compare these cams:

[CRASH]

I have a Renix based stroker. I like it, but feel it lacks bottom end punch. Seems it really comes alive at 2800, which is too high for me. Maybe I'm just asking too much from too small a motor, but I'd like a bit more on the bottom. Problem is, I cruise around on the highway at 3,000 RPM, and it gets 17 mpg fully loaded on 35's. ~5,000 lbs

So, did I chosse the wrong cam? I don't mind spending a weekend switching it if there is something that will give me similar highway performance, but gets me better bottom end. Also, I have an adjustable cam gear, and I suppose I could move it 4 degrees or so for a little more bottom?

This is what I have in my Jeep:

http://www.iskycams.com/timingchart.php?product_number=133125/26

This is the popular Crane cam:

http://www.cranecams.com/index.php?show=browseParts&action=partSpec&partNumber=753905&lvl=2&prt=5

More lift and longer duration on the crane, which seems opposite of what I need for bottom end gains. Yet everyone says they like that crane cam a whole bunch. :huh:

 

[5-90]

You know, I've run a bunch of cams (in simulation - I don't have a run stand or a dyno cell...) and the best one I've found for "low" RPM use is the Blue Racer WG5121. I don't have the numbers handy, but I suppose I could regenerate them if asked. If you want me to run a bunch of cams, I'll need to know the folowing:

Final Bore
Final Stroke (3.895", isn't it?)
Camshaft part numbers (I have data files for most, I'll let you know if I don't.)

I'll run them under Dyno2000 in the next couple days, and let you know what's going on. Still, with stock, RENIX, HO, or stroker, the WG5121 looked like the best of the lot...

5-90

 

[Ed A. Stevens]

Crash,

I believe the Crane 905' is the same one as 5-90's Wolverine, as they are cut on the same line (Crane & BRW have been the same grinds for decades).

Look at the cam timing between the two cams listed.

Look at the intake opening timing (at 0.050", after equalizing the terminology).

Crane = 5 degrees ATDC
Isky = 9 degrees ATDC

The Crane is a little wilder (longer duration at 0.050" and higher lift) cam, but it's intake lobe is also advanced 4 degrees compared to the Isky.

Advancing the cam will lower the peak rpm point, and tends to extend the low rpm volume under the torque curve. Not only is the peak torque lower in rpm, but the curve makes more torque earlier and is flatter leading to the lower rpm peak (even if the actual peak torque is slightly lower, the quality of torque below the peak is usually improved).

The short answer/advice is have the Isky cam timing checked with a degree wheel (make sure you know where it is set up now), and advance the cam timing 2-6 degrees to get the torque produced where you want it.

Crane tended to exploit high lift and long duration (relative to other cam designers, making great advertisement claims) to target the peak rpm, and then widen the lobe center (advance the intake lobe) to fatten the torque below the rpm of the torque peak. Isky's cam timing is a little different, less radical lift and duration but a tighter lobe center to extend the torque more past the rpm peak. The difference is how the eventual torque curve looks: fat & flat before the peak and then a quick drop off (Crane), or a little less low end fat traded for a longer extension of the torque curve after the peak (Isky). With the typical hot rodder engine enhancement manner the Isky method allows a little more flexibility to pick up more power after the next engine modification (higher rpm intake, heads, carb/TB, etc.), while the Crane method promotes you to make a cam change earlier to exploit subsequent modifications (good marketing and racer obsolescence program). In either case advancing or retarding the cam will rock the peak 200-400 rpm for each 2-degree change in cam timing (the change in intake opening event).

Cloyes makes a timing gear/chain set that allows you pick the keyways on the gears to adjust the timing. You can also purchase offset key's in 2 & 4-degree settings.

Degree the cam and then advance it to gain torque below the current peak rpm.

HTH?

 

[CRASH]

Yes, Ed, that helps. I have an adjustable cam timing set in there now, some australian brand double row timing set with +/- 8 degrees of movement. I think this would be my simplest move, advance the timing +4. I degreed the cam in myself, and it is in their straight up. The cut was very accurate on the gear.

 

[Lincoln]

I'll second Ed. Advance it a bit.

I'm running the Crane you listed though I remember the numbers on the cam card being a little different. It's been in there since 2000 and I know my memory isn't that good.

I do remember setting it a few degrees advanced. I couldn't get it exact and decided to error on the torque side. Mine does come on very strong on the bottom and is sometimes a PITA. It really likes to lurch when cracking the trottle. It does seem to go flat a little early and I always contributed that to still having the stock valve springs. Somehow in 5 years I still haven't gotten around to changing those.

Just in case you don't remember mines renix, non-stroked, ported and polished head, the Crane cam you listed, and a borla header. I swapped in an HO motor when changing and used it's intake and throttle body.

BTW, wouldn't getting the heater working time better spent?