# Engine knock...



## PisnNapalm (Aug 28, 2010)

When I first took possession of the car the engine knocked like crazy under hard acceleration. The previous owner was running 87 unleaded in it. (Yeah I know... He was a dipstick.)

After two fillups of premium unleaded and octane booster in each tank full, the knock seems to have disappeared. I eased on the accelerator yesterday while carefully listening for the knock to start. It didn't happen. So... I floored it for the first time.

It bogged down for a bit and then took off like a raped ape. :willy: (The carb really needs alot of work, but it did take off... eventually.)

I filled up with Sunoco 93 and then added STP booster to each tank full. 

Have I found the magical fuel combination? What fuel do you all run in your stock engined GTO's? (Mine is a '67 with a 400 in it.)

Thanks for your replies.

PN


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## geeteeohguy (Feb 2, 2008)

Highest octane in CA is 91. My '67 will not run on it. I had to change the heads to lower the compression. For my '65, I run octane booster. Haven't been able to get decent fuel out here since about 1991. It's terrible. You're lucky you can get the 93....probably just enough octane to let you get away with it!


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## PisnNapalm (Aug 28, 2010)

Thanks for the reply. Why is 91 the highest you can get in Cali? I think we've got some stations that sell 94 here.

EDIT:: Also... does anyone know what the octane rating was for the "Premium" leaded gas back in the day?


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## Jerry64 (Apr 20, 2010)

I'm thinking it was around 98 with lead........JB.


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## ppurfield001 (Jan 21, 2008)

PisnNapalm said:


> Thanks for the reply. Why is 91 the highest you can get in Cali? I think we've got some stations that sell 94 here.
> 
> EDIT:: Also... does anyone know what the octane rating was for the "Premium" leaded gas back in the day?



Premium unleaded "back in the day" was 102-104, if I remember correctly. It also was about 30 cents per gallon. Enjoy your classic.


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## PisnNapalm (Aug 28, 2010)

Thanks guys.


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## geeteeohguy (Feb 2, 2008)

I remember my folks buying 100 octane Ethyl for 29 cents a gallon. That was here in Calif, and that was a loooong time ago!! I don't know why we can only get 91 octane in California....not only that, it's oxygenated, too. When the fuels were reformulated in the early '90's out here, before the MBTE fiasco, my cars got noticeably worse fuel mileage. Pinging is compounded out here too, by the hot, dry climate. I think if I lived in a more humid and cooler climate, I might be able to drive my '65 on straight pump 93 octane without any booster added. Sigh......


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## twinjracing (Aug 28, 2010)

E85 is the way to go from what i hear. I'm go to chang over next year on my race car. 
112oc.-108oc


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## PisnNapalm (Aug 28, 2010)

I thought I read that E85 gas was bad for rubber components in the carb? gaskets and such...


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## geeteeohguy (Feb 2, 2008)

Any alcohol blend fuel will promote rust in fuel lines and non-stainless metal parts. It absorbs water. You will also need to re-jet for a richer mixture. Those who run alky or e85 know the tricks to get around any issues, though.


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## PisnNapalm (Aug 28, 2010)

A buddy of mine is an Amsoil distributor. I'm gonna talk to him about their octane booster.

AMSOIL - Series 2000 Octane Boost (AOB)

Seems a bit pricey, but if it does the job, I'm all for it.


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## ppurfield001 (Jan 21, 2008)

geeteeohguy said:


> I remember my folks buying 100 octane Ethyl for 29 cents a gallon. That was here in Calif, and that was a loooong time ago!! I don't know why we can only get 91 octane in California....not only that, it's oxygenated, too. When the fuels were reformulated in the early '90's out here, before the MBTE fiasco, my cars got noticeably worse fuel mileage. Pinging is compounded out here too, by the hot, dry climate. I think if I lived in a more humid and cooler climate, I might be able to drive my '65 on straight pump 93 octane without any booster added. Sigh......



That's why I refer to California as "The People's Republic of California." :lol:


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## twinjracing (Aug 28, 2010)

it dose have problems with rubber your carb has to be aiky based


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## Rukee (Feb 8, 2007)

PisnNapalm said:


> A buddy of mine is an Amsoil distributor. I'm gonna talk to him about their octane booster.
> 
> AMSOIL - Series 2000 Octane Boost (AOB)
> 
> Seems a bit pricey, but if it does the job, I'm all for it.


A 3 point increase doesn't sound that impressive.


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## PisnNapalm (Aug 28, 2010)

Rukee said:


> A 3 point increase doesn't sound that impressive.


A bottle of STP booster only gets you one point.... maybe.


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## Rukee (Feb 8, 2007)

PisnNapalm said:


> A bottle of STP booster only gets you one point.... maybe.


But adding a quarter to half a tank of 110+ race fuel will get you tons more.


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## PisnNapalm (Aug 28, 2010)

I've no idea where to buy race gas though. Maybe it's time I find out.


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## Rukee (Feb 8, 2007)

PisnNapalm said:


> I've no idea where to buy race gas though. Maybe it's time I find out.


Yes it is! Find any circle track in the area or drag strip, call'um and ask which stations in the area sell the race gas. :cheers


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