Cam ICL

[JimNolan]

Guys,
   I've got a question about ICL of the cam. I've got an engine that's going to be putting out about 450 ft. lbs. of torque and @360 horsepower. The cam I'm using is a Comp Cam's 268H which the calculators say will give me peak horsepower at 4500-5000 rpm. I'm putting it in a car with a 3.50 tru-trac, traction bars and Tremec TKO 600 with a good clutch. The tires I'm using are Hoosier Street Pro's ( they look like mud and snow tires ) These tires took a second off my ET over street tires but they still spin quit a bit with my little 300 horse 390. I can't go with better tires because I drive the car all the time and race it rarely. Soooooo!!!!, My question is this. Should I retard the cam when I install it to try and take some of the torque out of the bottom end. And, if I do, will it really help me very much to change it a couple degrees. Jim PS. I've read everything I can on the subject and I just ended up being more confused. Thanks

[machoneman]

I say a big NO.....but opinions here may vary....LOL  !

One should always try to build as much low end torque in a streeter (race it rarely) since it makes the car an easy driver and very responsive. Retarding a cam IMHO in a streeter is akin to applying race car adjustments in a mufflered, pump gas environment, cruiser type car.....not a good idea. If you had a high revving engine in a regularly raced car and had traction issues, sure!

Another way of saying this is the loss of low end torque (and lesser 0-60' times) likely can't be overcome at the track in your low revving engine combo...all at the expense of lesser driveability for 95%+ of your fun driving time.   

[My427stang]

You could, but it wont be dramatically different.

In my truck 445, I installed the cam at 110 ICL to ensure that dynamic compression was in check, but don't expect a significant change in the curve, it will change a little though

With a cam as small as a 268H, you have room to roll it back IMO. 

Have you measured everything to calculate static and dynamic compression ratio?

[JimNolan]

My427stang,
    I cc'd the pistons (Z381NP Sealed Power) and they were 15cc's. I cc'd the heads (C1AE-A) and they are 75cc's. The rods ended up being the Eagle H-Beam and they say those are 6.49" long. I'm using .020 X 4.42 steel shim head gaskets also. My machinest is leveling the top of the block so I figure that's approximately .010 off the deck. I should be in the neighborhood of a .040 quench.
   From what I deduce the engine should be 9.46 CR / 7.84 DCR with the cam set on 106 ICL. My 63 390/406 engine is 10.3 CR / 7.8 DCR with a  .045 quench and it has to have 89 octane gas.
   After reading machoneman's post I think he may be right. Install it straight up and go buy a set of tires for it if I want to reduce the wheel spin.

[My427stang]

Not straight up, you mean dot to dot.

Straight up means ICL = ECL, so a 110 LSA cam, installed sraight up, would be 110 ICL, and 110 ECL

You mean install as designed, or dot to dot, which should be 106 ICL ebcause the cam is 4 degrees advanced as ground

Semantics, but it does mean something.

However, your DCR seems low with such a small cam, what are you using for a tool to calculate?

[JimNolan]

My427stang,
    I use a Dynamic Stroke Length, Cam Timing, Static Compression Program made by Pat Kelly. 9.46 CR / 7.8 DCR
    I use Wallace Racing Dynamic Stroke Calculator.  9.47 CR / 7.85 DCR
    I use Virtual Engine Dyno Pro Dynamic Stroke Calculator.  9.3 CR / 7.71 DCR.

 Out of the three I just pick the highest numbers.  I just found out that if you include your altitude, (example 900 ft.) it will drop your DCR by .19  ( 7.66 ) without altitude the Pat Kelly program and Wallace Racing are almost the same.

[My427stang]

I like Pat Kelly's, I have used it on so many builds that I know the engine acts like the calculator predicts

There isn't much you can do with that cam to kill 1st gear torque, you have 10:1 compund ratio in 1st, that's going to make the tires work hard LOL

I'd just make sure you have a good timing curve for your fuel concerns.  14 initial, 36 total, all in by 2800 should run on anything, even with the short cam. 

FWIW a small cammed 428 can easily handle a later ICL, stock CJs were 114 ICL, so dont worry about lack of torque. 

Thats why I went 110 ICL in my 445, and I have even considered putting it at 112, but it's together now and I am lazy LOL

Keep cylinder pressure in check a little, offsetting for too small of a cam, knowing I'll still have torque to spare, even in a 4100 lb 3.50 geared truck with 33 inch tall tires.  .....  270 in a 445, 268 in a 428, same difference IMO