Griffith octane rating?
Discussion
My pre-cat pops and bangs on the over-run no matter what octane is in the car. Sometimes (like north of Ullapool) I could only find 95 and the car (or perhaps the ignorant driver) doesn’t seem to notice.
Are you sure it’s fuel/oil under the exhaust outlets? That’s not normal but spitting condensation (ie water) which can be sooty and a tiny bit oily out the back is normal for mine on starting. I think it’s caused by hot exhaust gases hitting the cold exhaust piping when you first start the car but others might correct.
Cheers,
Simon
Are you sure it’s fuel/oil under the exhaust outlets? That’s not normal but spitting condensation (ie water) which can be sooty and a tiny bit oily out the back is normal for mine on starting. I think it’s caused by hot exhaust gases hitting the cold exhaust piping when you first start the car but others might correct.
Cheers,
Simon
cavebloke said:
My pre-cat pops and bangs on the over-run no matter what octane is in the car. Sometimes (like north of Ullapool) I could only find 95 and the car (or perhaps the ignorant driver) doesn’t seem to notice.
Are you sure it’s fuel/oil under the exhaust outlets? That’s not normal but spitting condensation (ie water) which can be sooty and a tiny bit oily out the back is normal for mine on starting. I think it’s caused by hot exhaust gases hitting the cold exhaust piping when you first start the car but others might correct.
Cheers,
Simon
On reflection, I think you're right, sooty water it may be, looks like it, now you mention it.Are you sure it’s fuel/oil under the exhaust outlets? That’s not normal but spitting condensation (ie water) which can be sooty and a tiny bit oily out the back is normal for mine on starting. I think it’s caused by hot exhaust gases hitting the cold exhaust piping when you first start the car but others might correct.
Cheers,
Simon
The whole octane thing depends on how advanced the ignition timing is. Burning Higher octane fuel allows you to run slightly more advance without risking detonation, more advance produces more power.
Popping and banging on the overrun is not really related to the octane rating and usually indicates that the engine is far too lean at that point, so lean that the charge will not ignite under compression but it does when in the exhaust. Not convinced it is entirely desirable to have lots of small explosions in the exhaust system, or indeed to run the engine very lean.
Popping and banging on the overrun is not really related to the octane rating and usually indicates that the engine is far too lean at that point, so lean that the charge will not ignite under compression but it does when in the exhaust. Not convinced it is entirely desirable to have lots of small explosions in the exhaust system, or indeed to run the engine very lean.
Its been mentioned before but i'll bring it up again 500 engines have varied CR figures some being quite a bit higher than I would feel happier using with regular UL (well unless you want to retard the timing but then it will run s
t) not forgetting that pistons are a weakness in this engine (well they wasn't but they were modified) so I would be reluctant to take chances unless your engine builder says otherwise , you wont hear damaging detonation under power on these cars IMO 
relative to what we spend on these cars piece of mind gets my vote fuel wise
t) not forgetting that pistons are a weakness in this engine (well they wasn't but they were modified) so I would be reluctant to take chances unless your engine builder says otherwise , you wont hear damaging detonation under power on these cars IMO relative to what we spend on these cars piece of mind gets my vote fuel wise Edited by Sardonicus on Tuesday 10th July 10:18
griff59 said:
Thanks folks, I'm not getting any pinking at all, it's just a little bit of back-firing on the over run.
There's quite a bit of unburnt fuel/oil...? on the garage floor below the exhaust outlets when I start the car, but I guess that's normal?
I'm probably repeating what has already been said but the popping and banging is one of the 'charms' of a Griff, most do it. Popping and banging is very different from 'pinking'.There's quite a bit of unburnt fuel/oil...? on the garage floor below the exhaust outlets when I start the car, but I guess that's normal?
The blast of dirty water on start-up, mine does it as well.
I think its all down to a fairly old Buick engine being tuned to a level it was never designed for but having said that cars like the th F Type seem to have this popping and banging actually designed in.
I do run mine on the higher octane fuel but not too bothered whether it is 97 or 98.
Hope this give you reassurance.
Pete
Pete Mac said:
I'm probably repeating what has already been said but the popping and banging is one of the 'charms' of a Griff, most do it. Popping and banging is very different from 'pinking'.
The blast of dirty water on start-up, mine does it as well.
I think its all down to a fairly old Buick engine being tuned to a level it was never designed for but having said that cars like the th F Type seem to have this popping and banging actually designed in.
I do run mine on the higher octane fuel but not too bothered whether it is 97 or 98.
Hope this give you reassurance.
Pete
I agree, it is a bit of a charm, I'm not getting "any" pinking at all. I'm just going to stick to BP97 from my local...I mean garage...not pub...The blast of dirty water on start-up, mine does it as well.
I think its all down to a fairly old Buick engine being tuned to a level it was never designed for but having said that cars like the th F Type seem to have this popping and banging actually designed in.
I do run mine on the higher octane fuel but not too bothered whether it is 97 or 98.
Hope this give you reassurance.
Pete
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