100-102 Octane??
Thread Starter
Instructor
Joined: Jan 2001
Posts: 227
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From: Las Vegas, NV
100-102 Octane??
Hi Guys,
I am looking to achieve the 100-102 octane recommend in my owner's manual for my '65 L76 (30-30 cam 11.1:1 compression) by mixing Sunoco 110 and 91 pump gas and I could use the help of someone who understands the fuel chemistry here. Can someone help me calcuate the right mixture of these two fuels to achieve my goal?
I know that:
1. Pump gas today is rated by the (R+M)/2 method (giving a lower rating than how fuel was measured in '65), and
2. Fuel does not mix linearly. (e.g. 50% 91 oct mixed with 50% 110 oct <> 100.5 oct)
3. I should be able to reach 100-102 octane on less than 50% racing fuel.
Any advice/knowledge here?
thx,
L76
I am looking to achieve the 100-102 octane recommend in my owner's manual for my '65 L76 (30-30 cam 11.1:1 compression) by mixing Sunoco 110 and 91 pump gas and I could use the help of someone who understands the fuel chemistry here. Can someone help me calcuate the right mixture of these two fuels to achieve my goal?
I know that:
1. Pump gas today is rated by the (R+M)/2 method (giving a lower rating than how fuel was measured in '65), and
2. Fuel does not mix linearly. (e.g. 50% 91 oct mixed with 50% 110 oct <> 100.5 oct)
3. I should be able to reach 100-102 octane on less than 50% racing fuel.
Any advice/knowledge here?
thx,
L76
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,262
Re: 100-102 Octane?? (L76)
The 100-102 rating is Research Octane Number, which is equivalent to about 95 PON. The pump premiums from the sixties were typically 98-100 RON and the "super premiums were 102-103 RON. The fact of the matter is that your engine will probably run without detonation on modern pump premium if you run the initial timing at the lower end of the 10-14 degree OE recommended range.
Your actual CR is more like 10.5:1 because the engine was assembled with two head gaskets, and the late closing inlet valve yields a dynamic CR of only about 8:1.
Just run pump premium and experiment around with how much initial timing you can run without significant detonation.
Duke
Your actual CR is more like 10.5:1 because the engine was assembled with two head gaskets, and the late closing inlet valve yields a dynamic CR of only about 8:1.
Just run pump premium and experiment around with how much initial timing you can run without significant detonation.
Duke
