V8 EFI timing

[jensencars]

Hi,
After major eng problems eng not starting (see previous thread) eng now runs but I am having trouble setting it up book says 1degree before or 6 degrees before depending on lucas distributor number, I am running a powerspark dizzy due to lucas unit being worn out,
At 1 degree running stationary it's flat on rev up and coughs back at 6 degrees it's better but still seems flat,( seems to run very happy around 25 degrees before whilst stationary as mentioned by someone before, ) anyway at either 1 degree or 6 degrees before if you open throttle slowly it revs up quite nicely but on a fast opening as said it's flat, have checked throttle butterfly, throttle pot with meter on millivolts and it reads within tolerance.

Any one have any ideas? Also any idea what sort of vacuum hg I should be getting out of dizzy vacuum advance pipe
Thanks all....

[Boosted LS1]

Have you tried 10-12 degrees static advance, vac pipe disconnected. I had an engine that loved more but I was worried it would kick back and go backwards.

With a mild cam I'd expect 19 hg at idle or even a bit more. Been yonks since I've looked at this sort of thing.

[KKson]

Powerspark dissy ....... I had problems with the new one I bought. If I set the timing correctly then engine pinked like a silly bugger. Advance weights on the dissy were just not suitable. Only option on mine was to reset ignition from 8 degrees BTDC back to 0 degrees then it ran okay. I ditched the new Powerspark unit and got a good second hand original item and normal service was resumed. When i spoke to Powerspark about it they suggested "tack welding" the weights so they couldn't advance too far. You can guess my thoughts on that butchering option.

[stevoj]

With todays fuels and even with the correct dizzy, i found it better to do it the old fashioned way and advance it until it pinks on decent acceleration (on the road of course), then knock it back slightly. Or you take the expensive route of a rolling road, not much good though if it is a useless dizzy.

[Boosted LS1]

OP, are you able to use a Mallory Unilite, it's optical? You can use a simple tool to set the maximum centrifugal advance and a spring set to set the rate of advance. I never needed to use the spring kit. It was a really nice dizzy. Way nicer then the old fashioned twin point things.

[adam quantrill]

Start with vacuum disconnected. (Plug the port)

Check the mechanical advance as you increase the revs slowly up through ~2500. I forget the figures but you should see 15? degrees as it get to the maximum.

Next run at idle, and suck on the vacuum pipe. You should get at least 6 degrees of advance.

The dizzy should add these two together, but with wide open throttle there will be negligible vacuum of course, it's probably your mechanical advance that's the culprit.

I had a dizzy where the weights had frozen, and had exactly the same problems, the guy who had sold the car set the timing to 12 degrees BTDC and it ran, but not great. As soon as I swapped the dizzy over it really revved well. I then soaked my original dizzy in an oil bath for a few months and the weights freed up.

Here's the irony, as soon as I had done this, I read about locking the advance weights up on purpose, and using an electronic advance system instead, which is supposed to be much better, but by then I had fixed my spare dizzy!

[SuperApeInGoodShape]

You need to know how much mechanical advance your powerspark dizzy actually has.

For a 3.5 in a heavy RR you don't want to exceed more than ~34 degrees total (forgetting about Vac advance for now)

34ish minus your mech advance gives you your idle advance figure.

Genuine Rover/Lucas dizzies came in flavours from 14 to 28 degrees mech advance, no idea what the powerspark is though.

[mrzigazaga]

stevoj said:

With todays fuels and even with the correct dizzy, i found it better to do it the old fashioned way and advance it until it pinks on decent acceleration (on the road of course), then knock it back slightly. Or you take the expensive route of a rolling road, not much good though if it is a useless dizzy.

+1

Are you actually road testing it or is this all stationery?...Also didnt the powerspark units have the vacuum diaphragm in a different position that restricts the adjustment...and a different curve?

If it were me I would try to get the old one rebuilt....Im sure someone bought a new pick-up a while back and did just that?

[SLB]

stevoj said:

With todays fuels and even with the correct dizzy, i found it better to do it the old fashioned way and advance it until it pinks on decent acceleration (on the road of course), then knock it back slightly.

Mine felt a bit flat, just advanced it a tad so now when in hot weather it pinks on hard acceleration which is a sign I have to put the super unleaded in - it then doesn't pink at all. I assume it must be about right.

[mrzigazaga]

SLB said:

stevoj said:

With todays fuels and even with the correct dizzy, i found it better to do it the old fashioned way and advance it until it pinks on decent acceleration (on the road of course), then knock it back slightly.

Mine felt a bit flat, just advanced it a tad so now when in hot weather it pinks on hard acceleration which is a sign I have to put the super unleaded in - it then doesn't pink at all. I assume it must be about right.

My 350i hates unleaded ...pinks like a dog and will only run on super unleaded 98ron or higher...V-power etc...my static timing is 4 degrees BTDC...any higher then it rattles like a rattle snake, initially I thought cam but its still pushing just over 184bhp, which is not too shabby for a 30 year old car..there was some engine work done in 2006 but it doesn't say what, hopefully it was a cam...however I havent noticed an unusually high fuel consumption, idle is smooth and engine still has good power...oil pressure is also spot on.

I know that the timing marks can actually be out by as much as 20 degrees as this was apparently contained in a bulletin that RR sent out to its dealerships/service centres.

I think as a rule 9-10 degrees base base idle but can be retarded to between 4-6...Also the amount of added ethanol in modern fuels can have a deciding factor.

[Sardonicus]

Concentrate on the all in total advance figure rather than idle figures, we don't drive around at idle engine speeds , advance pipe disconnected when checking of course, but this will not affect total advance figure with engine under load or big throttle etc