Mild or Wild Cam?

[Bluedog]

I have a Comp Cam Hydralic Roller with the following specs:

242 - 248, .645 -.635, 112 degrees LS

I'm not sure what these values represent (from the build sheet) but I'm curious about your opinions whether this is a mild or wild cam. I can get it to idle at 900 RPMs but it "feels" like it would be happier at 1000 - 1100 as I sometime need to pump the pedal keep it idling at 900. In fifth gear, I'm doing about 2600 RPM at 75 mph and it runs great (.82 OD, 3.54 diff)! Thoughts? Thanks!

[RICK LAKE]

Bluedog. Did you give KCM the info for the motor you wanted? Did you tell them what you where going to do with the car? KCM sells many hydro roller cams from .700" lift to under .550". You have not given any specs on the motor so it is hard to give you an idea or answer about your question. I have a 452 that is getting a cam swap right now. I got a KCM cam with .568 & 588 lifter. I am looking for alot of tork with a 6500 rpm limit. If you want every last HP out of a motor and spin it to 7,500 rpm GO BIG and live with the idle and some of the drivabilities that go with large cams. The smaller the cam, the easier it is on the motor and valve train. You want to have the tork power band at about 500 rpm into it. This will stop the car from lugging at highway speeds. Bigger is no always better on the street. Racing that's another story. I have a 368 hp motor with 446 of tork, 9.2 compression, shelby heads and block. Car idles smooth, pulls like a tractor to 5,800 rpm, ( I installed beehive springs on the shelby heads and added an Aluminium flywheel to add rpm before the motor goes flat and is out of power) I run 12.5 in the 1/4 mile and can run regular gas of 87.I have and FI system on the car also. A 500 hp motor and 550 ft of torque is a nice motor for a cobra. If you are racing, there is about 10% of the cobra owners that have MASTERED the driving skills, and drive a cobra to it's limit. This is a whole different subject. Rick Lake

[427SnakeSC]

I just picked up my 427 SO from Keith Craft. When I ordered the motor, I told him that I would not be racing the car and that I wanted my power before 6000 rpm. He installed a mild hydralic roller cam that gives me 560 hp at 5800 rpm and 594 lbs torque at 4700 rpm. I will be running a toploader tranny with a 3.54 rear end. When I was specing the motor with Keith, I gave him all this info and that helped him placing the right cam for the right application for me. Now just have to wait on the car to put it in! Although it would make a great snowblower!
My cam specs are 248/252 .635/.633 3170B/3151B 110+4, not sure what all that means, but that's it.
To watch the Dyno of my motor, click on this link. http://www.youtube.com/watch?v=JPs2TXEwzsM I believe that I noted that the idle on my motor during the dyno was 1,100 rpm.

[Bluedog]

I had three criteria for the engine: 1) streetable, 2) low maintenance, and 3) plenty of torque. The 427 engine (stroked to a 468) dynoed at 570HP and 601lbs of torque. It has KC stage 1 ported Edelbrock heads and a Holly 750. So, it seems like Keith nailed the requirements.

What's interesting is that in first gear, it's like a bucking bronco and it feels like it wants to run. It's pretty hard to drive especially in traffic in 1st! People in the FE community who have heard the lop in the engine have commented that it sounded like it has a very aggressive cam. So, I'm just trying the reconcile the cam specs to how the car behaves and sounds.

One thing thats probably not related is it stalls out of the drive way after a few minutes of warm-up. Now I wouldn't normally think to much of it but it will also stalls a stop lights or coming off the freeway off ramps when the engine is warmed-up. I have to keep tapping the gas pedal to keep it idling at 900 RPM.

TTT

[RICK LAKE]

Bluedog If your car is stalling on turns and stopping, your carb floats may need adjustment, The float levels could be too low causing this. If it is really hot under the hood, the gas could be boiling and causing the same problem. I would adjust the floats and look at the idle screws and back them out 1/4 of a turn and road test, if car runs better go a 1/4 turn more. You maybe running lean. Rick L.

[cosbytnkid]

Originally Posted by RICK LAKE

Bluedog If your car is stalling on turns and stopping, your carb floats may need adjustment, The float levels could be too low causing this. If it is really hot under the hood, the gas could be boiling and causing the same problem. I would adjust the floats and look at the idle screws and back them out 1/4 of a turn and road test, if car runs better go a 1/4 turn more. You maybe running lean. Rick L.

I concur Rick. After reading Bluedog's post my first thought was A. He is running too lean and B. Depending on how aggressive a cam grind he has he may need to bump the idle up to around 1,000-1,100 RPM idle.

[DAVID GAGNARD]

Mild, not in my opinion, wild, yes.......but that is only my opinion......I consider anything over 625 lift wild, but thats me, other may think it just right.....

With your cam/motor specs, I'm surpised you can get it to idle at 900 rpms, I would think it would need more like 1100 rpm idle to run right.....I have seen motors with less camshaft and other goodies than you have that would not hardly idle under 1000 to 1100 rpms.....

High lift cams do not like a very low idle, the reason your car stalls is lack of vacum at the low idle rpm........put a vacum gauge on it and you'll see what I mean........

My street car is the very definition of a mild motor and idles at 800 rpms,while pulling 17 inches of vacum, on the other hand my race motor idles at 1000 rpms and pulls about 10 inches of vacum.....if I idle the race motor down any, it will stall just as you have described...

BTW: both motors have a lot of KC components in them!!!!!!!!

David

[cosbytnkid]

Originally Posted by Bluedog

I have a Comp Cam Hydralic Roller with the following specs:

242 - 248, .645 -.635, 112 degrees LS

I'm not sure what these values represent (from the build sheet) but I'm curious about your opinions whether this is a mild or wild cam. I can get it to idle at 900 RPMs but it "feels" like it would be happier at 1000 - 1100 as I sometime need to pump the pedal keep it idling at 900. In fifth gear, I'm doing about 2600 RPM at 75 mph and it runs great (.82 OD, 3.54 diff)! Thoughts? Thanks!

Unless I'm mistaken here is what you've got. Out of a 360 degree circle your intake stays open 242 degrees, your exhaust stays open 248 degrees. You've got a little over 1/2 inch of lift on the valves. 645 thousandths of an inch lift on the intake valve, with 635 thousandths of an inch lift on your exhaust valves. With 112 degree seperation between the lobes of the cam or better known as lobe seperation. You'll notice your exhaust valve stays open a bit longer than the intake so that with both valves temporarily open, the burnt gasses are scavenged out of the cyclinder and aiding the incoming charge of fuel mixture. If I'm wrong somebody please correct me and I'll take no offense what so ever. I think I'm on the right track though.

[Excaliber]

Good analysis Dick. One thing to bear in mind is that the crank turns TWICE to make the cam turn ONCE. Now that will leave them scratching their heads about a 360 degree circle...

Comp Cams 292S flat tappet solid here. Idle speed around a 1000, can't get lower, nice 'lumpy' idle and yet tame enough to cruise around in 1st gear, street friendly. Spec'd by Gessford Machine Shop (2004 Machine Shop of the year winner). George nailed it!

[Bluedog]

Thanks guys, you've given me some great suggestions to explore!