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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Sodium Filled Valve Stems. Why?
Dumb question I guess, but why do engine manufacturers make
valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. -- 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 0:-) Artemia Salina (-:0 0:-) Surrounded by Angels (-:0 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 |
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Artemia Salina wrote:
Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. Better heat conductivity aids in transferring the heat away from the valve head. So I was taught during my time at trade school, regarding aero engines. Cheers Trevor Jones |
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On Sun, 06 Mar 2005 15:48:35 -0500, Artemia Salina
wrote: Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Heat transfer and dissipation. |
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"Trevor Jones" wrote in message ... Artemia Salina wrote: Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. Better heat conductivity aids in transferring the heat away from the valve head. Curious that aluminum and copper both have a much higher thermal conductivity than sodium http://web.mit.edu/3.091/www/pt/pert14.html But I have a feeling that the relatively low melting point of sodium(371K) with copper(1356K) has something to do with transfering heat better. I dunno. http://web.mit.edu/3.091/www/pt/pert12.html the sodium would be a liquid at internal engine temperatures. |
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Lawrence L'Hote wrote:
"Trevor Jones" wrote in message ... Artemia Salina wrote: Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. Better heat conductivity aids in transferring the heat away from the valve head. Curious that aluminum and copper both have a much higher thermal conductivity than sodium http://web.mit.edu/3.091/www/pt/pert14.html But I have a feeling that the relatively low melting point of sodium(371K) with copper(1356K) has something to do with transfering heat better. I dunno. http://web.mit.edu/3.091/www/pt/pert12.html the sodium would be a liquid at internal engine temperatures. AFAIK sodium filled valve stems operated on the thermosyphon principle. The sodium "absorbed" heat by evaporating at the part of the stem near the valve head and delivered it to the other end where the sodium condensed and the heat it gave off was transferred out through the valve guides. Somewhat similar to "heat pipes" but without the wick inside: http://www.thermacore.com/hpt.htm Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "As long as there are final exams, there will be prayer in public schools" |
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The valve stems are not completely filled with sodium. As the valve heats
up, sodium vapourizes and rises up the valve stem by convection. This carries the heat up to the top of the stem where it is dissipated by the oil and air surrounding it. The sodium condenses and falls back to the bottom of the valve and collects heat from the seat and continues the cycle. It effectively forms a "heat pipe" to transfer the heat away from the seat . Tom "Artemia Salina" wrote in message news Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. -- 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 0:-) Artemia Salina (-:0 0:-) Surrounded by Angels (-:0 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 |
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On Sun, 06 Mar 2005 16:39:01 -0500, Jeff Wisnia wrote:
AFAIK sodium filled valve stems operated on the thermosyphon principle. The sodium "absorbed" heat by evaporating at the part of the stem near the valve head and delivered it to the other end where the sodium condensed and the heat it gave off was transferred out through the valve guides. Somewhat similar to "heat pipes" but without the wick inside: http://www.thermacore.com/hpt.htm Thanks for all the responses. As food for thought, what got me looking at IC engine valves was the idea to remove the cam, rocker arms, lifters, and etc. and replace it all with computer controlled solenoid actuators. Needless to say, someone is already working on this, with several enticing prototypes under his/her belt: http://rbowes1.11net.com/dbowes/index.htm That's almost exactly the idea that I'd had! Neat! -- 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 0:-) Artemia Salina (-:0 0:-) Surrounded by Angels (-:0 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 |
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Gravity
The liquid sodium is heavier than the vapour. Tom "Tom" wrote in message ... Tom Miller wrote: The valve stems are not completely filled with sodium. As the valve heats up, sodium vapourizes and rises up the valve stem by convection. This carries the heat up to the top of the stem where it is dissipated by the oil and air surrounding it. The sodium condenses and falls back to the bottom of the valve and collects heat from the seat and continues the cycle. It effectively forms a "heat pipe" to transfer the heat away from the seat .. Tom "Artemia Salina" wrote in message news Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. -- 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 0:-) Artemia Salina (-:0 0:-) Surrounded by Angels (-:0 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 This, in a reciprocating valve? What would keep the sodium at the head end of the valve? Tom |
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Tom wrote:
Tom Miller wrote: The valve stems are not completely filled with sodium. As the valve heats up, sodium vapourizes and rises up the valve stem by convection. This This, in a reciprocating valve? What would keep the sodium at the head end of the valve? Yes, exactly. The valves are hammered with hundreds of G's every time they slam open and shut. Convection would be totally insignificant under such extreme acceleration. Every time the valve opens, the sodium is thrown against the rocker arm or lifter, every time it shuts, it is slammed back to the head. (Maybe it bounces, and makes TWO round trips every valve cycle.) Jon |
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On Mon, 7 Mar 2005 09:30:39 +1100, "Tom Miller"
wrote: Gravity The liquid sodium is heavier than the vapour. Yeahbut... which way is up? I thought the heat transfer was effected by the sodium being shaken from one end of the cavity to the other by the G forces inherent in a rapidly operating valve. Just my impression tho, I haven't seen the theory of the things written down anwhere. |
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Jon Elson wrote:
Tom wrote: Tom Miller wrote: The valve stems are not completely filled with sodium. As the valve heats up, sodium vapourizes and rises up the valve stem by convection. This This, in a reciprocating valve? What would keep the sodium at the head end of the valve? Yes, exactly. The valves are hammered with hundreds of G's every time they slam open and shut. Convection would be totally insignificant under such extreme acceleration. Every time the valve opens, the sodium is thrown against the rocker arm or lifter, every time it shuts, it is slammed back to the head. (Maybe it bounces, and makes TWO round trips every valve cycle.) Jon I recall first hearing about sodium filled valve stems in relation to IC aircraft engines and some racing cars. I just did a little Googling. Further supporting the theory that "You've got to take the bad with the good", I found this text related to aircraft engines which claims that sodium cooling the valve heads can accelerate valve guide wear. It's from this web page: http://www.prime-mover.org/Engines/Marvel/tbo3.html ********************************** The Problem of Sodium Filled Valves As revealed above, sodium filled valves in the O-320 engine did not eliminate valve distress problems. To the contrary, our question is whether or not they either cause or increase these problems. Sodium filled valves are an extremely expensive component that we believe are greatly to blame for valve/guide distress incidents. They do not make heat magically disappear, as some would have you believe. All these valves do, at great monetary expense, is transfer heat from the valve head to the valve stem, or more generally, from the combustion chamber to the cylinder head via the valve guide. They merely move heat from point "a" to point "b." It still has to be eliminated from the cylinder head by either air cooling or oil cooling or both. The problem is that valve guides are wearing out prematurely and are doing so in spite of operators keeping CHT levels in the proper range. Excess heat is the primary cause of premature guide wear (in a properly assembled cylinder), as most engine shops will tell you. The problem with sodium filled valves is that they serve to import even more heat into the guide by transferring it up from the valve head. Lycoming's long history of valve/guide failure incidents in the parallel valve cylinders has shown that there is simply no way that the guide can shed all of its higher heat load via the cooling fins alone, and Lycoming's design provides for very little oil to aid in that process. The irony here is that Continental uses solid stem valves that dissipate most of their heat into the valve seat. Relatively little comes up the stem and into the valve guide and yet Continental has an abundance of oil in this area to aid in heat transfer. If sodium filled valves are needed at all, one wonders why Continental doesn't use them, since their barrel style hydraulic lifters provide substantial oil for additional cooling of the guide and valve. Lycoming's mushroom style lifters do not. We think that without any change in oil flow to the rocker boxes, Lycoming valve and guide longevity might well benefit from simply going to solid stem valves. Unfortunately, these are not available. ************************************************** **** Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "As long as there are final exams, there will be prayer in public schools" |
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On Sun, 06 Mar 2005 18:28:02 -0500, Jeff Wisnia
wrote: ********************************** The Problem of Sodium Filled Valves As revealed above, sodium filled valves in the O-320 engine did not eliminate valve distress problems. To the contrary, our question is Snip.. Whoever wrote that never owned a turbo charged Volvo. Regards, Boris Mohar Got Knock? - see: Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca |
#13
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Below was cribbed from a website:
From MB tech literatu "Sodium is a heat-conducting element. Sodium fuses and becomes liquid at an approximate 97 degree in running engine and conducts the heat on valve head to valve stem by convection. Heat on the valve stem first conducted to valve guide second to cylinder head then finally transferred to the cooling water. Cooled sodium sinks to the bottom and fuses again. Cooling of the valves continuously repeated by this method. When a sodium filled valve is compared with the same dimensional valve without sodium, a heat difference of 80 to 150 degree is reported at valve head circle as well as at the critical point where the valve stem and head radius intersects. This is one of the major facts on resistance of the material. Furthermore valve weight is reduced by 7% - 16% by the drilled volume. This enables a considerable reduction of mass effect on high performance valves." -- Steve Walker (remove wallet to reply) |
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David R Brooks wrote:
Sodium boils at 883C = 1620F (Kaye & Laby). Do they really run that hot? 1625F is commonly cited as peak exhaust gas temperature for IC aircraft engines. The measurement is usually taken several inches from the exhaust port, so valve temperature could run a little higher. "Tom Miller" wrote: :The valve stems are not completely filled with sodium. As the valve heats :up, sodium vapourizes and rises up the valve stem by convection. This :carries the heat up to the top of the stem where it is dissipated by the oil :and air surrounding it. The sodium condenses and falls back to the bottom of :the valve and collects heat from the seat and continues the cycle. It :effectively forms a "heat pipe" to transfer the heat away from the seat . : :Tom Most aircraft engines today have horizontal cylinders, thus horizontal valves. :"Artemia Salina" wrote in message :news : Dumb question I guess, but why do engine manufacturers make : valve stems that are filled with sodium (I think only exhaust : valves are sodium filled). Is it a heat expansion issue? : : Thanks. : : -- : 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 : 0:-) Artemia Salina (-:0 : 0:-) Surrounded by Angels (-:0 : 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 : : |
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Artemia Salina wrote:
On Sun, 06 Mar 2005 16:39:01 -0500, Jeff Wisnia wrote: AFAIK sodium filled valve stems operated on the thermosyphon principle. The sodium "absorbed" heat by evaporating at the part of the stem near the valve head and delivered it to the other end where the sodium condensed and the heat it gave off was transferred out through the valve guides. Somewhat similar to "heat pipes" but without the wick inside: http://www.thermacore.com/hpt.htm Thanks for all the responses. As food for thought, what got me looking at IC engine valves was the idea to remove the cam, rocker arms, lifters, and etc. and replace it all with computer controlled solenoid actuators. Needless to say, someone is already working on this, with several enticing prototypes under his/her belt: http://rbowes1.11net.com/dbowes/index.htm That's almost exactly the idea that I'd had! Neat! There is an article in the current HSM with instructions to build a 4-stroke engine using solenoid-operated valves. -- - - Rex Burkheimer WM Automotive Fort Worth TX |
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On Sun, 06 Mar 2005 17:01:45 -0500, Artemia Salina wrote:
On Sun, 06 Mar 2005 16:39:01 -0500, Jeff Wisnia wrote: AFAIK sodium filled valve stems operated on the thermosyphon principle. The sodium "absorbed" heat by evaporating at the part of the stem near the valve head and delivered it to the other end where the sodium condensed and the heat it gave off was transferred out through the valve guides. Somewhat similar to "heat pipes" but without the wick inside: http://www.thermacore.com/hpt.htm Thanks for all the responses. As food for thought, what got me looking at IC engine valves was the idea to remove the cam, rocker arms, lifters, and etc. and replace it all with computer controlled solenoid actuators. If you're looking for a solidly made, easy to work on engine with sodium valves, any Saab 2 Liter engine since about 1978 (maybe earlier) will have the sodium filled exhaust valves. I'd pick a mid-1980's or later turbo engine, personally, but you can choose between an 8 valve and a 16 valve head for the later ones. Well built engines, excellent for experimentation. If you get one with the Bosch CIS fuel injection (up to about '86), fuel management is simply handled. |
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On Sun, 06 Mar 2005 18:28:02 -0500, Jeff Wisnia wrote:
I recall first hearing about sodium filled valve stems in relation to IC aircraft engines and some racing cars. I just did a little Googling. Further supporting the theory that "You've got to take the bad with the good", I found this text related to aircraft engines which claims that sodium cooling the valve heads can accelerate valve guide wear. Saab engines typically do many hundreds of thousands of miles, and I've never done or even heard of anyone having to redo the valve guides. |
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Artemia Salina wrote:
Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. -- 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 0:-) Artemia Salina (-:0 0:-) Surrounded by Angels (-:0 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 It is a misnomer, the stems were generally only filled to 60% of the cavity space which included that in the valve head. At operating temps, the sodium was molten and transfered heat from the valve head to the cylinder head via the stem & valve guide. Tom |
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Tom Miller wrote:
The valve stems are not completely filled with sodium. As the valve heats up, sodium vapourizes and rises up the valve stem by convection. This carries the heat up to the top of the stem where it is dissipated by the oil and air surrounding it. The sodium condenses and falls back to the bottom of the valve and collects heat from the seat and continues the cycle. It effectively forms a "heat pipe" to transfer the heat away from the seat . Tom "Artemia Salina" wrote in message news Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. -- 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 0:-) Artemia Salina (-:0 0:-) Surrounded by Angels (-:0 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 This, in a reciprocating valve? What would keep the sodium at the head end of the valve? Tom |
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Tom Miller wrote:
Gravity The liquid sodium is heavier than the vapour. Tom "Tom" wrote in message ... Tom Miller wrote: The valve stems are not completely filled with sodium. As the valve heats up, sodium vapourizes and rises up the valve stem by convection. This carries the heat up to the top of the stem where it is dissipated by the oil and air surrounding it. The sodium condenses and falls back to the bottom of the valve and collects heat from the seat and continues the cycle. It effectively forms a "heat pipe" to transfer the heat away from the seat . Tom "Artemia Salina" wrote in message news Dumb question I guess, but why do engine manufacturers make valve stems that are filled with sodium (I think only exhaust valves are sodium filled). Is it a heat expansion issue? Thanks. -- 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 0:-) Artemia Salina (-:0 0:-) Surrounded by Angels (-:0 0:-) 0:-) 0:-) 0:-) (-:0 (-:0 (-:0 (-:0 This, in a reciprocating valve? What would keep the sodium at the head end of the valve? Tom Yeah right. You've never shaken a halfilled bottle of water up & down? |
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Jeff Wisnia wrote:
Jon Elson wrote: Tom wrote: Tom Miller wrote: The valve stems are not completely filled with sodium. As the valve heats up, sodium vapourizes and rises up the valve stem by convection. This This, in a reciprocating valve? What would keep the sodium at the head end of the valve? Yes, exactly. The valves are hammered with hundreds of G's every time they slam open and shut. Convection would be totally insignificant under such extreme acceleration. Every time the valve opens, the sodium is thrown against the rocker arm or lifter, every time it shuts, it is slammed back to the head. (Maybe it bounces, and makes TWO round trips every valve cycle.) Jon I recall first hearing about sodium filled valve stems in relation to IC aircraft engines and some racing cars. I just did a little Googling. Further supporting the theory that "You've got to take the bad with the good", I found this text related to aircraft engines which claims that sodium cooling the valve heads can accelerate valve guide wear. It's from this web page: http://www.prime-mover.org/Engines/Marvel/tbo3.html ********************************** The Problem of Sodium Filled Valves As revealed above, sodium filled valves in the O-320 engine did not eliminate valve distress problems. To the contrary, our question is whether or not they either cause or increase these problems. Sodium filled valves are an extremely expensive component that we believe are greatly to blame for valve/guide distress incidents. They do not make heat magically disappear, as some would have you believe. All these valves do, at great monetary expense, is transfer heat from the valve head to the valve stem, or more generally, from the combustion chamber to the cylinder head via the valve guide. They merely move heat from point "a" to point "b." It still has to be eliminated from the cylinder head by either air cooling or oil cooling or both. The problem is that valve guides are wearing out prematurely and are doing so in spite of operators keeping CHT levels in the proper range. Excess heat is the primary cause of premature guide wear (in a properly assembled cylinder), as most engine shops will tell you. The problem with sodium filled valves is that they serve to import even more heat into the guide by transferring it up from the valve head. Lycoming's long history of valve/guide failure incidents in the parallel valve cylinders has shown that there is simply no way that the guide can shed all of its higher heat load via the cooling fins alone, and Lycoming's design provides for very little oil to aid in that process. The irony here is that Continental uses solid stem valves that dissipate most of their heat into the valve seat. Relatively little comes up the stem and into the valve guide and yet Continental has an abundance of oil in this area to aid in heat transfer. If sodium filled valves are needed at all, one wonders why Continental doesn't use them, since their barrel style hydraulic lifters provide substantial oil for additional cooling of the guide and valve. Lycoming's mushroom style lifters do not. We think that without any change in oil flow to the rocker boxes, Lycoming valve and guide longevity might well benefit from simply going to solid stem valves. Unfortunately, these are not available. ************************************************** **** Jeff -- Jeffry Wisnia An opinion specific to a particular engine design, hardly an opinion shared by Pratt & Whitney, Wright, Allison, Ranger, RR, de Havilland, Daimler-Benz, Alfa Romeo, Junkers, Hispano Suiza and also Continental to name just a few makers who used sodium cooled exhaust valves in their aircraft engines. Tom Tom |
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http://www.prime-mover.org/Engines/Marvel/tbo3.html
The Problem of Sodium Filled Valves It appears this pertains to air cooled aircraft engines. Water cooling is much better at eliminating hot spots. That said, there are lots of auto engines with sodium valves and I'm sure that major car manufactures would not do it if there wasn't benefit. chuck |
#23
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one
wonders why Continental doesn't use them, since their barrel style hydraulic lifters provide substantial oil for additional cooling of the guide and valve. Lycoming's mushroom style lifters do not. Lycoming uses hydraulic lifters in all but the O-235 series engines, and whether hydraulic or not, they send oil up the pushrod to the rocker and valve stems. They are located above the rocker shafts and valves, and get plenty of oil on them. Lycoming's camshaft is above the crank and tends to get little cam lube at idle. Continentals have their cams at the bottom, getting lots of oil, but the valves are high and get a bit less drip. They have a gallery thru the rocker to make sure some oil gets to the rocker tip and valve stem. Lycomings problems are not so different from Continentals. I've had much more valve trouble in the small Continentals than in the Lycs, and what valve trouble Lycs give is due more to the guide material (appears to be bronze), which doesn't have really good wearability at high temps. First sign of trouble is a leaky exhaust valve, as the guide is allowing it to seat a bit off-center and wearing one edge. Dan |
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I had a 1976 with a simple fuel injection system, I also worked at a dealer
in 1986 ish the 1974-1989 (I think 1989) had more power than the next generation. same specs but the older "b" motors just ran like raped apes, I think they under rated there HP. "Dave Hinz" wrote in message ... On Sun, 06 Mar 2005 17:01:45 -0500, Artemia Salina wrote: On Sun, 06 Mar 2005 16:39:01 -0500, Jeff Wisnia wrote: AFAIK sodium filled valve stems operated on the thermosyphon principle. The sodium "absorbed" heat by evaporating at the part of the stem near the valve head and delivered it to the other end where the sodium condensed and the heat it gave off was transferred out through the valve guides. Somewhat similar to "heat pipes" but without the wick inside: http://www.thermacore.com/hpt.htm Thanks for all the responses. As food for thought, what got me looking at IC engine valves was the idea to remove the cam, rocker arms, lifters, and etc. and replace it all with computer controlled solenoid actuators. If you're looking for a solidly made, easy to work on engine with sodium valves, any Saab 2 Liter engine since about 1978 (maybe earlier) will have the sodium filled exhaust valves. I'd pick a mid-1980's or later turbo engine, personally, but you can choose between an 8 valve and a 16 valve head for the later ones. Well built engines, excellent for experimentation. If you get one with the Bosch CIS fuel injection (up to about '86), fuel management is simply handled. |
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On Thu, 10 Mar 2005 23:05:04 -0500, Waynemak wrote:
I had a 1976 with a simple fuel injection system, I also worked at a dealer in 1986 ish the 1974-1989 (I think 1989) had more power than the next generation. same specs but the older "b" motors just ran like raped apes, I think they under rated there HP. Yes, the 8-valve B engine with turbo, really really goes. Mine is in a '78 99 Turbo, so it's lighter than the 900, which probably helps. Hella fun car. |
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