Use of avgas?

[daren007]

Sand blasting spark plugs? Bead blast yes but sand?

[40 Deluxe]

Originally Posted by daren007

Sand blasting spark plugs? Bead blast yes but sand?

Yep, sandblasting! From at least the '40's through the 60's just about every dealer and independent shop had a spark plug cleaning machine that used sand and compressed air to clean carbon deposits off plugs. Most were sold by AC (the spark plug company). First you put the plug into a rubber grommet on top of the unit and hit the blast valve, which blasted the plug electrodes with sand using shop air. Then you hit another valve to blow the grit off the plug. Next you threaded the plug into the test chamber and attached a high voltage lead to the plug terminal and turned on the high voltage, which sent a steady arc across the plug. There was a mirror so you could see the arc going across the plug gap. Then you added compressed air to the chamber and watched to see at what pressure the spark was blown out or started going down the center insulator instead of jumping the gap. I forget what the minimum pressure requirement was for the plug to pass but if it didn't pass after cleaning and re-gapping, it was time for new plugs. Yes, "clean and re-gap spark plugs" was a standard tune-up procedure.

[Benson]

Yes thanks 40 D

We used blasters with an aluminum case with small bag of sand, a valve to select sand or air.

I had a new 1970 "Black Tank" with yellow stripe Yamaha RT-1 360 and a couple of DT-1 250s.

When I got 1976 XT-500 4 stroke I never cleaned that one as it never got fouled.

I never used it on the Model A plugs.

Just waited until electrodes on plugs got rounded before replacing them.

The plugs on A never got fouled,,, stayed clean.

[Karl]

The local Gas station sells AV gas but we have a racetrack nearby and the boy racers need Av gas for their insanely high compression engines. I have tried it in all my vintage and classic cars Didn't notice any performance difference from my standard 91 Octane . What i did notice was a nice white deposit on the exhaust pipe after a long trip- like we used to get in the old days with leaded gas -not a surprise given the lead contained in AV gas.

[rotorwrench]

We use two different types of spark plugs currently in aviation engines. Some folks want the massive electrode types since they are about half the price of the $110 each fine wire irridium electrode plugs. With massive electrode types, they will last about 200-hours if your lucky. The iridium tip fine wire type can last up to 800 hours so they are worth the price.

All of the folks that sell spark plug cleaning equipment are glad to sell you their abrasive. They use gray to black aluminum oxide for the most part. The glass beads will erode the sealant between the insulator and both the center electrode and the outer casing so it isn't recommended. The glass sort of jams in the crannies inside there. I know folks that have used glass bead and never had a problem but these engines have huge pistons so it likely doesn't matter all that much as long as the plugs are blown out well before reinstallation.

On car plugs, you just run them till they start missing and then throw them away & put in new ones. I don't know too many folks that take them out and clean them unless they are original type spark plugs. Now those can be cleaned.

[Benson]

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Rotowrench,


Thanks for the information on spark plug blaster usage.

[30 Closed Cab PU]

Had a basic auto shop class in high school, instructor was adamant about not using blaster cleaners to clean plugs. May have said something similar to Rotowrench's post, but do remember him saying blasters can pit/etch the porcelain - not a good thing. Was what I was taught.

[40 Deluxe]

Originally Posted by 30 Closed Cab PU

Had a basic auto shop class in high school, instructor was adamant about not using blaster cleaners to clean plugs. May have said something similar to Rotowrench's post, but do remember him saying blasters can pit/etch the porcelain - not a good thing. Was what I was taught.

Blasting did etch the porcelain, but with leaded gas and oil burning engines, plugs became fouled with carbon fairly often, especially with a lot of low speed, in-town driving. Thus the habit of getting out on the highway and "blowing the carbon out" when an engine started missing. It often worked, at least temporarily. it was cheaper to have the plugs cleaned than to replace them. Electrodes didn't last nearly as long back then,either. So, "clean and re-gap" was standard procedure. New plugs every 10,000 miles and points every 20,000 was the rule of thumb I was taught 60 years ago.

[JohnI]

Originally Posted by woofa.express

I've burned considerable avgas through motor cars including Model A's.
This was because it was available, I used to buy a tanker load at a time.
It gave no extra performance, neither before or after lead content was significantly reduced.
High compression engines may have been different due lead. Many people came with jerry cans to buy it but I think they were just kidding themselves.

I’m considering using avgas100LL in my 1934 Ford flathead. No ethanol and a little lead. The engine is original. Any thoughts?

[rotorwrench]

It won't hurt it but it may experience some lead fowling if it is straight 100 Low Lead. 100LL still has more tetra ethyl lead than auto gas ever did. It's a very stable fuel but it's also very expensive. I'd mix it with Mogas and preferable Mogas with no alcohol just to make it stretch farther.