Liquid cooled heads

[ozbear]

How many Jabirus have had engine fires? Not talking about a 70 litre radial engine burning 2 gallons of oil per hour with a 18 gallon sump. 4Ltrs oil max.Let me remind the nanny staters that the merlin engined planes all had side exhausts...

Whats a nanny stater?Havnt heard that one before lol. Sorry I got off subject with the radial thing I just meant that if you wanted to see something that leaks a lot of oil look at one of those.Im not knocking Jabs at all one reason aircraft engines leak is because of positive crank case pressure if you want to minimise oil leaks a pcv system helps.

 

 

[Guernsey]

It probably would lift your arm if it was shaped like an airfoil havnt you ever stuck your hand out of a car and played with the airflow as your dad drove along .

I knew somebody who did that, he was a strong headed risk taker, as a result he is now quite 'armless'.

 

Alan.

 

 

[bexrbetter]

I knew somebody who did that, he was a strong headed risk taker, as a result he is now quite 'armless'. Alan.

He was later trying to understand what the hell went wrong but he couldn't put a finger on it .....

 

 

[bexrbetter]

By the way, for your cooling shrouds, I suggest you might try decreasing the mouth opening size and test which way the temps go, sometimes if the opening is too big you can actually get flow stagnation or even reversal - just something to try, it may be worse.

 

maybe make a better cooling fence than the supplied fiberglass ones.

 

 

 

[ozbear]

I knew somebody who did that, he was a strong headed risk taker, as a result he is now quite 'armless'. Alan.

He still had one arm left so not completely armless lol

 

 

[ozbear]

Back on subject did anybody have a look at the LCH heads at Temora this year?

 

 

[VFR Pilot]

I did.

 

They looked good but they were on an older motor with external top end oil feed and solid lifters.

 

I dont think the thin finned head rockers will fit.

 

 

[ozbear]

I did.They looked good but they were on an older motor with external top end oil feed and solid lifters.

I dont think the thin finned head rockers will fit.

Yes I did as well I like the idea there was just a few things I thought could be improved upon first the castings were a bit porus with inclusions towards the pushrod tube holes probably the top of the mould when cast ,two the machine work on the combustion chambers was very rough and 3 I would have liked to see more thread in the holes for the water outlets just my thoughts.

 

 

[VFR Pilot]

Yes I did as well I like the idea there was just a few things I thought could be improved upon first the castings were a bit porus with inclusions towards the pushrod tube holes probably the top of the mould when cast ,two the machine work on the combustion chambers was very rough and 3 I would have liked to see more thread in the holes for the water outlets just my thoughts.

All good points ozbear. I like the idea of water cooling but i think i will be giving them a miss all the same.

 

 

[geoffreywh]

A bit porus? Isn't that like a bit pregnant? Either they leak or they don't. If they leak then they are porus and no good at all................. I f they don't leak then they are not porus and thus fine..................The set I saw at the factory were beautiful

 

 

[ozbear]

Hi Geoff I dont know whether they would leak or or not I would not accept the ones I saw for my aircraft they may have been just demos I don't know .where the porosity was they would tend to leak oil.Are you going to fit some to your aircraft ?

 

 

[VFR Pilot]

ozbear

 

I was wanted to fit them originally, but now i don't think so.

 

I didn't really notice the porosity of the castings, but i didn't really check them out that closely.

 

My motor is brand new and i know my late model rockers wont line up properly with the valve stems when in the liquid cooled heads.

 

I have had motors in the past where the rockers didn't line up properly and it was ok, but that was in motorcycles and they did wear adversely on the rocker surfaces. But you know what its like i don't think i want that in my plane.

 

There are things you can do to improve the cooling with the air cooled heads, so that's the way i will go i think.

 

Cheers

 

 

[geoffreywh]

I was going to build another aeroplane. But now I may update my engine to a later type. If I do that I would almost certainly use the 3300. But only with LC Heads. I have worked on a 3300 from new , and the struggles we have had with overheating are almost unbelievable. fortunately that is all over now (fingers crossed).................. Pluses?- Availability/price, excellent bottom end, excellent power, ...Negatives ...Poor cooling, poor generator , poor carburation. All are easily fixable.....IF starting from scratch...

 

 

[ozbear]

ozbearI was wanted to fit them originally, but now i don't think so.

I didn't really notice the porosity of the castings, but i didn't really check them out that closely.

 

My motor is brand new and i know my late model rockers wont line up properly with the valve stems when in the liquid cooled heads.

 

I have had motors in the past where the rockers didn't line up properly and it was ok, but that was in motorcycles and they did wear adversely on the rocker surfaces. But you know what its like i don't think i want that in my plane.

 

There are things you can do to improve the cooling with the air cooled heads, so that's the way i will go i think.

 

Cheers

I myself would not fit them to a brand new engine only a situation where you had a severe overheating problem and you had warped and damaged heads in need of replacement.Did you see the Bristol at Temora with the 3300 in it they had made up their own alloy ducting system it looked very neat but I don't know how we'll it works.With the rocker geometry I would say you need it spot on so as not to push the valve sideways causing valve guide wear.You want the rocker to roll on the valve tip without wiping and causing valve tip and rocker face wear after all its an aircraft engine not a Briggs and Stratton lawn mower.

 

 

[geoffreywh]

Unfortunately RAA hasn't caught up with my Rego YET.....So I didn't get to go . I think that LCH manufacturer will/ has addressed any discrepancy in valve gear alignment. I'll go and ask him in fact. That sideways valve thrust has always been present on engines since OHV were invented and it's not that bad. If the guide is long enough. The only way around it is with OHC and buckets. But that brings complication and extra weight. If I used a 3300 I would buy a short motor and LCHeads......Never overheating it has advantages in longevity.

 

 

[ozbear]

Unfortunately RAA hasn't caught up with my Rego YET.....So I didn't get to go . I think that LCH manufacturer will/ has addressed any discrepancy in valve gear alignment. I'll go and ask him in fact. That sideways valve thrust has always been present on engines since OHV were invented and it's not that bad. If the guide is long enough. The only way around it is with OHC and buckets. But that brings complication and extra weight. If I used a 3300 I would buy a short motor and LCHeads......Never overheating it has advantages in longevity.

There is another way roller rockers and they add very little weight and yes I agree overheating any engine is one of the worst things you can do to it . Your idea to build a custom engine is a good one 。

 

 

[DrZoos]

Does anyone have photos and or a list of the mods they have done to get better cooling.

 

Also what do you think of running an intake scoop backwards to create a low pressure and draw more air past the engine.

 

 

[Old Koreelah]

Does anyone have photos and or a list of the mods they have done to get better cooling.Also what do you think of running an intake scoop backwards to create a low pressure and draw more air past the engine.

Exit the cooling air in a low pressure area. Easy with a low-wing.

 

 

[jetjr]

In Jabiru aircraft theres lots of details on getting more air through - basically increase lip on lower edge of cowl, sucks more in.

 

Jabiru USA has good tech guide on evening out CHT with ram air ducts modification

 

Watch high oil levels, overheats if too full

 

Fine fin heads worked well for me.

 

 

[Old Koreelah]

...Watch high oil levels, overheats if too full...

I've heard that before, but can't understand the mechanism. I've also read often that over filling with oil results in it being spat out into the overflow container. There has been advice to keep oil just above the empty mark. My oil level has been half way between empty and full and there is no evidence of it using oil, but the oil temp has been pretty high.

 

 

[Guest Andys@coffs]

In mine the suggestion to keep the oil at the lower dipstick level is non optional....If I fill it to the top and go fly for 30 minutes then the oil level will be near the lower dipstick level on return and the overflow bottle will be fuller than it was.....

 

Constant top up will fairly shortly result in oil all over the belly as the overflow bottle becomes full.....

 

I though about making one of those traps that uses stainless steel wool to condense and collects the oil and prevents it being blown down to the overflow bottle....but Nevs suggestion that I'll catch all the moisture that boils off as well in the end suggested that I just leave it alone and know what is normal.

 

Andy

 

 

[DrZoos]

I presume your talking about this

 

http://www.usjabiru.com/uploads/AirDuctInstall.pdf

 

Ta. Any other tips. Anyone got photo of the lip mod

 

 

[jetjr]

Plenty on jabiru oz website, think there was a long SB on it. They even make cowl extensions to help too.

 

 

[jetjr]

The too full oil and overheating has happened to me, it gets abnormally hot, if you keep flying it spits it out and all ok.

 

Did get hot enough for me to turn around and land and chase the problem which of course was fixed by then

 

 

[hyundai]

Talking about LCH I fitted them 2 years ago had so much trouble I am putting aircooled heads back on.