Stag V8 Engine - Detonation on over-run
Posted By : David Balfour, 20-Jan-2004, 00:30am
Hi Angus,
It's not much help I know, but our Stag does this too. The sound isn't particularly pronounced, but there is a gentle detonation on over run as you say. This happened both before the engine was completely overhauled and after, so we never did anything about it.
It's an interesting idea about manifold leaks. Although I haven't tried it, I expect if water was poured onto the areas where the inlet manifold meets the head then any leaks would be shown as bubbles. In our car, often the carbs' pedestal comes loose and this throws the mixture off.
David
'77 Tahiti Blue Stag
It's not much help I know, but our Stag does this too. The sound isn't particularly pronounced, but there is a gentle detonation on over run as you say. This happened both before the engine was completely overhauled and after, so we never did anything about it.
It's an interesting idea about manifold leaks. Although I haven't tried it, I expect if water was poured onto the areas where the inlet manifold meets the head then any leaks would be shown as bubbles. In our car, often the carbs' pedestal comes loose and this throws the mixture off.
David
'77 Tahiti Blue Stag
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Stag V8 Engine - Detonation on over-run
Posted By : Nigel Gibbins, 20-Jan-2004, 10:24am
David,
The usual way of checking for manifold leaks would be to spray a mist of water over the joints and listen for an engine change (revs). I would generally avoid using an aerosol as with some cars (eg Spitfire etc) this would also cover the exhaust which could be hot enough to ignite the vapours. (not such a problem in the Stag though).
If you were to pour water onto the manifold you would be unlikely to see bubbles as the manifold is sucking the water in rather than blowing it out.
For the record, my GT6 does this too and I don't think it's a problem. What I think is happening is - as the throttle is shut, there isn't a proper mixture to burn so, if you have enough overlap the piston will suck some fumes back in an try to ignite it. So what you are hearing is the exhaust gases being 'messed' with - a kind of 'crackling'. Race cars do this a lot as they have stacks and stack of overlap.
NiG
*talking off the top of my head here*-
Stag V8 Engine - Detonation on over-run
Posted By : Daniel James, 24-Sep-2004, 08:56am
sounds quite cool actually....what's the best way of getting my car to do this?
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