3.5lt v8 timing.

Hello All !!
Can i pick you brains about timing set up on my 1987 90 V8,
During a bit of a nightmare waterpump replacement i had to remove
the distributor to aid the drilling out of a snapped waterpump bolt,
My query is ive got to check my ignition timing this weekend,
and although the manual says it should be 6 deg BTDC , i thought id
read somewhere that 4deg BTDC was better, just wondered if
you guys had any ideas whats best.

12 degrees BTDC at 800rpm idle with no vaccuum, is it not?

I think 6 degrees is most likely but the actual amount of advance depends on which engine it is - high or low compression. Are you running carbs or efi?

Normally the procedure for dynamic timing is set to TDC then adjust from there once the engine is warm.

My high comp EFi 3.5 is specced for 0 degrees, whereas a 3.9 is 6.

I used to set mine to around 12 degrees at idle, much better top end that way and slightly more eager idle.

Anywhere in between 0 and 12 at idle will be fine for you, choose the most you can without it pinking in any case...

Lengthy resurrection, but the rotation of the distributor tip help massively here to. 3.5efi flapper. Had to drop the revs at idle afterwards using the idle adjustment screw, but went from decidedly sluggish to borderline spritely! Many thanks.

From elsewhere:

''Its also worth noting that the best ignition timing in any given engine, is to achieve the most advance it can tolerate without pinking. ( Audible pre-ignition).

This is achieved by setting your V8 timing to about 4 deg. BTDC (assuming you've been through the distributor check list completely). Then tighten the distributor so that you can (with effort) still turn it by hand. ideally put a tip-ex mark or small scratch on the distributor body and engine block to record this spot.

Next road test the car and simulate high load by quickly shifting into a high gear or if Auto allow to change quickly up to 3rd or 4th Ideally you need to find a small hill or incline, now if you apply full throttle the engine should respond without pinking, find a safe place to pull over, open the bonnet and turn the distributor through a couple of degrees only, anticlockwise, this will add slightly more advance timing and if you do the same test, and repeat it until pinking is noticed you will be very close to your absolute best timing criteria

So now all you need to do is turn the distributor clockwise by the same amount by an amount to counteract the last adjust, retest for the absence of pinking and that the job done, you will have just achieved the best maximum timing position for your car''

When you've done it, go home, get the timing light out & record the point on the crank pulley that the pointer aligns with.

interestingly the handbook and haynes have different views on advance. Handbook is 3 degrees BTDC, Haynes is 1 degree static and dynamic. Any other offers?

Ratten said:

interestingly the handbook and haynes have different views on advance. Handbook is 3 degrees BTDC, Haynes is 1 degree static and dynamic. Any other offers?

Click to expand...

First make sure your dizzy or electric sparko maker is set in the right place, the a bulb to fine tune, not sure how that'll work with electric sparko tho ?

it was set at static zero TDC (engine moved while distrib was out because you can't adjust the PS pump without taking out the distrib....and the spec belt for PS was too short..long, long story) which made it very lethargic even though haynes was talkinga about +- 1 degree this would appear to be bollocks. So have rotated anticlockwise and made it a lot more sprightly without any pinnging noises. Will check with lamp later, but there appears to be no consensus on where the numbers should lie!

Land Rover factory workshop manual for mine - 1986 3.5EFi flapper auto - says TDC+/-1deg at 600 rpm.
For carb models it gives 6deg at 650-750 rpm (vacuum pipe disconnected)
Mine set up as per my other post above it's just over 6 deg BTDC at 600 rpm.

Ok, so lamped it yesterday and we're running 12 at idle (600 rpm) rising to 22 -23. Seems to be within the general parameters discussed across tinternet. There's some TVR discussion here https://www.pistonheads.com/gassing/topic.asp?t=828064 that's quite interesting and covers some RR material.

It looks like we could go further, but this isn't a racing car! I usually stick the posh juice in it (lot cheaper these days!) so hopefully risk is reduced.

Ratae's advice in post #6 is (in my humble opinion) is the best method. My '87 RRC auto is TDC +/- 1 degree & despite a low mileage of 59k from new won't tolerate a greater advance without pinking on hard acceleration, up even a slight hill.
What you have to remember is (1) the timing marks may not be dead accurate from the factory & (2) wear/tear of the engine over the years will mean experimentation will tune the timing to the engine's needs. Also 'marketing' played a greater part in LR's fuel octane recommendation than any actual change in engine spec. over the years.
Back in the 'seventies LR used to say that the Series 3 would run on 2 star fuel, because the company was competing with a Japanese invasion of 4x4's that DID run on the cheaper fuel. Following a plethora of piston melt -downs (even amongst MOD fleets) LR had to admit that 3 star was the minimum octane required