rpm cam question
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
A cam designed for idle to "x" rpm operation is designed to cover things like low-rpm pulling or parking lot trolling, etc... 1500 rpms is high enough that you COULD be ignoring some common "driveability" characteristics by choosing it. For example, in a ZF car you're running below 1500 rpms using 6th gear at 65mph.
With that 1500-XXXX rpm cam you might not notice overt affects but you'll most likely have a bit less power/response compared to an idle-XXXX cam. You might feel I tiny bit of cam surge at low rpm hwy driving. And, you'd most likely get worse MPG with the 1500 cam. (Street driving spends a lot of time at idle/off-idle conditions.)
Lift, duration, overlap, and ramp rates can affect low-rpm driveability.
With that 1500-XXXX rpm cam you might not notice overt affects but you'll most likely have a bit less power/response compared to an idle-XXXX cam. You might feel I tiny bit of cam surge at low rpm hwy driving. And, you'd most likely get worse MPG with the 1500 cam. (Street driving spends a lot of time at idle/off-idle conditions.)
Lift, duration, overlap, and ramp rates can affect low-rpm driveability.
As others have said, post the cam's specs, and intended usage and you'll get better help.
X2. Big time.
Le Mans Master
Joined: Dec 2009
Posts: 6,397
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From: Saskatoon Saskatchewan
An idle-3500 cam is designed to produce its best power from idle to 3500 rpm. a 1,500-3,500rpm cam is designed to produce best power from 1500-3500 rpm. Which is best depends largely on your gearing with the idle-3500 rpm cam being better suited to a car with higher (lower numerically) gearing than a 1500-3500 rpm cam would be.
Drifting
Joined: Feb 2006
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From: Magnolia Tx
Race Director
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From: moraga ca
Thread Starter
Instructor
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No I'm sure bigger is better, but what I want, Is torque. If I were to go bigger. Id get a LT and go crazy with it.
But in this case, if "bigger" means more low end power then yea I'm all for it.
I don't want to sound like a broken record, I've posted my first thread on here about cams and a lot of people put time aside to respond. More so Greggpenn and vetteoz and you 383.
I just want harder launches off the line. My setup now is mostly stock but I like it. Of a cam can get me harder launches then ill budget over the summer.
I love my stock cam, I'm in rush to change it, just opinions.
And all of you guys have been helpful
But in this case, if "bigger" means more low end power then yea I'm all for it.
I don't want to sound like a broken record, I've posted my first thread on here about cams and a lot of people put time aside to respond. More so Greggpenn and vetteoz and you 383.
I just want harder launches off the line. My setup now is mostly stock but I like it. Of a cam can get me harder launches then ill budget over the summer.
I love my stock cam, I'm in rush to change it, just opinions.
And all of you guys have been helpful
Race Director
Joined: Jan 2005
Posts: 10,641
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From: Slidell Louisiana
Honestly if you add 1.6 or 1.7 RR you will be PDC to the real C4 torque monsters cam specs... the LT4* assuming your valvetrain and heads can handly the lift.....
Mike
Last edited by aboatguy; Mar 17, 2013 at 02:50 PM.
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Racer
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From: Eden Utah
Le Mans Master
Joined: Dec 2009
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From: Saskatoon Saskatchewan
Race Director
Joined: Jan 2005
Posts: 10,641
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From: Slidell Louisiana
and what displacement does the cam company list?
Often cams are advertised for a range of displacement and a larger displacement engine makes the cam behave SMALLER.
Mike
Thread Starter
Instructor
Joined: Jan 2013
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Here's a my setup sum'd up. I'm stock with some weight shedded, 1.5 rollers, ported plenum,base and some porting on the runners, 3.07 rear, rebuilt distributor witha accel coil, rotor, wires and plugs, delet ac n smog pump. Stock cam. I'm tryin to keep it as a baseline but stock
Racer
Joined: Dec 2007
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From: San Antonio Texas
That's an old school way of telling the layman what to expect.
Don't let the 111 LSA fool ya......all B-bodies from 1994 to 1996 got this cam......including cop cars, taxis, and Grand Pa's cushy Roadmaster.
And I doubt that you'll have to get a reflashed PROM, but if you feel a need to, www.pcmforless.com can do the honors. They have extensive experience with the performance specs of the B-Body cam.
KW
And I doubt that you'll have to get a reflashed PROM, but if you feel a need to, www.pcmforless.com can do the honors. They have extensive experience with the performance specs of the B-Body cam.
KW
Safety Car
Joined: Jan 2004
Posts: 3,556
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( which is what gives the off the line grunt you seek ) of a L98; lack of traction from too much torque is a more common problem for L98 owners.
Maybe a higher stall convertor may give you the feel you want without opening up the engine
and some sticky tires
Drifting
Joined: Feb 2006
Posts: 1,423
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From: Magnolia Tx
other mods the make a cam swap worth the trouble. I don't think OP does
either.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
To make more power, tq etc you need to hang the valve open longer (duration) and open the valve farther (lift). Going smaller than stock you will lose all the above.
Some co's like to open and shut the valve super fast to make the cam act larger than it is.....it works but is hard on the valvetrain.
Now if it were highly modded and had too big a cam/heads then yes you could go smaller and probably pick things up.
Use a 256, 260 or meybe a 262 type cam and youll get your torque.
Had good results with the 256 Lunati. More tq everywhere smooth idle (just sounded throaty) pulled good everywhere. Lots of choices out there.
Some co's like to open and shut the valve super fast to make the cam act larger than it is.....it works but is hard on the valvetrain.
Now if it were highly modded and had too big a cam/heads then yes you could go smaller and probably pick things up.
Use a 256, 260 or meybe a 262 type cam and youll get your torque.
Had good results with the 256 Lunati. More tq everywhere smooth idle (just sounded throaty) pulled good everywhere. Lots of choices out there.
although I have no real additional information to add to this topic, it would be cool. 
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
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What he said, but also know that those ratings ("From idle to xxxxRPM operating range") -those things are wicked subjective. The same basic cam, one may say "1500-3500" and another brand may say "idle-3500". Also, the actual rev range depends SO much more on other things the advertiser has no clue about -displacement, induction, etc. So those things are really, very vague, rough/loose guides.
As others have said, post the cam's specs, and intended usage and you'll get better help.
X2 [on more cubes]. Big time.
As others have said, post the cam's specs, and intended usage and you'll get better help.
X2 [on more cubes]. Big time.
Everything about cam rpm range is subjective. Put a 1500-6500 cam in a large ci motor and the effective rpm range will lower. Put it in a 305 and they'll be higher. Cam timing can affect the outcome. Mechanically install that 1500-6500 cam at 4 or even 8 degrees advanced and the useable rpm range will drop at least 500rpms. Retard it, and the range goes up.
In general, I think cam ratings will be fairly close for the giving CI installation. So, for a stock(ish) 350 TPI, look for something with idle-5000 (or even 4500rpm) range. Basically, you'll be looking for more lift (and a little more duration) than your stock cam.
I also think it's good (actually great) to add a little extra duration and overlap, then install the cam with some mechanical advance. Combined with some longtubes and you'll reap some scavenging benefits that make the motor add a bit larger.
Last edited by GREGGPENN; Mar 18, 2013 at 02:05 AM.