Camshaft characteristics?

Engine, Transmission & Driveline

  1. bajajoaquin

    bajajoaquin Senior Member

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    Is that :
    CID / D X Vs X Vl
    or
    CID / (D X Vs X Vl)

    Or does it matter? I mean one way it seems to have a higher index when you give it more cam, and the other way lower.
     
    Last edited: Dec 29, 2017
  2. CBODY67

    CBODY67 Old Man with a Hat

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    It should be the CID/(DxVlxVs). The whole idea is that if you find one cam that works great in a particular size motor, that you can approximate those same characteristics in a different CID engine by varying the .050" duration and/or valve lift, as valve sizes usually aren't that changeable and port flow has limits. The basic orientation is for stock production engines rather than race engines.

    In many of the smaller V-8s of the '50s, the cams were rather short and "small" compared to what came later in the '60s. At the time I came up with this formula, the Comp HE268 was "the" street performance cam in Chevy 350s, but I wanted one for my 305 instead. I ended up with a Cam Dynamics (later Crane) 266 (similar specs to the HE260, but obviously with normal lobe configuration (rather than the Comp Assymetrical lobes).

    The whole thing is for relative comparisons. Once you do cams for a few engines and engine sizes within a given engine family, the way the numbers work can become more obvious. I suspect this can also play into a particular engine's "rod ratio", but haven't contemplated that just yet.

    Short rod ratio . . . less piston dwell time at TDC, greater "yank" on the mixture in the intake port, ports and manifolds less important. More potential piston side-loading against the cylinder bore

    Rod ratio approx. 1.90 . . . more piston dwell time at TDC, "smoother yank" on the mixture in the intake port, ports and manifolds more important as to "matching" the engine's needs.

    CBODY67
     
  3. 69 300 vert

    69 300 vert Well-Known Member

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    FWIW, I found this article pretty interesting.

    Camshaft Comparison Testing

    On one hand, it sounds like a custom grind hydraulic roller lifter cam is the answer to the more power / smooth operation tradeoffs we're looking for in a cruiser type big car. On the other, the numbers aren't really much higher than the basic generic grind roadrunner equivalent type camshaft? Thoughts?
     
  4. bajajoaquin

    bajajoaquin Senior Member

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    Yeah. I have that article saved In my computer in case it ever comes down or gets put behind a paywall.

    That article has had a big impact on how I look at cams and my interest in a retrofit hydraulic roller. The main question to me is how big and fast (valve speed) can you go before you start to see big drops in valvetrain reliability?

    I wish I had the resources to dyno test a few options. That cam looks a little soft on the bottom for me (I want at least the 480 ft lb at 2800 I have stock), and revs higher than I’d want. What’s the best way to move the power down? LSA? Duration? Probably some of both, but I don’t know how much.
     
  5. CBODY67

    CBODY67 Old Man with a Hat

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    In watching the Engine Master videos, I get amused at the cams they consider to be "tiny".

    I ventured off into Gen III Hemi cams a while back. Seems that most of the stock-oriented cams are in the 200 @.050 duration range, but with over .500" lift. With factory rocker ratios of 1.70. Seeing this dyno article makes it all make sense. The factory later model engines obviously have some outstanding ports, compared to the earlier engines.

    I'll have to check the particular pistons used in that 383, but I wasn't aware that that much lift could be used without notching the pistons for valve clearance?

    The one issue with the high-lift/high-rate lobes is the valve springs. I think some of the factory springs are the "bee-hive" springs?

    Personally, I'd like to see a retro-fit roller with timing specs very similar to the factory RR/GTX cam but with about .475" lift and factory-spec lobe separation. No worries with oil specs in that situation.

    Along about 1968, Isky had a B/RB cam listed with 260 degrees advertised and .480" lift. Apparently only lasted for that ONE year.

    CBODY67
     
  6. PontiacJim

    PontiacJim Member

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    Many factors go into cam selection. You can't have it all in any one cam. You should select an RPM range you want your engine to make power; lower to mid-range, mid-range to upper, or upper end power. If you plan on doing street cruising and not open the engine up much, then lower to mid. Most of us will run in the mid to upper RPM's of our engines if doing some pedal stomping. Bigger engines will run upper RPM's.

    So selecting an RPM range will affect the other range that you won't be running in - it is a trade off. If you run lower to mid, the engine will run out of steam early. Mid to upper may sacrifice lower RPM's and upper RPM's if you have an engine that will spin comfortably past 5800 and on up. Upper RPM cams will lose most of the bottom end power. This is where you may have to compensate for lost power in those ranges with torque converters & gearing.

    You also have to build the engine according to the RPM range it will be turning or if you add any power add-ons like nitrous, turbo's, or a supercharger. Senseless to put forged pistons in a 5000 RPM engine and you'd be nuts to put cast pistons in a 7500 RPM engine. Point being that you will have to match parts to the RPM band the cam you select run in and it can mean the difference between a comfortably priced stock rebuild or a high dollar deep pockets build.

    Next is the drive train. Often people forget this aspect. This is why the cam manufacturers recommend, and yes it is only a recommendation, as to what type of stall your converter should be used and what gearing is needed. These recommendations are best, but it does not mean you can't run what you have. More HP/Torque also means heavier duty parts which means more $$$.

    I ran a 409 Chevy I built which should have never worked according to the armchair engine building geniuses. Big .530" lift 320 duration solid cam, factory dual valve springs, cast pistons, pair of 460 Ford AFB's rebuilt without re-jetting, factory dual point distrib. with no vacuum advance, 4-speed (and later a stock TH400) and 3.08 posi with those good old M50 rear tires. I could pull the front wheels off the ground in a heavy 1965 Impala SS convert if I dumped the clutch and could get traction. The car would rip your head off - but the combo should have never worked and I never knew any better at the time. It ran very rich due to the big gas dumping carbs so I installed those JC Whitney aircraft spark plugs and an MSD ignition. Ended the fouling plug problem. Still only got 8-10 mpg's no matter what I did. The engine would pull from 2500 RPM to infinity and never stop pulling - which was found to be 6500 RPM when the outer valve springs would break(had plenty of spares from other engines I had). Never a problem with the heavy cast pistons. Don't ever recall getting beat with that car and I raced quite a few on the street and some top end runs as well. Here, the HP/torque/mid to upper RPM cam took up for those things that would have not worked such as carbs that were too big, highway gearing, and car weight. If I had chosen a much smaller cam, you can bet all of that would have indeed affected the engine's power and I would have been disappointed because I did not match the drive train to the cam's power band.

    My point here is that cam selection may have recommendations by the manufacturer with regards to requirements, but this is not an absolute. You want to definitely match the cam to the RPM range you plan on running, build the engine with parts to match the RPM range you want to spin, and then match that to the drive train. A higher stall converter or 4-speed can offset some of those stiffer rear-end gears - as does bigger HP/Torque numbers.

    Today's 91-93 octane pump gas will generally support up to 9.5 (but personally like to limit to 9-9.3) compression with iron heads and up to 10.5 with aluminum heads. Quench, or squish area between the top of the piston and head, is a big factor in building a Pontiac engine and I suspect a Mopar? Tighter is best and I shoot for .045" using forged piston, but your machinist will advise you on this. The tighter quench area forces the fuel mixture into the combustion chamber and will eliminate or minimize detonation so you can take advantage of a higher compression (up to the safer 9.5 range) on pump gas rather than have to retard your timing to compensate and lose power or go to racing gas octane.

    Read up on Static Compression versus Dynamic Compression - very important in cam spec selection. There is a calculator on the Wallace Racing site that can help you here. Lobe Separation Angle (LSA) can come into play here. Some of the tighter 110 LSA cams will build compression pressure in lower compression engine which can be good for them while not so good on higher compression engines unless you want to use high octane racing gas. Here a wider LSA may be better. The tighter LSA's are usually more "explosive" power wise but have a narrower power band. A wider LSA provides a wider and typically flatter HP/Torque power band - something else to consider when figuring the RPM band you want to run your engine in.

    Single plane, dual plane, or tunnel ram intake? Another factor to consider. Head flow, exhaust flow, carb size - just more things to consider.

    Camshafts - not always a simple choice and one cam that your buddy uses and recommends may not be the cam choice you want to use. You really have to have to look at all things and match them up and not be looking for that lumpty lump sound only to find out, yeah, you got the sound alright but you also got a dog of a car because you did not select the right cam/combo for your application. Just my 2-cents worth.
     
  7. CBODY67

    CBODY67 Old Man with a Hat

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    Desired rpm range is important, especially when related to cam duration. Duration will generally move the power band up or down, with LSA and lift fine-tuning it somewhat.

    When the L69 Camaro engine appeared in the middle '80s, pre-TPI, everybody raved about it's performance. Cam was no wilder than the stock 350/300 cam. Main difference was that it was the first time that a Gen 3 Camaro had a really decent under-car exhaust system. Plus a decent dual-snorkel air cleaner. Basically, a torque motor that would rpm, as I termed it. The other thing is that the heads were nothing to write home about, stock as they'd been for a good while, but not terrible either. Then the 350TPI motor arrived, with dual cat converters and they had more torque and were the new silver standard of sorts.

    In those times, I had a friend who purchased a '67 Chevelle SS427/375. 4-spd, 3.08 axle (ordered that way). It still had the stock Holley, but sitting atop an Edelbrock Tarantula. It ran very strong, but with complaints of having to "granny-shift" it to save the clutch, with those 3.08s in the back. Once rolling, it was fine, to me. Almost considered buying it, but by that tie, he'd done other things to it.

    To me, one reason for the looser converter is to put less load on the motor at lower rpm for a better idle quality and quicker response for it to get into the power band quicker. A tighter converter would strangle it, so to speak.

    Key thing in cam selection is to not get too big that it takes longer to get through the lower rpm ranges and to the power band. In many cases, that "top end rush" comes too late to make up for the time it took to get there. A smaller cam would run past it.

    When looking at stock cam specs, if you know how to interpret them, it's relatively easy to see which engine is cylinder-head-port limited and which one has the better ports . . . as it doesn't take as much cam to make power. Buick Nailheads, for example, was one such motor, cylinder head port limited. Or you can further determine which head has better exhaust ports, for example. All of this for relatively stock motor configuration.

    Our Mopar club guys were some good drag racers. They also had some very-well-finessed cars with the stock Chrysler cams, intakes, carbs, AND exhaust manifolds. There was a standing offer to the Brand X guys to run them, IF they had stock exhaust, and street tires on them. NO takers! LOL. All of the Chevy guys had headers and turbo mufflers.

    Happy New Year!
    CBODY67
     
  8. PontiacJim

    PontiacJim Member

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    You just have to do some research and reading on different engine combo's in the same brand/block size you are looking to build. Cubic inches rule and if you can, go bigger cubic inches with a stroker kit and build for more torque than HP which you can get at lower RPM's so you don't have to build your engine on the more expensive "race" side - you can use more of your stock parts and clean 'em up with better valves/springs, 3-angle valve job, intake, exhaust, etc. and the like and save a little $$$.

    I have a 1979 edition of the Direct Connection "Special Parts Catalog." In it they provide the parts, part numbers, and modifications to do to get your car into the 14 - 13 - 12 second bracket under "Engine Package A, B, C" for the 273-318CI, 340-360CI, 361-383-400CI, 413-426W-440, and 426 Hemi. I think the Mopar guys were one of the best supported by corporate backing and had the parts, knowledge, and experience to back it.

    So when building any Mopar engine, there really doesn't need to be a lot of guessing - its already been done before. I kinda get tired of hearing how the factory cams or older grinds are "old school" and better technology has improved today's cams. These "old school" cams were that better technology at that time and they worked. If you ever look through an "old school" cam catalog, you will see a ton of differing grinds available and each maker had his own line of grinds, and then you could get custom ground cams - so really, why are "today's" cams better then the "old school" grinds which came in any configuration you could dream up, either hydraulic, solid, or roller?

    Promote enough BS in any magazine or by any engine builder and soon it becomes "the cam," "the intake," "the pistons," "the rings," "the ignition," "the header," etc. to have on your car because it is "the best" and will make your car go faster and put "old school" technology & parts out to pasture. Yeah, right. All you have to do is read some of those "old school" drag tests & road reports and see for yourself that "old school" wasn't so bad when the factory could put out a 15, 14, or 13 second 1/4 mile car off the showroom floor with a stock suspension, brakes, and full interior and by adding some of our hot-rod goodies like slicks, headers, open air cleaners, re-curved distributors, carb/intake change, or gear changes and put them into the 13 & 12 second 1/4 mile times. The factory and specialty dealers showed us what the full potential of some of these engines/cars were capable of doing, with the Camaro ZL-1 dipping into the 10 second 1/4 mile.

    Today it seems everyone wants to have a 10 second 1/4 mile street car with 500-700 HP. I say get a ride in an "old school" 12 second car and tell me if you really need to spend all that money to go 10 seconds. LOL

    You might want to check this link out just for fun.
    DRAG TESTS 1960 - 1972
     
  9. PontiacJim

    PontiacJim Member

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    Roller cams are a great way to go on the street, BUT, it is usually the additional cost factor over the flat tappet hydraulic or solid cam setup. You also are investing a greater dollar and IF you select a grind that really does not perform as you had hoped, it is not as cheap to go with a different grind.

    You should purchase a "kit" which has all matching parts rather than just a cam/lifters and then go from there. You can be looking at over $1,000 to go roller. Assume you are going to also need to get new pushrods which don't seem to come with any of the kits. The same kit in a flat tappet cam is under $450. If I could use my old valve springs & retainers, it would be even less.

    I see it as about a $900 savings when all said and done and with me, 'cause I am cheap, that's $900 I can invest somewhere else in my engine build.
     
  10. CBODY67

    CBODY67 Old Man with a Hat

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    One thing that made Chrysler engines generally perform better was that Chrysler built "combination" engines. Everything worked together, rather than just an "assemblage of parts", it seems. And when the combinations were well-finessed, they REALLY worked.

    Looking at the '60s roller cam lobes, they appeared to be vertical from the base circle, round, then vertical back to the base circle. Opening rate was obviously much quicker than a normal flat tappet or even a mushroom lifter (which Ford used on their Y-blocks). All other things being equal, a roller should probably have more area under the curve at a given total duration, for more power and torque. Only thing is that as a roller will obviously tolerate higher lobe lifts, cam manufacturers seem to desire to capitalize on that with higher lifts and longer durations, which can put them out of the street-tolerable range of things. Otherwise, a roller cam set-up, with roller-tip and roller-pivot rocker arms take rubbing friction out of the motor, so that power can get to the flywheel . . . IF you can afford the price of admission for the roller cam. You can still used the roller-ized rocker arms, though.

    One thing I haven't really figured out is that all of the magazines talked about how finicky and tough to keep in tune the early-60s factory hot rods were. When I finally got a chance to spend some time around some of them in the middle 1980s, that didn't really seem to be the case.

    There usually were two sets of ignition points to set, but the procedure was the same as with a single-point system, just do it in sequence for a total of two sets. If the car spit-back for any reason, there went the Holley power valve (especially on a 3x2bbl 440). Keep the plug wires routed normally and away from the exhaust system, with some quality wires, and no significant issues, either. So all of this made me wonder about those earlier statements. OR if the magazine guys flogged those cars in the "media fleet" such that things broke due to "user issues"?

    Our former service manager used to race jet boats, in the jet boat drag race circuit. He used 468 or 486 Chevys. One of his friends did KB Hemis in the blown flat-bottom class. Mike was always tweaking his Chevy motors, like a good racer is allegedly supposed to do. Several years later, he bought a pickle-fork hull that came with a KB Hemi. He learned how to do the Chrysler-architecture engine deals. He soon learned how much LESS work it took to keep the Hemi running at its peak, compared to the Chevy. When I heard him say that, I smiled!

    CBODY67
     
  11. bajajoaquin

    bajajoaquin Senior Member

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    My guess is that cam ate lobes in a pre-roller era.

    It's interesting that you single out the 375 cam as a pattern. That small Lunati roller has more lift, but is otherwise pretty close. Looking at the Comp master lobe catalog, you can find a couple lobes that look like

    216/0.474 (lobe 3303)
    224/0.474 (lobe 3307)

    I don't see any reason you couldn't have it ground on a 115 LSA. Can I ask why you've settled on those lift numbers?
     
  12. CBODY67

    CBODY67 Old Man with a Hat

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    The thing that bothers me about many of the rollers is their .500+ lift. As the old Purple Shaft Street Hemi cam had about .475" lift with no piston clearance issues on the 10.0CR motors. If I was going to build a motor, then the pistons would be clearance as a matter of course, with the .500+ lift cams. The other consideration is the head port flow at those higher lift levels. No need aiming for .500"+ lift if the heads don't flow that well past .475" lift and the exhaust system needs some upsizing, too.

    That Isky cam probably did have some lobe wear issues as it was a flat tappet cam. I've known of some drag racers that went for more lift and duration, only to find that after a few weeks of racing, the valve springs were either breaking or going soft. When they backed the cam down a notch on the lift, there were no more issues in that area. ETs were not really affected either. This was in the 1990s, before the beehive springs appeared.

    There probably is a close-match set of lobes in the master catalog, for some of the factory cams. My Mopar club associate with a '70 Swinger 340 was playing around with cams, trying to find something better than the stock 340 cam. He got hooked-up with Racer Brown and they did some cams for him with shorter LCAs and such. As they predicted, the power output "hit a wall" at a particular rpm. He later tried some of the new Purple Shaft cams (with the 110 LCA), but eventually put the stock cam back in. To me, that Purple Shaft cam sounded "happier", but with the 110 LCA it took some re-tuning to optimize it. He was more comfortable in how the stock cam performed as he'd optimized the tuning for it (stock specs).

    Some people have better luck with the stock HP items. When our guys deviated from that, the cars slowed down some, which needed other things to hopefully regain the performance decrease, which was a never-ending quest. A return to the stock HP parts and things happened good again.

    In '69, CAR LIFE magazine did a test of a '69 Road Runner that Chrysler had upgraded with their Direct Connection Street Hemi cam, Edelbrock 4bbl intake, and 780 Holley. Probably some headers, too. End result was the car ran right at where the stock 426 Hemi did, which was their target. It was deemed a success in their quest for Street Hemi performance without the Hemi "issues" of that year. And without the cost of the 426 Hemi option.

    CBODY67
     
  13. 65Fury440

    65Fury440 Senior Member

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    You know Andy, our cars are as close to being the same as you can get.
    The 440 that was in my car before the stroker, was a 440 with flat top pistons, 509 hydraulic cam, Performer RPM intake, 906 heads with what looks to be gasket matching on the intake, and headers.
    I hear a lot of people hate on the 509. Granted it is old school single pattern tech, it worked just fine with a 4 speed and a 3.23 gear.
    The car was plenty fast, and totally drivable. I have manual brakes and steering, so 8" of vacuum doesn't hurt.
    Point of this post is, you can probably go with a rumpier grind with the 4 speed.
    Do you have power brakes or manual?
     
  14. Andy Blaisdell

    Andy Blaisdell Member

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    Power brakes
     
  15. Andy Blaisdell

    Andy Blaisdell Member

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    I'm going to run it. If need be I'll run a vacuum chamber (reservoir) with a vacuum pump our of an old Ford diesel truck. I do that currently in another vehicle.
     
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  16. Luke Pokrajac

    Luke Pokrajac Member

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    Are you still happy with this cam? I'm going to be installing the same one in my 68 sport fury with original HP 383 engine. My car is a factory original 4 speed.
     
  17. Zwap

    Zwap Member

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    I'm still very happy with the cam. I went from non HP 383 cam to Lunati 10230701 and that was a real difference.
    I don't know how much difference it will be with the Lunati compared to the original HP 383 cam but I really like the 10230701.
     
  18. CBODY67

    CBODY67 Old Man with a Hat

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    Which Lunati "series" is that cam from? Just curious.

    In looking at cams, I now find more that I like in the Lunati line than in the past. Wish there were more "street rollers', with normal valve lift figures, though, that would last 100K miles or more.

    Enjoy!
    CBODY67
     
  19. Zwap

    Zwap Member

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    The "series" 10230701 would be VooDoo and I bought it late 2016.
     
  20. CBODY67

    CBODY67 Old Man with a Hat

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    Thanks!

    CBODY67