That was the question posed on Quora today.
My opinion on the 409 (and 348) was formed during my HS years when I heard of a number of them 'blowing up' and throwing rods thru the side of the block, so I adopted the common attitude that the 348/409 were 'truck blocks' and not suited to higher rpm uses... (whether right or wrong? I don't know)
A funny response was listed along with the question:
"I was not sure of why the 409’s blew, but an old boss of mine was a foreman at the St. Louis chevy plant, and he said he saw them blow up waiting in line to load on the car haulers… "
Some other responses were: from a 30 yr senior automotive technician)..
"Biggest issue was the connecting rods as they were not much strong than the 283 connecting rod and would spin bearings and break under RPM. I believe the reason for using them was to reduce Bob weight with the extreamly heavy forged pistons.
Having built several we always upgraded the rods. Even race bullet aluminum were immensely strong as I had one guy with well over 10,000 miles and 200 races on a set and only measured 0.001 stretch and he RPM'ed the snot out of it with 4 speed. Local street racers hates him."
And from a BSc in Physics from a Cal State graduate:
"The Chevy “W” engine, including the 1958 released 348 cu in, later 409 cu in and 427 cu in Z-11 (NASCAR engine) were known to be somewhat more powerful than standard in-line valve wedge engines. A beneficial feature of these engines was that the intake valve was offset closer to the valley of the engine and the exhaust valve offset to the outside. This twisting of the valve alignments made the gas paths slightly shorter. The cylinder head bottom was flat, not containing a combustion chamber, thus leaving the valves completely unshrouded by chamber walls. These engines breathed a little better than standard pushrod wedge engines. They were basically bullet proof reliable. I never heard of a complaint of any disadvantages to the design. They were followed by the Chevy Mark III and IV engines that also had twisted valve alignments and added different valve angles for intake and exhaust valves. These engines, the Big Block Chevy, had an even better advantage over in-line valve engines. Playing with the valve orientations was possible because Chevy used rocker arms individually mounted on studs instead of all being mounted on a common shaft, an expedient innovated by Pontiac.
The flat cylinder head surface had no combustion chamber. The chamber was shaped by a space bellow the head formed by the fact that the block was milled at an angle. This strange arrangement was also introduced by Ford with its MEL (Mercury, Edsel, Lincoln) engine also in 1958. The Chevy and Ford MEL engines were partial copies of a Mercedes Formula One engine of 1954 with respect to the flat head surface and combustion chamber in the block and the Chevy engine also staggered the valves. What was left out from the Mercedes engine were the desmodromic valve actuation and the direct fuel injection.
So, the 409 was an impressive engine with a romantic image. Jan and Dean sang a song about it! On the other hand…. (yes there is more than one hand), neither Mercedes, Chevy nor Ford ever made another engine with the chamber in the block. In my suspicion, its a NG, no good, design! A cylinder pressure graph showed a slowing of the pressure rise just before peak pressure in the Chevy engine. Curious. I notice that the cylinder head/block mating crevice where the head gasket is recessed slightly, creates an extra band of relatively cold metal arching right over the combustion chamber, harboring residual unburned mixture to add to that hiding between the piston crown, above the top ring, and the cylinder wall. In any case, never seen again.
Edit: The Mercedes engine described was used in its SL300 sports car, not Formula One."
This should kick off a good discussion of the W engines...
My opinion on the 409 (and 348) was formed during my HS years when I heard of a number of them 'blowing up' and throwing rods thru the side of the block, so I adopted the common attitude that the 348/409 were 'truck blocks' and not suited to higher rpm uses... (whether right or wrong? I don't know)
A funny response was listed along with the question:
"I was not sure of why the 409’s blew, but an old boss of mine was a foreman at the St. Louis chevy plant, and he said he saw them blow up waiting in line to load on the car haulers… "
Some other responses were: from a 30 yr senior automotive technician)..
"Biggest issue was the connecting rods as they were not much strong than the 283 connecting rod and would spin bearings and break under RPM. I believe the reason for using them was to reduce Bob weight with the extreamly heavy forged pistons.
Having built several we always upgraded the rods. Even race bullet aluminum were immensely strong as I had one guy with well over 10,000 miles and 200 races on a set and only measured 0.001 stretch and he RPM'ed the snot out of it with 4 speed. Local street racers hates him."
And from a BSc in Physics from a Cal State graduate:
"The Chevy “W” engine, including the 1958 released 348 cu in, later 409 cu in and 427 cu in Z-11 (NASCAR engine) were known to be somewhat more powerful than standard in-line valve wedge engines. A beneficial feature of these engines was that the intake valve was offset closer to the valley of the engine and the exhaust valve offset to the outside. This twisting of the valve alignments made the gas paths slightly shorter. The cylinder head bottom was flat, not containing a combustion chamber, thus leaving the valves completely unshrouded by chamber walls. These engines breathed a little better than standard pushrod wedge engines. They were basically bullet proof reliable. I never heard of a complaint of any disadvantages to the design. They were followed by the Chevy Mark III and IV engines that also had twisted valve alignments and added different valve angles for intake and exhaust valves. These engines, the Big Block Chevy, had an even better advantage over in-line valve engines. Playing with the valve orientations was possible because Chevy used rocker arms individually mounted on studs instead of all being mounted on a common shaft, an expedient innovated by Pontiac.
The flat cylinder head surface had no combustion chamber. The chamber was shaped by a space bellow the head formed by the fact that the block was milled at an angle. This strange arrangement was also introduced by Ford with its MEL (Mercury, Edsel, Lincoln) engine also in 1958. The Chevy and Ford MEL engines were partial copies of a Mercedes Formula One engine of 1954 with respect to the flat head surface and combustion chamber in the block and the Chevy engine also staggered the valves. What was left out from the Mercedes engine were the desmodromic valve actuation and the direct fuel injection.
So, the 409 was an impressive engine with a romantic image. Jan and Dean sang a song about it! On the other hand…. (yes there is more than one hand), neither Mercedes, Chevy nor Ford ever made another engine with the chamber in the block. In my suspicion, its a NG, no good, design! A cylinder pressure graph showed a slowing of the pressure rise just before peak pressure in the Chevy engine. Curious. I notice that the cylinder head/block mating crevice where the head gasket is recessed slightly, creates an extra band of relatively cold metal arching right over the combustion chamber, harboring residual unburned mixture to add to that hiding between the piston crown, above the top ring, and the cylinder wall. In any case, never seen again.
Edit: The Mercedes engine described was used in its SL300 sports car, not Formula One."
This should kick off a good discussion of the W engines...
