what are dual overhead cams?

Cooper · September 29th, 2003, 09:57 PM

i'm writing a song with a lot of car stuff in it. of course i know nothing about cars. so i have a few questions for those of you who actually understand this stuff:

can a corvette have a 396?

what are dual overhead cams? i've heard this term but have no idea what it means. i'd like to know before i put it in my song.

five speed is better than four, right?

thanks!

fenderfreak · September 29th, 2003, 11:05 PM

A DOHC engine has two camshafts ;one shaft controls the opening and closing of the intake valves, the other camshaft controls the exhaust valves , the shafts are located on top of the cylinder head , a corvette has a conventional over head valve engine ,, which means it has one camshaft located in the engine block and the valves are opened and closed by pushrods that ride on the cam also i dont think a Vette ever had a 396 try theese cubic inch displacements 283,327,350,427or454 its not really as complicated as it sounds later JB

Dacious · September 29th, 2003, 11:29 PM

396 was a standard Big Block size, but most big-block Vette's had 427s. 66 'vettes did come with them. 396s were usually used in trucks and standard-type cars although the Chevelle SS used them.

Camshafts are a shaft with 'cams' which are elliptical lobes or bumps to open the valve and allowing it to close gradually. They are turned by a gear, belt or chain off the crankshaft, and critically timed to operate the intake and exhaust valves so they don't hit the piston in the cylinder to let fresh air-fuel mix in and burnt gasses out.

Older motors (setting aside flatheads which haven't been made since the fifties) used overhead valves, where the camshaft opens both intake and exhaust valves, is in the engine block, and operates the valves via lifters and pushrods. Examples of this include the current cast iron GM V6, and aluminium V8 and Harleys which on the Sportster 4 cams - one per valve!. Advantages include lighter and simpler cylinder head castings and simplified drive, lower tolerances required in manufacture. Disadvantages include heavier valve trains with lower rev limits and heavy wear on components in high-performance applications. The intake and exhaust port shape and cylinder head/piston top shape is severely compromised meaning higher-octane fuels are needed for the same performance and economy as more advanced designs. Fitting multi-valves per cylinder serverely constrained by the restrictions on the valve train. 'Valve float' where the springs lose control and can't shut the valve is a problem, and a precursor to piston/valve contact which is usually catastrophic. 1920s technology

The next is a single overhead camshaft (per bank of cylinders - so one on each head on a v-engine like the older Mitsubishi V-6), where the cam sits in the head and again operates all the valves. You can easily get multi-valve setups, but the valves still need rockers to operate them, the cylinder head shape is compromised by the need to design the valvetrain components correctly to reduce wear on the cams and rockers which have high loadings on the bearing parts. In high-performance applications the rockers bend and break, they still weigh a lot at high revs needing stiffer springs which cause more wear problems to contol them etc. 1930's technology. Generally used in economy vehicles where performance is no issue.

Double overhead cams means on one cylinder bank there are two camshafts. So quad cams on a V6 or V8. An exhaust cam operates all the exhaust valves. An intake cam operates all the intake valves. They are sited directly above the valve, and push on it through a lifter.

These are a natural for multi-valve setups. 4 smaller valves have more valve lift area than 2 big ones and can intrude less into the cylinder for any given cam-lift while still flowing more air-fuel mix meaning more power, and reduced piston-valve clearances can be used while maintaining control of the valves so they don't touch the piston at high revs.

Advantages include better combustion chamber/piston shape for better burning meaning lower octane fuels can be used without sacrificing performance. That's how come my wife's 1800cc shopping trolley can get 42mpg at a constant 65mph and do 115 mph, and happily run on on 93 octane standard unleaded fuel in all conditions with no pinging, fluffing or farting.

The lack of anything except a clearance adjusting pad between the valve and the cam means lower reciprocating weight, which means lower string tension to control and return the valves to their seat, and less wear, friction and stress. The intake and exhaust ports can be straighter and larger, which increases efficiency of the motor for more power.

The disadvantages are a more complex, taller and heavier head casting, and a more complex drive arrangement and bigger parts count. Friction is also higher - a Cosworth V8 Formula 1 motor loses nearly 60hp just to drive it's four cams and 32 valves.

End of the day, every serious performance vehicle today or in design, from Ferraris, Lamborghinis, street and racing bikes, Formula 1 cars etc all use 4 or 5 valves per cylinder operated by double overhead cams. Twin cams with 2 valves per cylinder were in use by the Italians in the late 30's. Twin cams with 4 valves were in use by the 50's on MV Augustas and the like. GM US is about to introduce a new V6 (made here in Australia) for passenger cars which is quad-cam, 4-valve per cylinder and around 20-30% more powerful than the old one, which has been jiggered with about as much as it can to keep it modern.

Yamaha used 3 intake and 2 exhausts valves in the 80's.

Alboggs · September 30th, 2003, 10:12 AM

It's really thoughtful of you to want to get your terminology correct in your songwriting. One of my favorite country tunes of late is Brooks & Dunn's "Red Dirt Road"... I really like the tune... but I wince every time I hear the line "...her Daddy didn't like me much, in my 'shackled up GTO'..." Apparently Brooks & Dunn didn't care as much about correct terminology as you do because GTO's are coil spring rear suspension automobiles and shackles can only be used to raise or lift the rear of leaf spring rear suspended cars. Like Brad says... "...when you're a Celebrity, it's adios reality..."

bjammin · September 30th, 2003, 10:27 PM

Quote:

Originally Posted by Alboggs

It's really thoughtful of you to want to get your terminology correct in your songwriting. One of my favorite country tunes of late is Brooks & Dunn's "Red Dirt Road"... I really like the tune... but I wince every time I hear the line "...her Daddy didn't like me much, in my 'shackled up GTO'..." Apparently Brooks & Dunn didn't care as much about correct terminology as you do because GTO's are coil spring rear suspension automobiles and shackles can only be used to raise or lift the rear of leaf spring rear suspended cars. Like Brad says... "...when you're a Celebrity, it's adios reality..."

Maybe he was talking about a 1974 GTO, based on the nova/ventura/ chassis, ha ha ,I never considered those 74s real GTOs but they had the name on them.......... I think you are right they just used it because it fit :)

Dennis_UK · October 1st, 2003, 08:38 AM

...and here I am making do with an 8-valve, 4-cylinder, pushrod, direct-injection diesel!
However, it does 30-35mpg (imperial), and weighs in excess of two metric tonnes! So not bad.

Steve Perry · October 1st, 2003, 09:23 AM

The big block 396 was available in the Corvette in 1965 (the first year for that engine) but was replaced with the 427 in the '66 Vette.

Steve "the son of a Chevy Dealer from that era" Perry

11 Gauge · October 1st, 2003, 12:25 PM

you're from NC and you know nothing about cars, in particular old Detroit muscle? not a putdown, but NC has a big history of this stuff, especially with NASCAR...

go knock on some of your neighbor's doors and they could probably give you a great history of it all.

that said, i used to be a bit of a musclecar/hotrod enthusiast, so i can probably help a bit with 'authentic lyrics.'

first of all, forget about dual overhead cams. not to be found in all the old American stuff.

5 speeds are cool, but back then it was just 3 or 4 on the floor.

no turbochargers. not cool or common years ago (unless you lived in Italy or Germany).

supercharged is an okay term. blown or blower is better.

injected is cool terminology.

dual CARBS (not cams) is big with hot rods. also cool is the '6 pack': 3 2 bbl. carbs on the 440 c.i. big block motor.

V8s are cool. big block V8s are cooler (lyric wise).

other cool hot rod terms - 9" rear (Ford), 4 bolt mains (mainly Chevy), hemi, headers, posi rear, 12 bolt rear (Chevy), glasspacks, velocity stacks, tubbed out in the back.

popular engine sizes-
Chevy: 327,350,427,454
Dodge:426 Hemi, 440 6 pack
Ford: 351 Cleveland, 428
Cadillac: 500 cubic inches!

hopefully some stuff for lyrics. as to which car got which engine and other stuff in what years, you'll have to research that, or this reply will go on for another 40 paragraphs or so.

and hopefully no erroneous information...

slauson slim · October 2nd, 2003, 12:39 AM

Get some early Beach Boys, Jan & Dean, etc. car songs and try them for some ideas. Also, other folks had car songs...Little GTO, Little Red Corvette, 2-4-6-8 Motorway, Pink Cadillac, Cadillac Walk....

As to engines don't forget MOPAR 413s and Chev 409s and 348s. Guess I'm showing my age.......

Cooper · October 4th, 2003, 12:33 PM

that's a lot to consider. i think my current lyrics are decently accurate. as long as a corvette COULD conceivably have a 396, i'm good. but i have saved this post and will refere to it in the future, because i write mostly about my friends who live in the car world.

thanks!

September 29th, 2003, 09:57 PM	#1 (permalink)
Cooper Tele-Meister Join Date: Mar 2003 Location: Asheville, NC Posts: 498	what are dual overhead cams? i'm writing a song with a lot of car stuff in it. of course i know nothing about cars. so i have a few questions for those of you who actually understand this stuff: can a corvette have a 396? what are dual overhead cams? i've heard this term but have no idea what it means. i'd like to know before i put it in my song. five speed is better than four, right? thanks! __________________ I said, "I don't think so, Scooter!" And I was wrong.

September 29th, 2003, 11:05 PM	#2 (permalink)
fenderfreak Tele-Meister Join Date: May 2003 Location: lancaster ca Posts: 275	DOHC A DOHC engine has two camshafts ;one shaft controls the opening and closing of the intake valves, the other camshaft controls the exhaust valves , the shafts are located on top of the cylinder head , a corvette has a conventional over head valve engine ,, which means it has one camshaft located in the engine block and the valves are opened and closed by pushrods that ride on the cam also i dont think a Vette ever had a 396 try theese cubic inch displacements 283,327,350,427or454 its not really as complicated as it sounds later JB __________________ Help Mr.Wizard! Help

September 29th, 2003, 11:29 PM	#3 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,605 35 Photos	396 was a standard Big Block size, but most big-block Vette's had 427s. 66 'vettes did come with them. 396s were usually used in trucks and standard-type cars although the Chevelle SS used them. Camshafts are a shaft with 'cams' which are elliptical lobes or bumps to open the valve and allowing it to close gradually. They are turned by a gear, belt or chain off the crankshaft, and critically timed to operate the intake and exhaust valves so they don't hit the piston in the cylinder to let fresh air-fuel mix in and burnt gasses out. Older motors (setting aside flatheads which haven't been made since the fifties) used overhead valves, where the camshaft opens both intake and exhaust valves, is in the engine block, and operates the valves via lifters and pushrods. Examples of this include the current cast iron GM V6, and aluminium V8 and Harleys which on the Sportster 4 cams - one per valve!. Advantages include lighter and simpler cylinder head castings and simplified drive, lower tolerances required in manufacture. Disadvantages include heavier valve trains with lower rev limits and heavy wear on components in high-performance applications. The intake and exhaust port shape and cylinder head/piston top shape is severely compromised meaning higher-octane fuels are needed for the same performance and economy as more advanced designs. Fitting multi-valves per cylinder serverely constrained by the restrictions on the valve train. 'Valve float' where the springs lose control and can't shut the valve is a problem, and a precursor to piston/valve contact which is usually catastrophic. 1920s technology The next is a single overhead camshaft (per bank of cylinders - so one on each head on a v-engine like the older Mitsubishi V-6), where the cam sits in the head and again operates all the valves. You can easily get multi-valve setups, but the valves still need rockers to operate them, the cylinder head shape is compromised by the need to design the valvetrain components correctly to reduce wear on the cams and rockers which have high loadings on the bearing parts. In high-performance applications the rockers bend and break, they still weigh a lot at high revs needing stiffer springs which cause more wear problems to contol them etc. 1930's technology. Generally used in economy vehicles where performance is no issue. Double overhead cams means on one cylinder bank there are two camshafts. So quad cams on a V6 or V8. An exhaust cam operates all the exhaust valves. An intake cam operates all the intake valves. They are sited directly above the valve, and push on it through a lifter. These are a natural for multi-valve setups. 4 smaller valves have more valve lift area than 2 big ones and can intrude less into the cylinder for any given cam-lift while still flowing more air-fuel mix meaning more power, and reduced piston-valve clearances can be used while maintaining control of the valves so they don't touch the piston at high revs. Advantages include better combustion chamber/piston shape for better burning meaning lower octane fuels can be used without sacrificing performance. That's how come my wife's 1800cc shopping trolley can get 42mpg at a constant 65mph and do 115 mph, and happily run on on 93 octane standard unleaded fuel in all conditions with no pinging, fluffing or farting. The lack of anything except a clearance adjusting pad between the valve and the cam means lower reciprocating weight, which means lower string tension to control and return the valves to their seat, and less wear, friction and stress. The intake and exhaust ports can be straighter and larger, which increases efficiency of the motor for more power. The disadvantages are a more complex, taller and heavier head casting, and a more complex drive arrangement and bigger parts count. Friction is also higher - a Cosworth V8 Formula 1 motor loses nearly 60hp just to drive it's four cams and 32 valves. End of the day, every serious performance vehicle today or in design, from Ferraris, Lamborghinis, street and racing bikes, Formula 1 cars etc all use 4 or 5 valves per cylinder operated by double overhead cams. Twin cams with 2 valves per cylinder were in use by the Italians in the late 30's. Twin cams with 4 valves were in use by the 50's on MV Augustas and the like. GM US is about to introduce a new V6 (made here in Australia) for passenger cars which is quad-cam, 4-valve per cylinder and around 20-30% more powerful than the old one, which has been jiggered with about as much as it can to keep it modern. Yamaha used 3 intake and 2 exhausts valves in the 80's. __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat!

September 30th, 2003, 10:12 AM	#4 (permalink)
Alboggs TDPRI Member Join Date: May 2003 Location: Baltimore, Maryland Posts: 25	Automobiles and songwriting... It's really thoughtful of you to want to get your terminology correct in your songwriting. One of my favorite country tunes of late is Brooks & Dunn's "Red Dirt Road"... I really like the tune... but I wince every time I hear the line "...her Daddy didn't like me much, in my 'shackled up GTO'..." Apparently Brooks & Dunn didn't care as much about correct terminology as you do because GTO's are coil spring rear suspension automobiles and shackles can only be used to raise or lift the rear of leaf spring rear suspended cars. Like Brad says... "...when you're a Celebrity, it's adios reality..." __________________ What a great collection of guitars I'd have... if I'd known then... what I know now...

October 1st, 2003, 08:38 AM	#6 (permalink)
Dennis_UK Tele-Holic Join Date: Mar 2003 Location: Tavistock, Devon, UK Age: 55 Posts: 676	Good grief, Dacious... ...and here I am making do with an 8-valve, 4-cylinder, pushrod, direct-injection diesel! However, it does 30-35mpg (imperial), and weighs in excess of two metric tonnes! So not bad. __________________ Fender MIM Precision, all black, 2004. Fender MIJ Precision, '51 RI, Butterscotch, 1996. Squier VM Precision TB, 3TS, 2007 The Rock'nRoll Outlaws

October 1st, 2003, 09:23 AM	#7 (permalink)
Steve Perry TDPRI Member Join Date: Apr 2003 Location: Elizabethtown, KY Posts: 54	Big Block Vettes... The big block 396 was available in the Corvette in 1965 (the first year for that engine) but was replaced with the 427 in the '66 Vette. Steve "the son of a Chevy Dealer from that era" Perry

October 1st, 2003, 12:25 PM	#8 (permalink)
11 Gauge Friend of Leo's Join Date: Mar 2003 Location: The East Coast Posts: 2,638 12 Photos	wow... you're from NC and you know nothing about cars, in particular old Detroit muscle? not a putdown, but NC has a big history of this stuff, especially with NASCAR... go knock on some of your neighbor's doors and they could probably give you a great history of it all. that said, i used to be a bit of a musclecar/hotrod enthusiast, so i can probably help a bit with 'authentic lyrics.' first of all, forget about dual overhead cams. not to be found in all the old American stuff. 5 speeds are cool, but back then it was just 3 or 4 on the floor. no turbochargers. not cool or common years ago (unless you lived in Italy or Germany). supercharged is an okay term. blown or blower is better. injected is cool terminology. dual CARBS (not cams) is big with hot rods. also cool is the '6 pack': 3 2 bbl. carbs on the 440 c.i. big block motor. V8s are cool. big block V8s are cooler (lyric wise). other cool hot rod terms - 9" rear (Ford), 4 bolt mains (mainly Chevy), hemi, headers, posi rear, 12 bolt rear (Chevy), glasspacks, velocity stacks, tubbed out in the back. popular engine sizes- Chevy: 327,350,427,454 Dodge:426 Hemi, 440 6 pack Ford: 351 Cleveland, 428 Cadillac: 500 cubic inches! hopefully some stuff for lyrics. as to which car got which engine and other stuff in what years, you'll have to research that, or this reply will go on for another 40 paragraphs or so. and hopefully no erroneous information... __________________

October 2nd, 2003, 12:39 AM	#9 (permalink)
slauson slim Tele-Holic Join Date: Mar 2003 Posts: 667	Er, steal Get some early Beach Boys, Jan & Dean, etc. car songs and try them for some ideas. Also, other folks had car songs...Little GTO, Little Red Corvette, 2-4-6-8 Motorway, Pink Cadillac, Cadillac Walk.... As to engines don't forget MOPAR 413s and Chev 409s and 348s. Guess I'm showing my age.......

October 4th, 2003, 12:33 PM	#10 (permalink)
Cooper Tele-Meister Join Date: Mar 2003 Location: Asheville, NC Posts: 498	wow . . . that's a lot to consider. i think my current lyrics are decently accurate. as long as a corvette COULD conceivably have a 396, i'm good. but i have saved this post and will refere to it in the future, because i write mostly about my friends who live in the car world. thanks! __________________ I said, "I don't think so, Scooter!" And I was wrong.