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Thumpr cams-any input on SBC use?

Discussion in 'The Hokey Ass Message Board' started by Groucho, Jan 21, 2014.

  1. On a basic stock 350 SBC is it really lumpy at idle? Bad on low RPM power? Loose torque converter needed? Discuss. THX
  2. KIRK
    Joined: Nov 17, 2005
    Posts: 384


    I have a Thumpr in my 327. Has a lumpy idle and seems to pull good a low RPM. If I had it to do over I would have gone with at least a 2500 converter. Would let it rev a bit more idling in gear. All in all I like it.
  3. Its a good cam, but needs 2500-3000 converter and a good, matching intake setup.
  4. 66tintop
    Joined: Nov 7, 2012
    Posts: 450

    from Canada

    Typical rumpty rump cam, sounds great at idle , parking lot camshaft , need great amount of tuning on ignition and carb, IMHO will drive u fugly crazy until u replace it, comp cams should spend more money on r and d , then mass advertising over rated shit, I do admit it does sound great at low rpm idle , but that's all !

  5. DRD57
    Joined: Mar 5, 2001
    Posts: 3,913


    I had one in a 350 for a couple of weeks. Took it out and replaced it with a high energy cam. The Thumper hit the convertor too hard when you put it in gear. It would have been OK with a 2500 convertor.
  6. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,684

    from Oregon

    It depends on which Thumpr you use. I've installed 3 of them, and all three were flat tappet versions, and each a different grind. Put one in my buddy's fairly stock 350 that was the entry level and he's extremely happy with it. It has a nice lopey idle, and plenty of low end torque. Also works well with his stock TH350 trans. The mid level needs good heads and a higher stall to really work. Sounds good, but not much low end torque. The higher level Thumpr needs lots of stall, and really good heads to work.
  7. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    from florida

    I used to think they were a gimmicky cam, just designed to give a rough idle and no more, but the guy who does our engines (and who builds some serious race engines ) says they are actually a very good cam and has recommended one for the 350 I am putting together right now.

    As was mentioned, you need something like a 3,000 stall converter, deeper gears, and other hop up parts to take advantage of it.

  8. Any more info on that entry level one? Specs/pt#? THX
  9. This is the smaller of 2 I found and it seems pretty big for a stock 350-I would never recommend it

    High performance street/strip, needs 9:1 compression, 2500+ stall, intake, gears and headers, rough idle.

    Thumpr Application Chart (GIF)

    282-126014 Specs (PDF)


    Stock springs cannot be used
    50-State legal on ‘93 & earlier S.B. Chevrolet V8, 262-400 c.i.

    RPM range: 2200-6100
    Valve timing: .006
    Lobe-center angle: 107
    Intake centerline: 102
    Valve lash: intake/exhaust - hydraulic
    Duration: 287 intake, 305 exhaust
    Duration @ .050" life: 235 intake, 249 exhaust
    Valve lift: .489 intake, .476 exhaust
    Lobe lift: .327 intake, .317 exhaust50.
  10. Spud
    Joined: Oct 13, 2006
    Posts: 123

    from Ohio

    I have one I like it but I have a 4-speed and 4:11 gears, sounds good and runs good.
  11. tjet
    Joined: Mar 16, 2009
    Posts: 1,272

    1. Early Hemi Tech

    What model Thumpr cam did you use?
  12. 4 speed/4.11's a HUGE help;)
  13. 230's, the tipping point for needing a looser converter.
  14. kuhn1941
    Joined: Feb 15, 2013
    Posts: 194


    Back in the day me and my dad rebuilt the stock chevy v8 in a 84 Bonneville . Put a aggressive rv / towing cam in the 305- . With dual exhaust that car rumbled and thumped . My mom called the car thumper , that totally stock 350c trans - stock lock up converter - stock rear 282 gear ratio . Good luck on choice you pick .

    Posted using the Full Custom H.A.M.B. App!
  15. Boones
    Joined: Mar 4, 2001
    Posts: 9,662

    from Kent, Wa
    1. Northwest HAMBers

    good info, getting ready to upgrade the cam in my 327. I have a 2500 converter for it and was planning on a set of aluminum heads. (not sure which yet)
  16. bobkatrods
    Joined: Sep 22, 2008
    Posts: 687

    from aledo tx

    If you want the FACTS look at back issue of HOT ROD , they did a dyno test on the thumper along with other cams close to same specs, the numbers are on black and white and you can make your own decision based on some true tests rather than here say,, i have the small one and it is just fine almost any performance cam will benefit from a little more converter, Look at the specs @ ,050 lift.
  17. That's the smallest the Thumper comes. So maybe it's time to move on to something else.
  18. SmokinBill
    Joined: Sep 18, 2009
    Posts: 760


  19. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    Here is a 350, 600 CFM, Dual Plane, headers/mufflers Vortecs, 9.5, Thumpr vs 268H, Thumpr vs XE274, info only, not recommending anything, if you have a cam to compare tell me the adv, 050, LSA, ICL, lift

    Dyno Sim5

    Attached Files:

  20. look at edelbrock perf. RPM cam. 488-510 lift. With the RPM heads , loose conv. gears , RPM intake and headers, should make about 400- 410 HP, and be a great runner, with thumpy idle.
  21. The rv / towing grind is really the best there is for street cruisers.
    More power down low, maxed out at high mid range Rpms.
    I wonder how many minutes out of an hour cruise the Rpms are over 3500?
  22. Captain Chaos
    Joined: Oct 16, 2009
    Posts: 596

    Captain Chaos
    from Missery

    never heard anything good about them.
    maybe if you post other details and/or intened use , a suitable cam can be suggested . a lot of good cams out there w/ o breaking the bank and work well,
  23. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    Left brain, right brain :)
    To me this kind of cam is like a blower or 6/8 deuces, or a car sitting on the bump stops, there are more functional/practical choices, but that's not the point.

  24. I don't understand what you mean, you lost me.
  25. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,684

    from Oregon

    Here's the entry level Thumpr CL12-600-4:

    Cam Style:Hydraulic flat tappet

    Basic Operating RPM Range:2,000-5,800

    Intake Duration at 050 inch Lift:227

    Exhaust Duration at 050 inch Lift:241

    Duration at 050 inch Lift:227 int./241 exh.

    Advertised Intake Duration:279

    Advertised Exhaust Duration:297

    Advertised Duration:279 int./297 exh.

    Intake Valve Lift with Factory Rocker Arm Ratio:0.479 in.

    Exhaust Valve Lift with Factory Rocker Arm Ratio:0.465 in.

    Valve Lift with Factory Rocker Arm Ratio:0.479 int./0.465 exh.

    Lobe Separation (degrees):107

    This car is a 350/TH350 with stock converter, 3.73 posi rear, and 27" tall tires. Driven mostly street miles, and he loves it.
    The car on the left next to my Austin.
    Last edited: Jan 22, 2014
  26. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    6 or 8 deuces are high maintenance and will likely make less power than a single 4 barrel setup. But they have the "look".

    A RV grind will be the best choice for >85pct of operation, but doesn't sound like some want.

    Style vs practicality....
  27. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    from Texas

    Intake Centerline 102

  28. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    from florida

    Has anyone used one of the "house brand" cams from someone like Summit or Jegs ? How did they work ?

    Years ago I ordered a cam from PAW, when they were in business, and it came in a plain box but with a Crane timing card inside, so I called Crane. The guy quietly admitted the PAW cam was just a reboxed Crane. I suspect the Summits and Jegs are the same and can be bought cheaper.


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