jab 8 cylinder

[rhtrudder]

anyone had any experience with the jab 8 cylinder engine, reliability etc

 

 

[Bruce Tuncks]

I think the 8 cylinder was a failure. There was one on a replica Spitfire which failed. They only made a few.

 

Possibly the crankcase distorted too much or the cooling was too hard.

 

 

[Jaba-who]

As best I recall they had insoluble problems with cooling.

 

They stopped making them some years go.

 

 

[Rastus]

A friend of mine has had one in an RV-7a for more than 10 years. Can't remember any cooling issues at all.

 

I think he had a rocker arm break a long time ago, but nothing else that I can recall.

 

It is very smooth and sounds awesome. Looks pretty good with the longer snout to fit the 8 in too. It seems to perform much the same as another friends 7a with a 180 Lycoming.

 

I think he has got it for sale. He is a serial builder and has nearly finished his latest build, so the RV has to go.

 

 

[rhtrudder]

I reckon I spoke to him , the Rv is pretty cheap but to change the engine over to a lycombing if it failed not much change out of $60k

 

 

[Oscar]

A friend of mine has had one in an RV-7a for more than 10 years. Can't remember any cooling issues at all.I think he had a rocker arm break a long time ago, but nothing else that I can recall.

It is very smooth and sounds awesome. Looks pretty good with the longer snout to fit the 8 in too. It seems to perform much the same as another friends 7a with a 180 Lycoming.

 

I think he has got it for sale. He is a serial builder and has nearly finished his latest build, so the RV has to go.

If that fit-up was done at the Jab. Factory, I saw it just before it was ready to fly - very, very nice job of building the RV-7, too, and the installation was looking excellent. He must have had it propped just right (and flown it with good sense), as there were potential issues with crankshaft harmonics and twisting over the long shaft. An RV7 isn't a lot of airplane to be hauled along with that much grunt and there should never have been much of a need to flog the thing too hard. I don't think they would have lasted well at all if flown by someone in an unsympathetic way or in a draggy aircraft. Too much (or too big in diameter) a prop. would have caused problems with the standard Jab. prop. hub but the RV7 can't carry - and doesn't need- a big prop AFAIK..

 

Cooling should not have been a huge issue; with the heads 'paired' as per the 2200, only the 3-5 and 4-6 heads would have had the exhaust ports alongside (as happens in the 3300 anyway) and while the head bolts do restrict the airflow down to the exhaust ports somewhat, that is workable with attention to the cooling set-up.

 

With CAMit gone, there's no chance of getting a new replacement crankshaft (or even a crankcase) if they fail; AFAIK everything else was standard Jab. parts apart from the intake and exhaust runners, obviously - and could even have been bought up mostly to CAE specs with (very careful!) hand-drilling of the crankcase to accept the CAMit through-bolts, barrels and heads. CAMit could have even installed the piston-cooling jets in the crankcase..

 

Sadly, with CAMit gone, your mate had an engine that has to be considered 'no user-serviceable parts inside', so his aircraft is now an airframe with a thing out the front that is a dead engine walking... Good on him for having the courage to try a new engine, and it's great to hear he has had a good run with it. CAMit had the capability of supporting 'bespoke' variants, Jabiru does not. There is no Rotax equivalent, nor Ul power or d-motor, so it's Lycoming or Continental, and that's going to involve not just the raw cost of the engine but the mount, prop, cowl mods etc.

 

 

[bexrbetter]

Has to be one of the most beautiful engines ever created.

 

Of course there's plenty of cheap replacements, it's only a 160hp engine. Not in 8 cylinders though.

 

 

[frank marriott]

The only 8 I know anything about was Rob Pavan's RIP, in a J230, and his opinion was nothing short of glowing, quite opposite to the posted problems. Unfortunately as he is no longer with us so can't be called on to argue/refute any allegations.

 

Certainly one owner/builder was happy. I can only reflect his statements to me in answer to questions.

 

 

[rhtrudder]

That's what I thought , everything from the firewall forward , and maybe some of the gauges will need to be changed, he said it cruised at 150 using just over 30lts ran smooth and sounded great

 

 

[ben87r]

Might be a stupid question but with 160hp and 30lph that puts it right in IO320 territory, what was its advantages? Was it purely cost op purchase/maintenance?

 

 

[bexrbetter]

Might be a stupid question but with 160hp and 30lph that puts it right in IO320 territory, what was its advantages? Was it purely cost op purchase/maintenance?

Would have been cheaper, I'm estimating about half(!) the price of the Lycoming, but obviously a natural model for Jab based on modular construction through the range.

 

 

[frank marriott]

Might be a stupid question but with 160hp and 30lph that puts it right in IO320 territory, what was its advantages? Was it purely cost op purchase/maintenance?

I suspect weight would also be a consideration.

 

 

[facthunter]

Smoothness and the sound, but long crankshafts are a harder to "tame". Nev

 

 

[Litespeed]

Why?

 

Just look at it- that is enough for me. It is a visual feast of billet alloy, tech but old school.

 

 

Besides its looks, it should be a lot lighter as a package and sounds lovely, smoother and is not a lycosaurus .

 

It also has a smaller frontal area, so would be great for something real slick and quick.

 

General characteristics

 

• Type: Flat-8
   
   
  
• Bore: 97.5 mm (3.84 in)
   
   
  
• Stroke: 85.0 mm (3.346 in)
   
   
  
• Displacement: 5,077 cm³ (310 in³)
   
   
  
• Length: 960 mm (37.79 in)
   
   
  
• Width: 638 mm (25.12 in)
   
   
  
• Height: 445 mm (17.54 in)
   
   
  
• Dry weight: 117 kg (257 lbs) with exhaust, carburetors, starter motor, alternator & ignition system
   
   
  

 

 

Components

 

• Fuel system: Mechanical fuel pump
   
   
  
• Fuel type: AVGAS 100/130
   
   
  
• Oil system: Wet sump
   
   
  
• Cooling system: Air-cooled
   
   
  

 

 

Performance

 

• Power output: 126.8 kW (170 hp) at 2,700 RPM (continuous); 134.2 kW (180 hp) at 3,000 RPM (intermittent)
   
   
  
• Compression ratio: 8:1
   
   
  
• Power-to-weight ratio: 1.10 kW/kg
   
   
  

 

 

Now do 9:1 compression ratio and at a few more revs you would have 210hp max.

 

Yum.

 

Oh and would have been half the cost.

 

Now a injected version with lower fuel would be a ripper.

 

 

[bexrbetter]

I'm surprised a few of the historic Porsche race car replica guys haven't purchased them.

 

Smoothness and the sound, but long crankshafts are a harder to "tame". Nev

It's no longer than many other cranks throughout history and obviously shorter than V and Flat 12 cranks. The longer Buick straight 8's didn't have any problems.

 

 

[facthunter]

The straight 8's always had problems. They are extinct and all those motors had harmonic balancers and didn't rev high. It's a question of stiffness where length, metal type (modulus of elasticity) and cross section, (large and hollow) and weight play a part. Extra bearings can make it worse if the journals are small cross section and if you "stretched" a "mainbearing every throw" crank out it would be longer than one with less bearings. Length and lack of stiffness is the enemy.. it's one of the reasons the Vee motors are so popular. Nev

 

 

[bexrbetter]

The straight 8's always had problems. They are extinct and all those motors had harmonic balancers and didn't rev high.

They were in mass production for over 20 years, revved up to 4000rpm, and had a very good reputation.

 

Your post smells like one of a manufacturers preference, eg: Holden Vs Ford, are you a bogan Nev?

 

 

[Oscar]

My family owned a 1938 Straight 8 Buick in the 50's; engine no problem (other than its drinking problem; the only car I've every had that was thirstier was my XJ12, which could get as low as 4 mpg if given the berries.) I also owned a 1938 Packard straight-8 Hearse - and it went rather well; I used to drive it between Mittagong and Canberra and the look on other driver's faces when you passed them doing around 80 mph would have kept me in petrol if YouTube had been around.in those days. But the Packard was splash-feed poured big-ends and it ran several going up Red Hill with 13 (live!!!) Duntroon Cadets in the back, also at nearly 80 mph. It had been a good party, that evening.

 

http://www.hearse.com/images/to_file/robers01.gif

 

My mother once drove a Packard Straight-8 convertible between Geelong and Derrinalum and averaged 90 mph for the trip; her obnoxious passenger had to be hosed out of the left-hand seat at the end of the trip.

 

With one rod per throw and a main every throw, the Jab. 8-cylinder was a long engine with a very light shaft. Twisting of both the shaft and the cam was always on the cards. You have to look at the necessary cylinder spacing for an air-cooled engine to appreciate why the Jab. went one main per single rod, and Jabs. have an excellent reputation for their bottom-end strength - shafts have never been an issue. But the 8 pushed that to the edge. If you don't understand why, then you don't understand the dynamics of an engine.

 

Alfa Romeo in the '30's tackled that problem in the 8Cc 2900 by joining two supercharged fours in the middle, with two separate shafts and cams joined in the middle with the cams chain-driven at the middle. The famous 'Batmobile' Le Mans coupe was the first vehicle ever to make 200 mph down Mulsanne. A restored 8C coupe in South Africa blew a newly refurbished 4.2 E-type into the weeds in the early 60's.

 

Alfa Romeo 8C 2900B Le Mans Berlinetta (Chassis 412033 - 2010 Goodwood Festival of Speed) High Resolution Image

 

The Straw Boater hat worn by one of the 'Batmobile' drivers at Le Mans was, I believe, conceived as a bit of a joke..

 

 

[Oscar]

They were in mass production for over 20 years, revved up to 4000rpm, and had a very good reputation.Your post smells like one of a manufacturers preference, eg: Holden Vs Ford, are you a bogan Nev?

4K rpm? Horsedung. But what would I know? - only had personal experience of the Buick and Packard Straight-8s. Haven't had a ride in the local Stutz Straight-8 Sedan, it could be a screamer for all I know.

 

 

[bexrbetter]

4K rpm? Horsedung.

Buick's own figures, but what would they know.

 

Max B.H.P. @ RPM.

 

Syncromesh - Series 40 120 @ 3600 ---

 

Syncromesh - Series 50 124 @ 3600 ---

 

Dynaflow - All Series 128 @ 3600 168 @3800

 

 

[Oscar]

Since when was 3.6K the same as 4K?

 

 

[facthunter]

I would be incapable of the simple pleasures bogans derive from their feelings for their particular brands. That's my loss. Packards are excellent cars and the Buick is General motors third best car. Cadillac, La Salle and then Buick. the straight 8's are super smooth and quiet but in line motors have their problems as well as the one of fitting them in. Few makers even make straight sixes these days. Cadillac and La Salle made V8's. Ford made the first ONE piece V8 cast block for 1932.BB model. A foundry masterpiece at the time with poured babbit mainbearings. Try pouring and align boring those young Harry. Nev

 

 

[skeptic36]

Since when was 3.6K the same as 4K?

Add the GST, you get bloody close

 

 

[jabpilot]

I had the privilege of flying off some of the test hours of Ian Bents own RV6 with the 8 cylinder engine. Ran like a dream. However, "hoped-for" supply levels evaporated when Lycoming & Continental started "dumping" engines at uneconomic prices (to Jabiru). Jabiru would still provide these engines but on an on-demand basis.

 

 

[kaz3g]

I pushed a Marmon straight 8 up a hill with half a dozen other kids to get it to roll start when I was a young teenager.

 

The rumble seat was awesome!

 

Kaz