Ignition timing

[ntel]

I've recently noticed that the engines "pinks" slightly sometimes. I only use Optimax and no the manifolds arn't leaking.

Just to tide me over until the next service, I am thinking of retarding the ignition timing slightly. Is this done simply by rotating the distributor. If so which way do I turn it.

Thanks in advance

Dave C

[chimtvr]

if you dont know what you are doing on this particular one get a proffesional to do it

[Ribol]

IIRC the rotor arm turns clockwise(worth checking) in which case you would turn dizzy in the same direction to retard it.

We are talking small movements here

[tahiti450]

Be sure that the vacuum advance capsule hasn't come loose on the distributor boby (2 small Torx screws). Its a common problem which mine had and took all of 2 minutes to rectify. If the pinking is 'occassional' and 'slight' it may not be worth doing anything, any retardation of timing will bring power loss (unless it is genuinely over advanced which is unlikely). I know you said the manifold isnt leaking (presumably you mean inlet), but check that none of the vacuum hoses (brake servo / distributor) are loose or perforated, as any leaning up of the mixture by air bypassing the air flow meter may cause problems. Plug deposits will also promote pinking so make sure they are clean / new (and - importantly - the correct heat value).

[GreenV8S]

chimtvr said:

if you dont know what you are doing on this particular one get a proffesional to do it

Very quick and easy job to do right, but one slip and it can end in tears. Surprised that it is pinking in this weather using optimax though, wonder what is causing it? Tahiti's suggestion about the vac advance capsule is a good one, might also be worth disconnecting the vac line completely (sealing the port at the throttle body) in case the vac capsule has failed or the one way valve (if fitted) has become blocked.

>> Edited by GreenV8S on Friday 18th February 00:27

[taylormj4]

ntel said:

.....Thanks in advance Dave C

No pun intended?!

Matt

[ntel]

tahiti450 said:

Be sure that the vacuum advance capsule hasn't come loose on the distributor boby (2 small Torx screws). Its a common problem which mine had and took all of 2 minutes to rectify.

Absolutely bang on the money! The bloody thing is hanging off.I'll put it back on properly in the morning. In the mean time

The vac tube from the plenum to the vac advance module does not appear to have a non-return valve fitted to it but it is clear. Should it have a non return valve or are some different?



>> Edited by ntel on Saturday 19th February 07:20

[chim1974]

The non retun valve is in the vac advance module (or that end somewhere... To check all is well take the pipe off the plenum end and suck the air out of the pipe. If the vacumn is maintained it should be ok.

[GreenV8S]

It would (should) have had the valve fitted as standard. But they are routinely removed because of the trouble they can cause if they become blocked, or fitted back to front (which is easy to do deliberately or by mistake). If you don't have one, I'd say you're better off without it.

[tahiti450]

[quote=ntel]

Absolutely bang on the money! The bloody thing is hanging off.I'll put it back on properly in the morning. In the mean time

The vac tube from the plenum to the vac advance module does not appear to have a non-return valve fitted to it but it is clear. Should it have a non return valve or are some different?

Has it sorted it?

As regards the vac tube, my '99 450 doesnt appear to have a valve and I've no reason to think that it has been interfered with, certainly many installations (including early RV8s - pre SD1) dont have this. I wonder if the later cars have dispensed with this fitment? Incidentally a quick check on vac capsule function: remove manifold end of vac line and suck hard then (excuse the intimate details) whilst sucking put the tip of your tongue over the hole (to trap the vacuum). If the vacuum is retained and there is a small sucking in of air on removing the tongue then the diaphragm must be intact (or theres a blockage in the pipe of course). To be completely sure remove the distributor cap and watch for movement of the base plate as suction is applied and released. Takes all of a couple of minutes and requires no tools.

>> Edited by tahiti450 on Monday 21st February 18:45

>> Edited by tahiti450 on Monday 21st February 18:46

[ntel]

tahiti450 said:

[quote=ntel] Absolutely bang on the money! The bloody thing is hanging off.I'll put it back on properly in the morning. In the mean time The vac tube from the plenum to the vac advance module does not appear to have a non-return valve fitted to it but it is clear. Should it have a non return valve or are some different? Has it sorted it? As regards the vac tube, my '99 450 doesnt appear to have a valve and I've no reason to think that it has been interfered with, certainly many installations (including early RV8s - pre SD1) dont have this. I wonder if the later cars have dispensed with this fitment? Incidentally a quick check on vac capsule function: remove manifold end of vac line and suck hard then (excuse the intimate details) whilst sucking put the tip of your tongue over the hole (to trap the vacuum). If the vacuum is retained and there is a small sucking in of air on removing the tongue then the diaphragm must be intact (or theres a blockage in the pipe of course). To be completely sure remove the distributor cap and watch for movement of the base plate as suction is applied and released. Takes all of a couple of minutes and requires no tools. >> Edited by tahiti450 on Monday 21st February 18:45 >> Edited by tahiti450 on Monday 21st February 18:46

Yes mate, All sorted now. Followed your advise regarding checking the vacuumm advance unit and all seems OK.

Took the car out to the SYTVRCC meet on Sunday and it ran like a dream. I was amazed how nuch better it felt.

Once again, thank you for your input.

[red griff 500]

My '94 500 has the valve, but this is not a simple one way valve as it would serve no useful purpose at all. It allows a very slow bleed from the dissy to the plenum, and full flow in reverse i.e. from the plenum to the dissy. This means that the vacuum advance only actually advances the timing during steady state cruising conditions for economy reasons, but immediately removes the advance when you take your foot off the Go pedal.

My philosophy is, if it was fitted originally (and some later cars were not fitted with this, I believe) then leave it or replace it - do not remove it because the engine set-up was designed to include it.

Steve

[ntel]

red griff 500 said:

My '94 500 has the valve, but this is not a simple one way valve as it would serve no useful purpose at all. It allows a very slow bleed from the dissy to the plenum, and full flow in reverse i.e. from the plenum to the dissy. This means that the vacuum advance only actually advances the timing during steady state cruising conditions for economy reasons, but immediately removes the advance when you take your foot off the Go pedal. My philosophy is, if it was fitted originally (and some later cars were not fitted with this, I believe) then leave it or replace it - do not remove it because the engine set-up was designed to include it. Steve

Thanks RG500. On mine there is no evidence, at all, of a valve being fitted, nor does it appear that it has ever been modified. So, like you say, I will leave that well alone.

[tahiti450]

ntel said:

Yes mate, All sorted now. Took the car out to the SYTVRCC meet on Sunday and it ran like a dream. I was amazed how nuch better it felt. .

Brilliant, glad to have been of help

Incidentally, on the subject of vacuum advance systems; if you want a laugh, take a look at the one on the Jaguar V12 HE engine, truely arcane..... about 6 vacuum pipes, numerous manifold tappings, check-valves , electric valves, dump valve; quite amazing! I just love it, brilliant engine to look at too, like an oil refinery. The more complex the better I say.