Camshaft characteristics?

Engine, Transmission & Driveline

  1. CBODY67

    CBODY67 Old Man with a Hat

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    How do we know which lobes are for which lifter diameter? I've seen the lobe catalog listings, but don't recall any spec as to which lifter diameter they were meant for.

    CBODY67
     
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  2. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    I would say they are mostly all based around the .842 Chevy diameter no matter what they say. Just my opinion no I can't prove it, don't ask.
     
  3. saylor

    saylor Senior Member

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    city motor supply down in dallas will build you a claimer engine.
     
  4. CBODY67

    CBODY67 Old Man with a Hat

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    City Motor Supply used to have a 392 Hemi in their showroom/order room. Quite a true "re-man" operation, rather than "rebuild".

    One of our Mopar club members thought he want to go dirt racing. He found a chassis, had it modified for a LA 360. Got a 50K mile junkyard engine, put the alcohol Holley fuel system on it. He was running "mid-pack", as a general rule, in a group of Chevy guys and a few Fords. They knew what they had in their motors to do what they were doing, but this Chrysler engine made them re-think their strategies. He became a better driver and started to finish higher, no where near others needing to invoke the "claimer situation". If they did, they couldn't just bolt in the LA 360 were their 350 Chevies had been. It was funny to hear him tell of the head-scratching the Chevy guys were doing! After a few seasons, he went back to drag racing.

    The claimer engine deal was supposed to keep racers from spending $15K on a raised-deck SMB engine. In some circuits, it worked. But for those races, you don't need quite the full-block race engine to be competitive.

    CBODY67
     
  5. CBODY67

    CBODY67 Old Man with a Hat

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    In looking at cam specs and the broad range of CIDs they can cover, as the SBC can range from 265-400 and use the same cam, generally. A cam that's "wild" in the 265, or even 283, will be verrry mild in a 350 or 400. Timing event specs related to cubic inch displacement.

    When I was trying to determine which cam to put in my 305 Camaro, the Comp Cam HE268 was out and worked well in 350s. So I wanted to take that good experience and transfer it to my 305 or a 372 I was proposing. I devised a simplistic formula to do that.

    CID / (Duration @.050") x (valve size) x (valve lift) Do this for intake and exhaust for the baseline engine/cam combination you like.

    With that baseline, then vary the duration, lift, and valve size with the new engine size (larger or smaller). Timing specs would increase/decrease as needed, with lift and valve size to fine-tune things some.

    There are some givens, though. That within a given engine family, the port flow will be somewhat similar, although some heads are better than others. Valve sizes will be more limited, due to normal packaging situations. At some point, increasing duration is a better way to do things than to stuff a larger valve in the port, for example.

    When I put all of these things on paper, it became clear how radical a cam optimized for a 400cid engine would be in a 283, for example, and vice versa.

    This was before the Computer Dyno programs started to come out, in the later 1970s. There can be other considerations, too, as rod length/stroke and bore/stroke ratios and how they can affect engine performance.

    Something to play with in your spare time . . .

    CBODY67
     
  6. Bighead440

    Bighead440 New Member

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    The minimum lifter diameter is listed. Comp, for example, has a dozen or more .904"-specific listings, hydraulic flat tappet and solid. I have used their "Purple Plus" and "904 race" hydraulics as well as the "MP" and "MM" solids.
     
  7. CBODY67

    CBODY67 Old Man with a Hat

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    Thanks for that information! When I was looking at the lobe specs, the lifter diameter spec was something I wasn't interested in at that time (a good while back) or knew that it might matter. But I knew there must be a reason for that large number of lobe profiles.

    Back in the later 1980s, a friend was trying to fine a better-than-stock 340 cam for his '70 Dart Swinger 340 He was talking to Racer Brown's tech people. They'd cut him a cam a little different (LSA or similar) and they didn't run as well as the stock cam on the drag strip. He tried one of the MP cams and the motor sounded much better to me, but he ended up going back to the orig cam

    The engine combo in the car was a very well finessed stock 340 w/AVS, TF, 3.91s, and BFG Comp T/A (autocross oriented) radials in the same physical size as the orig D70-14 tires. The autocross radials (Z-rated) tires warmed quickly and sounded like slicks in the launch. He later sold the car, which was stolen and then recovered. One of those cars that was very well finessed and all it was meant to be. "The Ultimate".

    Our Mopar Club guys had very good results with the stock Chrysler configuration. Those that varied from it seemed to always be looking for that elusive "right combo" the factory parts offered, but better. We had a "street tire, exhaust manifold" challenge to the Chevy guys. NO takers! Of course, to make a Chevy generally run well, back then, it took headers to unlock the breathing potential of the small block heads and then the requisite "jello bowl" suspension (for allegedly better weight transfer) and too-big carb (which meant they usually had to keep revving the engine to keep the plugs clean, as they drove through the pits and such. Much sound and "fury" and they still wouldn't run with our factory-spec Mopars.

    These successes cemented Chrysler "combination approach" to engine specs that worked, for me.

    CBODY67
     
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  8. Andy Blaisdell

    Andy Blaisdell Member

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    Anyone have any idea if the P4349449 280/280 234/234 .474/.474 int c/l 110 camshaft / the Street Hemi cam would be a good combination and work well with a Offenhauser 5206 Intake, dual quad (2 - 450cfm) Holley set up with 516 heads running 2.08/1.74 valves and headers on a 440? I am looking for a somewhat rough idle (old muscle car sound) and not so much 6000 RPM+ turns.
     
  9. moper

    moper Well-Known Member

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    There hasn't been much in terms of big break throughs with camshafts for years. The spintron is really what's bringing the latest advances, but these are not what goes into developing a profile like what we're discussing here. Hughes is full of shit. The fast rate cams were part of Ultradyne's line up in the 70s. "Ultradyne" Harold Brookshire developed them. He also did r&d work for Comp's XE line, and Lunati's "VooDoo" line. Here's the deal - the steeper the ramp, the more likely to have problems due to wear and production machining and tolerance stacking. So most major companies don't push the limits. Because the occurrences of failures will go up as one gets closer to the diameter limit. All Hughes did was push the envelope and market the crap out of "his" idea. The result was a rash of failures. Read his site now and you'll see all the BS he puts out there about cam failures and how they're not his fault.
    IN any event, ALL cam manufacturers have fast rate lobes. Some faster than the given manufacturer's lifter size. They can rival roller profiles in some cases. But - pushing that envelope means as a builder one has to be very, very careful. A worn lifter bore, or a cam bore slightly out of place, and the engine will eat the cam no matter what you do. I spec most of my custom cams with the Ford .875 "fast rate" profiles. They are more than adequate to make the power my customers need, and require less spring, and are easier on the valvetrain. There's also much less potential for failures due to wear or tolerance stacking.
    My advice, in this case, is to run the Comp XE268. Much more than that will create potential vacuum issues for the brakes. Lunati has some good profiles too. Something like the 10230702. I would not waste much time on MP offerings unless you can find them NOS, made prior to the 2000s. Even then the profiles are dated and more power and better manners are given up by using them.
     
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  10. CBODY67

    CBODY67 Old Man with a Hat

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    Thanks for those comments. Interesting that you mention spring durability. Several years ago, my machine shop operative (whom I used to share a shadetree car shop with for many years) had a customer who wanted a particular cam. More lift than the cam he had, maybe a minor bit more duration. End result was that springs started to fade, which he hadn't had happen in all of the time he had the earlier cam. The ramps were steep and tall and QUICK, which affected spring life. He downsized to where he had been, lost about .05 seconds on the ET, and had a trouble-free drag motor again.

    Tommy had a saying . . . 'Don't go to the bottom of the (catalog) page to buy your camshaft." As that's where the "big numbers" usually are, that you don't really need to make power. Sometimes, once you find this "great" cam that others think is great, go one notch smaller and it'll probably be better to live with on the street. Upside the exhaust for better flow, even add headers. Finesse the carb/ignition tuning and the whole package will probably be much better, in the end.

    I've looked at the VooDoo cams and they have some nice ones for a good street car. Even mention assymetrical lobes and "most area under the curve" in their comments. Prior to that, the last time I'd looked at Lunati (what my machine shop guy called "Lunatic") was in the 1980s and I didn't see that much in there that was appealing to me. Much different now!

    CBODY67
     
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  11. Zwap

    Zwap Member

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    I'm glad to read this as my choice became Lunati 10230701 about a year ago, maybe on the mild safe side but I'm very pleased with that cam in my mild street 383/727 -66 Polara 3.23 rear end, it pulls good from idle up to at least 5.500rpm
    • Advertised Duration (Int/Exh): 256/262
    • Duration @ .050 (Int/Exh): 213/220
    • Gross Valve Lift (Int/Exh): .454/.475
    • LSA/ICL: 112/108
     
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  12. bajajoaquin

    bajajoaquin Senior Member

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    Some disjointed thoughts while I’m getting ready for work:

    The Comp cams .904 lifter profiles start at around 230 degrees of duration IIRC. That’s more lift than we probably want in these heavy cars.

    The smallest lunati roller can looks really nice. I’m seriously considering it

    I’ve put together a spreadsheet that compares lift to duration ratios. I’ll find the time to post it sometime soon.

    Factory cams have a lot of duration for their low torque peaks and lots of LSA. I’d love to hear from someone who was there and knew the grinding philosophy.
     
  13. CBODY67

    CBODY67 Old Man with a Hat

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    The factory cams' duration numbers are measured according to ah SAE spec procedure. Something like .006" lift. A year of so in the '60s, Chevy measured their cams at .001" lift, which gave their base cams HUGE duration figures, as it included the lobe's "ramp" in the numbers. I think that Mopar Perf stated that to get to .050" duration with factory numbers, to multiply them by about .80?

    The .050" duration specs were strictly from the aftermarket as a better and consistent measurement spec procedure.

    When I did a cam upgrade in one of my cars with a 5.0L (not Ford) V-8, I used a cam with 210 @ .050 and .440 lift, with 110 LSA. This was in the later 1970s, when LSA had been talked about somewhat little. Tighter LSA (110) shifts the power in one direction, with poorer idle manifold vacuum. Factory LSA of 114 has a different power band shift, rpm-wise, but has "normal" idle intake manifold vacuum levels. Some have 112, which is still good for vacuum.

    The tighter LSA will take a different timing advance curve than the stock cam, by observation. This means more "tinkering" to get it to "act better". It can be "plug and play", but you might not like it that way.

    There are various theories about intake/exhaust duration and lift issues. Whether the duration needs to be the same, intake and exhaust, or have different durations for intake/exhaust. It might depend upon which direction you want to look.

    IF an engine's exhaust ports don't work as well as they might, then lengthening the duration on the exhaust side can help compensate for that and make the flow orientation better. Same if stock exhaust manifolds and under-car exhaust are being used.

    On this orientation, if you use a "single duration" cam, you'll probably need to use headers and an improved under-car system to get the same balance. Freeing-up the output flow, so to speak. But there are some theories in this area too.

    Key thing is that you improve air flow through the motor and have exhaust scavenging high enough that little residual exhaust remains after the overlap period.

    In the earlier days of emissions regulations, some makers added "humps" in the floor of the exhaust ports. A flow restrictor that also increased residual EGR without needing an EGR valve. Many people got the die grinder after them! Once they were discovered.

    And then there is the issue of lift vs. head flow. If you read cam specs for various engine families, it became obvious that Pontiac cams had greater duration but lower lift numbers. As it turned out years later, when flow benches became "available", their ports didn't flow very well, so they opted for increased duration to compensate for that.

    The Buick Nailhead ports had issues, too, other than their small valves. So in the later 1950s, with an increased engine size (401), they increased the duration enough that complaints about "rough idle" were made. The cams were more radical, to help compensate for the poorer (torque oriented?) port flow characteristics.

    Ford FE engines and Olds V-8s all seemed to have cams with huge lifts, compared to normal Chevy or Mopar cams. Both had generous valve sizes, but apparently the ports didn't work too well, or they wouldn't have needed the "help" or high valve lifts?

    When you look at cam specs in stock engines, use the cam specs as a barometer of how well the ports work and such. Total air flow capabilities. A "good engine" would build lots of power with modest cam specs, IF the heads worked very well. So when you see large durations and lifts in an engine family's specs, you can tell if the engine has good intake flow and how exhaust flow relates to it. Also consider the factory exhaust manifolds and what was under the car from the factory. It was a huge balancing act, especially back in the '50s and earlier '50s, when each maker had their own Chief Engineer who ran their engine programs, most of which started in the then-new '50s V-8 engines.

    CBODY67
     
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  14. Andy Blaisdell

    Andy Blaisdell Member

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    asking one more time since you all seem to know your cam stuff.

    Anyone have any idea if the P4349449 280/280 234/234 .474/.474 int c/l 110 camshaft / the Street Hemi cam would be a good combination and work well with a Offenhauser 5206 Intake, dual quad (2 - 450cfm) Holley set up with 516 heads running 2.08/1.74 valves and headers on a 440? Guessing about 10:1 compression. Running 2 1/2" dual exhaust and a 4 speed transmission in a 65 Sport Fury. I am looking for a somewhat rough idle (old muscle car sound) and not so much 6000 RPM+ turns.
     
    Last edited: Oct 27, 2017
  15. Bighead440

    Bighead440 New Member

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    Personally, I would go with something more modern and with higher lift, but the StreetHemi V2.0 will sound rumbly and have good torque in your 440. The 4 speed really opens-up the options as far as rough idle, but remember that you have modest rearend gearing, so you'll be riding the clutch to get that weight moving.
     
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  16. moper

    moper Well-Known Member

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    Don't choose a camshaft for idle sound. If that's what you want to do, you MUST lower performance expectations and buy for sound. A couple companies have grinds marketed just for the sound. But they are not big performers in any aspect aside from the noise. Also be aware that rough idle means impacted idle vacuum levels. It may struggle to run power brakes.
     
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  17. max1196

    max1196 Member

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    Read up on this.
    Dynamic compression ratio
    and this
    Dynamic CR
    Size of the cam is a balancing act, not enough (Static) compression and a late Intake closing event and yeah that sound will be there but driveability will be compromised.
     
    Last edited: Oct 29, 2017
  18. LocuMob

    LocuMob Fluid Technician with a hat FCBO Gold Member

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    Forgot to ask when you initially posted, but ehy the adjustable valvetrain? When I asked Dulcich, I stated I'd be using the stock rockers. Just curious is all.
     
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  19. Bighead440

    Bighead440 New Member

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    The fast-acting lobes and anti-pump-up lifters really need adjustable valvetrain. If you use regular stock replacement lifters and stock rockers, check your pushrod length carefully. You may need slightly longer pushrods due to reduced base circle on the cam, due to the high lift.
     
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  20. Bighead440

    Bighead440 New Member

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    What more info do you want Andy?
     
    Last edited: Oct 30, 2017