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Technical Hemi reground camshaft advance

Discussion in 'The Hokey Ass Message Board' started by kevin31, Apr 9, 2019.

  1. kevin31
    Joined: Oct 1, 2011
    Posts: 35

    kevin31
    Member
    from ottawa

    [​IMG]

    Does anyone from experience know what these motors prefer for camshaft timing? This motor just wants to scream..... I’d like to get the power band down a little bit. The motor is a 345 desoto stock compression ,the cam is reground to 220 degrees @.050 108 lsa, I know they say most new cams have about 4 degrees advance built in, I don’t race the car, just street driven, it was set advanced 2 degrees by the timing marks( never degrees the cam) looking for some input.


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  2. jimmy six
    Joined: Mar 21, 2006
    Posts: 4,350

    jimmy six
    ALLIANCE MEMBER

    I'd get a wheel and pair of mag base dial indicators and see where it is..... I put 6* in a RV cammed 355 in the mid 80's and really woke it up. An Isky "Mile-a-More in 70's had 8* in it and wouldn't turn a 400" over 4200, but could pull a trailer and cabover camper up a 5000' pass at 60-65 mph no sweat.
     
  3. 108* LSA seems like a lot for the street... You might look into another cam with a 110*-112* LSA.
     
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  4. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 8,959

    Rusty O'Toole
    Member

    There is an old trick for setting up a cam especially for street use. Turn the engine over on the starter and take the compression. Move the cam around until you get the highest reading. That timing will give the best idle and low speed to mid range. Generally speaking a little more advance is better for low and mid range torque, a little less for max HP at high RPMs.
     
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  5. gimpyshotrods
    Joined: May 20, 2009
    Posts: 15,992

    gimpyshotrods
    Member

    I disagree. A wider lobe separation angle moves the power peaks UP, not down. Sure 110º to 112º might make more power at higher RPMs, but the OP is specifically asking to go away from that. Besides, how much time do you spend holding revs at 4400rpm?

    My daily-driver has a custom ground cam, with a very intentionally chosen 108º LSA.

    With the stock compression of the Desoto, I would say that he has the perfect cam.

    I generally advance 3-4º, but that is from straight-up. Without knowing if this cam was ground with advance, that number could vary, in what it would need to be set to, at the timing set.
     
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  6. 6sally6
    Joined: Feb 16, 2014
    Posts: 568

    6sally6
    Member

    Really need to know "where-the-cam-is-at" by degreeing it in. My custom ground cam was ground "straight-up" (NO advance). I don't know if ALL custom cams are that way or not and....neither do you! That's why the degree wheel is a must.
    You said it really wants to scream?!! Advancing the cam timing WILL move the power range down some. That's why a radical grind cam (lotsa duration and tight LSA) will sometimes calm down some if you move the power range down some...by advancing the cam. It lets the cam sorta "come on" at a lower RPM.
    But....that is sort uva band aid approach. If its a "high winder"perhaps a cam with less duration is in order. If you lik'em kinda snotty.....then 108* LSA will give it to you . The smaller the cubic inch engine......the snottier(is that a word?!;)) they will be at that lobe separation angle.
    Hey.........I'm just an unemployed welder...what the heck do I know about camshaftery(is that a word too?!:()
    Degree it and we will all know what it is.
    6sally6
     
  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 15,992

    gimpyshotrods
    Member

    It is now.
     
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  8. This is an excerpt from a technical article dealing with cam selection for the DeSoto hemi, it may be of help. In addition a longer lobe separation angle degree (i.e. 110 ) will smooth out the idle characteristics
    New cams for these motors are not available. However, re-grinds (on your own good used cam) are available from some major cam manufacturers, but few specialize to the point where they can make a specific suggestion (rather than just tell you the specs of what’s available). Chris Neilson is an exception, see Source Table. The array of possible choices is not only frustrating, but the selections are usually based on intended use (RV, street, drags, oval track, fuel, etc.) and not really helpful. Re-ground cams (except welded overlay) have smaller base circles than stock cams, and therefore frequently need longer pushrods, depending on the new lift.
    I have a very simple rule for cam selection. It’s based solely on motor size, since many other variables are known and similar: all the original cars are relatively heavy (3500 - 4000 lbs.), have low-number axle ratios, almost all have 2 or 3 speed transmissions (Powerflite or Torqueflite; no 5 speeds or O/D), no EFI, under 400” displacement, with moderate compression ratios, cast-iron heads, restrictive intake manifolds, etc. Forced induction or nitrous cams are special, don’t use these rules.
    My cam selection rule does provide a safe choice for a warm street motor, with good manners and acceptable idle, suitable for a stock converter and highway axle ratio, but still provide a nice power increase when the “best” cam is not known, and too many choices are available.
    To predict a useful cam for a “warm” street motor:
    1. Take the size of the motor when completed. Divide by 10, and round off (330” becomes 33, 276” becomes 28, etc.).
    2. Add 180. The result is the cam’s “duration @ .050” lift” (look for it in the cam manufacturer’s specs). For a 330” motor in this case: 213° (330 ÷ 10 = 33; 33 + 180 = 213). More power? Like that “racy” idle? Afford to lose a bit of low speed power? Add 10 to the .050” duration figure to get a hot motor (for a 330” motor in this case: 223°), best used with high compression (9-1 minimum), 4 bbl. or more, standard transmission or a loose torque converter, dual exhaust and high numerical gears (3.55, not 2.76). Heavy vehicle? Stock torque converter? 7-1 compression? 2 bbl. carburetor? Subtract 5 from the .050” figure (for a 330” motor in this case: 208°).
    3. Advertised (total) duration: use the lowest figure you can find for the .050” duration value predicted in Step 2 above (i.e., 290° advertised duration is preferred to 300°, if both have the same 220° @ .050” lift).
    4. Lift: as much as you can get, limited by the choices in Steps 2 & 3.
    5. When in doubt, select the smaller of the two choices. More is not better here.
    Is this the “very best” cam? No, but unless you ask an expert who has successfully built motors very similar to yours, it’s better than guessing, and will provide satisfying results. It will not be the “optimum” cam, which will require extensive testing and dynamometer work.
    Don’t be too aggressive with motors under 300”, or under 8-1 compression; too much cam will make them hard to drive.
    If the cam manufacturer suggests a specific valve spring, use it, don’t be creative. The motor will not last longer with weak springs, or develop more power with stronger springs.
     
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  9. kevin31
    Joined: Oct 1, 2011
    Posts: 35

    kevin31
    Member
    from ottawa

    By the cam card the cam has no advance built in, it’s a reground original cam in this motor so it was 108 lsa from the factory, not really a wild grind.... I should add that last year I was using a torque converter that ended up having a stall rating of 1800rpm, that probobly did not help low end power at all, changed it out for a 2800 stall, I’ll degree the cam tonight and see where it’s at and then I’ll go from there, the engine idled very well.... almost too well for the cam that’s in it..... I was actually thinking of setting it back straight up


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  10. 73RR
    Joined: Jan 29, 2007
    Posts: 6,203

    73RR
    Member

    First, please note that my old friend Chris Nielson passed away some time ago so he won't be taking calls.
    https://www.legacy.com/obituaries/s...aspx?n=chris-nielson&pid=187566790&fhid=19566

    I'll add my 2¢ to the cam question.
    First, I have never seen a 108° cam in a oem EarlyHemi. Nearly all are in the 110°-112° range except for the DeSoto which actually used some at 122°. No, that is not a misprint.
    Also, what are the rest of the cam specs? Lift and overlap are useful numbers.
    If your cam is a regrind then either someone piled on the weld metal to move the lsa or, they ground the lobes very small to move the 4° or, it is a very old replacement cam (from the days when replacements were available).

    As to finding a profile, I like the simple approach that 'dry lakes wheel man' uses and his result of 213° is about what I would recommend. In fact, I recently finished a 330 project for a customer and used a 218° x 0.450" profile at 110°.
    The problem with DeSoto cams, as well as Dodge cams, is that there is very little material at the base circle before you hit the core of the shaft itself. Unless the regrinder has the proper cutting stone or, like us, has a dedicated machine to relieve this area then high lift and big duration will be very difficult.

    .
     
  11. kevin31
    Joined: Oct 1, 2011
    Posts: 35

    kevin31
    Member
    from ottawa

    Donny Johanson ground the cam and from what I remember did not move lsa


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  12. kevin31
    Joined: Oct 1, 2011
    Posts: 35

    kevin31
    Member
    from ottawa

    [​IMG]


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    Montana1 likes this.
  13. Thanks for the timing chart. Now we know the rest of the story.

    Like I said, another cam with less duration (around 270*) and overlap (in the 50*-55* range, plus or minus a few deg.) would be much more enjoyable on the street. Use a 110*-112* LSA to help extend the power range past peak power, and install it straight up. You will be much happier with the motor.

    ^^^73RR has the goods for you.
     
  14. kevin31
    Joined: Oct 1, 2011
    Posts: 35

    kevin31
    Member
    from ottawa

    Well it turns out that after checking with a degree wheel it was retarded 3 degrees not advanced 3 degrees, I guess I I mixed up the mark on the crank gear. I think I’ll be happy with it set straight up, I appreciate all the input from you guys


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  15. Pete1
    Joined: Aug 23, 2004
    Posts: 1,630

    Pete1
    Member
    from Wa.

    You need to go back and repeat Cam design 101.
     
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  16. gimpyshotrods
    Joined: May 20, 2009
    Posts: 15,992

    gimpyshotrods
    Member

    No, I don't. I have been designing race-winning cams for 25-years.

    But hey, don't take my word for it:

    "'Changing the lobe separation angle,' says Doug Patton of Pro Line Race Engines, 'changes the amount of overlap that exists during the time the intake and exhaust valves are both open. On a naturally aspirated engine, the lobe separation angle has an effect on whether the engine reaches peak torque a little earlier or later in the rpm range. Typically, narrower lobe separation develops peak torque at lower rpm and widening the separation tends to build peak torque higher in the rpm range. Nitrous engines, which make plenty of power and torque, often run wide lobe separation angles to moderate cylinder pressures and temperatures.'

    'Lobe separation angles,' he continues, 'are influenced by the camshaft grind. If a street car has smaller lift (the amount the valve lifts off its valve seat) and duration numbers (the degrees of crankshaft rotation for which the valve is held open) they might run 112 or 114. Widening their separation angle helps increase upper rpm power output. Alternatively, if you are running a bigger camshaft to gain maximum top-end power, cam makers often suggest reducing the lobe separation angle to recover power lost in the lower rev range.'"

    Given otherwise identical specifications, on the same engine, grinding a narrow LSA will produce power peaks at a far lower RPM than a wide LSA.
     
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  17. Pete1
    Joined: Aug 23, 2004
    Posts: 1,630

    Pete1
    Member
    from Wa.

    25 years? I have been at it 65 years. I will continue doing it my way. I can get 1.2 hp per cubic inch from a naturally aspirated flathead Ford V8. (on gas)
    And, I will be the first to admit, I haven't learned it all yet.
     
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  18. gimpyshotrods
    Joined: May 20, 2009
    Posts: 15,992

    gimpyshotrods
    Member

    I daily-drive a car with naturally aspirated engine, equipped with a log manifold, and a torturous airflow path, that manages .995hp per cubic inch, on 87 octane.
     
  19. town sedan
    Joined: Aug 18, 2011
    Posts: 1,020

    town sedan
    ALLIANCE MEMBER

    I know I don't know it all. But, I do know how to listen to people who do know more than me.

    As 73RR points out some Desoto cams had a LSA as wide as 122*. I saw a chart here on the HAMB awhile back that listed factory cam specs for both 2bbl & 4bbl Desoto hemis. The 4bbl engines were shown to have narrower LSA than the 2bbl engines.

    Ted Eaton has pointed out {on Y-Blocks Forever, if I'm remembering right} that a wider LSA will promote a smoother idle quality and will perform better at low speeds with a stock automatic transmission. I also read that Desoto was know for it's smooth idling 1950's engines.

    Anyway this is my take on it and when I finally get around to rebuilding my 325 Dodge, gasoline will be illegal know how my luck runs.
    -Dave
     
  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 15,992

    gimpyshotrods
    Member

    Smooth idle quality, and a stock automatic do not a hot rod make.
     
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  21. town sedan
    Joined: Aug 18, 2011
    Posts: 1,020

    town sedan
    ALLIANCE MEMBER

    Never said they did. But, if you pulled a stock flathead and replaced it with a stock Desoto hemi the car might feel like it's been hopped up..., maybe just a little...
    -Dave
     
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  22. kevin31
    Joined: Oct 1, 2011
    Posts: 35

    kevin31
    Member
    from ottawa

    By chance do you know what the oem cam specs for a 57 345 2x4 were?


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  23. Looking at the info in my archives from the EARLY HEMI OWNERS assoc. it reads 280 degree duration intake, 270 degree duration exhaust. Valve lift .431 Intake .413 Exhaust , LSA no info given.
     
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  24. Hemihead_NHRA
    Joined: Dec 2, 2017
    Posts: 56

    Hemihead_NHRA

    Yeah they ran really smooth, but with open headers, and if they are bone stock; sound like a truck, Im still building my "Baby Hemi" 291cui thats been bored .030" over and even though my focus right now is the rotating assembly (ie pistons, rods, bearings, etc) Im still looking around and scrounging for specs for mine by modeling off other specs. I have a feeling my core is junk, which is kind of why Im searching. Take that for what you will, but will a wider LSA make it sound more choppy like a dragster from the '50s or make it run smoother?

    -The Baby Fireflite Project
    -"That kid with the hemi"
     
  25. Fordors
    Joined: Sep 22, 2016
    Posts: 1,914

    Fordors
    Member

    Wider LSA will lessen the overlap and smooth out the idle.
     
  26. 73RR
    Joined: Jan 29, 2007
    Posts: 6,203

    73RR
    Member

    Just an update for anyone interested; I just finished a 291 DeSoto cam and it was barely 109 lsa to start with and it cleaned up nicely at 108. This is the first 108 DeSoto I have ever cut so it all goes back to ..."never say Never when dealing with MaMopar of the 50s".....

    .
     
  27. Truck64
    Joined: Oct 18, 2015
    Posts: 3,160

    Truck64
    Member
    from Ioway

    Bumping this for a ?, is there a definite peak to be found as the camshaft timing is advanced, and then it starts to drop off, I take it?
     
  28. Desoto291Hemi
    Joined: Apr 21, 2009
    Posts: 400

    Desoto291Hemi
    Member

    Hey 73RR,
    Sorry to hear about Chris passing.
    He did 2 cams for me several years ago.
    They were both for Mopar 3.9 hyd. Rollers
    He did a very good job and was reasonably priced.
    I still need to have a Desoto 291 cam reground someday,,,are you up to it?

    Tommy
     
  29. Desoto291Hemi
    Joined: Apr 21, 2009
    Posts: 400

    Desoto291Hemi
    Member

    Typically, narrower lobe separation develops peak torque at lower rpm and widening the separation tends to build peak torque higher in the rpm

    'Lobe separation angles,' he continues, 'are influenced by the camshaft grind. If a street car has smaller lift (the amount the valve lifts off its valve seat) and duration numbers (the degrees of crankshaft rotation for which the valve is held open) they might run 112 or 114. Widening their separation angle helps increase upper rpm power output. Alternatively, if you are running a bigger camshaft to gain maximum top-end power, cam makers often suggest reducing the lobe separation angle to recover power lost in the lower rev range.'"

    Given otherwise identical specifications, on the same engine, grinding a narrow LSA will produce power peaks at a far lower RPM than a wide LSA.[/QUOTE]
    Nitrous engines, which make plenty of power and torque, often run wide lobe separation angles to moderate cylinder pressures and temperatures.'



    I don’t have a dog in this fight but the wording here is confusing.
    At one instance it states that narrower lobe sep. develops peak torque at lower rpm.
    And then it states that wider sep. angles help increase upper rpm power output.
    If the power is all produced at low rpm,,how can it increase max power at the upper rpm range.? Just asking?

    Tommy
     
  30. Desoto291Hemi
    Joined: Apr 21, 2009
    Posts: 400

    Desoto291Hemi
    Member

    The reason I ask is because all the old Dyno numbers were only given as torque and the operator had to calculate the horsepower.
    Torque xRpm divided by 5252.
    If max torque is at low rpm it can’t possibly increase hp at the upper range
    Or am I thinking wrong?
     

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