Dual pattern cams...Black Magic or Legit?

[DSGcoupe]

Interested to see what some of the knowledgeable people on this forum think.

I have seen them in circle track engines and a few of those guys around here swear by them, but have never used one personally. I have always preferred to put the time into balancing out the intake flow with the carbides and testing. In theory, it makes some sense; but I am looking to see if anyone actually has any first hand experience with them.
So, are 4 pattern cams just Black Magic/ snake oil or are they legit and based on sound testing?

[Tommy]

Blykins has my proxy vote on this matter.

[kanuck]

As a rule of thumb fords run better with dual pattern cams.

[Gaz64]

My 2 hot V8 road cars both have dual pattern cams. Both have around 10-12 degrees more on the exhaust. The inlet closing point is the first event to consider. The exhaust opening point is not as important and so hence why dual patterns make more sense.

[Tommy]

If you can access Motor Trend's Engine Masters TV series, they cover this topic in Season 7, Episode 17.

[DSGcoupe]

I do apologize all for any confusion. In my mind I was thinking about about 4 pattern cams and somehow my fingers typed dual pattern. I run lots of dual pattern stuff. What I was really asking about is the 4 pattern cams(ie inside runners have different duration and lift than outside runners). I will correct my original post. Again, sorry for the confusion.

[eschaider]

Originally Posted by DSGcoupe

Interested to see what some of the knowledgeable people on this forum think.

I have seen them in circle track engines and a few of those guys around here swear by them, but have never used one personally. I have always preferred to put the time into balancing out the intake flow with the carbides and testing. In theory, it makes some sense; but I am looking to see if anyone actually has any first hand experience with them.
So, are 4 pattern cams just Black Magic/ snake oil or are they legit and based on sound testing?

I like 12-pattern cams where six of the eight cylinders get different patterns. Two are almost the same but not, and three use counter-rotating patterns. The other seven are tied to the air speed in their individual ports, factored by their linear distance, measured in SI units, from the car’s center of gravity with a half-full tank of gas. This modifier is necessary because of the lateral effect on the car's CG. The gas in the tank needs to have a minimum specific gravity of 0.693.

The remaining four cams use custom 5-cycle dynamically configured ramp profiles and therefore velocities, again factored by their distance (this time in Imperial units) from the car’s CG. Be sure when you take the measurements this time, you do it with a three-quarter full tank of gas.

This type of valve event requires the use of a hybrid fuel delivery system. The design incorporates a Holley 850 double pumper with two of the diagonal squirters disabled, blocked-off main jets with operating power valves, and individual port injection installed in each manifold runner.

For the ECU, you will want to use a Motec custom M1 ECU with their multicylinder Pro Analysis upgrade. This upgrade is available for the current version of MoTeC's i2 data analysis software to provide advanced mathematics, multiple overlay laps, and unlimited components, workbooks, and worksheets that will allow you to correctly phase each of the counter-rotating patterns vis-à-vis the nine non-counter rotating cams.

Properly configured, you will experience engine operating events, unlike anything you ever have previously known.

[eschaider]

Duplicate post deletion

[DSGcoupe]

Originally Posted by eschaider

I like 12-pattern cams where six of the eight cylinders get different patterns........
Properly configured, you will experience engine operating events, unlike anything you ever have previously known.

Sooooooo, long way of saying snake oil? Or just trying to sniff out hackers? In any case, your response made me chuckle. Thanks

[Tommy]

This source makes the gains seem real but small enough to not matter unless you are racing near the edge. Motor Trend

[eschaider]

It is what Tommy said. The difference (when there is one) is essentially down in the noise level — not worth pursuing.

[DSGcoupe]

Kind of what I thought. Seemed potentially beneficial when using old cast iron intakes (read inefficient). I doubted that the gains would be enough for the headache. As stated before, I have personally had good luck just matching up the intake runners with good old fashion port work and thought. By doing this, I have never really seen any exhaust temp difference between cylinders and the plugs all looked good across the board. Guess I will stick with what I know works.

[eschaider]

Build an equal runner length fabricated aluminum manifold with a suitably sized plenum, have it welded up at a local aluminum welder's shop and use a 90mm throttle (or larger if you want), pair it up with a good EFI. You will not be able to improve on the air or fuel distribution that the project provides you and you will be able to use a 'normal' camshaft. You will also permanently scratch that itch you are experiencing over uneven air supply to adjacent cylinders and do it the right way.

[Gaz64]

In a single 4 barrel carb engine class, ie 390 Holley, the rules could be free as far as cam timing is concerned. They run a restrictor plate, or the carbs can be measured by scrutineers.
With an oval track car that spends a lot of time at wot high rpm, it would advantageous to exploit the cam timing on the dyno for the differences between the four short intake runners versus the 4 longer runners.
Valve timing is way too complex for scrutineers, hence the rules would be more lax. They make up for it by setting strict rules for airflow. Carburetor, cylinder volume, exhaust can all be verified easily.
For a street engine, you are better off with equal intake lobes, otherwise you'll lose even more low rpm torque, just to gain a screaming top end.

[eschaider]

One of the universal truths is that if an intake runner is wrong for the cylinder and the operating range of the engine it is being used with, you can not tune out the wrong and make that cylinder behave the way the same cylinder with a correctly designed intake runner would. You might be able to alleviate some of the poor performance, but you can not eliminate the damage a badly designed intake path does to the power output of a cylinder — w/o redesign.

If you are racing the car competitively, then I would suggest you have four alternatives;

1. Accept the impact of the short length runners,
2. To the extent allowed by the rules, change the intake runners to be more similar,
3. Choose an engine/intake without the problems,
4. Get a different race car.

If you are not racing the car competitively either;

1. Enjoy it as is,
2. Build your own intake,
3. Get a different car.

Fretting over 6 HP on an engine that will likely make well north of 550 HP is foolishness. You are fretting about an effective 1% horsepower difference (less by the time it gets to the tire) that not only can not be felt by the driver but requires instrumentation to measure on track!! Good driving skills vs poor or mediocre driving skills will make a much bigger difference.

If you have excess energy that needs dissipation, buy a set of worry beads and rub them regularly. It is less expensive and equally as effective.

[DSGcoupe]

Originally Posted by eschaider

Build an equal runner length fabricated aluminum manifold with a suitably sized plenum, have it welded up at a local aluminum welder's shop and use a 90mm throttle (or larger if you want), pair it up with a good EFI. You will not be able to improve on the air or fuel distribution that the project provides you and you will be able to use a 'normal' camshaft. You will also permanently scratch that itch you are experiencing over uneven air supply to adjacent cylinders and do it the right way.

I have one on the shelf that I fabricated with a 105 TB. However, it won't fit under the hood of the cobra (too tall by about 8 inches). Sure is pretty holding the shelf down though and made hella power on my turbo car.

[DSGcoupe]

Originally Posted by eschaide62r

One of the universal truths is that if an intake runner is wrong for the cylinder and the operating range of the engine it is being used with, you can not tune out the wrong and make that cylinder behave the way the same cylinder with a correctly designed intake runner would. You might be able to alleviate some of the poor performance, but you can not eliminate the damage a badly designed intake path does to the power output of a cylinder — w/o redesign.

Absolutely, completely agree!

Originally Posted by eschaide62r

If you are racing the car competitively, then I would suggest you have four alternatives;

1. Accept the impact of the short length runners,
2. To the extent allowed by the rules, change the intake runners to be more similar,
3. Choose an engine/intake without the problems,
4. Get a different race car.

If you are not racing the car competitively either;

1. Enjoy it as is,
2. Build your own intake,
3. Get a different car.

Not racing the car competitively. I'm more of a drag racer, but I have other weapons for that in the shop. I bought/ inherited this car from my dad because he was no longer able to drive it and I have many fond memories in this car with him. This winter it is getting the 418 stroker I have been working on. I just need to contact Blykins for a cam and some other small parts.

Originally Posted by eschaide62r

Fretting over 6 HP on an engine that will likely make well north of 550 HP is foolishness. You are fretting about an effective 1% horsepower difference (less by the time it gets to the tire) that not only can not be felt by the driver but requires instrumentation to measure on track!! Good driving skills vs poor or mediocre driving skills will make a much bigger difference.

If you have excess energy that needs dissipation, buy a set of worry beads and rub them regularly. It is less expensive and equally as effective.

Not fretting at all. The motor that is going in should be over 500 hp (more than enough for the car). I was just asking if anyone had knowledge on the 4 pattern cams as it is not something I have dealt much with first hand over the last 20+ years. I am sorry if I have rubbed you the wrong way but I thought this may be a good place to ask as I have read numerous posts with good information. Even though I have been racing, fabricating, and building engines for quite some time, no one knows everything.

[eschaider]

You didn’t rub me the wrong way. I am attempting to be factual while drawing comparisons that illustrate why the effort and money could be better spent elsewhere. While your current fabricated manifold may be too tall for a Cobra installation, it is anything but impossible to fabricate an air only low profile version that would fit. Of course, that would probably require an EFI-style solution and not look period correct.

Perhaps a good data point to remember is that most of these cars are attitude adjustment vehicles and the difference between 550 and 556 hp makes no difference in the accomplishment of the car’s mission. It only lightens your wallet. There are any number of more worthy endeavors in the areas of ride, handling, appearance, etc.

[DSGcoupe]

Agreed and all points noted. I had looked at fabricating a lower profile efi style intake like I imagine you are talking about. However, I decided to keep it looking as period correct as possible as that was always the plan for the car.
I have had my hands on every nut, bolt, weld, etc on this car over the years and still have a few things that I plan to change (are any of our cars ever truly finished?). We always wanted the car to appear as period correct as possible, with modern touches in a few places (ie suspension, lighting, interior, amongst other things).
As far as the original question goes, it was more curiosity. When I retired from the service, I started a shop building engines and chassis's for drag racers around my local area. Had a few roundy round guys wander in once in a while and even a few friends that truck pull. Engines have always been my passion and have built everything from 2.3 turbo 4's to a couple of mountain motors and lots in between. I am always looking for different ways to optimize what I am playing with. Then COVID hit...since I am a RN first, I shut down my shop to the public because working 16-18 hours a day in an ICU COVID unit didn't leave much time for anything else. Now I just putz around with my stuff, my families stuff, and help a few friends out once in a while. OK, enough rambling, thank you for your thoughts and comparisons eschaider.

[eschaider]

If my memory serves me correctly, there is a pic of this style manifold on multiple engines somewhere here on the site. I have been unable to find it despite my best efforts. I did find a picture out on the net. This is what it looks like;

The manifold is built from components; my guess would be to allow fitment to more engines w/o the effort and expense of building limited demand, engine-specific manifolds.

The beauty of the design is the uniformity of runner design from cylinder to cylinder, which speaks directly to the intake runner length issue you were looking to mitigate. A nice spinoff of the design is that it appears low enough to fit under a Cobra hood.

If you employed a Viper-style air box model and built two box-style air plenums over the air horns for each bank, sort of like a Viper uses, it would have a high under-hood wow factor — but it would not be exactly period correct. The bling factor, cool factor, and corrected runner metrics could possibly offset some of the period-correct angst ...

Another oh-by-the-way sort of issue that needs to be considered is that it would force you to EFI.