Small Block Cam

[Wbulk]

I built my 302 when I thought I was going to have to pass emissions. They have since changed the law for classic cars so it is no longer an issue. I am now reevaluating my cam choice (Comp HE 260H) as to conservative without needing to pass emissions test. I have a 71 302 , 9:1 CR, stock heads with mild porting with exhaust smog hump removed, Edelbrock dual plane, T-5 Trans, 3.50 rear gears. I don’t want to change the heads.

This is a street car, not a race car. I am looking for a cam that will give me a little over 5,000 rpms and 270 to 290 hp. I plan on setting the rev limiter at about 5,300 rpms. Most of the driving will be between 1800- 4,000 rpms. I have read a few articles where this is doable. I have been evaluating the following cams and am asking if anyone has experience with these.

Comp HE 268H @ .050 218-218 dur., Lift is .456/456, LC is 110

Comp XE 256 H @ .050 212-218 dur., Lift is .477 and .484, LC is 110

Edelbrock 2122 @ .050 204-214 dur., Lift is .448 and .472, LC is 112
This cam is advertised to rev to 5,500 and seems to be a very popular street cam, as many other brands have copied it exactly.

Opinions and advice would be appreciated.

Wayne

[DAVID GAGNARD]

A buddy of mine put a cam with very similar specs as the first one you listed in his daily driver Ranchero with a 351-W........idles like the stock cam and pulls really good from idle to about 5500 rpms, also gave great mileage on the highway.........
I was impressed with the performance considering he changed nothing else from a bone stock 1972 351-W..........
I think this would make a good combo for your intended use.........

David

[bobcowan]

Out of those choices, I would use the XE 256H http://www.compcams.com/Company/CC/c...x?csid=20&sb=2

You live at 5,000' ASL or so. And your static compression ratio is only 9.1. If you use a cam that's too big, your intake valve closing point will be fairly late. That means your cylinder pressures will be low. Cylinder pressure is what makes power and efficiency.

The Edelbrock cam is is what used to be called a "RV" cam. It's designed for heavy vehicles to try and make low end grunt, but also have no top end. No reason to use that in a Cobra.

The 268H closes the intake valve at 60* ABDC. That will bleed off some pressure. And, it's a single pattern cam. SBF's generally do better with dual pattern.

The 256H closes the valve earlier at 56* ABDC. That will help build pressure. And it's a dual pattern cam. I would suggest using a 1.7 rocker for a little more valve lift; if your heads can handle it.

[Wbulk]

Good information. I think the frustrating part of cam selection is the companies give very little information about the cams they are tying to sell. Dyno results are mostly non-existent. Then it appears they mix and match their specs so it's very hard to compare apples to apples. One will give opening and closing specs at .006, another at .050 and another at .004. The only thing that would give you an idea of comparison was the standard .050 duration comparison and I'm seeing that is missing on some of the cam adds now.

[blykins]

The cam companies can't give you that much information.

The cam's performance depends on every single aspect of the engine build. For instance, a cam that is matched for a stocked headed 302 will not be the right cam for that same 302 with AFR heads. Also, keep in mind that the catalogs will say "For a Ford 302", but in all actuality, that cam will work in a 302, 331, 347, 351, 392, 408, etc. They simply can't provide all the information for that cam in each engine.

The first two cams that you listed will be too much for the criteria that you listed.

The Edelbrock cam will be more like it as you're looking for something that mostly mimics the stock cam in a 5.0L Mustang. Comp Cams makes several cams with specs around that particular scenario.

Keep in mind that you can get away with a little more in a Cobra than you can in other vehicles. If you're dead set on having a low hp peak and setting the rev limiter low, that's your decision, but I would choose a cam that will peak somewhere around 5500.

It can be tricky, deciphering all the information. I can help answer any questions that you have, and I have dyno results for a lot of engines with a lot of cams.

[bobcowan]

Originally Posted by Wbulk

Good information. I think the frustrating part of cam selection is the companies give very little information about the cams they are tying to sell. Dyno results are mostly non-existent. Then it appears they mix and match their specs so it's very hard to compare apples to apples. One will give opening and closing specs at .006, another at .050 and another at .004. The only thing that would give you an idea of comparison was the standard .050 duration comparison and I'm seeing that is missing on some of the cam adds now.

You're right. Sometimes comparing cams from differant makes is difficult for exactly that reason.

For duration, pay attention to the .050 number. That's really the only one that counts, as that is where airflow is generally considered to start and end.

As for power, way too many variables involved for a cam m aker to tell you that. Programs like Desktop Dyno are helpfull in comparing components.

[blykins]

Duration at .050" (along with engine size, head flow, etc.) is what I use to determine where the peak hp will be. However, it's not the only one that matters. Advertised duration and duration at .200" will give you an idea of how fast a valve will be opening and closing and how radical the lobe is. Of course advertised duration is used to determine DCR.

You will get a lot of differing opinions on things like cams, but the easiest way to get the right one is to call a guy that builds and dynos engines for a living.

[Wbulk]

This is a good article on the subject. Same engine as mine with three dyno pulls with stock and other heads with the same cam. The stock heads with a Crane cam #363902 pulled 285 hp at 5,000 rpms, and 273 hp at 5500 rpm. You have to click on related photos to the right and then click on the cam picture. At .050 it's 204-216 duration, lift is .456 and .484. The opening and closing specs are very, very, close to the Edelbrock cam.
http://www.mustangandfords.com/techa...dyno_test.html

[bobcowan]

Originally Posted by blykins

You will get a lot of differing opinions on things like cams, but the easiest way to get the right one is to call a guy that builds and dynos engines for a living.

I think that's the best advice I'v heard in a long time.

[blykins]

Originally Posted by Wbulk

This is a good article on the subject. Same engine as mine with three dyno pulls with stock and other heads with the same cam. The stock heads with a Crane cam #363902 pulled 285 hp at 5,000 rpms, and 273 hp at 5500 rpm. You have to click on related photos to the right and then click on the cam picture. At .050 it's 204-216 duration, lift is .456 and .484. The opening and closing specs are very, very, close to the Edelbrock cam.
http://www.mustangandfords.com/techa...dyno_test.html

I can get you a Comp cam (may save you some money as the Crane stuff is generally more expensive) that will meet your requirements. Keep in mind that a 302 with that cam will also sound pretty mild with just a noticeable idle.

[Dwight]

I called Keith Craft and told him what parts I had, what type of driving I would be doing and what hp I wanted. I bought a KC Custom Comp cam from him $50 less than what others wanted for a off the shelf Comp cam.
I very happy with the 402 rear wheel horsepower that my Cobra makes. Very
Dwight

[Wbulk]

Brent, I will call you tomorrow. I've been looking at the XE 262H also.

[blykins]

I'll be more than happy to talk to you about it. I like the XE lobes...they're generally a little more aggressive than the High Energy and Magnum lobes. We can go over what your wants/needs are as well as what will physically work (piston valve clearance, spring pressures, etc.)

[Keithc8]

I like the XE 256 but depending on springs and valve weight you might want something a little less agressive. I would run a little bigger lobe on the exhaust myself. The smaller camshafts that you mention are not much bigger than stock camshafts. You need to watch material they are made of as well because we have cam gear wear problems with some of them. We use a billet core like a solid roller so that we can run a steel gear. The core is more and thus the cam cost a little more but I feel safer with it. They run about 329.00 in most cases.
As with any flat tappet camshaft make sure you break it in with the right oil so that you do not lose a lobe.

Good luck, Keith

[Wbulk]

I just wanted to report what the final decision was on the cam selection for the purpose built street engine with max rpms of around 5300 rpms. It was great to consult with Brent and to discuss his experiences and possible options. In the end we agreed that the best course of action was to stay with the Comp HE 260H, 212 dur. at .050 cam that I have in the engine. The cam will rev to about 5300 and will meet my needs for the low end, and allow me to cruise in 5th at around 1800-1900 rpms. Brent felt that if the engine was being built again he would use the XE 256 or the XE 262, but it's not worth changing over now to pick up 5-10 hp on the top end that I may not even notice. Thanks Brent.

Wayne

[blykins]

You're welcome Wayne.

To spend another ~$150 on a cam/shipping then taking the risk of wiping the lobes on a break-in, it's just not worth it for a few extra ponies.

Don't forget, there is a tolerance on the peak hp rpms....5300-5500 was an educated guess....your results may vary.