Instant death of my 464

I'll get the bearing in and checked when I get a chance just to see.....on an interesting side note I did cc 2 different cylinders in my heads to see.......again I have a cheap setup for this......but its at least close I came out 67...I checked 1 on each head.

Not that it matters really cause in the end I have broke ass motor....but that drops the compression to 11.75ish.

Not going to have much time the next few days to do any more digging but it is interesting to see how 1 dies

 

I work in a hanger that has piston and turbo shaft engines in aircraft and helicopter.

The current piston engines are 6 cylinder 540 cu in.
They turn 2400 to around 2600 rpm.
They still use magnetos (2) with advance
2 spark plugs per cylinder 1 at the top the other at the lower side of the combustion chamber
Mechanical fuel injection/ air through a throttle body and fuel injected into the cylinder head combustion chamber.
They turn slow enough that the combustion event has time to complete
They run 100 LL
The typical TBO or running Time Before Overhaul is 2000 to 2400 hours, some more some less.
For years we never had a engine reach TBO not because of a catastrophic part failure but due to low compression or cylinder or head cracking.
These days they usually make TBO ok.
They run a synthetic 20/50 weight oil, some engines straight 50 or 70 weight.
You always ALWAYS take 4 to 7 minutes to warm the engine. You don’t quickly increase or decrease engine rpm
They are designed / built / operated to run in a fairly narrow engine operation .
But with proper maintenance, they usually run a Long, Long, long time.
The combustion chamber is typically fairly clean, not bright metal, but little to no buildup
The pistons crowns never just wipe clean. There is always a burned in carbon deposit buildup. Usually less around the valve pockets on our engines, but a near TBO time engine, yes buildup,
These engines are NA not turbocharged.
And they are operated running mainly at a constant running speed.
Fuel mixture is adjusted during flight by monitoring intake manifold pressure / and individual exhaust temp, plus the pilot also monitors cylinder head temperature.

The fuel mixture monitored / run more optimum that a carbureted ground automotive engine.

Still a burned in/on carbon buildup on the piston crown on the aircraft engine.

A bad fuel nozzle will change that and wash the crown a bit. A pilot who does not understand and maintain good fuel mixture/ exhaust temp operation can also affect that piston crown deposit accumulation.

The 464 is running at a higher compression/ rpm / and combustion event length that what the fuel was blended or intended for. I am not saying 100 LL is bad or wrong for cars or bikes. I buy and use it in my track bike and 13,000 rpm street bike. The fuel is not designed for what I buy it for but it works for what I use it for.

The wiping the crowns clean with a rag on an engine more than 100 hours or more, I have not seen before in my years of experience. I am sure an engine with 25 hrs or less running time “may” ?

But I have not seen everything either.

But just my experience around Avgas and aircraft applications.

 

I knew someone on here would have much more day to day experience with the fuel than me. And I'm sure my mixture is richer than planes run.....but I try to stay on rich side......plugs are easy and cheap to replace. I knowthe set of plugs I took out at 60 passes had an orange color, like lead contaminated....this is the 1st time in all my years running the fuel I noticed that.

My egt on top end was about 1400........at the 660 more down in 1250. My iron headed motor used to go 1475-1525 on top end. I tried adding fuel to the old motor to bring temp down just slowed the car down...

 

Ben I edited my post a couple of times, mainly to add and clarify some parts. Wanted to make sure that you saw the entire novel….

 

I'm sure this motor had 2x the amount of time running below 1500 rpms than it did above. I'm very careful to warm everything up b4 running. I often burn a couple gallons driving around the pits getting engine, trans, a gear and all fluid warm. I keep the oil and coolant warm with heaters......im a big believer in constant temp.

I'll put a picture tomorrow of a je piston from my 1st build.....it had about 2200 passes on it b4 it got a pin hole in #4 cylinder and when I tore it down I found a chip out #7 ring land......never knew it...it was actually cleaner than these and wiped up the same way.

Just like the pistons that were in a customer's 355 sbc.....it was a 9.5:1 motor

 

Cheap insurance to run 110 or 112.....
Was talking to a guy with a nice street driven 470 Buick Regal (11.70s) at the track who said he runs 93 with 11-1 and alum SE heads. Never opens the hood to cool it. Starts it up and leaves it running as cars pull up in the lanes.
Anyway he was checking my car out last time I was at track and I asked him if he was running. He said no rod bearing ate crank and needs to be turned .020. Never asked him how much timing he was running but he said he had 60 lbs oil pressure. Not enough IMO. Also I bet there was some detonation hammering rod bearings.

 

That guy probably read too many "pump gas build" articles in Car Craft.
Like you said more octane is cheap insurance. Running on the edge is just that. Everything has to be perfect with no room for error in the tune. Just not worth saving a few bucks a gallon.

 

I don't have any experience w AV fuel but is there something in the mix that reduces carbon buildup?

 

Here is my je piston from the 1st 464, these were used when Mike from AMP installed them in our motor and this have about 2200 passes all on avgas. There some signs of detonation on this piston......alot more than shows on any of my current slugs...... you can see the peppering of it and the surface does not feel smooth like my current slugs do.

Now I honestly can't say if it came from my tune or previous owner.....I tried all kinds of timing and settled on 31 for that iron head combo. We never lost a bearing in it, the block got a pinhole, the rest of the piston besides this one were reused in another block and had over 700 more passes b4 the motor was sold carb to pan.

This has been an ashtray in shop for years nows, never been parts washed just wiped the oil off with a rag.

 

In the mid ‘70s I lived in an area where race gas was very difficult to get and I raced a BBC with 11.5 compression. I decided to use av gas from the local airport. They offered 2 types, a lower octane product and “purple” high octane stuff rated at 110.
I bought the 110 and it seemed to work fine until I entered an event on a hot July day where we ran “round robin” eliminations ( no cool down). I developed a rod knock on the final pass.
When I tore it down there was evidence of detonation and my bearing looked like the OP’s. This was pre-internet so I called Smokey Yunick (You could do that back then, and he would answer questions if he had time). I asked him how 110 octane fuel could cause detonation with 36 degrees of timing.
He told me that he was an avid pilot and had tested av gas in race cars. He found that av gas was formulated for use at altitude, where atmospheric pressure is minimal. Also, pilots can monitor manifold pressure, EGT, etc, and adjust mixture accordingly. Therefore, detonation was not really a consideration.
He explained that, unlike automotive fuel, av gas has no additives to control burn rate and resist detonation. He said that if I wanted to use it I must mix it with the best automotive fuel available.
I never used it again. I have no idea if what Smokey said remains true, and I don’t pretend to be an authority on aviation gas. But it made sense to me then. As I understand it, high octane av gas is no longer readily available, so it is even less attractive for automotive use. Now that race gas is available everywhere it seems like cheap insurance, especially considering the time, money, and effort it takes to build a race motor.

 

Purple and Green AvGas are pretty much gone in the southern US at least. Blue / LL100 is what is left.

 

Blue is all that is available around me in Alabama.

 

I think green is/was the same octane just more lead

 

I could be wrong....but 110+93/2 = 101 octane????......im guessing super close to octane of avgas???

 

The point of my earlier post is that octane is not the critical issue with av gas. The problem is that it is not formulated for automotive engines, so it doesn’t have additives to control the rate of combustion. The higher octane may make it less prone to detonation, but once it does detonate it becomes uncontrollable.

Unlike pilots, we racers have only limited ability to monitor engine parameters and adjust the tune up for conditions like ambient temp, drivetrain loading (traction), etc. Unless you have an engine management system, you’re pretty much limited to manual timing adjustment and jet changes.
My information may be dated but I think it remains valid. It’s possible that 93 octane pump gas is safer for your engine than 100 octane ll aviation fuel. And race gas is far safer.

 

Premium" or "Super unleaded" gasoline in US and Canada (10% ethanol blend)
97 (research) 87-88 (motor) 92-93 (r+m/2)

Also 10% ethanol makes for a leaner fuel mixture. Plus no lead.
Not even close to Sunoco 260 in the 60s-70s. It was 104-106 research.