Latest and greatest timing and deck height?

[kane]

... An interesting side note, with Fai fuel there is no Nitro. We usually don't use after run oil. If you disassemble one a week or even a month after the last one you don't find Rust. Completely coated with Castor on the inside. The only difference is the Nitro. You hear rumors about the alcohol evaporating out and leaving moisture if that was the case why don't the FAI
Motors rust like quarter midget and quickie Motors.

Our fuel has more than just Nitro... Some have color added, some have a mixture of synthetic oil and castor, as well as some other additives. What causes the rust? Not sure, but there is something that keeps it inside motor and absorbs it.

DK

[Wondo]

One of the byproducts of burnt nitromethane is nitric acid. Have you ever noticed after a flying session your hands seem to be dry and chapped. This is the spent fuel and oil etching your skin.
This may explain why the FAI aircraft engines that burn methanol do not rust.

[diggs_74]

Methanol is hygroscopic, meaning it absorbs water.. Once the methanol evaporates, all that's left is water.. It will pull water right out of the air.. As is mentioned above, the byproducts left over from the burnt nitro probably aids greatly in the steel parts rusting.. However, for rust to form , you need a low nobility metal (steel, the contact with aluminum aids in corrosion also "galvanic" ), an electrolytic path (the water and particulates pulled from the air by the hygroscopic action of the methanol and/or the byproducts from combustion), and oxygen.. Remove just one of those ingredients and no more rust..

[splatt]

Speaking of low nobility , how you doin, Lee? I wonder if the brass cone used at the front of the crank contributes to that corrosion in the croak of the crank, hence the need of a anti corrosion crank croak process to keep the front of the crank connected to the croak. On man, is it Friday yet? My process is full disassembly and wiping the crud from the croak and reassembly with power steering fluid as my preservation lubricate.

Lee, any Q-40's in the works?

[rocket]

Dumb question but, the case is full of raw fuel not burnt fuel. How would the Nitro conversion to acid affect if it never sees it.

[diggs_74]

Doing good Jess.. Actually, the Aluminum case the steel bearings are mounted in would be enough.. I hadn't considered the brass cone.. Got Q-40 on paper but haven't started the hard part yet.. want to get the new quickie done first since all I have left is a fuse mold..

I guess I was just throwing out the nitric acid based on the comment above, if it's in there, it would/could contribute to corrosion over FAI fuel.. Personally, I thing it's the methanol sucking up water more than anything.. But hell, it's a guess at best

[rocket]

Another cool trick, the brass gasket is often the cause of leaking between the pipe and case. A little annealing will take care of that. Let them cool naturally. Softer metal seals better.

[Dave N]

Damn, how did I ever go fast without all this info Great thread..

No wonder I was never as fast as Rocket.

[rocket]

Plugs and mother nature.

The plane I flew at the Nats has been on the shelf since we got back. No changes, never even removed the prop. Took it to Markham on Monday afternoon to get a couple flights. It needled the same as I remember "this motor don't like to leave with no pinch, this is a discussion for another time". Radio in takeoff mode I let her fly. 10 pretty hard laps but didn't seem like it was unloading like before. An uneventful landing and back to the pavilion. Pulled the plug and I'll be dammm its crunched. Here is where the mother nature part comes into play. WHY did it crunch the plug. This plug went fast in muncie but one flight in ft liquordale and it's Frazer on a six pack. Well let's visit the weather in muncie in july. The barometric pressure for most of the day was 29.9. The motor was at 188/18. The prop was 7.6. The plug went the whole event, except for my first heat where I found the new plug I put for the first heat was a dud and I got a zer0. Fast forward to Markham and the crunched plug. Here's the same graph for the atmosphere on monday. The flight was around 3:30. The pressure in muncie was 1015 mbars, Markham was 1017 mbars. If muncie was a base line and motors were adjusted to suit the air on that day then the pressure at Markham would indicate the head needed to be raised. I did, I raised it .002 and no more crunched plug and it unloaded hard. So, the lesson here is pressure up, head up, pressure down head down.

[gsjames]

Rocket: Are the barometric pressures you showed the "local" pressure altitude or are they the sea level pressure? Ft Lauderdale is at sea level and Muncie is at 932' thus the same "altimeter setting" at Muncie and at Ft Lauderdale would have very different actual pressures at the field. But of course the "pressure up, head up and pressure down, head down" makes perfect sense because you have more or less dense air to start with. Thanks!

[rocket]

The altitude is important when you get real high. From sea level to 1000' not so much. No real experience above 1000' so someone else will have to chime in.

[DaveG]

Would be interesting to see the numbers from the Denver race.

Where did you get the graphs Ray ?

[rocket]

weather underground Dave. there's humidity there also.
https://www.wunderground.com/history/ai ... reqdb.wmo=
Here's a link, you can change it as needed.

[rocket]

The tangerine is in the books, great time, great friends, great racing as usual. Randy and I made a good team lol I think we're starting to think alike too. To bad for him haha. Anywho, here's the breakdown of the blue too sweets rebuilt motor. This motor threw a rod at Julian two races ago. I gave the case to Mike and asked for new bearings and a rod. Mike couldn't get the rear bearing out so I ended up with a new case with bearings. The old case sat in my shop, I got bored with nothing to work on so I ordered a venturi, fai spray bar, crank sans glue a backplate and screws. The rest of the parts I had already. The liner is no shims with an 8, 5 and 3 under the head. 189 and 19 is the set-up. The head had been peppered so I cleaned the inner bowls with mother's and the squish band with 1500 on a glass top. Thus pic is fresh off the motor. next I removed the crank. In the discussion about after run oil, this is the look of a well saturated motor. This is the rust I wiped off the crank at the front where the bearing rides. This crank has been in there for a month, after run must not make it this far north so I'm trying a little something with o-ring silicone. Well see after the next disassembly if it helps keep raw fuel from causing rust.

[rocket]

The o-ring silicone is from a Jett tanker rebuild kit. The thinking is it will take the place of fuel between the bearing and crank, thereby reducing the rust. It's fuel proof.

next is the piston, again out of the same motor that threw the rod. You can see the marks from being forced out of the liner. I finished the top of the piston with 2000 on the glass top. Here you can see the damage to the inside of the case, it still has the original bearing mike couldn't get out.