gas
Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 15
From: Mobile Alabama
In regular pump gas, the higher the octane, the less "explosive" it is. So, with higher compression it could act like diesel and explode just from compression and no spark. Same for the pinging and detonation, it explodes before the spark plug ignites it or too quickly. You may need to just back off of your timing.
Last edited by 74modified; Jul 18, 2015 at 01:51 PM.
Thread Starter
Racer
Joined: Jul 2009
Posts: 350
Likes: 7
From: springstead wi
haven't heard that sound but I don't have any hills here to pull . when I lived in tn. 20 years ago and had my 308 gear and 750 double pumper I use to run blue fuel ( not all the time was a little pricey even back then ) which was either 105 or 108 octane cant remember which. that's when I came close to pegging the speedo hit 152 according to it and it still had more .
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Burning Brakes
Joined: Oct 2008
Posts: 1,037
Likes: 15
From: Mobile Alabama
Octane ratings are not indicators of the energy or power content of gasoline. Octane rating is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. If you have an engine with high compression, the higher octane will allow you to tune it to make more power. It is a waste of money to use higher octane if your engine doesn't need it - the fuel doesn't have more power- with the exception of some oxygenated race only fuels.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Read the spark plugs, paying particular attention to the white porcelain insulators (internal) for any fusing of tiny black or shinny specs or tiny spheres. Next step up the detonation scale is damaged insulators or even electrodes, then holing a piston and associated carnage. Best to read them immediately upon shutting down at the big end from a WOT 1/4 mile pass or a full dyno pull, but you don't want to do either if already seeing/hearing any signs beforehand. Plenty else to learn from reading them... HTH
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,172
From: Hermosa
You running 64 cc heads with .025 in the hole and a .021 or less head gasket? What cam do you have? Figure your DCR and CR accurately for an idea of what it needs. Aluminum or cast iron heads?
Thread Starter
Racer
Joined: Jul 2009
Posts: 350
Likes: 7
From: springstead wi
world sportsman 202/160 cast heads with angle plugs crane roller rockers .the one thing I cant find a record on is my cam . im pretty sure ( 25 years ago back then I had bought a 350 hp rebuild kit then after that I went to the 11 to 1 and one size up cam ) its a 488/ 50 something .for the heck of it I just checked gas mileage . running it pretty hard got 8