Whats the difference between a single pattern and a dual pattern cam that share the same rpm range??

Which type is easier on the rockers etc.??

Most important which one produces more torque within the given rpm range??


Thanks for any info provided.

 

Not every engine should have or would benefit from a dual pattern cam. If your exhaust ports flow above 75 percent of your intake ports then you are more than likely wasting your time. On the stock FE headed engine it helps a lot as it lets the exhaust breath better. There is no direct relationship as to how easy it is on the valvetrain. On an engine where the exhaust doesn't need any help you are just wasting cylinder pressure by putting extra duration on the exhaust. An FE with the edel heads doesn't need a dual pattern cam in my opinion even though I have one. My next cam will either be single pattern or have only a slightly hotter profile on the exhaust lobe.

 

Mr. Ratsmoker:
I have a set of c4ae-6090 heads on a 352- will dual pattern cam work on this set up?? i am going to "ruff" port them and grind down the exhayust bump. thought about even openning up the exhaust valve size. Any points to ponder would humbly appreciated.Thanks.
clods64

 

Mr. Ratsmoker:
I have a set of c4ae-6090 heads on a 352- will dual pattern cam work on this set up?? i am going to "ruff" port them and grind down the exhayust bump. thought about even openning up the exhaust valve size. Any points to ponder would be humbly appreciated.Thanks.
clods64

 

oops

 

oops igues i submitted twice pardon me

 

If you open up the exhaust ports enough then a single pattern cam will be the best as long as it is around the 75% mark. Without a flow bench it is sorta hard to guestimate what it will be flowing. You are definitely on the right track though. Be careful with the bump as you cannot completely remover it. BTW I'm not Mr., that's my dad. I'm just Sean.

 

Ratwagon,

I would agree with Ratsmoker here.

An interesting phenomenon is now occurring with regard to single- and dual-pattern cams. Before the days of excellent aftermarket heads, most cam manufacturers built single-pattern cams. Once these companies discovered that dual-pattern cams made more power, these cams became the new hot ticket. The emerging pattern now is that most aftermarket heads offer such strong exhaust ports that the shift to a single-pattern cam will make more power. Expect to see the cam companies again move back to an emphasis on single-pattern cams as cylinder heads continue to improve.

Eric

 

Hey fastlane, welcome to FTE! I agree. In my opinion your exhaust and intake flow should be balanced in the heads, not with the cam. While the dual pattern cams offer great performance upgrades for the stock headed engines, the extra duration is letting off valuable cylinder pressure to give the extra flow. Sometimes it is just plain unfeasable to balance this in the head especially with forced induction engines. This is where dual patter ncams become even more valuable.

 

So if the Ebok heads dont need a dual pattern cam than Eboks with exhaust porting definately don't. So maybe I should look for a single pattern cam for my proposed stroker? ratsmoker, if you happen to read this, do think just stay with the crane that I talked about in a different post or look for something with a single pattern profile?

 

No I would stay with that cam in your case. There isn't much better of a choice for rollers out there. There really isn't too much of a split on it either. You could have a custom grind done but that really costs money. I run a dual pattern in mine but am considering changing to something a little hotter. I want a little more pull from 4,000 up and I want to increase my shift points to about 6,500 instead of 5,800.

 

what cam are you running in yours? I have a friend that is running a Crane 272 I believe. Dont remeber the number but it's 216/228, .533/556" lift at .050. He's running that in a 65 F100 2 wheel drive and that's a fun pickup to drive. it's fairly mild, standard bore 390, hypereutectic pistons probably around 9/9.5:1, stock heads, stock 4 barrel intake and edl carb. Damn good running motor. has a good idle too it's quite the sleeper. Point is, i recommend that cam because it seems to be a really good compromise of all around power.

 

I run the 343801 crane right now. It has a 222/234 duration at .050 and a 278/290 advertised duration. The lift with my 1.76 adjustable rockers is .548/.580. The Lobe Center angle is 114 degrees. It has a choppy idle but starts making great power before my stall is maxed out at 3,200rpm. I figure with a tad bit hotter single pattern I should be dropping my E.T.s as I spend most of my time at over 4,500 rpm on the strip. That cam you mentioned is a very nice cam for a mild truck engine. It has been recommended many times here. The 901 cam is the next step down and seems to be the choice for thos who want a little milder engine or have a very heavy truck.

 

I have run several configurations with Desktop Dyno both 2000 and 2003 versions and I have yet to find a situation where the single pattern cam will yeild more low end torque than a dual pattern cam. I am running the Edelbrock heads on my engine and have used the flow numbers from the Edelbrock heads in Desktop Dyno for the flow numbers.

After switching from a Dual pattern cam to a Single I had lost low end torque with the single and didn't really make up the difference further in the powerband.

Here is what I had entered in the specs for the cam all other input data stayed the same.

Dual Pattern:
Isky 256/262 Dual Pattern
@.050
IVO -10.0 IVC 31.0
EVO 35.0 EVC -6.0
511 Ft Lbs @ 2000
509 Ft Lbs @ 2500
512 Ft LBS @ 3000

Single Pattern
@ .050
IVO -6.0 IVC 38.0
EVO 38.0 EVC -6.0
494 Ft Lbs @ 2000
495 Ft Lbs @ 2500
503 Ft Lbs @ 3000

I have not checked every known configuration as I don't have that much time on my hands, But out of all the configurations that I did check the Dual pattern offered the best low end torque even using the Edelbrock flow numbers.

If anyone wants me to compare a couple of different cams for them just let me know and PM me with a E-mail address so I can return the files to you. They will be in a JPEG format.