The reason I'm making this thread is because I'm trying to revive my baby and I don't really know much about specs. I ended up getting a sunken lifter on my 351w (true hotrodders know why that happened ). I figured since I'm gonna have it apart, why not change out my cam too? I have a few things that need clarification and some advice.
1. What is the lopiest cam specifications I can get with factory heads and springs?
2. Horsepower really isn't a worry, it's more a show truck that I also plan on driving 10 minutes to and from work. I really want the most aggressive sounding cam for a decent price. Price isn't too big of an issue but I need it to be less than 300 or so.
3. After we get the cam worked out, I also need some help matching lifters to the cam.
Thanks in advance,
Dustin.

 

What kind of RPMs are you going to turn and what are your HP expectations?

In general, if the lift is over .500", I think you need to upgrade the springs. Not sure what RPM stock springs are good for. But why limit yourself to stock springs? Get a nice set of double wound springs and never worry about float again. They're not expensive enough to kill the deal.

 

Bottom line is that performance cams and stock heads, intake, and valve springs don't go hand it hand. Some of it is ramp rate, but most of it has to do with the RPMs you will be running to hit the sweet spot in performance cams higher in the RPM range.

Lope comes from the amount of time both valves are open (overlap), not lift, not duration. Obviously with more duration a cam inherently has more overlap.

More duration will move the torque curve up in the RPM band and hence make more horsepower if your intake and exhaust systems can flow enough air (stock parts just don't work here).

Can a duration, small lift cam have more lope than another similar duration and lift cam? Yes, yes it can. If you tighten your lobe separation angle you will induce more overlap. Surprisingly, a tighter lobe separation angle helps small duration cams make greater torque across the entire RPM band (at least on carbureted engines.

Here is one of many articles of dyno tests that prove the results.

Camshaft Shootout: Lobe-Separation Angle Tested and Explained - Hot Rod Network

With all this being said, you maybe want to no higher than something like an XE262 from comp cams with a 218-224 duration. I have one of these in a 408W and even that mild of a cam is a little slumpy off idle and hits peak torque in the 3500-3600 RPM range. Instead of getting it cut on a 110LSA you could have it cut on a 105-106 LSA. I want to do this some time in the 408W I have.

 

@tabascom16

Some more info I left out, I have a performer series aluminium intake, long tube headers and 3 inch pipe throughout with turbo thrushes. I also have a 4 barrel holley. I think its like a 650. Its kinda a scrounge pickup. I'm 18 and in college so money is tight lol. It already has a mild cam in it, but i want something that makes people search for it in a parking lot. I'm not sure about the current cam because i bought it like that. If i floored my pickup, it wouldn't get over 3,900 RPM if that helps at all.

 

Valve springs are pretty expensive though. I don't really have hp expectations honestly. I just want it to look good, and sound good just cruising around

 

Most of the time, when guys are looking for suggestions on cams, they have a specific instance in mind: torque at low RPMs, towing a camp trailer, big tires, mountain driving, racing, etc.

Not sure I can offer anything for "sounding mean in a parking lot"...please don't take offense, as I was 18 once also, and understand!

Understand, a bigger and lopier cam won't idle for squat, and you won't have any vacuum. The mileage will suck, but that's the price we pay for sounding awesome!

Under 4000 rpm: you've got the right manifold, and a good carb. The duals will be good. A big cam will need new springs. Maybe it's time to look into either roller rockers and/or roller lifters. It's overkill for a mall-crawler, but eventually you'll use the truck for truck stuff?

Another thing to consider is the ports. How well do the ports on the intake match up to the heads? And the heads to the headers? The ports might need some attention to really get the flow you're looking for with the cam you're thinking about.

I'm certainly not trying to talk you out of anything, just think about what you really to end up with before you start

 

comp 262h, or 268h and just for lumpy sounds any of the thumper series cams. tight cam gives rough idle, loose cam gives smooth idle. tight cam is like 106* lobe separation, loose cam would be 114* LSA. Check out engine masters on youtube with david frieburger. he has some very good cam tests, and explanations.

 

@Papabearyuma

I'm not worried about fuel mileage for two reasons: 1) work is ten minutes away. 2) I got 7 mpg before it broke down lol. I haven't pulled the heads, so I'm not sure about the matchups. How bad can a DIY port and polish go?? And I used to have a really gummed up 550 cfm on it before so i would have to put it in neutral at stop lights to keep it running, so idling isn't too big a deal either. I think low end torque may be what I'm going for because I've always enjoyed burnouts, and now that I drive a Kia, I don't get that joy anymore. So what are some spec numbers I should be looking at? I saw Igfuller posted 262h and 268h. Are those just part numbers?

 

I looked them up and that 268 sounds really good. Its only $120 here. COMP Cams 12-210-2: High Energy 268H Hydraulic Flat Tappet Camshaft Lift: .454" /.454" Duration: 268°/268° RPM Range: 1500-5500 C.A.R.B. Approved* | JEGS

Could yall help me match lifters? And maybe valve springs. Do guides need to be changed?

 

Most of the cam manufacturers also sell the cam in a kit with matched lifters and springs. Check Summot or Jegs for the kit. Also, check Summit for "house brand" cam with the same specs to save some money

 

The link you listed is for a Chevy cam.

You what this one:
COMP Cams: High Energy™, 268H <BR> Mild Street Machines, Stock Drive Line, Noticeable Idle

They have links for kits

 

COMP Cams 35-218-3: High Energy 268H Hydraulic Flat Tappet Camshaft Lift .456"/.456" Duration 268°/268° RPM Range 1500-5500 | JEGS





This is the route I'm going. Anyone see any errors before I purchase??

 

If you aren't driving this thing over 4000 rpm then the 268 cam is just too much cam. To get the sound you are sacrificing low RPM torque and hence seat of the pants power.

Comp cams will grind a custom cam for very little extra, if any extra cost, depending on the cam core that is needed. You can call and talk to them about it. I would go no bigger than the duration you would see on a 262 cam and get something like a 105-106 lobe separation angle. More torque and hence more power than the stock 262 cam and the 268 cam, and will sound like the 268 or even more aggressive.

 

In regards to the RPM talk, my pickup is an automatic and always shifted before then. The cam wouldn't change that would it? That's a tranny thing.

What exactly does too much cam mean? Not being rude, I'm just ignorant on the matter. Also its about 70 more. This all added up pretty fast lol so 70 seems like a lot to me right now.

 

I learned the same as you at your age, reading and asking questions. I bought a classic Bronco when I was 19. At 33 now, the Bronco is completely restored after 8 years apart and working on a frame off on my 79 F250.

An engine has an RPM band for torque. The torque starts out weak, rises and peaks at some point, and then the torque fades off in the upper RPM band. Torque is what really makes you accelerate, not horsepower. Horsepower is nothing but a calculation from torque. Don't let peak horsepower numbers lead you on.

Cam duration is the main factor that determines a cams RPM band. Lower duration (small) cams have greater low RPM torque than a higher duration (big) cams. Lower duration cams have peak torque lower in the RPM band than higher duration cams.

So here is the catch. If you have a restrictive intake, heads, and exhaust, it actually helps make great low RPM power because it keeps the velocity of the incoming air moving. Of course this combination doesn't make high RPM power. A very free flowing intake, heads, and exhaust, struggles to make low RPM power because it cannot keep the velocity of the incoming air up, but it makes great power in the upper RPM ranges because the air flow gets to a velocity that makes power.

So if you put a high duration cam in a restrictive system, the cam and engine are out of phase as far as their sweet spots for power go. The cam likes high RPMs but the engine likes low RPMs. The opposite is also the same.

An automatic adds yet another level of complexity. A bigger cam needs a high stall torque converter to allow the engine get higher in the RPM range to capitalize on the fact that the bigger cam makes power in the higher RPMs.

A poorly matched system will not run as good as it can. I had a friend who built a Pontiac 454 with stock heads and a huge cam. Guess how much power it made on the engine dyno (on the engine stand...not power to the wheels)....352hp! And the torque curve sucked. Why...because the engine and cam were grossly mismatched.

Your 268 cam will make poor torque under 2000 RPM and will not make peak torque until about 4000 RPM and peak horsepower closer to 6000 RPM. Your stock heads will not support that cam very well.

It is up to you, but $70 is worth it. It is a few out to eat meals, a few fun nights with friends, etc. At some point you can't nickel and dime yourself.

I saved for years through college and summer jobs to build a 408W and I was very aware of matching all the components. I chose an XE262 with AFR 185 heads. Even that cam you need to be over 3000 RPM to make it feel happy.