Thumper

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Wyrmrider

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WEll I've been wrong before so I'll try again
I first thought the thumper style cams were a fix for low compression motors
but now I think just for those that want a lopey idle and are not aware of the torque they leave behind.
An Oxymoron
Comp lists their thumper lobes on page 12 of their lobe catlogue
surprising they have different lobes for .842, .875, .904 all good- but why, comp turning over a new leaf? Here's the two basic thumps for .842 and Mopar size lifters at 1.5 rocker
........................006.........050......,200........lift w/ 1.5
Thumper SBC 279/297 227/241 138/148 479/465 107 PONTIAC

Thumper SBM 279/296 227/241 142/149 .486/473 107 BBM AMC CRS lobes int & ex/
note with the same seat timing the Mopar version has enough additional duration @.200 to make a difference (AMC and Magnum will have more lift with 1.6 rockers)
Neither has a lot of lift at those durations, either .006 or .050
Why?
not having to trim the guides? springs? target "poser" market?
any ideas on why the large spread between intake and exhaust durations?
 
I think you nailed it... Made for the 'that sounds badass' crowd..
 
They are designed for the Harley crowd that needs their ride to "sound" a certain way at all costs. i.e. get that "big cam" sound with better drive ability.
 
Well nothing screams classic car without a big lopey idle. If I'm being honest I love a nice lope. I'm not close with my dad but some of my memories I do have with him was with him and an late 70s chevy stepside he had. That thing had a lope and ate tires for breakfast.

Sometimes it's not all about how fast you get down the track. Some people are ok leaving a couple of 1/10s on the sidelines to get Their perspective of the Perfect car. Some people like looks and sound, some like to go fast, some like chevys and then theres the guys/girls who like 1973 chargers...
 
There’s tons of videos on line of cars with those cams idling.
It’s not the type of busy racy idle I like myself....... it’s just “choppy”...... but they’re apparently pretty popular.
 
So let's look at some shorter lobes with more area

HRS 710461 273/ 277 226 .525 Garrett Ellison used for 9.5 340 110LCA 7104461
HR 274 274 ........ 224 .538 .573 w/ 1.6 110LCA Rumble used in 360
Howard est 268/276 206/208 434/434 113 in at 110 American Muscle is the standard 484 440 cam not the HP/Magnum Mopar adv 260/268


DC260 269 @.006 212 @.050 115@200 42@275 430 (34 ovlp) 113LCA P4286669 LA “-113 110icl early cam P4286669 284 @.004 single pattern
MP 260 [email protected] 221/[email protected] 430/450 110LCA P4452759AE later cam

Lunati 269/296 224/236 .485/.485 108 LCA 104ICL Bootllegger for SBC

Engle K56 274 224 149 .336 .504 I estimated the Engle (which Hughes used to sell) at .006 but it has 149 degrees @.200

XE 274 H 274 230 .487 110lca not more area (not UD Harold) big brother to XE268 by Billy Godbout

XE275HL 275/287 231/237 145/151 .525 110LCA IC 64 ABDC here we get a 145 @200 on the Intake and
comp gives us an Intake Close of 64 ABDC Moper suggested this one for a build
Not as big a split intake and exhaust as Thumper but still a bunch for modern heads with headers (IMHO)
Nostalga Plus 276 229 140 .312 .468 .842 minimum lobe not more area

Lunati 704 276/284 234/242 .513/.533 110LCA
Lunati 108 277/304 232/244 .500/.500 108LCA 104 ICL SBC Bootlegger

Howard 277/283 230/236 531/537 110 LCA
Lunati and Howard have less split than Comp HL, less overlap
all on 110 so intake close and overlap are in the same ballpark
-devil is in the details

340 cam 279 210 .429 2899206 intake @.006

318 Whiplash ??? 213 480 109 LCA

340 Whiplash ??? 223 550 107 LC

ThumperSBM 279/296 227/241 142/149 .486/473
36-63 76-41 ---77 overlap Intake closes 63 ABDC

so the intake closes about the same place as the 275 HL but the overlap???

Hughes HE2430AL 276/282 110/115comp/112pwr/Ica of 65*/50* E-overlap see post 36 Hughes advertised is 270/276 I adjusted to .006
 
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Not everybody is wanting to squeeze every last ounce of power or torque out of their build. I know that's hard for some to get their heads around. The Thumpr series cams are a good mix of power and sound. "Just pick one and go" kind of mentality, instead of pulling your hair out. They have mostly great reviews. If they did not work as advertised, they wouldn't sell so well.

Lastly, this is by far not new technology. Crower was grinding similar cams fifty years ago. Tight LSA, BIG duration split, lots of overlap. It's nothing new.
 
XE 274 H 274 230 .487 110lca not more area UD Harold big brother to XE268
Click to expand...

I thought this was cleared up on the B body forum.

Harold did not design the Comp XE or the XE/HL lobes.

People that buy Thumpr style cams aren’t looking for fast rate cams with short seat timing that provide better idle characteristics.

They want the long seat timing and the rough idle.
That is afterall, the primary attraction for these cams.

The fact that these cams use smooth lobes with moderate lifts and can run lower springs loads is just a bonus.
 
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They have mostly great reviews. If they did not work as advertised, they wouldn't sell so well.
Click to expand...

Despite being kind of “gimmicky”, they still seem to make pretty decent power, all things considered.
 
PRH said:
Despite being kind of “gimmicky”, they still seem to make pretty decent power, all things considered.
Click to expand...

......no more gimmicky than the "Xtreme Energy". Everything has to have a snappy name. Remember "Hydraulic Hauler"?
 
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318 with a Whiplash. Nice sound but I bet at 2000 it sounds like grandma's 318.

 
Best sounding cam in my opinion is the 292 mopar purple cam. Just needs to be set up with the right combination of parts to make some nice power!
 
QuickDart360 said:
Best sounding cam in my opinion is the 292 mopar purple cam. Just needs to be set up with the right combination of parts to make some nice power!
Click to expand...
Yep. Great for a 340/360 but pretty radical for a 318 and forget about a 273. LOL
 
QuickDart360 said:
Best sounding cam in my opinion is the 292 mopar purple cam. Just needs to be set up with the right combination of parts to make some nice power!
Click to expand...

The Comp version is even better. The Purple Plus grind.
 
toolmanmike said:
Yep. Great for a 340/360 but pretty radical for a 318 and forget about a 273. LOL
Click to expand...
There's a member on here I think it's rocket. He runs a 292 mopar purple cam in a 318 and he loves it! Not too sure of his set up. I put one in my 360. Don't know yet how it runs. Still need to break in. Dart Sport 360 and 3.91's out back.
 
If you get close to 300 duration with a cam it get's pretty radical. The old Purple Shaft cams were old technology. Lot's of duration and not a ton of lift. (less than .500. Easy on the valve train) The bigger the duration and the smaller the engine, the more radical the cam acts.
 
PRH: I remember UD designed the xxxH line of course not the HL or Dual energy or Purple Plus etc
Then the NF series at Ultradyne including the NF .904 FT but no .904 Hyd then to Lunati
any links?
Purple Plus coming up
MP cam mentioned should work just fine in a 360 with 3.91s
 
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I left just off before the 280 Purple Plus
ThumperSBM 279/296 227/241 142/149 .486/473 107 BBM AMC CRS int & ex/ 36-63 76-41 ... 77 overlap

Purple Plus280/287 233/240 148 .474-.474 7 degree in/ex spread note 6 bigger at .050 and .200 and than the Thumper
Rattler 281 227 .480 Howard .842 lobes

XE279-HL 279 235 153 .356 .534 same intake duration as Thumpette but 8 more at .050 and 11 more at .200

Howards 279 232 152 .357 .535 intake lobe

68 4 SPEED CAM
276/284 444/453 114 LCA 112 ICL LCA P3423044 68 340 MT
276/284 @.008 Mopar advertised
282 @.006 220 @.050 444 68 4speed intake lobe @.004
[email protected] note 13 degrees longer @.004 than at .008
Int open: 26° BTDC
Int close: 70° ABDC
Exh open: 78° BBDC
Exh close: 26° ATDC
Overlap: 52° Mopar degrees around .008
Per the 68 factory service manual... Thanks Krazykuda

Engle K58 282 230 148 ,343 ,514 [email protected] .006 my est big nose for great wear

THUMPER HR 283/303 227/241 513/498 107 SBM BBM AMC Olds HR
Magnum ??? 222/226 .464/464 110 not magnum 268/276 adv cam
Purple Plus 284 239 154 .323 ,485
XE285HL 285/297 242/247 .545 110LCS
Voodoo 284 242 .533
Bootlegger 285/312 240/252 515/515 10.5 cr 3:91 gear SBC
Voodoo 287 242 .533

Purple Plus .. 287 240 153 .316 .474
MP 280.474 287@,006 .474 almost the same folks

Thumper 287/305 235/249 158/165 .507/494 Mother Thumper
Bracket II 292 239 480 109 LCA Lunati Bracket Master see post 32
Lunati 298 232 .462 Lunati's version of 340 cam LMFAO


The catalog I'm looking at says Nostalga Plus/ Purple Plush but I see only PP lobes there- Nostalga Plus was .842 lobes
I'd certainly go for a Purple Plus over Thumper
Or I'd grab one of the other lobes listed and put the appropriate exhaust on it for my build at the appropriate timings
Even if someone wants the Thumper sound why give up so much at .200 That's power left on the table
 
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I really liked that Mopar 292/108; at 11.3scr, with Eddies; but it was only in my engine for one summer.
And the reasons were;
1) that with 3.55s and a manual trans, the second-gear power-peak didn't come around until after 60 mph, long after. I'm a streeter, and that don't help me.
2) A spin around the block was a half a tank of gas.
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It just wasn't right for my combo. I tried different gears, and that was ok, but then a spin around the block was a 3/4 tank of gas. I tried the A833od box, but that was a disaster. Now a whole tank to spin around the block.
I tried retiming the cam .... several times. I tried different intakes and different carbs. I mean I really loved this cam and tried everything I knew how to make it work.
In the end I swapped it out for a Hughes 270/276/110, and lost nothing except the top-end rush. But I got a big fat midrange. and back in went the 3.55s. and the od box. And then I got me a GVod........ and now I could drive hundreds of miles on the same tank of gas,lol

But that 292 did have a great idle,except the turn-downs would blow gravel and dirt up like the Tasmanian Devil, just idling around the parking lot.
And it did have a great top-end rush no doubt about it; top of third gear with 3.55s was around 115 mph.
 
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