I don't quite understand what the RPM ranges are for on cam specs. Is it their only operating range or what. And what range suits our cars best. Thanks,


big tex

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1992 305 TBI RS
Flowmaster cat-back exhaust, 14X2.5 open air element...and a T-5 on the way!

 

Yes that is the best idea of where the power is going to be. Notice no cams have a power ban from idle to say 8000rpm! Because that is the problem with single pushrod engines, valve lift isn't adjustable like in the porsches and BMWs. So at idle the valve lift and duration is the same as at redline. Those hot rods with super choppy sounding engines have extream cams in them. They produce lawnmower torque and hp at idle but have an extream redline ~7500. A stock 305 would be best with a cam from idle to 5500. That is why you see trucks with not so extream cams, they need low end torque from idle to only 4500. Since the 305 is a truck engine per say (intake and bore/stroke design), the best cam for stock would be the idle - whatever. See what I'm saying? Another big factor is the cfm of the intake system. The head intake port size and the general TB cfm rating are a big factor. Too big of a cam and small stock intake and you get bad low end and bad high end. With a mild cam and a super sized intake you'll have okay power up high but a terrible hesitation from lack of intake air velocity. That is why the demon carbs are so great, they have smaller bores than holley but same cfm rating. Reason demon makes more power is because of the actual intake velocity = smooth power. Got any more questions?

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, Jon (91 RS too many mods to list), getting new engine in summer

 

well, someone mentioned the crane cam, compucam series, and the range on it was 1500-5000. that doesn't sound too good to me, but maybe i'm wrong.

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1992 305 TBI RS
Flowmaster cat-back exhaust, 14X2.5 open air element...and a T-5 on the way!

 

The biggest limiting factor in the RPM capability of a cam is duration. The Compucams have low duration numbers to work well with stock or mildy modded factory EFI setups/computers and to work well with stock trannies and gears. They are actually pretty good cams, and they are a lot better than stock cams. The RPM range of 1500-5000 is actually the range that the cam makes it's most power, that doesn't mean you can't turn them a little harder than that. For instance, our stock TBI cams are actually dead, meaning out of is peak power making range, at around 4500 RPM. If it were rated by an aftermarket cam company, they would have it listed idle - 3500. Look in a Crane or Summit catalog and you will see chart that lists cams in the 190-205* duration range at 3500 max. But do we shift our cars at 3500?, no, because its better to turn them higher, especially in first gear, so when you shift the engine has momentum and is in its power range to make the car faster. I shift my peanut cammed 305 at 5200, so The Crane Compucam would probably still work great a 5500-5800 rpm shift. My 82 Z28 had the Edelbrock Performer RPM cam, ran 12.52 in 1/4 and it was fastest when I shifted at only 6100. You will need to run your car on the clock at a track to see exactly what shift-point will be faster, And beware, on the street, My 82 Z28 FELT like it was faster shifting a 6500-6600 RPM, but on the clock, where it counts, it ran faster at 6100. I hope this helps.

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82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page

R.I.P. Dale Earnhardt #3

 

you said that the compucam works good with the stock trannie and gears, I plan on getting some bigger gears. That wouldn't effect the new cams performance would it.

------------------
1992 305 TBI RS
Flowmaster cat-back exhaust, 14X2.5 open air element...and a T-5 on the way!

 

Tex, are you looking for a roller cam? or non-roller?

 

No, gear would only make the car perform better. I was only saying that the Compucams are ground on the conservative side so that they can be used with stock gears, injection, computer, etc. Fastbroker does raise an intesting question though, are you going with Hyd or Hyd Roller?? You would see much better gains in performance with a Hyd Roller, which is the design of cam that is in your car now. You can most likely reuse your lifters if the engine has been cared for decently, meaning it hasn't gone 10,000 -20,000+ miles between oil changes all its life. Besides Crane, SLP and Comp makes some good computer compatible Hyd Roller cams. So you have more than just Crane to choose from.

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82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page

R.I.P. Dale Earnhardt #3

[This message has been edited by Basett Racing (edited February 19, 2001).]

 

IMO great/inexpensive ($140?) roller cam is OEM LT4. Too late for me to rattle off the specs but nice numbers and plently of LobeSep for EFI. Use 1.6 rockers, if you can.

EDIT: Sorry Tex, didn't answer the question. buy a cam that has the CRUISE rpm bout where your cruise rpm is on the highway. If you REALLY like racing, go higher thn actual on the cruise rpm. If you want mileage and/or tow, go lower on the cruise rpm. Above LT4 cam would probably cruise best at about 2000-2500 rpm with EFI, IMO...

And you are right about operating ranges. Best place to operate cam... Can go a little higher but not much gained. There will be lots of lost torque below the lower rpm operating ranges, too, so a 2500-6500 cam will be terrible off the line with an OEM converter and AT... 2600+ converter or standard (both with low gears) with that cam should be ok...

Get it?

[This message has been edited by FastBroker (edited February 19, 2001).]

 

you know when your pretty much stopped in a parking lot and you punch the gas for less than a second and you car jumps and your exhaust rumbles...i like that, and will a cam that hits its lowest operation range at 1500 give a better jump or a worse jump. I want a cam that will be streetable (everyday driver) and that doesn't require computer work. Hydrolic roller sound like what i am looking for. I want the cam to give my better off the line acceleration with some better low end torque. Thanks for all of the help guys, it has brought up some good points and some very helpful information.

steven

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1992 305 TBI RS
Flowmaster cat-back exhaust, 14X2.5 open air element...and a T-5 on the way!