another stupid cam ?

swtstang · 06-20-2001, 01:07 PM

Can some explain to me what exactly the duration of the cam means. Also what it means @.050".... The lift is how much it opens the valves up right?????? Any help would be greatly appricated. Also what is the best more lift or duration or do you want high in both? Thanks again

Lexicon · 06-20-2001, 03:54 PM

Mustangs Monthly and Fast Fords had an excellent article on cam basics about 3 months back. Duration is the time the valve remains open, @.050 is just a notation indicating (pretty much standard) where the measurement is taken from. More lift allows the valve to travel futher down from the valve seat (valve closed means it is against/in the seat). This allows more are to clear past any obstruction that the back face of valve may create. You do not wish to go the bigger is better route when looking for a cam. Many factors are applicable in this situation. Are you a NA car or power adder, if so you would wish to have a longer duration on the exhaust valve to allow for increased velocity and amount of the gasses to exit the engine and spool up the turbo and dump that added compressed volume in the cylinder. If you go to big and too wild you will suffer a stumbling idle, which in effect leads to daily driver headaches. Your best bet is to contact any of the cam manufactures and ask them to specify a grind for your particular application. As always, perform more research if you are wanting to make the selection yourself.

MiracleMax · 06-21-2001, 01:47 AM

Well that depends on several factors as far as how much lift & duration you want/need.

Like Lex said it really depends on your combo? Is drivability, emissions an issue? Do you use a factory based efi setup?

Anywhosit more lift with a more aggressive rate of lift (rather than increased duration I beleive this is termed area under the curve) will probably give a more satisfying increase in power. As this would diminish the trade off in torque for horsepower that typically acompanies installing a bigger cam.

Now wanna see somthing funky! check out valve curtain area? If its a given that the three valves below are saddled with ports that flow exactly the same at the specified lift despite varying sizes then they all have the same valve curtain and effectively flow the same amount of air despite having varing amounts of lift and valve size.

1.84 x .500 = .92

1.94 x .474 = .92

2.02 x .455 = .92

Okay where does this leave us? Well say for instance your heads have 1.84 valves that reach peak flow in the .500 region? That means you are going to have to run a cam with .500 lift to equal the flow that a 2.02 valve would get with a .455 lift.

swtstang · 06-21-2001, 12:03 PM

Ok, Emissions is not an issue, and here is my setup, rebuilt shortblock, trickflow heads, 1.6 roller rockers, torker II intake, 650 carb, 3.73 gears, with a good old t-5. What do you think I should do. It's not a daily driver. I can't have more than .540 lift right, with the stock pistons? That's what Trick flows ad says. What do you think?

06-21-2001, 12:15 PM

Edelbrock dyno'd their intake, cam, carb combo's and gave their recomendations for each specific part,,,,

you said you have a torker II manifold??

Edelbrock recomends their;

Torker-Plus Camshaft/Lifters/Lube Package #5082*
Use Edelbrock #7820 or #7811 timing chain set or #7892 Accu-Drive gear drive. DO NOT use stock timing set.

Duration at .006 Lift: Intake 290° Exhaust 300° Centerlines
Duration at .050 Lift: Intake 224° Exhaust 234° Lobe Separation: 110°
Lift at Cam: Intake .310 Exhaust .325 Intake Centerline: 106°
Lift at Valve: Intake .496 Exhaust .520
Timing at .050 Lift: Open Close
Intake 6° BTDC 38° ABDC
Exhaust 51° BBDC 3° ATDC

???

------------------
Black,84 GT,ground effects,shorty headers, 'open' dual exh.,302 HO(no pollution control crap),T5,89 ported heads,edelbrock Performer manifold, Edelbrock 2122 cam,600 Holley, high volume oil pump...

4:10's on their way!!!!

06-20-2001, 01:07 PM	#1
swtstang Registered Member Join Date: Apr 2001 Location: stockton, ca usa Posts: 160	another stupid cam ? Can some explain to me what exactly the duration of the cam means. Also what it means @.050".... The lift is how much it opens the valves up right?????? Any help would be greatly appricated. Also what is the best more lift or duration or do you want high in both? Thanks again

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06-20-2001, 03:54 PM	#2
Lexicon Registered Member Join Date: Jun 1999 Location: Evansville, Indiana Posts: 182	Mustangs Monthly and Fast Fords had an excellent article on cam basics about 3 months back. Duration is the time the valve remains open, @.050 is just a notation indicating (pretty much standard) where the measurement is taken from. More lift allows the valve to travel futher down from the valve seat (valve closed means it is against/in the seat). This allows more are to clear past any obstruction that the back face of valve may create. You do not wish to go the bigger is better route when looking for a cam. Many factors are applicable in this situation. Are you a NA car or power adder, if so you would wish to have a longer duration on the exhaust valve to allow for increased velocity and amount of the gasses to exit the engine and spool up the turbo and dump that added compressed volume in the cylinder. If you go to big and too wild you will suffer a stumbling idle, which in effect leads to daily driver headaches. Your best bet is to contact any of the cam manufactures and ask them to specify a grind for your particular application. As always, perform more research if you are wanting to make the selection yourself.

06-21-2001, 01:47 AM	#3
MiracleMax Registered Member Join Date: Apr 1999 Location: Hayes, Va, USA Posts: 798	Well that depends on several factors as far as how much lift & duration you want/need. Like Lex said it really depends on your combo? Is drivability, emissions an issue? Do you use a factory based efi setup? Anywhosit more lift with a more aggressive rate of lift (rather than increased duration I beleive this is termed area under the curve) will probably give a more satisfying increase in power. As this would diminish the trade off in torque for horsepower that typically acompanies installing a bigger cam. Now wanna see somthing funky! check out valve curtain area? If its a given that the three valves below are saddled with ports that flow exactly the same at the specified lift despite varying sizes then they all have the same valve curtain and effectively flow the same amount of air despite having varing amounts of lift and valve size. 1.84 x .500 = .92 1.94 x .474 = .92 2.02 x .455 = .92 Okay where does this leave us? Well say for instance your heads have 1.84 valves that reach peak flow in the .500 region? That means you are going to have to run a cam with .500 lift to equal the flow that a 2.02 valve would get with a .455 lift.

06-21-2001, 12:03 PM	#4
swtstang Registered Member Join Date: Apr 2001 Location: stockton, ca usa Posts: 160	Ok, Emissions is not an issue, and here is my setup, rebuilt shortblock, trickflow heads, 1.6 roller rockers, torker II intake, 650 carb, 3.73 gears, with a good old t-5. What do you think I should do. It's not a daily driver. I can't have more than .540 lift right, with the stock pistons? That's what Trick flows ad says. What do you think?

06-21-2001, 12:15 PM	#5
jerryIII Guest Posts: n/a	Edelbrock dyno'd their intake, cam, carb combo's and gave their recomendations for each specific part,,,, you said you have a torker II manifold?? Edelbrock recomends their; Torker-Plus Camshaft/Lifters/Lube Package #5082* Use Edelbrock #7820 or #7811 timing chain set or #7892 Accu-Drive gear drive. DO NOT use stock timing set. Duration at .006 Lift: Intake 290° Exhaust 300° Centerlines Duration at .050 Lift: Intake 224° Exhaust 234° Lobe Separation: 110° Lift at Cam: Intake .310 Exhaust .325 Intake Centerline: 106° Lift at Valve: Intake .496 Exhaust .520 Timing at .050 Lift: Open Close Intake 6° BTDC 38° ABDC Exhaust 51° BBDC 3° ATDC ??? ------------------ Black,84 GT,ground effects,shorty headers, 'open' dual exh.,302 HO(no pollution control crap),T5,89 ported heads,edelbrock Performer manifold, Edelbrock 2122 cam,600 Holley, high volume oil pump... 4:10's on their way!!!!