Im Rebuilding a 1991 f150 that had a 302 engine. The truck is a standard 5 speed. I did a mass air flow conversion allready. I ordered gt40p heads and headers. Now for the cam im not sure what to run some say the 91 was a roller ready block so im not sure what cam would be good for low end torque and mid range rpm.

 

Yes that should be a roller ready block. There isn't a lot of torque to gain at low rpms from this motor, you can gain some with the right combo of parts but it won't ever produce 5.8 like torque... unless you put a 347 stroker kit in it. A cam like the Comp 35-512-8 or 35-510-8 with a single 2.5" exhaust system will maximize low to midrange gains.

 

What's the difference between the two cams Comp 35-512-8 or 35-510-8. Also what do I need to order to use a roller cam. This is the first engine I'm rebuilding

 

The Comp 35-512-8 will make power slightly lower in the powerband and will be a little more computer friendly. You'll need roller lifters, push rods, the dog bones and hold down. You can get the hold down and dog bones used, but you should really buy the other stuff new. You should also get some springs to match the cam too.

 

Any idea much hp or torque will this cam add iver the original flat tappet cam in a 91 302.

 

Those two cams are similar, the 510 has more lift and more overlap(112 vs 114 LSA) so it produces more power, the 512 is more SD efi friendly but with MAF there is no reason you couldn't use the better cam. A dyno sim indicates about 280hp and almost 350 tq so this is a healthy upgrade from stock.

 

Thanks for the information any idea what would be a little better cam then the 512 since i have mass air if not that's probably what I'll end up getting.

 

Those cams will both be awful in a 302 inch engine that's trying to make some low end power. There's no way either will make 350lbs/ft. They both have too much duration and are ground on a lobe sep that isn't even close to optimum. A stock non HO 5.0 cam would be better.

 

The 510 is better.

 

What would you suggest Dave? Those cams both produce more lift than the HO but 0.050" duration and LSA are about the same so I don't see there being a lot of difference.

 

GT40 heads and one of those cams will get you at least 30-40 hp. As Richard Holdener says, it depends

 

As conanski said what would be a better camshaft the truck will spend its life at low rps. Not racing it.

 

The HO cam isn't very good because the lobe sep is too wide. The HO 5.0 cam is 210 @ .050 and ground on 114(almost 115 on the sample that I've plotted). If we want the engine and especially one with low compression to make maximum peak torque a wide lobe sep is bad because with it we're closing the intake valve too late and opening the exhaust too early. If the cam is advanced a whole bunch to get the intake closing early enough then the exhaust opens even more early and vice versa.

Having a dual pattern cam is also not helpful in this situation. A single pattern cam will always make the best peak torque numbers. A cam with extra exhaust duration tends to act sort of like a blend of cams with 2 different durations it tends to produce more torque above the peak, less at the peak and less below the peak and while that's great for HP it isn't so good when it comes to making torque that's useful at low speeds.

The non HO 5.0 cam is much different than the HO version. The non HO cam is ground on a 108 lobe separation and has only 181 and 195 duration at .050. This is why they are an awesome core to use for regrinding. It is mysteriously very short duration and it would be interesting to see what a cam using the intake lobe on both sides ground on a 104 in on 100 would do in a 5.0 engine in a truck. I think that it would run great if the actual static compression ratio was very low as it is in a 302 from the '70's.

 

is there a better cam I should be using then?

 

If I was selecting the cam for an application like this I would probably use a single pattern cam with a duration of about 190-195@ .050 on a 107-108 lobe sep and put it in the engine on about a 105. I think that would be pretty close. This is thinking that the actual compression ratio will end up around 8.5:1 which should be fine.

I have a 302 in a '65 Galaxie and I built that engine 30 years ago. It has an Engine Power cam that's a dual pattern 190 intake 202 exhaust on 108. That engine has 9.5:1 compression and it requires premium fuel. It runs surprisingly awesome in a 3800lb car. That cam would be better with lower compression if I wanted to run it on 87 octane but it was the first car engine that I ever built and that was a long time ago.

I never ran that engine on a dyno but based on my experience from other engines since then it probably makes about 310lbs/ft of torque, maybe 315.