Hypothetical?

[stirling33]

I am still fairly new to making the right choices in regards to mods so here is a hypothetical question to all the seasoned vets out there.

If you have a cam that may be to big for your setup - for example - 280/290 duration and 472/496 lift and then you swap that out for a cam with less duration and more lift. Do you change the horsepower rating on your engine or do you just have better matched components that will perform better?

 

[302 coupe]

the 472/496 cam you mentioned should be just right for all but the mildest engine. If its in your engine with the GT40 heads, I'd say it just right.

But to answer your question...more duration shifts the power band to a higher rpm. More lift at a given duration will increase torque. Since horsepower is calculated using torque and rpm, more lift and more duration means more torque and horsepower at a higher rpm. If you were to switch to a cam with less duration and more lift, you would move your powerband lower in the rpm range, while increasing torque at that rpm.

 

[stirling33]

the 472/496 cam you mentioned should be just right for all but the mildest engine. If its in your engine with the GT40 heads, I'd say it just right.

But to answer your question...more duration shifts the power band to a higher rpm. More lift at a given duration will increase torque. Since horsepower is calculated using torque and rpm, more lift and more duration means more torque and horsepower at a higher rpm. If you were to switch to a cam with less duration and more lift, you would move your powerband lower in the rpm range, while increasing torque at that rpm.

So if you where building a motor primarily for the street and wanted very useable torque as fast a possible you would want a cam with less duration too shift the power band lower in the rpm range.

 

[302 coupe]

to an extent yes. Tell us what the engine combo is. No sense being hypothetical, there is more to it than just the camshaft, other parts impact rpm range also.

 

[stirling33]

to an extent yes. Tell us what the engine combo is. No sense being hypothetical, there is more to it than just the camshaft, other parts impact rpm range also.

Well the cam would be for the engine and mods in my signature, and everyone actually gave me suggestions on a cam in a different thread. I was just trying to gain some knowledge on how a cam choice will affect your performance.

But any further cam choices would be appreciated since I am not all that happy with my cam I have up to this point. Seeing that my car is primarily a street car I would like some more useable lower end torque.

 

[302 coupe]

Is it a small block? You can't expect a 289 or 302 to have the grunt of a 429, no matter how its built. What gears do you run? IMO, you've got a nice street combo that will allow the engine to breathe up to 6k without sacrificing much, if any, low end torque. You could try using a smaller cam, but then you might not be satisfied with the power over 4500 rpm. Always a tradeoff.

 

[stirling33]

Is it a small block? You can't expect a 289 or 302 to have the grunt of a 429, no matter how its built. What gears do you run? IMO, you've got a nice street combo that will allow the engine to breathe up to 6k without sacrificing much, if any, low end torque. You could try using a smaller cam, but then you might not be satisfied with the power over 4500 rpm. Always a tradeoff.

Yeah it is a small block 302, and I am running 3.89 gears. Don't get me wrong it does very well for a street car and I know there is always a trade off on versus the other, but I guess you sometimes get bored and want to go faster. I do appreciate all the info very helpfull. Maybe it is time to build a stroker motor.

 

[Red5oh]

What ford cam are you running? E, B, F, X????

 

[stirling33]

What ford cam are you running? E, B, F, X????

FMS-M-6250-A312 Ford Racing Camshafts
Camshaft, Hydraulic Flat Tappet, Advertised Duration 290/ 300, Lift .472/ .496, Ford Small Block

 

[HistoricMustang]

the 472/496 cam you mentioned should be just right for all but the mildest engine. If its in your engine with the GT40 heads, I'd say it just right.

But to answer your question...more duration shifts the power band to a higher rpm. More lift at a given duration will increase torque. Since horsepower is calculated using torque and rpm, more lift and more duration means more torque and horsepower at a higher rpm. If you were to switch to a cam with less duration and more lift, you would move your powerband lower in the rpm range, while increasing torque at that rpm.

I knew I liked this guy the first time I met him!

Plus he has some of my un-needed parts on his nice early model!

HistoricMustang
www.historicmustang.com

 

[bnickel]

FMS-M-6250-A312 Ford Racing Camshafts
Camshaft, Hydraulic Flat Tappet, Advertised Duration 290/ 300, Lift .472/ .496, Ford Small Block

i have pretty much the same cam in my 351w, the only difference is that yours has a ford part number, mine is actually a speed pro, but if you do some reasearch you'll find that speed pro actually makes that cam for ford. anyway that cam in my car is pretty nice and i only have a 3.25 gear in it. plenty of low end torque, in fact just breathing on teh gas pedal causes lot's of tire smoke . that said you may actually benefit from a slightly less aggressive cam. seeing how i have almost 50 cubic inches on you and i stll have a fairly choppy idle. the next step down from cam in the speed pro line is .442/.468 lift and 270/280 advertised duration, i think the @.050 lift is like 218/224. mine and your current cam have 224/236 duration @.050.

hope this helps you out a little. you should look into some the comp cams extreme energy series cams. i think they have one that has about the same .472/.796 lift but less duration, the duration is actually what's killing your low end torque since it's allowing a lot of compression to bleed off. my 351w could actually benefit from a lower duration as well since my compression is already low at about 8.8:1. instead of changing cams on mine though i will just get a higher compression piston since i really don't like that low of a compression ratio, i'd rather have it up around 10:1 which should be just about perfect for my combo.

 

[Edbert]

290-300 duration is high but .45-.48 lift is pretty low for a hiperf cam. Mine is a 280 with a .506 for a 357W with perf-RPM (2.02/1.60) heads and intake.

 

[bnickel]

edbert, what is the @.050 duration on your cam? the cam he and i are both running is 224/236 degress @.050. i hardly ever go by advertised duration

 

[2nd Mustang]

I think Historic has a one track mind, no matter what the thread is about!

 

[bnickel]

I think Historic has a one track mind, no matter what the thread is about!

are we talking about his girlfriends?

 

[2nd Mustang]

are we talking about his girlfriends?

Saves me from "Googling".

 

[rbohm]

when selecting a cam, DO NOT start looking at the lift and duration numbers. the very first thing you want to look at is what rpm range the cam is designed to work best in. once you have selected the rpm range, THEN start looking at the lift and duration numbers, along with where the intake valve closes. oyu can take two cams with the same duration numbers, and the one where the intake valve closes later will work in a slightly higher rpm range than the other. as 302coupe stated, more lift and less duration means more low rpm torque. another number to look at the valve overlap. longer overlap means higher rpm power as opposed to one with less overlap. wider lode centers mean less overlap, and more low end power as well. for the street i recomend a cam with 110-112 degree lobe centers, 114 if you are building a turbo motor. if you plan on racing then a 106-108 lobe center helps build power in the upper rpm range. all these numbers are available from the cam grinders and their websites.

and historic, very nice ladies, i am going to have to make you introduce me to them sometime

 

[Route666]

Compression ratio takes back some of what big cames take out of the low-end though right? So if you were to up CR, you could up the cam even more and have the same change in low-end as you would have with a smaller cam and no CR increase, but also more high-end power.

Just chucking in an extra factor to cam choice.

 

[Edbert]

edbert, what is the @.050 duration on your cam? the cam he and i are both running is 224/236 degress @.050. i hardly ever go by advertised duration

My cam was a custom grind recommended by DSS so I have never found it (exactly at least, it is close to many different ones like RPM or 280h) in a catalog, but the card that came with it says 222I 234E with .506 on both.

I built my engine with cruising as the number one goal, some street perf for the Saturday night parking lots, and maybe one or two 1/4 mile runs a year. I wanted torque, large amounts of it, I should have tons on hand from 2,500 on up to 5K. Cam's advertised RPM range is 2,000-6,500, and my stall converter is rated at 2800, might actually flash closer to 3,000 with 400fwhp on tap.

 

[2nd Mustang]

Compression ratio takes back some of what big cames take out of the low-end though right? So if you were to up CR, you could up the cam even more and have the same change in low-end as you would have with a smaller cam and no CR increase, but also more high-end power.

Just chucking in an extra factor to cam choice.

I heard something about this and wondered about my engine. I have a mild hydraulic Crane Cam with roller rockers. The compression is 130 pounds in all 8 cylinders and the idle is somewhat rough or lopey. I lost the spec card for the cam, but I remember is was a very mild grind. It does have good low end torque.