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Grumpy Cynic
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Replacing the lines would involve a major disassembly of the aircraft. Plus weeks if not months of time. Could we do it? Yes. Are we going to? No.
If ground cooling turns out to be a significant problem after this even is sorted out then maybe a Reno style spray system on the radiator would be an easier 'fix'?
 

cheapracer

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We will do another hot and cold compression check.

Any thoughts? Is the engine "cooked"?
Engines can go a surprisingly long time overheated without damage, especially all aluminium engines.

I have found if damaged, one of the most noticeable things is loss of compression in some or all cylinders because the rings over heat and lose their tension. I have pulled engines apart that were overheated so badly I was able to remove the rings by merely unwinding them straight off the piston (a normal ring would typically just snap of course). Just spinning on the starter motor and listening is a good sign if bumping sounds normal.

Oil smell is also a big one, it's very noticeable, a horrible smell if you know it, but sounds like you avoided reaching that stage.

Do the usual compression test.

For blown gaskets, grab your self a pressure tester, pump it up and walk away for 5 minutes, great for checking for leaks too. Mind you, that doesn't tell you if you have burnt head gasket between cylinders, but a compression test will do that.

 

check6

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Tex,

Not privy to your exact installation, but I can tell you what works in a supercharged 540 c.u. Big Block Chevy installed in a Stewart S51. You must have a coolant expansion tank of at least 2 quart volume mounted at the highest point of the coolant system, either at the very top of the firewall or on top of the PSRU. I fabricated a “u” shaped tank that sets over the PSRU in the S51. The size of this tank must be adequate to contain the normal expansion of coolant without overpressurizing. I recommend a 15 psi radiator cap. High coolant temperatures are not necessarily harmful ( some versions of the Merlin engine had a max coolant temp of 250F) but are an indicator of a coolant system that is insufficient for the heat load that the engine generates. The normal weak link in liquid cooled engines is the head gasket. Stock head gaskets are generally the first part to leak in an overpressurized coolant system. I am not sure what your LS engine uses, but a MLS (multi layered steel) head gasket is the best choice to eliminate head gasket failure.
Most spark ignition engines will loose 35 to 40% of the energy generated from the burning of the fuel to heat loss. This heat has to be constantly removed or the components of the engine will eventually expand to the point of seizing. The more heat that the engine generates, the more cooling capacity will be required.
Heat is removed by your heat exchangers, both coolant and oil coolers. The size and type of your heat exchangers determine the maximum heat rejection that is available. What is the size of your coolant radiator? Is it a single or dual pass? Do you have a liquid/liquid oil cooler or liquid/air? We use piston squirters to remove heat from the pistons. I never found a liquid/liquid oil heat exchanger that would adequately cool the oil and had to resort to a liquid /air heat exchanger in stalled in front of the radiator.
The 1 1/2” diameter coolant tubes and high volume pump are sufficient to circulate enough coolant to keep the BBC between 160 to 180 degrees F utilizing the Stewart supplied radiator. In your case, I suspect that you have a circulation problem either due to being air bound or the coolant system that is undersized for the heat load.
I suggest that while you are trying to get your system squared away, use 100% water in your system instead of a water/glycol mix. Water has superior heat transfer abilities to glycol and is cheaper than glycol.
Prior to your first flight, your coolant system must provide sufficient cooling to allow for a tied down, two minute takeoff power test. Until your system can handle that test, it is probably non airworthy.
I believe you know Pat Stanley. Suggest you go speak with him.
 

TXFlyGuy

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Yes, I do know Pat.
The head gasket material from GM is multi-layered steel, and is standard on the LS3 series.
The overflow bottle is about 2 qt capacity. See the pictures, located in the upper right hand corner of the engine, the highest point in the system.
Not certain on the radiator, but it was designed and built by a company who specializes in racing applications, and is very well respected. C&R is who fabricates the radiators.
The radiators for both the liquid coolant and the oil are air type, with the oil cooler mounted in the belly scoop just forward of the liquid (glycol/H2O) cooler.

In flight, there are no problems with this setup. It is only during extended (15+ minutes) ground ops that the engine will get hot.

I guess this is very similar to the P-51 Mustang, based on feedback from a good friend who owns Buzzin' Cuzzin.

P1050781.JPG

P1050787.JPG

P1050782.JPG
 

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BBerson

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Why would you do a 15 minute ground operation?
Can't really expect a prop to blow enough air pressure.
 

TXFlyGuy

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Why would you do a 15 minute ground operation?
Can't really expect a prop to blow enough air pressure.
It was probably 10 to 12 minutes, actually. This was when we were doing the Garmin Magnatometer calibration which requires a bit of taxi time to accomplish.
 

BBerson

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Maybe that could be done after 20 hours of flight?
New engines run hotter. I would do the test flight after a two minute warmup or something.
Might even heat the oil pan to bring the oil up some without running the engine. And then takeoff just as the coolant temp is passing around 120°
 

Hephaestus

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Borescope it if you're concerned, sparkplugs out, camera in each cylinder will get you an idea on piston and valve condition.

As far as ground operations - got a little space behind the radiator? 1-2 electric fans would be able to get you the airflow needed. GM alternator wouldn't struggle to power them.
 

TXFlyGuy

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Borescope it if you're concerned, sparkplugs out, camera in each cylinder will get you an idea on piston and valve condition.

As far as ground operations - got a little space behind the radiator? 1-2 electric fans would be able to get you the airflow needed. GM alternator wouldn't struggle to power them.
Yes, plenty of space behind the radiator. Getting to it is another matter.

The coolant lines are 3/4" I.D. And the radiator is a dual pass design.
 
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TXFlyGuy

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We can install electric fans, but here is my concern...

1. At 250 mph, will the fans self destruct, over speed?
2. Will the fans impede the hot air exhaust flow when they are not running?
 

TFF

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If you are going to keep running this plane on the ground for extended times and for many more runs, install temporary fans. Once you are ready for flying, remove them.
 

Hephaestus

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Electric cooling fans are used on radiators in just about every application - I wouldn't go junkyard scrounge a set of ford taurus fans for your application but... That huge hunk of aluminum in front tends to slow the air a lot ;)

You'll loose a small % of airflow yes - there's a nice trade-off however, if you happen to have cooling issues in the pattern (I know we've never seen thqt particular issue pop up before) - you've got a fallback that isn't increase speed. Thermostat or flicking a switch to turn them on is a nice redundancy feature.
 

pictsidhe

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Having two sensors reading so differently suggests something is very wrong. You have not yet told us their locations, which is pertinent. The thermostat should have opened and let the coolant circulate properly, so, you'd have needed at least one other problem.

It does not mean the sensors are bad, so test them. It only means that they are reading differently. Take both sensors, put them in a cup and add some freshly boiled water. If they now read about the same, you have a coolant flow problem, quite likely from an air lock. Don't worry about mixing 12v and water for this test. Do not assume anything, test everything you can. Replacing a sensor and 'testing' it like that could be a 4th overheat. I suspect they are fine.

Some aluminium engines are built from heat treated aluminium. Overheat those ones, the head softens and will never seal properly again. After testing your sensors, consult an LS expert as to whether the engine could be damaged. Somebody will buy it for a few k.
If you do need a new engine, use the cooked one to work out the cooling gremlin before fitting a replacement...

If the airlock is from the backwards engines, drill and tap a bleed in each head, run small pipe to tee up or replace the existing bleeds. Small pipe means low 'wrong' flow, if it bridges something you need cooled. I don't like engines that aren't self venting, air bleed hoses at high points whenever possible and needed. For ground testing, you can spray water from a garden hose on the radiator if airflow is inadequate.
 

Voidhawk9

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Some kind of electric blower etc for temporary ground testing may be warranted. Permanently mounted fans tend to me more trouble than they are worth in-flight, causing more restriction than flow. Been tried many times.
 

pictsidhe

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Some kind of electric blower etc for temporary ground testing may be warranted. Permanently mounted fans tend to me more trouble than they are worth in-flight, causing more restriction than flow. Been tried many times.
I would get the cooling good enough for any aerial use. For ground help, a water spray set up should be simple and fairly effective. A pound of water does a lot of cooling. It would be less restrictive than fans.
 

TXFlyGuy

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The sensor was an AC-Delco which does not communicate with the Garmin, mounted in the block up near the nose (the hottest area). The MoTeC sensor is mounted towards the cockpit.
We have a new sensor now (UMA) which works with the G3X and is spot on accurate.

The G3X has a menu with a list of temp sensors that will work. The person who did this install obviously never checked.

I have been advised to keep the rpm's up around 2000 at all times during taxi to get air flowing thru the scoop. Yes, you have to ride the brakes when you do this. T-51 owners in Las Vegas use this technique without problems.
 
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