100 Octane Fuel

[mason_1958]

I have a 1969 S Code. The engine has 2000 miles on the rebuild (10.1)in 18 months the motor has started pinging under load when it warms up. I have retarded the timing 1.5 degrees from what the engine guy set it at 8 degrees. I was wondering if changing to 100 Octane would help I'm currently using 93 octane no ethonal. Would appreciate any thoughts on this.

 

[rbohm]

you can try 100 octane fuel, but is suspect that you have a hot spot in the combustion chamber that is causing your problems. try running something like seafoam through the engine and see if it cleans out some carbon deposits. you want to dribble it through the carb with the engine running at about 1500-2000 rpms. you may have to hold the throttle open a bit to keep that rpm level. run the whole bottle through and then get out on the freeway and blow out the carbon.

 

[mason_1958]

Thanks for the info I will give that a try before I try 100 octane.

 

[rbohm]

if you want to go even cheaper, take a clean 20oz coke bottle filled with water, and dribble that down the carb until its empty, then get out on the highway and blow the carbon out.

 

[mason_1958]

Hard to believe carbon would do that after 2500 miles interesting I will either the seafoam or the other thanks

 

[rbohm]

Hard to believe carbon would do that after 2500 miles interesting I will either the seafoam or the other thanks

not really. all it takes is a for a bit of carbon to stick up and create a hot spot, especially with 10:1 compression, to have a glowing ember act like a diesel glow plug.
heck it can happen even at 500 miles.

 

[barnett468]

are you saying it did not ping in the beginning but it pings now?

did you change anything from the beginning?

is your weather now noticeably hotter?

exactly under what condition does it ping?

pull your distributor vacuum line off and rev it to 2000 rpm and tell us what the timing is.

drive it with the vacuum line plugged and see what happens.

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