Hey guys, im lookin to put a cam in. My question is whats a good setup for a cam? And brand?
The trucks an 83 f250 with a 351W and np435 trans. The motors got a holley 650 carb, edelbrock intake, complete MSD ignition, and hooker long tube headers. Im looking more for low end torque but more horses would be nice too! Any ideas?

 

Low end torque and horsepower are at the opposite ends of the cam build spectrum. Torque cams have short durations (valves stay open for a shorter period) A typical duration would be around 210 degrees at .050" valve lift. HP cams have long durations so valves stay open longer to aid cylinder filling at high rpm. A typical duration would be around 230 degrees at .050" (for your engine). Also lobe seperation angle (LSA) needs to be considered. Narrow separation (like 108 deg.) is good for low end torque but also reduces vacuum at idle and gives that lumpy idle. Whereas a wider speration (112 dge) moves power band higher and provides a wider power band. Also note that long duration, high lift cams will need some valve train upgrades (higher rate springs, adjustable rockers, pushrod guide plates, etc.). Short duration, lower lift can usually get away with stock valve train (as these are closer to stock setups).

For your application, I would go with a cam with 210 deg on Intake and 216 on Exhaust, with a LSA of 110. And a valve lift around .500 to .550.

This COMP Cams Xtreme 4x4 Camshafts 35-235-3 - SummitRacing.com

or this
COMP Cams Xtreme 4x4 Camshafts 35-231-3 - SummitRacing.com

When you compare cam specs be sure you are looking at the duration at .050" lift. Advertised duration is also listed and it is much higher (but not as useful in comparing specs).

 

You might check out summitt's specs for the 351 W HO cam..
It is a little more cam than the 2bbl 351 HO..

If your engine was a 2bbl originally, it will have a milder version than the HO.

Would be a good time to go with the double roller gears and chain (factory on the 351W HO version)

Just throwing that out there..Trav..

 

Whats the point for double roller gears and chain? Is it just less friction to get better efficiency?

And as for which cam, i would much rather have the torque than hp. What can stock heads handle before i have invest in other new head parts? And whats stock?

 

I ran Comp's 252H in a 351W with a stock 2bbl intake and the 2150 Autolite carb. With a C6 and 3.50 gears it would turn the tires from a stop on rough concrete. Lots of low end torque. It is advertised as giving torque from 600 RPM up, and it certainly did. I would go back w/that cam if I were building a 351W.

The double-roller chain doesn't stretch as much so keeps the cam properly timed longer.

 

Oh ok thanks

 

The 252H is a single pattern cam (206 duration on both Intake and Exhaust). Fords like dual pattern profiles with more duration on the exhaust (5 to 10 dgrees) becuase of the poor exhaust flow charateristics (especially wth unported heads). A better choice is a cam with 206I and 214E degrees duration (measured at .050" lift). See the COMP 35-231-3 cam profile. 35-231-3 - Xtreme 4 x 4

 

I can believe the need for more exhaust duration. And, I didn't tell all of the story about my engine - I "ported" the heads on the 351W the 252H went in. I didn't do a superb job on the porting, as I found when I had them flow tested, but they certainly were better than stock. Especially on the exhaust side. So, it makes sense that the 252H worked great in my engine but might not in one with a stock set of heads. Good call, CB!

And, I will say that the Ford small-block heads have awful exhaust ports. Truly abysmal. Here's a cross-section of one with the top red line showing where I ported to in removing the bump that causes the problems. With the porting I did the truck ran like it had a 4bbl, although it was only a 2bbl. It would wind like there was no tomorrow.

 

How much is it to port a set of heads. Or if its a diy hows it done?

 

Here's a link to my thread entitled Porting Heads - What To Document wherein we cussed and discussed porting. IIRC I show lots of pictures, the results of the flow testing I had done, and endless other things. Make sure you have lots of time and a cup of coffee to stay awake.

I did all the porting myself using a air-powered die grinder and a Dremel tool, and had various carbide burrs and grinding stones. It takes a lot of time and it is messy. Very messy as cast iron bits go everywhere. And, as I think I documented in the thread, while my results were fairly good, the guru I took one to for flow testing equaled or beat my #'s with a simple valve grind.

So, I'm not sure I'd do it again, at least not by starting with the same head. Basically I think I proved that it is difficult to make a silk purse out of a sow's ear, and those small-block heads may not even qualify as a sow's ear. The exhaust side is awful. So I'd at least find a set of better heads, like maybe the GT40's.

 

Ill look into em

 

Gary, all I have ever done on my heads is knock out the emission bump, then blend the area.

JJray, GT40 heads can be found on 302 engined Explorers and Moutaineers. Later ones have the GT40P heads which are even better.

 

Bill - That's effectively what I did. Even though I spent time blending things and working on the short-side radius I think the major help was taking out the bump.

JJ - Here are my notes on heads.
Your stock heads probably have a combustion chamber size of ~69 cc's and your compression ratio will be ~8:1. If you are building the engine you need to think about deck height and you will have some control over that with piston selection and machining operations. But, if you are using a stock long-block then you are stuck with the deck height you have. And, that means you can't drop the combustion chamber size very much or your CR will go too high for pump gas.

Go to Comp Cam's web site and download their dyno program. It has a section to let you calc CR, and you can try different combustion chamber sizes to see what happens. And, try different cams as well. However, don't go to the bank with the HP & torque #'s that program gives you as their head flow #'s are very inflated.

 

It dont matter if there fuel injected or carbed?

 

Nope. The heads don't care.