Gasoline - 90 Octane, Ethanol Free (89), or additives, How to reduce valve knock Options

[dcecc1968]

We are having some Spring weather this week in Charlotte, NC (and no rain!) so I've been driving the 914 and noticed that after about 20 minutes of driving, the valves intermittently knock from "normal" to very loud for no apparent rhyme or reason.

Outside of the obvious that it may be time for a valve adjustment, I wondered what Gasoline grade folks are using.

What Petro are you using in your 914?

[bbrock]

At what compression should you start thinking about higher octane? More specifically, 8.0:1 compression?

Side question: Anyone know why they raised the octane of regular gas in high elevation states? Until a couple years ago, regular gas in Montana and surrounding states was 85, then a couple years ago, they suddenly raised it to 87. Emissions standards? I always thought it was better to run a little lower octane at altitude to compensate for lower atmospheric oxygen content. (IMG:style_emoticons/default/confused24.gif)

[Dave_Darling]

Side question: Anyone know why they raised the octane of regular gas in high elevation states? Until a couple years ago, regular gas in Montana and surrounding states was 85, then a couple years ago, they suddenly raised it to 87.

I'm betting it's cost. If they don't have to deal with making a separate grade of fuel for high-altitude states, it probably costs them less.



NOTE: These engines were not designed for leaded fuel. They have hardened valve seats from the factory, and the guides are a material that does not require lead for lubrication. If there are any Porsches that require leaded fuel, they would be fairly early 356 models. All others should be fine on unleaded fuel.

Heck, some of the 75-76 914s required unleaded gas because they ran catalytic converters.

--DD

[Mark Henry]

Side question: Anyone know why they raised the octane of regular gas in high elevation states? Until a couple years ago, regular gas in Montana and surrounding states was 85, then a couple years ago, they suddenly raised it to 87.

I'm betting it's cost. If they don't have to deal with making a separate grade of fuel for high-altitude states, it probably costs them less.



NOTE: These engines were not designed for leaded fuel. They have hardened valve seats from the factory, and the guides are a material that does not require lead for lubrication. If there are any Porsches that require leaded fuel, they would be fairly early 356 models. All others should be fine on unleaded fuel.

Heck, some of the 75-76 914s required unleaded gas because they ran catalytic converters.

--DD

(IMG:style_emoticons/default/agree.gif)
VW/Porsche only used steel seats, it's cast iron that needs lead.
Some shoddy rebuilders used cast iron seats and guides, a no-no for rebuilding our heads.