Can someone explain when to run a single pattern cam vs a dual pattern cam? How do they differ in power production?
Single Pattern vs Dual Pattern Camshaft
- Thread starter srduster340
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Generally speaking the dual pattern is for a more stock style exhaust with manifolds and the single pattern is for an HP exhaust with headers and such. You want more exhaust lift and duration with a more stock style exhaust to help the exhaust side.
TT5.9mag
Two atmospheres are better than one
Dual pattern will tend to carry the powerband out a little further than a single pattern will. 90% of the stuff you see built will benefit from a dual pattern cam. That’s why the cam manufacturers have gravitated to them. If what you’re building has a very very narrow operating range and you are trying to dial in that range to the Nth degree, I could see specifying a single pattern.
Ground that way for a head that has less than idea flow characteristics and stock exhaust manifolds. Usually ground with more lift and duration on the exhaust lobe to help scavenge exhaust out of the cylinder and pull more fresh charge into the cylinder. Stock heads are production pieces and are usually not at their optimum flow potential and stock mopar exhaust manifolds are not the greatest with the restrictions especially on the drivers side the way it has to get around the steering shaft especially in an a body.
1967 383 with the 516 closed chamber heads, 10:1 cr. 4bbl.
This is a prime example of a dual pattern factory camshaft because the exhaust valves are very small and need more duration to stay open longer than the larger intake to help expell the exhaust gases with the small exhaust valve.
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This is a prime example of a dual pattern factory camshaft because the exhaust valves are very small and need more duration to stay open longer than the larger intake to help expell the exhaust gases with the small exhaust valve.
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That's a fantastic cam too. The good old Road Runner cam.
325 factory Horse Power.
And how much torque? What? How much? Uh huh. 425 LB FT. ....and people say the 383 is a dog. I will admit though, I like Comp's version of the Road Runner cam better. Tighter LSA and ground for .903 lifter diameter.
So would a thumper cam with a much wider duration variation work better than a typical split pattern cam with just a 6 or 8 degree split?
Yeah for sound.
I suggest you go to the Isky Cams website, Tech Tips: is extra exh duration really necessary?
The cam companies have to have shelf grinds for the folks who think they need a dual pattern cam, so that is what you see. Many Jap & European engines have reverse pattern cams [ less exh duration ]. They are generally smaller 4/6 cyl engines & rev higher....but don't need extra exh duration to do it. Hmm.
The Willie Wanker, Thumper, Boot Legger cams have tight LSA & long exh duration to create more overlap to give the cackling exhaust sound to draw attention for those that want to be king of the kids, NOT for best power necessarily.
The cam companies have to have shelf grinds for the folks who think they need a dual pattern cam, so that is what you see. Many Jap & European engines have reverse pattern cams [ less exh duration ]. They are generally smaller 4/6 cyl engines & rev higher....but don't need extra exh duration to do it. Hmm.
The Willie Wanker, Thumper, Boot Legger cams have tight LSA & long exh duration to create more overlap to give the cackling exhaust sound to draw attention for those that want to be king of the kids, NOT for best power necessarily.
The sound is more so due to the narrow (numerically low) LSA.
The extra duration as said extends the lower band.
The thumper cam seems to work very well. I have one in my sons truck 360 engine now. It’s 10.5-1 w/RPM heads, 1-5/8 headers, chink air gap, 600 carb. Works well. Has a good upper rpm power.
Engine spins and pulls up until approximately 6500.
It has an intake duration @050 of 230*’s.
If it can actually use this extra duration, IDK for sure. How much is needed for a daily driver or mini hot rodded car, IDK
There is 2 engine masters episodes that demonstrate some of this.
I never had a problem using a single pattern cam before.
I never had a problem using a single pattern cam before.
From another member !!!
That’s me. But he said explain. Now that’s tough.
Thanks for all the replies. Still learning. Never too old!
Dont let the dilemma keep u up at night get a proven grind and enjoy your Hot Rod.
mderoy340
Well-Known Member
I run a SFT lunati voodoo with 1.6 rockers in my 340 with open headers and extensions. Car pulls to 7K at the stripe in good air.
Voodoo Solid Flat Tappet Cam - Chrysler 273-360 272/280
Voodoo Solid Flat Tappet Cam - Chrysler 273-360 272/280
Is there a way to determine the opening & closing events on Lunati cams? Lunati doesn't provide them.
I agree. It's splittin hairs at best.
Rat Bastid
Dunamis Metron
go to mgispeedware.com and click on their cam calculator. Put the number in that you know and it will tell you.
ir3333
Well-Known Member
As i understand it the single pattern cam will outperform the dual pattern everywhere until
higher rpms are reached at which point the split pattern start to produce more power.
For sure the best street performance will be with a single pattern cam.
You will have to decide how often you will be operating at high or maximum rpm.
Old Earl used to say "you can dress a 10 in rags and she'll still be a 10"
higher rpms are reached at which point the split pattern start to produce more power.
For sure the best street performance will be with a single pattern cam.
You will have to decide how often you will be operating at high or maximum rpm.
Old Earl used to say "you can dress a 10 in rags and she'll still be a 10"
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