Ignition Timing

Hi all,

Does anyone know how far before TDC (BTDC) the dynamic timing at tickover speed needs to be set? IOW, where should I paint me white dot on the crankshaft pulley gradations prior to breaking out the timing light? This is the normally aspirated 3.5 litre V8 with reluctor ring ignition (in case that matters.)

Cheers,
LL

Landlover99 said:

Hi all,

Does anyone know how far before TDC (BTDC) the dynamic timing at tickover speed needs to be set? IOW, where should I paint me white dot on the crankshaft pulley gradations prior to breaking out the timing light? This is the normally aspirated 3.5 litre V8 with reluctor ring ignition (in case that matters.)

Cheers,
LL

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Model year?
I don't put too much faith in timing lights as they are only a guide to the manuf. settings back when the engine was built. The readings don't take into account the years of wear 'n tear or the grade of petrol you are using.

I've only ever had (4) of the EFI versions but I would start at TDC & with the dizzy clamp just nipped up give the car a good run to get it properly warm, then see how far advanced you can set the timing without inducing pinking.

norseman said:

Model year?
I don't put too much faith in timing lights as they are only a guide to the manuf. settings back when the engine was built. The readings don't take into account the years of wear 'n tear or the grade of petrol you are using.

I've only ever had (4) of the EFI versions but I would start at TDC & with the dizzy clamp just nipped up give the car a good run to get it properly warm, then see how far advanced you can set the timing without inducing pinking.

Click to expand...

Er's a 1989. Advance until it pinks and then back it off 'a bit' is a novel idea to me. My rough and ready approach before I got a light was to twist the dizzy back and forth to establish where the engine was struggling in both directions, then set it right in the middle of those two extremes. But as I say, I do have light now - although if I'd known better I'd have got one with a tacho built-in.

Landlover99 said:

Er's a 1989. Advance until it pinks and then back it off 'a bit' is a novel idea to me. My rough and ready approach before I got a light was to twist the dizzy back and forth to establish where the engine was struggling in both directions, then set it right in the middle of those two extremes. But as I say, I do have light now - although if I'd known better I'd have got one with a tacho built-in.

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'89 .. the last of the 3.5's then.
Unusual to have carbs (assuming that's what you mean by the term naturally aspirated) as EFI was introduced in Oct '85, though carb variants were still available until the 3.9 was introduced near the end of that year.

norseman said:

'89 .. the last of the 3.5's then.
Unusual to have carbs (assuming that's what you mean by the term naturally aspirated) as EFI was introduced in Oct '85, though carb variants were still available until the 3.9 was introduced near the end of that year.

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Yeah, it's got the twin SU carbs. I've no reason to suspect it's not the original engine - no reason at all - but I suppose I ought to thoroughly check to be sure.

I'd suggest putting a mark at 8° BTDC and disconnect the vacuum hose to the distributor.
Depending on the stretch in your timing chain you could advance it a bit more than that.
It's easy enough to hear knock in Rover V8's. The timing marks on the front pulleys were never the most accurate from the factory anyway.

Landlover99 said:

Yeah, it's got the twin SU carbs. I've no reason to suspect it's not the original engine - no reason at all - but I suppose I ought to thoroughly check to be sure.

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Just read literature produced by Rimmer Bros. who claim the last of the RR carb. variants was the end of 1986
Your engine # should reveal more info.

I guess all old chains have some stretch to them, but this one certainly doesn't sound noisy. I've read a lot of instructions from various sources about disconnecting the vacuum hose, but I noticed today in the Haynes manual for the Range Rover with the 3.5 engine (the only manual I have which covers this same engine) it states to set the timing mark at 6' BTDC with the vacuum hose *attached* and I've never seen that advice anywhere before. I'd like to think it doesn't matter at tick-over speed anyway. The other thing that's often said is to cap open end-off, but they don't say whether they mean the end of the hose or the end of the diaphragm thing it pushes onto. I'm guessing they mean the end of the hose as I can't see the point of blocking the advance unit off to outside air.
Knowing the engine number would be very advantageous, but the lump's not too keen to disclose it! I can't find any number visible from the under the bonnet, anyway.