302 cams
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302 cams
ok what i got it a late 80s 302 carbed withaholley 750 4b.and im putin it in my ranger.and i wanted to put a good sized cam in it. one u can hear. .
but i know nothing about cams.. i wouldlike the biggest cam i can get without having to change vavles and springs and everything/
are if anyone knows where i an buythe whole kit from would be a GREAT
but i know nothing about cams.. i wouldlike the biggest cam i can get without having to change vavles and springs and everything/
are if anyone knows where i an buythe whole kit from would be a GREAT
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
See the link... http://farm5.static.flickr.com/4043/...03659361_o.jpg
Also sell that carb to sombody with a big block and go find a 550 or 600cfm 4bbl.. a 750 is WAY too big for a 302 with stock heads.
Also sell that carb to sombody with a big block and go find a 550 or 600cfm 4bbl.. a 750 is WAY too big for a 302 with stock heads.
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From: Earth
Yeah, it's just you.
Here's the deal with cams. To get one with a lumpy idle, you've got to keep the valves open for a long time so they overlap - both open at the same time. Problem is that to do that the engine really doesn't run well at low rpms - it only pulls maybe 12" of vacuum (which means even worse metering from your already too big carb) and bleeds off cylinder pressure so your effective compression ratio is even lower. A hot, nasty-idling cam in an otherwise stock long block will probably make less hp than a smaller grind.
In fact, you'd make more power with the stock cam and new heads than you would with a 270 cam and stock heads.
But if you're willing to sacrifice drivability and and total hp for a mean idle with what you've got then get one of Comp's Thumpr cams.
Here's the deal with cams. To get one with a lumpy idle, you've got to keep the valves open for a long time so they overlap - both open at the same time. Problem is that to do that the engine really doesn't run well at low rpms - it only pulls maybe 12" of vacuum (which means even worse metering from your already too big carb) and bleeds off cylinder pressure so your effective compression ratio is even lower. A hot, nasty-idling cam in an otherwise stock long block will probably make less hp than a smaller grind.
In fact, you'd make more power with the stock cam and new heads than you would with a 270 cam and stock heads.
But if you're willing to sacrifice drivability and and total hp for a mean idle with what you've got then get one of Comp's Thumpr cams.
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thanks im sorry i know nothing about cams. i guess its time for me to learn then look stupid on here. i will look into gettin a smaller carb. i dint put it on there i bought the motor and everything already built. ill look into a smaller one for it.. and about the heads? what about the gt 40 headswould they be worth it to put on my motor? and thanks for the info about all this
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another thing what does number mean about a cam like duration @ .050 int./ exh. 224 / 224
lift int./exh. .470 /.470
thats just a cam i looked at in a book just a exmple oto get a idea of what it means
lift int./exh. .470 /.470
thats just a cam i looked at in a book just a exmple oto get a idea of what it means
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From: Earth
If you can find a set of clean GT40's they would definitely help.
Cam duration is the number of degrees (out of a possible 360 - i.e. a full circle) a cam keeps the valve open. So 224/224@.050" means the cam holds the valve open at least .050" for 224 degrees. A higher number = valve open longer and a higher peak power rpm. That 224 grind would work okay with some GT40 heads, 9.5:1 compression, a good intake, etc. For a truck something around 212 would give you more low end grunt without giving up too much on the top end.
The other number is how much the cam opens the valve with stock rocker arms - .47". Don't focus on that number, other than making sure your valvetrain can handle it (anything <.5" should be fine) and you're not dinging the pistons.
Go check out Comp Cams website, they've got all sorts of tutorials on cams, etc. and even some free dyno simulation software you can download.
Cam duration is the number of degrees (out of a possible 360 - i.e. a full circle) a cam keeps the valve open. So 224/224@.050" means the cam holds the valve open at least .050" for 224 degrees. A higher number = valve open longer and a higher peak power rpm. That 224 grind would work okay with some GT40 heads, 9.5:1 compression, a good intake, etc. For a truck something around 212 would give you more low end grunt without giving up too much on the top end.
The other number is how much the cam opens the valve with stock rocker arms - .47". Don't focus on that number, other than making sure your valvetrain can handle it (anything <.5" should be fine) and you're not dinging the pistons.
Go check out Comp Cams website, they've got all sorts of tutorials on cams, etc. and even some free dyno simulation software you can download.
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FTE Legend
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From: Ottawa, Ontario
Duration is how many degrees of rotation a valve is held open, the two common sets of numbers you will see are "advertised" or from seat to seat and at 0.050" lift of the valve measured as it just begins to open and just as it's closing. The duration is the primary factor determining where the cam makes power, in general shorter durations make more low rpm TQ but sacrifice peak HP, while longer durations do the opposite.
Valve lift is simply how much the valve opens with the stock rocker ratio and is usually publishd in thousands of an inch.
Lobe seperation angle is the difference between the certerline of the intake and exhaust lobes. There is always some overlap between the intake and exhaust valves.. meaning they will both be open for part of the cycle. The amount of overlap determines certain engine characteristics like the strength of the vacuum signal and idle quality.
Valve lift is simply how much the valve opens with the stock rocker ratio and is usually publishd in thousands of an inch.
Lobe seperation angle is the difference between the certerline of the intake and exhaust lobes. There is always some overlap between the intake and exhaust valves.. meaning they will both be open for part of the cycle. The amount of overlap determines certain engine characteristics like the strength of the vacuum signal and idle quality.
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From: Rogue River, Oregon
Back in the day I put the biggest hydraulic flat-tappet cam I could find in my '65 fastback Mustang. It had 240 degrees of duration at .050" lift and an advertised duration of 305 degrees, plus a relatively mild lift of .512". The motor was otherwise stock, and it had a four speed and 3.89 gears. While it sounded positively wicked, it was actually slower than it was with the stock cam, and since I never sprung for guide plates, it would bend pushrods at random. I've since learned my lesson and prefer smallish (as in trouble-free) cams today and love the Comp Cams 268XE in my current Mustang.
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that engine with a cam swap on no valve spring is a shot in the dark.... the cam may eat the springs in a month or a year.... but it will eventually eat the springs....
How i would explain cams is this: it doesnt matter what it sounds like at idle.... how a cam sounds is a function of how it is intended to operate..... for trucks with 302 .480 is about as much lift as you want..... The higher the lift of the cam the higher the rpm band where it makes power is..... if you are driving on the street is doesnt matter a hill of **** what hp the motors makes at 7000 rpms... if you dont drive the engine at that rpm its useless.... as you increase lift, duration and lobe separation will all change so that the cam will make more power with the events of valve timing happening at an incredibly rapid rate.... the lump and lope of a .670 cam at idle is because at 7000rpms the motor has little time to fill the combustion chambers with air and fuel and therefore the motor relies on keeping the valves open longer to fill the chambers which is heard at idle as a lump... some engine with cams that big wont even idle below 1500 rpms....
what you need to start with is by asking yourself what is the max rpms you are going to drive and and select a cam that makes max power in that band.....
How i would explain cams is this: it doesnt matter what it sounds like at idle.... how a cam sounds is a function of how it is intended to operate..... for trucks with 302 .480 is about as much lift as you want..... The higher the lift of the cam the higher the rpm band where it makes power is..... if you are driving on the street is doesnt matter a hill of **** what hp the motors makes at 7000 rpms... if you dont drive the engine at that rpm its useless.... as you increase lift, duration and lobe separation will all change so that the cam will make more power with the events of valve timing happening at an incredibly rapid rate.... the lump and lope of a .670 cam at idle is because at 7000rpms the motor has little time to fill the combustion chambers with air and fuel and therefore the motor relies on keeping the valves open longer to fill the chambers which is heard at idle as a lump... some engine with cams that big wont even idle below 1500 rpms....
what you need to start with is by asking yourself what is the max rpms you are going to drive and and select a cam that makes max power in that band.....
Postmaster
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From: Earth
I'm going to have to disagree with you a bit on that Fett Man. Valve lift in and of itself doesn't affect a cam's powerband. Cams with high lifts do tend to have longer duration, and therefore a higher powerband. A lot of that has to do with putting a lobe with .6" of valve lift on a short duration cam without making the ramps so steep they would bind/gall flat tapped lifters and the cam lobe. That's one of the biggest advantages of a roller cam - big lifts and steep ramps are no worries.
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you are correct Baron... the poster wanted a simple explanation of cams.... so I gave him explanation 3.0..... In fact they used to use lift to compensate for bad airflow of cylinder heads and the small valves back in the day.... I only use rollers reallly.... thats a no brainer for performance...
Mountain Pass
Joined: Dec 2005
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From: Mackinaw City, MI
My 302 Ranger project consisted of a fresh stock long block, but I swapped the cam,lifters,springs,retainers, locks, for a Comp cams package, Xtreme 4x4, the largest one they offer for a SBF. It had lifts of .512I and .531E, can't exactly remember duration, I think 278, but all this worked without notching pistons or any other mods. It had a wicked choppy idle, pulled 16" vacuum at 1K rpms, and pulled very hard all the way to 6K. This was Manifolds and a 2barrel carb. My sole intent was to build and sell, so I didn't opt for 4bbl and headders. Frankly, it didn't need it. I had a 3.73Trak-lok out back from a Bronco 2, an AOD with a shift kit, and aluminum driveshaft. You didn't steer this truck, you aimed it. Guy I sold it to immediately put a 4bbl on it and wrecked it soon after
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