Pinking

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Firstly I'm not a retarded gibbon, but I must be a bit of a **** head for spending so much time on a Land Rover Petrol Engine. However, it's what I've got to play with and play with it I will...

It's advancing as per spec for a 45D I've drawn the graphs. I'm not arguing but all your saying is ooo baad but not saying _why_ (are landy pistons particularly soft?). From Wikipedia: (similar sentences in many of the the old engine and tuning books I've read) "Effects of engine knocking range from inconsequential to completely destructive." I know that running a motor bike at 16000rpm over advanced by a handfull of degrees at a race meeting will feck it up big time but a slight pinking at 2500 rpm that goes away at higher rpm is not the same...

I've already read the (self contradicting) hand books but the books are for timing a 8:1 or 7:1 head running on two or three star petrol with a carb that runs very rich so not a huge lot of help as I'm not running the engine like that. According to them I should be a few degrees ATDC in which case it would be quicker to walk.

The advance "curve" on a standard Lucas dissy is a pretty rough approximation of what is perfect. Two weights on quite rough pivots and held by two springs and a vacuum diaphram is never going to set the timing perfectly at all rpms and loads...thats why people spend time tuning. Again the mixture at different RPMs/loads makes a big difference. I've already swapped my dissy once cos the copy one I'd bought had crappy little weights in it and didn't advance properly and topped out at about 3000rpm. Like I said I've checked the dissy and its well within spec but spec is not necessarily _best_....
 
dominicbeesley said:
Firstly I'm not a retarded gibbon, but I must be a bit of a **** head for spending so much time on a Land Rover Petrol Engine. However, it's what I've got to play with and play with it I will...

It's advancing as per spec for a 45D I've drawn the graphs. I'm not arguing but all your saying is ooo baad but not saying _why_ (are landy pistons particularly soft?). From Wikipedia: (similar sentences in many of the the old engine and tuning books I've read) "Effects of engine knocking range from inconsequential to completely destructive." I know that running a motor bike at 16000rpm over advanced by a handfull of degrees at a race meeting will feck it up big time but a slight pinking at 2500 rpm that goes away at higher rpm is not the same...

I've already read the (self contradicting) hand books but the books are for timing a 8:1 or 7:1 head running on two or three star petrol with a carb that runs very rich so not a huge lot of help as I'm not running the engine like that. According to them I should be a few degrees ATDC in which case it would be quicker to walk.

The advance "curve" on a standard Lucas dissy is a pretty rough approximation of what is perfect. Two weights on quite rough pivots and held by two springs and a vacuum diaphram is never going to set the timing perfectly at all rpms and loads...thats why people spend time tuning. Again the mixture at different RPMs/loads makes a big difference. I've already swapped my dissy once cos the copy one I'd bought had crappy little weights in it and didn't advance properly and topped out at about 3000rpm. Like I said I've checked the dissy and its well within spec but spec is not necessarily _best_....
Click to expand...

aluminum pistons will melt, and valves will burn and crack valve seats. Are your spark plugs the correct heat range?

And did you read a poorly functioning coolant system can cause spark knock as well as poor quality petrol
 
Last edited:
dominicbeesley said:
Its hard to tell where the pinking stops (due to all the other noises and slight leak in exhaust manifold gasket) it just gradually gets less - it's never been _bad_. I just pulled the plugs and couldn't see any bits of metal flakes...I think I'll leave it at 12 degrees until I next fill up just been for another quick blast and if it is still pinking its not loud.

Thanks lads for all the replies and I'll post back when I get a hole in my piston!
Click to expand...

Make sure the little springs are tight in the dizzy, if not, and they have worn little grooves in the pin that they sit on then bend the pin to comensate. This will hold back the advance a little and may be all you need to stop it pinking at low rpm.
Could try bending the pin on the softer of the two springs to hold it back a bit or fit a stronger spring from another dizzy, then you can have your advance further up and she'll start better as well.:)
 
Thanks for the helpful (but answering a different question) answers. BTW: loose springs will cause _too much_ advance at lower revs the springs are to hold it back and reduce the advance as rpms increase

There's nothing wrong with the distributor I was just trying to have an informed debate about how far it can be advanced before it causes damage...never mind...
 
It doesn't really matter if you hole a piston if you have the time and money to fix it afterwards, its not a priceless performance motorafter all. So give it a go if it suits. If its purely an experiment then just make sure you report back what happens even if it does end in tears and your a bit embarrassed!:eek:
 
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