26 replies to this topic

[Edmonds87]

Hi just wondering if you guys can clear something up 4 me.

After finally gettin my rebuilt engine to run and drive as it should i now believe it is pinking.

Am i right in saying that pinking (in the easiest way of describing) sounds like a cricket chirping, usually occuring under engine load?

If this is correct ive tried retarding the ignition timing to stop the pinking however this hasn't solved the problem. All the way down to 4 degrees BTDC any more and the car doesn't want to run. Are there any other factors which could cause the pinking? Mixture adjustment?


I pulled the plugs out and the core noses are looking a tad brown is this normal??

 Plugs.JPG   1.56MB   14 downloads

[*DJH*]

Pinking (pre ignition) happens when there is a thick layer of coke (carbon) built up on the valves, head and piston crowns.
The only decent solution is to take the head off and de-coke the head, valves and crowns. (becareful not to scratch the bores)

[Edmonds87]

Have i diagnosed it correctly!? It sounds like a cricket chirping (sorry for the dodgy description) which continues under load, after about half throttle!? This is definatly pinking right? and not a blow from somewhere or vibration from the engine running or reaching a certain revs?

What do you make of the plugs?

Edited by Edmonds87, 17 July 2007 - 08:11 PM.

[*DJH*]

Have i diagnosed it correctly!? It sounds like a cricket chirping (sorry for the dodgy description) which continues under load, after about half throttle!? This is definatly pinking right? and not a blow from somewhere or vibration from the engine running or reaching a certain revs?

What do you make of the plugs?

Yes that is pinking. and the plugs have 'normal' colouring.

[Edmonds87]

Great thanks for that!

I have looked through the spark plug holes at the piston crowns and they do look a tad on the black side. Is there an additive i can add to the engine (something by redex or something) that will get rid of the carbon on the crowns, as the engine has only been driven for about 50 miles since the rebuild and i would like to avoid taking the head off if at all possible.

[dklawson]

Well... there is an additive but I can't tell you how to add it easily Water.

Years ago I had a Toyota whose head I shaved to bring the CR up to around 10.5:1 at the time that octane ratings were dropping and lead was being removed from gasoline. I added an inexpensive Spearco water injection system to the car to handle the pinging. It worked very well and when I took the cylinder head off two years later there was zero (0) carbon in the chambers or on the valves. The downside was, I went through two exhaust systems because I did a lot of city driving at the time.

There are other anecdotal stories of "things" to add to the combustion chamber to de-coke the head without removal but I'll let you Google them for yourself rather than promote urban-legends here.

EDIT: However, if you only have about 50 miles on a complete engine rebuild you shouldn't have much carbon build up at all... maybe just a little soot. You've retarded the timing to the point that the car is no fun. Perhaps you'll have to suffer with buying higher octane fuel from now on.

Edited by dklawson, 17 July 2007 - 08:37 PM.

[Edmonds87]

Rubbish! i topped the tank up with regular unleaded 2day just my luck! Isnt there an additive to raise the octane level of the fuel?

I shouldn't really run the car extensivley untill ive sorted out the pinking or it will do damage right?

Edited by Edmonds87, 17 July 2007 - 08:51 PM.

[Grayedout]

Whats the compression ratio of your engine ?

[Edmonds87]

Whats the compression ratio of your engine ?

I don't have the foggiest! the engine is a standard 1275 a+ 93 mayfair lump. It hasn't had a rebore only replaced rings and had a re hone. Would high compression cause or contribute to the pinking then?

[Silicon Skum]

High compression (say over 10.5 : 1) will probably have issues with normal Unleaded (95 RON) and would be better with super unleaded (97 - 98 RON) - especially if you have advanced the ignition at all. The increased RON rating (comaprable with the american Octane rating) means that the fuel is HARDER to burn, so reduces the chances of pre-ignition occouring.

Not sure if carbon is the cause of your ignition problems, BUT - if you want to try to use water as a decoke method, it's easy if your engine is on a carb.

ONLY DO THIS ON A WARMED UP ENGINE, NOT FROM COLD! :

Just remove the small vacuum line fron the dizzy vac advance, place into a milk bottle of water (more than enough to do the job), start the car and keep the revs at about 1500 - 2K rpm (the engine will try to bog down as the water enters the cylinders - DON'T let the engine stall) and continue untill ALL the water has been sucked up out of the bottle.

Note, you might NOT want the exhaust near any white sheets, the house, the neighbour's cat, / any objects, as the engine will flush all the soot out into the exhaust, and the carbon in the exhaust will ALSO be flushed out - and spray black carbon laden water EVERYWHERE !

IF you DO try this method (and it does work), first off - it's your OWN responsibility to do so, neither I nor TMF can be blamed if you blow something up. And secondly, If you do this - the engine MUST already be warm for it to work (the water flashes to STEAM - this removes the carbon) - do not try it on a cold engine (no carbon will be removed, the engine will probably stall and there could be a build up of water in the bores - which will NOT compress, and could lead to bent pistons and valves!) You have been warned.

Good luck!

SS

[Edmonds87]

Thanks for the advice SS. May try that if all else fails. Although sounds a bit daunting! Dont fancy screwin up my freshly built engine. Knowin my luck i will blow something up!

Thanks again!

[adr]

High compression (say over 10.5 : 1) will probably have issues with normal Unleaded (95 RON) and would be better with super unleaded (97 - 98 RON) - especially if you have advanced the ignition at all. The increased RON rating (comaprable with the american Octane rating) means that the fuel is HARDER to burn, so reduces the chances of pre-ignition occouring.

Not sure if carbon is the cause of your ignition problems, BUT - if you want to try to use water as a decoke method, it's easy if your engine is on a carb.

ONLY DO THIS ON A WARMED UP ENGINE, NOT FROM COLD! :

Just remove the small vacuum line fron the dizzy vac advance, place into a milk bottle of water (more than enough to do the job), start the car and keep the revs at about 1500 - 2K rpm (the engine will try to bog down as the water enters the cylinders - DON'T let the engine stall) and continue untill ALL the water has been sucked up out of the bottle.

Note, you might NOT want the exhaust near any white sheets, the house, the neighbour's cat, / any objects, as the engine will flush all the soot out into the exhaust, and the carbon in the exhaust will ALSO be flushed out - and spray black carbon laden water EVERYWHERE !

IF you DO try this method (and it does work), first off - it's your OWN responsibility to do so, neither I nor TMF can be blamed if you blow something up. And secondly, If you do this - the engine MUST already be warm for it to work (the water flashes to STEAM - this removes the carbon) - do not try it on a cold engine (no carbon will be removed, the engine will probably stall and there could be a build up of water in the bores - which will NOT compress, and could lead to bent pistons and valves!) You have been warned.

Good luck!

SS

never done this but sounds like a great method to clear all the C**p out the engine... if it's steam you need to do it would you not be safer boiling the kettle and using the hot water out the kettle to be sucked up???
just a thought like, as i say never done this or anything but thought having the water hoter may help the process along...

how long does this usually take to do to clear the engine out??

Edited by adr, 19 July 2007 - 11:48 PM.

[Se7enS1ns]

Well, you learn something new everyday, as they say! Ive never seen that done before, i like it!

[Silicon Skum]

never done this but sounds like a great method to clear all the C**p out the engine... if it's steam you need to do it would you not be safer boiling the kettle and using the hot water out the kettle to be sucked up???
just a thought like, as i say never done this or anything but thought having the water hoter may help the process along...

how long does this usually take to do to clear the engine out??

No, just cold water will be fine - the water is sucked up the vac advance pipe, which is connected to the intake manifold, and it is vaporised / tuned into a mist just as the petrol is, in the carb (so hot water would instantly cool down anyway). The fine droplets of water spray enter the hot cylinder along with the fuel, and during the burn of the fuel, is instantly turned to steam. The steam causes the carbon to swell and become porus, and durning the rest of the stroke the cylinder pressure drops quickly - which causes the steam trapped in the carbon to expand and loosen the carbon (it sort of explodes into carbon dust), which is then sucked out through the exhaust port (where the rest of the steam can continue to scrub carbon from the exhaust ports, manifold and exhaust system.

No actual liquid water enters the engine (or at least it should'nt) so there is very little risk if done correctly (I just gave a warning, that things *could* be a problem - worst case etc.)

It will only take about 3 mins to suck up the water and clean the engine (once the water is used up, the engine should be run for a little longer and reved lightly a couple of times to expell any water left in the system) then take it for a drive to help dry out the exhaust and remove any carbon left over. Don't forget to reconnect the vac pipe!

Another method would be to use a hand-pumped spray bottle (like used for kitchen cleaners, Windowlene etc.) into the mouth of the carb while on fast idle and controling the accelerator by hand, may be easier for some to do it this way.


This is not a new method to decoke engines, it's been used a LOOOOONG time, even heard of old time mechanics usings a garden hose with their thumb over the end to make a fine spray and aiming it straight into the carb while revving the hell out of the engine.....Somehow, I don't think I'll try that method.

SS

Edited by Silicon Skum, 20 July 2007 - 10:17 AM.

[not so mini dan]

So that method would theoretically work on any car with a vacuum advance system, yes?