Timing on a V8

[Spearos]

Hi all,

Whilst trying to get to the bottom of another problem on my 90, it was suggested to check the timing. That problem was down to something else but I would still like to check/adjust the timing anyway, trouble is all the info I have found seems to be varied. Please forgive my stupidity, it's all new to me!

First question is, in the photo, is the small lug on the block and the groove in the crank pulley the timing marks? If so would the groove be TDC?

Second question, what should the timing be set at? It's a 1987 3.5l engine with SU carbs. It also has an LPG conversion, I run it on LPG about 80% of the time.

Cheers,

Mark

[ThreeSheds]

First question is, in the photo, is the small lug on the block and the groove in the crank pulley the timing marks? If so would the groove be TDC?

No - the groove is not the timing mark on the pulley, and the pointer can only be seen from above by peering down at the pulley while leaning over the radiator and fan - which makes it interesting if you are trying to get a weak strobe light on it!

At the centre, just above the pulley and at 12 o'clock there should be a thin metal plate mounted on the block which points forward over the harmonic balancer (the fat disc on the back of the pulley stack). On said harmonic balance there are some timing marks stamped in. They are not too easy to see - I usually rub the dirt/corrosion off with a wire brush and then paint them with Tippex. They will say something like:

AFTER | | | TDC | | | BEFORE

and will show 15, 10 and 5 degrees either side and TDC

Second question, what should the timing be set at? It's a 1987 3.5l engine with SU carbs. It also has an LPG conversion, I run it on LPG about 80% of the time.

The conventional wisdom appears to be to start of with it set per the book, and then advance it a little at a time, testing it on petrol by pulling hard at low revs and listening for pinking. When you detect it, back off the timing a little. I would advise that you seek assistance with this though, since it is entirely possible to damage the engine if you get it wrong. Once you have set it like this it should be about the best you can do for the LPG with the standard dizzy.

Rog

[Spearos]

Spot on Rog, many thanks for that.

Ok, another question... Pinking, I understand what it is but I don't think I'd know it if I heard it. What does it sound like and can it only be detected by ear?

Mark

[Hybrid_From_Hell]

Some one tapping a spoon hard on your rocker cover really quickly as you accelerate

AND - before you CHANGE to timing check and write down what it is now

There are a range of timings on V8s, esp Carb V8s in 90s, is your a Pulsair Model V8,

and what is the number written on the dizzy, ?

do you have one or 2 pipes going to the vacumn advance ? 2 = pulsair and if so the timing on these is COMPLETELY different to normal V8s

Nige

[Spearos]

Cheers Nige.

When you say write it down how'd you mean? Also, where would the number be on the dizzy? I'll have a look tomorrow and get back to you.

Mark

[Hybrid_From_Hell]

Cheers Nige.

When you say write it down how'd you mean? Also, where would the number be on the dizzy? I'll have a look tomorrow and get back to you.

Mark

There is either a sticker of a number embossed into the dizzy

What I mean is get a timing light and see what it is saying now before you alter it, then if it goes awry you can reset it to what it is now ?

Nige

[Spearos]

I see Nige, thank you for your patience

[Landowner]

There are a range of timings on V8s, esp Carb V8s in 90s, is your a Pulsair Model V8,

and what is the number written on the dizzy, ?

do you have one or 2 pipes going to the vacumn advance ? 2 = pulsair and if so the timing on these is COMPLETELY different to normal V8s

Nige

Mine has two pipes , what is the second pipe for?

I advanced mine untill it pinked then backed off slightly which was OK for petrol but had to give it about 5 to 8 deg (guess) more advance for gas, so I carried a 15mm spanner and altered it to my tipex marks accordingly when changing from petrol to gas or vice versa.

Will do more experiments when I get back on the road.