Purple Cam Design Question

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SpeedThrills

SpeedThrills

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When Mopar designed the Purple cams, did they take advantage of the larger diameter lifters?
I've read on here that they are an out of date design. What makes them old? I have a 292-509 that was in the 360 I bought and plan on using it until I build a 408.
 
I have the same cam in a .040 over 318 with kb flat tops and it works great lots of mid to high end power and it sounds great too. I have heard the same thing its an old design but its still a good design no matter how old it is, lunati makes some really nice modern design stuff high lift low duration big power bands.
 
SpeedThrills said:
I've read on here that they are an out of date design. What makes them old? I have a 292-509 that was in the 360 I bought and plan on using it until I build a 408.
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Essentially and not to be a smart *** but their age. These cams were designed in the 70's. They work no doubt, but there are cams out now that can get you more HP and more vacuum at idle with a broader torque curve assuming the head can flow as high as the cam can lift the valve. Putting a .550 lift cam on head that stalls at .500 is a waste of time, money and motion.

There's a heck of a lot that goes into cam design other than just lift, duration and LCA including ramp design and asymmetrical lobe profiles. The geometry that goes into the newer stuff is very complex and more lift for a given duration can be obtained without wiping the lobes off or making a racket.
 
SpeedThrills said:
When Mopar designed the Purple cams, did they take advantage of the larger diameter lifters?
I've read on here that they are an out of date design. What makes them old? I have a 292-509 that was in the 360 I bought and plan on using it until I build a 408.
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I don't have an issue with the Purple cams. Though like ramcharger said, the modern designs are very very good and unless there is a need, not want, need, to run a single pattern cam, the Purple cam could be a good choice.

Could be.

Your 400+ cube engine is doing what? What do you want out of it? What heads?

The 292 comes in @ 248 @ .050. Use this to compare it against other cams advertised duration and duration @ .050. I've noticed there more stout than most cams but not as aggressive as race cams that are streetable in style.

Of course, full race cams are a different story.
 
Purple cams are actually pretty aggressive,thats when advertised vs. .050 still played a big role in determining a cams aggressiveness and as the specs show mopars have more duration at .050 vs. advertised than others of that time.One of the reasons for lower lifts across the board had alot to do with the technology (heads being a big part) of the era,most people were running nearly stock type heads and the main mods were to compression,intake and exhaust so lifts above the mid to high .400s were not necesarry for the majority of engine builds,compression and gears palyed the biggest role in performance.Modern cams are designed to take advantage of lower compression,higher flowing heads ect.,spread the power band out and make more vaccum to keep a vehicle streetable and they work,these things were not such big concerns back in the day.
 
rumblefish360 said:
I don't have an issue with the Purple cams. Though like ramcharger said, the modern designs are very very good and unless there is a need, not want, need, to run a single pattern cam, the Purple cam could be a good choice.

Could be.

Your 400+ cube engine is doing what? What do you want out of it? What heads?

The 292 comes in @ 248 @ .050. Use this to compare it against other cams advertised duration and duration @ .050. I've noticed there more stout than most cams but not as aggressive as race cams that are streetable in style.

Of course, full race cams are a different story.
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What is your opinion with MOPAR'S restroatiojn cam for 340's. I 'm going to build a 340 for a 66 cuda. Want it to be a nice street car, dont want the shake rattle and roll at stops. Was looking at making a stroker using 360 crank and rods. Bore is 40 over and looking at 360 heads. I plan on putting a 6 pak on it.
 
66silverfish said:
What is your opinion with MOPAR'S restroatiojn cam for 340's. I 'm going to build a 340 for a 66 cuda. Want it to be a nice street car, dont want the shake rattle and roll at stops. Was looking at making a stroker using 360 crank and rods. Bore is 40 over and looking at 360 heads. I plan on putting a 6 pak on it.
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WHAT!? It's a resto cam. Same cam that came in the 340. They have been selling that since the engine first came out. It should sound like a stock engine, idle like one, etc... stock stock stock. It's also on a 114 C-line, mello X 3 in idle and such. If you put the 360 crank into the 340 @ .040 over, you'll have 374 cube sized engine. It'll idle even nicer since theres a large jump in size.

I'll tell ya one thing though, it'll make mad torque!
 
I kinda thought it was about ramps, area under the curve, and all that. Newer cams having more lift because of better heads being more prevalent makes sense, too. Getting a better idle sounds good, too.
I bought this 360 not knowing what was in it. It idled at 1200 or so, and had 7" of vacuum. I've taken it apart just to see what was in it and what kind of shape it's in. So far, I've found ported 915 heads w/ 2.02 intakes, a purple cam that checks about .509", KB199 pistons (10.5:1). I'm going to check the actual compression ratio. It has a nice cross hatch, Not too much bearing wear, but there are some scratches in them. I'm going to replace them.
It had a Torker II w/ a 750 vac sec Holley, 1 5/8 headers and a Unilite ign.
It's going in my cloned 71 Duster, a street/strip car that's just going to be a toy. It'll be about 3000#. I also have a 727 auto w/ a loose converter (I forgot to powerbrake it and check the stall before I took it all out of the truck it was in.) and a 4.11 gear. I eventually am going w/ a 4 spd and a 408. But it'll be a while.
It sounds like this cam will be fine for my application. I don't need a nice idle for this car.
I guess they didn't take advantage of the wider lifters back then?
 
True, but, they also describe there cams as to haveing the best charteristics (sp) for the strip and streetabilty. Race cams they are not, able they are.
 
Why hasn't Mopar Performance come out with newer cam design over the years? It's like they made the cams we have today, shut the doors, and said "That's good boys it's a wrap!"

I run a .474 MP cam in my 360 by the way. lol
 
MP purple cams are old but work well. I have a .030 over '71 340 with 2.02 "J" heads with a .509" hyd MP cam in it. It ran 11.98 @ 111.6 MPH in a '73 dart sport (3360 lbs) with a 3500 stall Turbo Action convertor , 727 trans, 4.10 suregrip and 26" tall slicks. I carry car around on a trailer but it could easily be a street driven vehicle.

Maybe if you have the money to invest in modern high flowing cylinder heads then you should get a modern cam, but if you are on a tight budget using the old style heads and cam combo still goes pretty fast at an affordable price!

Bob
 
The difference is the old grinds can make power in a fairly narrow way. You lose low end and vacuum to get horsepower. In the same identical engine, a modern cam will make the same or more horsepower, but you also get things like idle quality, no less loss of low end, and longer flatter power peaks throughout the range. MP cams also are made terribly. The QC is as good as the low bidder can get them. So overall, they work but not as well. I'll spend to get what I need for results, and the base parts mean nothing. If the cam's matched well to the parts, any cam will make power if it's made right.
 
racerbob said:
MP purple cams are old but work well. I have a .030 over '71 340 with 2.02 "J" heads with a .509" hyd MP cam in it. It ran 11.98 @ 111.6 MPH in a '73 dart sport (3360 lbs) with a 3500 stall Turbo Action convertor , 727 trans, 4.10 suregrip and 26" tall slicks. I carry car around on a trailer but it could easily be a street driven vehicle.

Bob
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Your combo is very close to what mine will be. I was hoping for very low 12's. Sounds like I should be ok. I'm hoping that the future brings me a 10 second 408. I'll have to save my nickels and dimes...
 
The 416 I r3ecently bought has the 292 Comp "nostalgia" cam in it that I think is the same grind. Made 500 HP. Haven't installed the engine yet so no report on how the engine sounds.
 
The Mopar Purple cams were all redesigned in the mid 1980s to take advantage of the .904 lifter diameter. This is actually in print in the latest edition of the MP engine book. While it's true they are an old design, they still work well. There are simply some instances (more often than not on the street) where you just don't need lightning fast rates of lift. In fact, it can be really bad on the valvetrain in some cases.
 
StrokerScamp said:
The Mopar Purple cams were all redesigned in the mid 1980s to take advantage of the .904 lifter diameter. This is actually in print in the latest edition of the MP engine book.
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In addition, didn't some folk here work around these cams only to find out the Lunati cams have a larger duration @ .050 than the MoPar cams?
 
rumblefish360 said:
In addition, didn't some folk here work around these cams only to find out the Lunati cams have a larger duration @ .050 than the MoPar cams?
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Yes, that's true.....BUT only since ....I forget what his name is that ran Ultradyne went to work for Lunasty. That's what the Voodoo cams are essentially.....they are very close to some of the old Ultradyne stuff. Good grinds, too. But Ultradyne always ground on the .904 lifter reference......even before MP finally got their heads outta their back sides.
 
StrokerScamp said:
Yes, that's true.....BUT only since ....I forget what his name is that ran Ultradyne went to work for Lunasty. That's what the Voodoo cams are essentially.....they are very close to some of the old Ultradyne stuff. Good grinds, too. But Ultradyne always ground on the .904 lifter reference......even before MP finally got their heads outta their back sides.
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Harold Brookshire is the guy's name.

I usually stay out of the Purple cam threads because they quite often turn into pissing contests, but here's my .02 -

Purple cams have fast open rates, but also have very fast closing rates (more than likely a mirror image of the opening side), which can make the valvetrain noisy and can induce valve bounce. Not good when you're trying to close the intake valve at a precise time and then it bounces off the seat, losing some of the intake charge back that was starting to compress in the chamber.

Also, the quality control is not great. I've had problems with other MP parts fresh out of the box, but that's another thread.
 
some really good info here
I stayed with my MP 268\272 .450/.455 after getting some excellent advice from guys here - I too was going to swap to a voodoo cam of the same duration thinking the newer design would be an improvement and power increase over the MP cam - but was told the difference would not be worth the money (heard good things about Harolds theory and design at Ultrdyne)
the application was for a heavier truck not an abodied car - so anyhow just curious about the newer MP's vs other cams as well

also - I read once that the actual durations were measured and advertised differently on MP cams - they were actually smaller than the competitions cams - this true?
 
Yeah, that's him. I cannot argue any of your points about the MP cams.....especially the quality control issues.....but to my knowledge, that has only popped up in the last 10 or so years.


lilcuda said:
Harold Brookshire is the guy's name.

I usually stay out of the Purple cam threads because they quite often turn into pissing contests, but here's my .02 -

Purple cams have fast open rates, but also have very fast closing rates (more than likely a mirror image of the opening side), which can make the valvetrain noisy and can induce valve bounce. Not good when you're trying to close the intake valve at a precise time and then it bounces off the seat, losing some of the intake charge back that was starting to compress in the chamber.

Also, the quality control is not great. I've had problems with other MP parts fresh out of the box, but that's another thread.
Click to expand...
 
lil red said:
some really good info here
I stayed with my MP 268\272 .450/.455 after getting some excellent advice from guys here - I too was going to swap to a voodoo cam of the same duration thinking the newer design would be an improvement and power increase over the MP cam - but was told the difference would not be worth the money (heard good things about Harolds theory and design at Ultrdyne)
the application was for a heavier truck not an abodied car - so anyhow just curious about the newer MP's vs other cams as well

also - I read once that the actual durations were measured and advertised differently on MP cams - they were actually smaller than the competitions cams - this true?
Click to expand...

It is true that they measure .050 duration differently, but it makes their cams actually larger, not smaller compared to the competition.
 
If I remember right, MP uses .850 as a .050 standard and the industry uses both .777 and .750.
 
"Ultra-Dyne Harold" is a valve control wizard...
From what I know, a few of the MP cams were altered in the 90s. The lobes were not. The lobe timing was... The lobe shape of an MP is nothing special, which is half the reason they are considered old-school now. Bear in mind, I'm not saying they are poor designs. They are poor executions of a good design, and better more modern profiles exist now. Both because of more modern understanding of valve motion and airflow, and because of better equipment to grind more accurrate shapes. If you have some grasp of cam design and how the valves need to be worked, you can compare the different lobes and see big differences between older designs and newer ones. MP has never altered the lobes. They did change the LSA on them, and guys have also figured out that they like to be in advanced beyond what MP recommended.
As far as using the ".850" figure.. That's simply a percentage that lets you have an idea where the duration at .050" is on a medium performance level cam. And most cams if you simply multiply the advertised duration by .850 (85%) you will get close to the manufacturer's duration at .050. The more you get away from mid-level performance (smaller or larger), the more skewed the result that the ".850" figure generates. Plus, with a modern design, the opening rate is different than the closing rate. The ".850" deal assumes the lobe is symmetric. Think of it as running an engine design through a simulator program vs running a real engine on a dyno. It's ok for an idea of trends, it's not a good way to make a cam choice. If you want to see the big differences in lobes, get the lobe catalogs for the manufacturer you are thinking of using and review the other stats they give you. Or better yet, physically profile some of them. Someone on this board profiled a few MP grinds at some point... I cant recall who. Maybe they can post one of them.
 
Moper, I know who your talking about, I just can't see a name to this. This idea was was what I was trying to think of on my last post. Someone sat down with a few good tools and a whole lotta time to do that.
 
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