cams...
10-05-2009, 02:35 PM
#11
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Yeah you should be fine then. The one's I'm looking only affect 1700 - 1900 rpm and lower negatively. Rest is above and scaling the higher it goes.
Which is fine by me as I'm hardly ever below 2k rpms unless at a light or something. lol
Which is fine by me as I'm hardly ever below 2k rpms unless at a light or something. lol
10-13-2009, 11:48 PM
#13
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your mpg will def go down, it just depends on how aggressive the camshaft is. The longer the duration the more fuel it will require. I would check around to see how responsive f150s are to aftermarket camshafts. I dont know about f150s and cams but there is probably a reason that it is not a common install on our trucks.
10-14-2009, 11:04 AM
#14
Senior Member
There's a REALLY good reason that a high lift/long duration/big overlap cam install is not normally done in a truck: They're not race cars!!! These types of motor mods are normally done for racing purposes only. It works out because that type of cam increases flow at high RPMs, and since an engine is essentially an air pump, the more air you move thru it, the more HP you generate.
The lope that you THINK you want is actually a result of both the intake and the exhaust valves being open at the same time, with the intake valve actually opening before the end of the exhaust stroke and the exhaust valve being open after the piston starts the intake stroke. Why this is good at high RPMs is that the mass and high velocity of the exhaust gases actually help scavenge the combustion chamber and pull in a larger charge of fresh air/fuel mix from the intake side. What happens at low RPM, however, is a different matter. At low RPMs, the exhaust gas velocity isn't great enough to 'pull' the new charge thru as it does at higher RPMs and you actually end up with a stale mix of combusted exhaust and fresh air/fuel mix on your compression stroke. This results in a a drastic reduction in low RPM HP and torque at normal "street use" RPM (1500-2500 RPM) which will result in real-world driveability issues, especially if you're running an automatic tranny and the factory torque converter with a stall speed well below your cam's effective operating range. This will be especially problematic in a heavy vehicle such as your truck.
Bottom line, if you plan on using your truck strictly for racing--kind'a stupid, IMHO--go for it. If you plan on using your truck for any type of normal street use, leave it as is and invest your cash in a small-block V8-powered manual-tranny car (preferably a Ford....but SB Chevs are cheaper to build parts-wise) and get your lopey idle fix with that!
The lope that you THINK you want is actually a result of both the intake and the exhaust valves being open at the same time, with the intake valve actually opening before the end of the exhaust stroke and the exhaust valve being open after the piston starts the intake stroke. Why this is good at high RPMs is that the mass and high velocity of the exhaust gases actually help scavenge the combustion chamber and pull in a larger charge of fresh air/fuel mix from the intake side. What happens at low RPM, however, is a different matter. At low RPMs, the exhaust gas velocity isn't great enough to 'pull' the new charge thru as it does at higher RPMs and you actually end up with a stale mix of combusted exhaust and fresh air/fuel mix on your compression stroke. This results in a a drastic reduction in low RPM HP and torque at normal "street use" RPM (1500-2500 RPM) which will result in real-world driveability issues, especially if you're running an automatic tranny and the factory torque converter with a stall speed well below your cam's effective operating range. This will be especially problematic in a heavy vehicle such as your truck.
Bottom line, if you plan on using your truck strictly for racing--kind'a stupid, IMHO--go for it. If you plan on using your truck for any type of normal street use, leave it as is and invest your cash in a small-block V8-powered manual-tranny car (preferably a Ford....but SB Chevs are cheaper to build parts-wise) and get your lopey idle fix with that!
10-15-2009, 12:17 AM
#15
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There's a REALLY good reason that a high lift/long duration/big overlap cam install is not normally done in a truck: They're not race cars!!! These types of motor mods are normally done for racing purposes only. It works out because that type of cam increases flow at high RPMs, and since an engine is essentially an air pump, the more air you move thru it, the more HP you generate.
The lope that you THINK you want is actually a result of both the intake and the exhaust valves being open at the same time, with the intake valve actually opening before the end of the exhaust stroke and the exhaust valve being open after the piston starts the intake stroke. Why this is good at high RPMs is that the mass and high velocity of the exhaust gases actually help scavenge the combustion chamber and pull in a larger charge of fresh air/fuel mix from the intake side. What happens at low RPM, however, is a different matter. At low RPMs, the exhaust gas velocity isn't great enough to 'pull' the new charge thru as it does at higher RPMs and you actually end up with a stale mix of combusted exhaust and fresh air/fuel mix on your compression stroke. This results in a a drastic reduction in low RPM HP and torque at normal "street use" RPM (1500-2500 RPM) which will result in real-world driveability issues, especially if you're running an automatic tranny and the factory torque converter with a stall speed well below your cam's effective operating range. This will be especially problematic in a heavy vehicle such as your truck.
Bottom line, if you plan on using your truck strictly for racing--kind'a stupid, IMHO--go for it. If you plan on using your truck for any type of normal street use, leave it as is and invest your cash in a small-block V8-powered manual-tranny car (preferably a Ford....but SB Chevs are cheaper to build parts-wise) and get your lopey idle fix with that!
The lope that you THINK you want is actually a result of both the intake and the exhaust valves being open at the same time, with the intake valve actually opening before the end of the exhaust stroke and the exhaust valve being open after the piston starts the intake stroke. Why this is good at high RPMs is that the mass and high velocity of the exhaust gases actually help scavenge the combustion chamber and pull in a larger charge of fresh air/fuel mix from the intake side. What happens at low RPM, however, is a different matter. At low RPMs, the exhaust gas velocity isn't great enough to 'pull' the new charge thru as it does at higher RPMs and you actually end up with a stale mix of combusted exhaust and fresh air/fuel mix on your compression stroke. This results in a a drastic reduction in low RPM HP and torque at normal "street use" RPM (1500-2500 RPM) which will result in real-world driveability issues, especially if you're running an automatic tranny and the factory torque converter with a stall speed well below your cam's effective operating range. This will be especially problematic in a heavy vehicle such as your truck.
Bottom line, if you plan on using your truck strictly for racing--kind'a stupid, IMHO--go for it. If you plan on using your truck for any type of normal street use, leave it as is and invest your cash in a small-block V8-powered manual-tranny car (preferably a Ford....but SB Chevs are cheaper to build parts-wise) and get your lopey idle fix with that!
you have good points.... i've had a couple of fast cars in the past and love having a truck but have had to embrace the fact that i can't make it fast, maybe faster lol, but not fast especially a 4x4 that weighs just over 6000 lbs ..... i can't afford a toy just yet....
so no i don't want to make my truck a race car lol.... but the sound of a cam and a big v8 gives me a chubby haha i don't want it for HP, strictly just the sound
10-15-2009, 12:13 PM
#16
Senior Member
You probably wouldn't be able to hear the lopey idle inside your truck, 'cause you'd be cussing so loud about how crappy your truck was running! Save your bucks--Don't ruin your truck!