The V8 Owners Forum -

Ok, i have a rover v8 4.6 running a hotwire injection system and a different cam (john eales) and cloyes timing chain, trouble is if i set the timing to around 6 degrees it stalls when i back off the throttle, but if i advance it to about 14 it runs sweet..... Does this sound right or is it too far advanced ?

Mine's running about 12 degrees, the factory spec is a bit conservative. So long as it's not pinging under load it should be fine.

maximotorsport wrote:Ok, i have a rover v8 4.6 running a hotwire injection system and a different cam (john eales) and cloyes timing chain, trouble is if i set the timing to around 6 degrees it stalls when i back off the throttle, but if i advance it to about 14 it runs sweet..... Does this sound right or is it too far advanced ?

You'd be best to check the timing at full advance. With such a large variation at static, I'd be looking for a dizzy fault.

I am only going off the marks on the bottom pulley, would it be best to find tdc by taking the plugs out and lining it up manually?

I've heard of the marks being 'out' but dunno by how much - unless a non standard combination of front cover and pulley, etc.

RPI website says they have seen it out by as much as 20 degrees, i think mine is a tvr front as the alternator bracket is low so i can only fit the dizzy where the vacuum points to the front.

You can check the timing marks using the piston dead stop method, you can make a dead stop by modifying an old spark plug. I have seen the marks being a fair way out as standard. It can take 2 hours just to sort out the timing pointer if its out!

I run a programmable MSD ignition system which allows me to run any advance at any RPM. (I don't run a vac system because it does not suit my carb although it might be possible to run an MSD MAP sensor if I could be bothered)

I run my 4.6 with 8 degrees advance from 0-700 RPM. (The 'cranking' RPM)

The timing then ramps up to 16 degrees at 800 RPM and stays there until 1000 RPM (tickover RPM, 850 in my case)

The timing then advances to 28 degrees at 2700 RPM and stays at this figure until 4800 RPM.

From 4800 to 5000 RPM another 4 degrees are ramped in, I did this because I feel that the VE of the engine must be dropping like a stone above 5000 RPM therefore the cylinder pressure before the plug fires is also dropping.

34 degrees is maintained until 6000 RPM at which point the rev-limiter calls it a day.

You can see that with a bob weight dizzy you won't be able to do what I have done but you should still be able to run 12-14 at tickover and 28 all in around 2700-3000 RPM. My old bob weight dizzy ran these figures but I did have to modify it in order to get what I wanted.

AJMHO!