Severe Backfire

[eastendjohn]

Having been told the donor car was a Mk2 I have been setting the timing at the prescribed 8* BTDC. A recently acquired manual for the 420G triple carb engine, that is actually fitted, I discover that the 4.2 420G with a compression ratio of 8.1 and triple SU HD8 carbs should have timing set to 9* BTDC. Could this be the remedy to my inability to set a steady idle speed and horrendous backfire upon increasing revs? I was begging to think it could be the fuel pump not delivering. This would have prompted the question how to test a fuel pump efficiency. I hope though the latter question will now not arise though the knowledge would be useful if there is anyone can oblige please.

[eastendjohn]

Following discussion with Anthony of Autotune (Rushton)Ltd I double checked all possible air leaks on the inlet Carb side plus fitted the air filters and perfect firing. Off up the road for my first drive with the biggest smile. Thanks for the support.

[steve_m]

Hope it goes ok!