VACUUM ADVANCE OR BACK BOX ??

[barriesheene]

Ok peep's this should be an easyone for you all  :? I have recently done a full service on my rangie (3.9 v 8) all oil's, dissy cap ,rotor arm, plugs, leads etc, but since ,I seem to have lost some power  :roll:  It seem's to run ok but just not as spritely as it was before the service. I've checked plug gaps etc but all seem's ok. I've narrowed it down to two possible thing's
1) While changing dissy cap I noticed that the vacuum advance on the dizzy was loose and shooting forward on exceleration ( was this right to move ) so tightened it up where it looked as though it should be  :lol:  
2 I've cut the back box off to give it that authentic v8 burble  :twisted:
Any idea's guy's
Baz

[Range Rover Blues]

Yes, I had the same.

Cheap tatty dizzy cap, it was running on about 5 cylinders when under heavy throttle, the richer mix is harder to ignite so it only showed up then.

[Rossko]

If the vac unit was hanging off and you've moved or re-fixed it, it WILL have changed the timing.   It might be back where it's supposed to be .. or it might not.  You need to check the basic timing.

[barriesheene]

Thanks Rossko  :D  I take it then that the vacuum advance isnt supposed to move, But I could have fixed it back slightly out  :roll:  I've also noticed that when starting after a spin or two just as the engine catches to start there is a popping sound like a backfire just as it start's  :?:  Strong smell of petrol coming from exhaust to  :oops:

[Range Rover Blues]

Hmmm, unburnt fuel and backfiring.  Could well be timing, over edvanced makes starting harder.

[disco-v8]

check your timing first

if yours has got CATS then it should be set to 5 degrees BTDC
if youve havent got CATS then 4 degrees BTDC


dont be worryed to advance the timing alittle, as it make a big difference you can hear the engine rev abit higher straight away and the pick up in the engine is great..... i dare bet you that you will save a few quid in fuel aswell, as you wont need to floor it asmuch....
dont go to far tho im running mine at 10 degrees BTDC and ive had no problems what so ever!!!!

also you can try a little thing to see if your vacuum advance is working.... take off the pipe that goes from the vac advance to the plenum chamber and suck on it... you should see the engine rev up more and you can watch the timing marks move aswell, dont forget to put your finger over the hole in the plenum so that you dont mess up the fuel mixture



if this is all fine but doesnt cure it then check the plug/wires on the airflow meter, i once had a problem with fuel been to rich, backfiring through the airbox and running like it was on 5 pistons when my airflow meter plug wasnt pushed on enough... 1 quick push on the plug and the engine was WROOOOM WROOOOOOOOOOMMMMMMM!!!!!! again  :D

[barriesheene]

Thanks guy's. To be fair range Rover Blues, you did say that I would have krackered my dissy when i pulled the barrel up when taking the rotor arm off  :oops:  So unburnt petrol, occasional back fire, loss of power oh and when checking the plugs gaps I noticed that one of the plugs was wet and smellt of petrol. It SEEMS to run ok tho, just not as well as it was. I mean if you drove it now without driving it before hand you wouldnt think anything was wrong. Guess i need to get a strobe light, I hope they come with instructions  :lol:  :lol:  :lol:

[grizz]

I notice in at the bottom of your message you say you've got a straight through exhaust, was the rear box the only one in the system, if so then you will loose torque with the lack of back pressure, I'm currently running mine with just a cherry bomb but I'm going to put the centre box back in tommorrow as the drop in power is noticable, shame because it sounds awsome

[barriesheene]

Grizz I've also got a middle box. To be honest there was a hole in the front box which has been filled untill the mot in feb when i will get a new full system anyway for the mot. Thats why i took the back box off cos I gotta get a new one anyway  :roll:  Nice of landrover to put the box after the last mounting point to allow for easy removal with a hacksaw  :twisted:   :lol: