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Thumpr cam installed

Discussion in 'The Hokey Ass Message Board' started by pokey, Jan 20, 2011.

  1. pokey
    Joined: Apr 3, 2009
    Posts: 217

    pokey
    Member

    The thumpr cam has been installed. The idle is affected alot. Those who have this cam I am looking for fine tuning points to start at. We have inceased the idle. The cam we have is the one that uses a stock converter. I have also installed a adjustible vac. advance What timing should I be looking at? I am sure the take off is sluggish at this point what should I do to correct that?
     
  2. scottybaccus
    Joined: Mar 13, 2006
    Posts: 4,132

    scottybaccus
    Member

    It's pretty normal in the baselines. Start with maybe 32-34 degrees when your all in. That should equate to 10-12 initial. You'll have to experiment from there. It may tolerate as much as 38, depending on compression and such.

    Tune your idle mixture a little higher than usual, then you can turn the idle way down, about 600 rpm.
     
  3. Lincolnlock
    Joined: May 29, 2010
    Posts: 9

    Lincolnlock
    Member

    I ran one these cams in my rock buggy for a couple of years. Just lean it out a bit at idle so it doesn't load up. I ran stock timing also. Other than that it performed really well with no issues. (except bending most of the stock push rods while racing)
    HA!
     
  4. One Finger John
    Joined: Mar 18, 2009
    Posts: 458

    One Finger John
    Member

    The usual suspects. Where is your timing set, how big is the engine, what kind of carburetor, what kind of intake, rear end gears, what kind of trans, did you put the cam in advanced, retarded, or straight up, and most important, what are YOUR expectations after the install? Are they realistic? Take the distributer to a shop that has a distributer machine. Tell them everything you have done to the car. DO NOT LIE !!! Have them set the vacuum advance also. Bring it home, install as directed (prob 12* BTDC, vac. adv. blocked). Test. Review results. Check drivability as far as carb. Test. Review results.

    John
     
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  5. Abomb
    Joined: Oct 14, 2006
    Posts: 1,577

    Abomb
    Member

    Install a smaller cam......:D


    Actually, the advice above is a good start, get your timing set, then start adjusting the idle circuit until you get a good idle that's not loading your cylinders up. From there, you can work on the jetting and the accelerator pump volume to help with off idle acceleration.... though depending on your transmission and final drive ratio, you still may have driveability issues because of the cam.
     
  6. joe_padavano
    Joined: Jan 18, 2010
    Posts: 262

    joe_padavano
    Member

    But isn't the whole point of a Thumpr cam to have crappy idle of a long duration cam without the pesky extra horsepower? :confused:;)
     
  7. 31Vicky with a hemi
    Joined: Nov 11, 2008
    Posts: 13,003

    31Vicky with a hemi
    ALLIANCE MEMBER

    Choosing a cam from an audio file- hummm is that the new flat black? Lmao
     
  8. chopt top kid
    Joined: Oct 13, 2009
    Posts: 956

    chopt top kid
    Member

    There's a good read about Thumper cams in TRJ no. 49. Yea the whole point is to have a rumpty bump idle and a mild streetable cam. Check it out here...
    www.compcams.com/thumpr
     
    Last edited: Jan 24, 2011
  9. and set your power valve to match the news cam vacume reading, check the Holley book on how to do it
     
  10. x2 on TRJ article....it's a good read and explains the Thumpr cams a little better.
     
  11. So-cal Tex
    Joined: Aug 24, 2005
    Posts: 976

    So-cal Tex
    Member

    I have a thumper cam in my '55 chevy and it is the .480 lift version. I have a mild 350, 194cc heads, roller rockers and 10:5:1 compression motor .These Thumpr cams seem to like a little more advance timing. I set mine at 6-8 depgrees and it was sluggish. I then advanced it to 10-12 degrees at idle and it seems to really like it with good throttle response. I then hooked up a vacume gauge and played with the mixture screws until it made the most vacume. I am still a little rich, but at 7,000 ft elevation I have 30% less air so I need to jet it down some.
     

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  12. 31Vicky with a hemi
    Joined: Nov 11, 2008
    Posts: 13,003

    31Vicky with a hemi
    ALLIANCE MEMBER

    I've not seen the write up in TRJ, was it done by comp cans?

    Yea the whole point is to sound like you have a built motor correct?
    " Lets face it, nothing grabs attention at cruise night like a hard hitting ...... " first line from the link provided.

    The sound of a well tuned hi performance engine is better than music. Not everyone will agree but everyone on the hamb will agree to that. That lopey idle is a by product of an engine designed to run hard correct? That lopey idle was not the goal correct? Its lopey because its having a hard time idling smoothly because of the huge compromise made so that it will run extremely well at WOT.

    Marketing the sound track of a cam at idle is purely an exploitation of the human desire to get attention. Just like fake tits.
     
  13. pokey
    Joined: Apr 3, 2009
    Posts: 217

    pokey
    Member

  14. 64Cyclone
    Joined: Aug 30, 2009
    Posts: 1,508

    64Cyclone
    Member

    Sounds great...I am a fan of the Thumprs!
     
  15. pokey
    Joined: Apr 3, 2009
    Posts: 217

    pokey
    Member

    This cam is truly great however it don't idle in drive worth nothing what do I need?:confused: A stall converter will that do the trick?
     
  16. moefuzz
    Joined: Jul 16, 2005
    Posts: 4,896

    moefuzz
    Member

    x2....


    .
     
  17. AAFD
    Joined: Apr 13, 2010
    Posts: 585

    AAFD
    Member
    from US of A

    It sounds like it supposed to at idle in gear.
     
  18. FritzTownFord
    Joined: Apr 7, 2007
    Posts: 989

    FritzTownFord
    Member

    It does sound great! But that guy needs a higher stall so the engine doesn't "push"against the converter. I hate that.

    As for "look at me" parts on a hot rod, uh, that covers most of hobby, no?
     
  19. Johnny1290
    Joined: Apr 20, 2006
    Posts: 2,841

    Johnny1290
    Member

    what fun is a cam that sounds like that without driveability problems?!?
     
  20. davey_shumard
    Joined: Jun 28, 2010
    Posts: 151

    davey_shumard
    Member

    best advice i have for tuning after a cam swap is to go straight to the company you purchased it from. know the specifics on your own personal application before calling, they will want to know everything. if you give them every detail, they will return the favor, by telling you everything they know from their own testing and product development.....its kinda their job! good luck man!
     
  21. falcongeorge
    Joined: Aug 26, 2010
    Posts: 9,980

    falcongeorge
    ALLIANCE MEMBER
    from Surrey BC

    sweet!!!Was wondering when someone was gonna say that!!:D:D
     
  22. falcongeorge
    Joined: Aug 26, 2010
    Posts: 9,980

    falcongeorge
    ALLIANCE MEMBER
    from Surrey BC

    I'd tell you to run a looser converter and a bunch more initial, but then it wont idle like a sack of crap, PLUS, with the looser converter, then you may as well have just put a bigger cam in it, instead of one that just has more overlap and a delayed exhaust closing point to make it "rap" in the pipes. So that would kind of defeat the purpose.
    No, really, just having a little fun, "Thumpr" cams are kewl.
     
  23. pokey
    Joined: Apr 3, 2009
    Posts: 217

    pokey
    Member

    You guy's a tit on the wild side. Yeah I called the guy that I ordered the cam from. He said I may need a converter so I was kinda prepared. The other car I have a big cam in is my Dodge Charger. I have the Purple cam shaft in that. I had to use a converter in there as well. It is very radical however It idles very well and has great hole shot. It almost comes off the ground. I figure If you are going to have one of these street rods it should sound and look like a hot car. The car is so light launching it is not the problem it's the idle at the light or stop sign. If I can get it to idle like it does in park. I will have a great time at the cruz in. That's all I want. I don't have the nerve to race anymore:cool: I'm pretending! Ah ha.
     
  24. pokey
    Joined: Apr 3, 2009
    Posts: 217

    pokey
    Member

    I just went back and heard it again......Dam that thang does sound goood!:)
     

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