[Hottarod]

I think there was something about the design of VW air cooled engines that also liked lead to help seal up a new engine and cool the valves as well. The cylinders just slip fit into the heads and there is no o-ring or gasket to seal that. It depends on build up from combustion to make those areas seal once you start up the engine and run it for a while. I built my first air cooled VW engine and it was quite an experience. That is the oddest engine design I have ever contemplated but it apparently works. I have all the parts to put a 10 psi turbo on it. It should do well in my little street buggy.

One advantage my buggy engine as well as my 289 have is that I'm running quality, 1 piece stainless valves and phosphor bronze guides. After reading all these posts I'm more confused than I was before, LOL. Would a mix of 1 to 1 or 2 to 1 93 pump gas to LL100 hurt my engines or would it be fine to run?

 

[JimNolan]

One of the things people confuse with Premium gas or high octane gas is the words used to sell it. 80 octane gas is better than 100 octane gas when it comes to being volital. If you replaced the word premium with the word junk, it would make more sense. The higher the octane the more junk it has in it to keep it from exploding. That junk gets on your valve stems and spark plugs and will eventually causes problems. It's the junk that stops up catalitic converters. Junk, Junk, Junk.
You need this junk to keep a high compression engine from exploding the gas too soon. I would suggest to anyone with a high compression engine to try to use the minimum amount of junk required to keep his engine from pre-detination ( pinging ). It's junk guys, pure and simple. If they could have got dirt to mix with the gas they'd have used dirt to make super dupper high octane premium racing fuel. Jim PS. Hottarod, to make a pre-determination on what octane you'll need to run in your car you need to know the DCR (dynamic compression ratio). Standard compression ration won't factor in your valve opening and closing. You need this to determine what octane will be required. I've seen a couple of graphs on the web that depict octane rating vs. DCR. You need to figure that first. If you are just bound and determined you want to use 100LL Avgas go get some and use it straight up. Cars will run just fine with more octane than what's needed, just not as long. I've used thousands of gallons of 100LL and I've overhauled my engine at a cost of $20,000 dollars, had broken valves, cleaned spark plugs and done God knows how many leakdown tests twice because of pieces of junk caught between the valve and seat. You can believe me or some guy that knew a guy that had a brother that used 100LL and just loved it and didn't cause any problems whatsoever.

 

[n2omike]

I think there was something about the design of VW air cooled engines that also liked lead to help seal up a new engine and cool the valves as well. The cylinders just slip fit into the heads and there is no o-ring or gasket to seal that. It depends on build up from combustion to make those areas seal once you start up the engine and run it for a while. I built my first air cooled VW engine and it was quite an experience. That is the oddest engine design I have ever contemplated but it apparently works. I have all the parts to put a 10 psi turbo on it. It should do well in my little street buggy.

One advantage my buggy engine as well as my 289 have is that I'm running quality, 1 piece stainless valves and phosphor bronze guides. After reading all these posts I'm more confused than I was before, LOL. Would a mix of 1 to 1 or 2 to 1 93 pump gas to LL100 hurt my engines or would it be fine to run?

Your engine isn't high compression, so it will probably run just fine on straight 93. But, if you want some insurance, adding 1 part Av-Gas to 1,2,3 or even 4 parts pump gas... and you should be fine.

If you drove the car on straight Av-Gas every day at a constant low rpm load, after a few thousand hours, you may have to do some decarbonizing. But, that's not how you run it. Plus, you'll be running it mixed, and it's not like you're running it with constant use for 200 miles every day. I've run plenty of it, no problem. It's the best, most cost effective octane booster you're going to find.

Good Luck!

 

[tcbpdb]

Well, I have a 1970 mach 1 with the 428CJ engine and because the engine doesn't have hardened valve seats and runs 11-1 compression this is what I use most of the time, 100LL AVGAS. It doesn't have a negative effect on the engine they way it operates at all, but does give it that peppy throttle response when mashing it to the floor. And having it in the tank and carburetor it will not degrade the seals or turn into varnish over time. If I'm out cruising with it and it gets low on gas I will stop and put enough unleaded premium just to get me home, but will mix in avgas with what's left and then make a trip to the airport to fill gas cans up. There is also Turbo Blue race gas which is almost twice the price of Avgas and have been told by multiple people that it's the same product as Avgas. They are both blue in color as well.