Camshaft selection and vehicle weight

[73azbronco]

Hi, I was poking around the comp cams Camquest camshaft software and noted an interesting point: Vehicle weight has a larger effect on camshaft selection than I had fully considered, and I'm willing to bet most who select camshafts don't think a lot about this issue either.

Here are some findings using a 5.0 roller, x303 heads, 1.9/1.6 valves, 9.0 compression, carb, headers, default selection #2 for truck with improved economy and torque (selection 1 resulted in no camshafts available):

The default weight comes up as 2500# (a very light mustang), this is a problem as I bet most folks don't change this setting or truly realize what their truck weighs empty or loaded.

At 2500#'s, the software recommends 20 camshafts, starting with XE258HR (1300-5300rpm range) and going as high as a 281HR (2000-6000rpm).

If I change the default weight to 4000#, which is much closer to our one or two person operating weight (my GVW is 4900#) the software only has 6 camshafts, starting with 258HR going to 266HR, I say 6, there really is only 5, because one is a NOS camshaft, and two repeat depending on if your motor was originally a roller motor or modifed to roller.

Now, what if we use our GVW? 5000#'s gives only two camshafts, the 260HR, and XE258HR. One is a carb only and one is an EFI camshaft. Powerband is 1200-4500/5000.

Interesting to find that only one camshaft was recommended in each weight category, the 260HR part number 35-410-8.

 

[broncnaz]

Well said I agree. Most people dont consider vehicle weight they just just take it forgranted that the common mustang cams are the hot ticket. I've always had good results with cams in the 260-270 duration range. I've also gone with lower duration with good results but not as much power where I wanted it. Just a ton a factors involved but for the most part something in the 260 range is usually the ticket for most of us. but mainly my experiacne is more with the flat tappet cams.

 

[lil red]

Yep, you have to dial in the weight in that program. Here is the cam I went with. Its powerband is from 600 to 4800 rpm. If you believe the program, I should be putting out 325 hp and around 400 #/ft of torque.

http://www.summitracing.com/parts/CCA-31-230-3/

Engine specs are:
-302 bored .030 over
-balanced
- 9.0 to 1 pistons
- new rods
- new harmonic balancer
- resurfaced flywheel
- ported GT40p heads
- cam matched springs
- roller rocker arms
- Weiand dual plane intake
- Holley 470 Truck Avenger carb
-

 

[broncnaz]

I'd recommend that you never put your engine on a Dyno as I believe you will be dissappointed. many people find out that out when they actually get there engines dyno'd but they still have good running engines.

 

[lil red]

I agree 100%. I do think with a program like Comp cams program, when you change the various components, it can give you a reference point to use.

 

[broncnaz]

Right but I'd put your engine at only maybe slightly more power than a stock explorer engine even then it would be very similar. but I dont see where they figure 325+ hp and 400 ft lbs from that combo.

 

[68ford]

almost positive the torque will be under 375, carcraft built an engine almost identical to mine about a year or so ago and it put down 400hp and 375ish torque and i also dont believe those numbers. it was .060 over 10to1 very ported heads with 1.94 1.60 valve and a isky mega 280 cam( more aggressive and tighter lobe seperation so it have higher peak torque) victor jr and 750 holley.

i have same thing down to the cam except run 10.5 to 1 and performer rpm manifold with a 1in carb spacer my engine place 330 hp and maybe 350tq

 

[73azbronco]

well, I'm laughing at the 390HP and 390FT/Lbs the 260HR will give my little ol 5.0, no way, maybe downhill with a tailwind.