Blow back on V8
 

Hello everyone, on our way to ghana and since leaving the Uk we seem to have a blowout happening with our 3.4 V8 in our landy. The last part of the exhaust is just new, we checked all filters and fuel stream (constant and fine) but somehow as soon as we drive around 15,35,65 it seems as if the engine holds back, then jumps forward. Several machanics say they cant see anything wrong, carbs are set correctly at 27 last moneth, but sometimes the little balc caps come off (mechanic said this should no a problem??) , no cables touching with metal.... Could it be the air pressure in the exhaust, and does anyone recognise this problem???

ANY IDEAS?????Hope you can help,

Many thanks Lotty

Hi Lotty

Do you mean the V8 is backfiring ???

'black caps coming off ' - which ones do you mean ? on the carbs ?

what year is you Landy and is it an original V8 or a conversion ?

a few things to try in order - simple first !


1 - are the ignition leads BRAND new ? if not replace them - this is a common cause of backfiring with Rover V8s - if they are new - clean them & use some silicon grease on all the lead ends to ensure a good connection.

2 - older Rover V8s tend to wear there points/rotor arms fairly quick - check for wear - even on what is a fairly new set, also the distributor cap while you are there - any pitting and carbon deposits removed.
The ignition coil and timing obviously have to be spot on too....

3 - check your plugs next if 1 & 2 does not improve problem.

4 - Rover V8s run hot - as youll know from the roasting transmission tunnel !!!this can cause a vapor lock in the fuel system - you say the fuel feed is good - does the problem occur when engine is is hot or cold - vapour locks will occur when engine is hot and the vehicle is travelling slow (less airflow through engine bay)

this can be a problem on V8 conversions with fuel lines run too close to the engine -also in line fuel filters can be where this happens if they get too hot- if this is the problem make up a 'heat shield' with some metal or non flammable material covered in cooking foil between engine and fuel line.

what carbs are they ? SU or Stromberg ? - if all the above does not work, then you might have a a problem with a carb

- the dash pots on SU s should be filled with 20 or 30 weight oil (if they empty quickly the carbs are worn) and the caps should not come off as they have a fine screw thread.....

let us know if these steps work.....

oh yeah - the exhaust - is it a standard or performance one ? - it shoudnt make much difference - if it is a performance box then you will tend to get some 'popping' on the overrun (when you come of the throttle under engine braking) but not full backfiring....

cheers
Grif

also if the timing is out, either through incorrect setting or a dodgy coil or codenser it could cause unburnt fuel to enter the exhaust where it will then ignite, causing a 'backfire'

yhanks for all the replies! we have just bought some carburator oil and are hoping that after reading loads on it, this may solve it all....
Lotty