100kms on 98 octane petrol. It currently is a useless figure as i don't know what i got before in normal driving conditions. But i will measure it again on my next off road 4WD trip.

This economy probably is not bad considering i run 33" (305/70 R16) tires, have a 50mm body lift and have a roof top tent on the 1/2 roof rack.

You've got huge rolling resistance, road-roller wheels that weigh a tonne... so there's more mass to be accelerated... body lift which adds a tad to wind resistance, as well as the roof-rubbish. (Only noticeable above 70 km/h) plus the added weight of the LPG tank etc. Then there's the usual suspects of jacks, recovery gear, spare bits & pieces all adding yet more useless weight....

The Buick V8 was designed by lazy folk living in the land of plenty, where Gas-O-Line was cheaper than water...

If you work out petrol use as low as 20 litres per 100km then you're doing Very Well indeed. Better than my '3.9, 235/70 H/T's and molly-coddled on highways only.

Just bear in mind that your speedo/ODO is reading 10% LOW... compared to the 'Recommended' 205-R16 standard tyres. (or 235/70 R16 that many folk use for average work) http://tire-size-conversion.com/tire-size-comparison/

When off-road.... toughen up and take a Jerry can or two.