Question about Comp Cams Thumpr?

[Swampdog]

I have a 1962 383 with Dual 4 Barrels, 3 inch exhaust, 10 to 1 compression ratio, 2500 Stall and a 3.91 rear end.
I presently have a Comp Cam 21-222-4 with 218/224 degree duration with 110 lobe separation.
I also have power brakes. I am only looking for a car show wicked idle. No racing.
Has anyone run a Thumpr or Mutha Thumpr with power brakes?

 

[Sweet5ltr]

I have a 1962 383 with Dual 4 Barrels, 3 inch exhaust, 10 to 1 compression ratio, 2500 Stall and a 3.91 rear end.
I presently have a Comp Cam 21-222-4 with 218/224 degree duration with 110 lobe separation.
I also have power brakes. I am only looking for a car show wicked idle. No racing.
Has anyone run a Thumpr or Mutha Thumpr with power brakes?

Wicked idle with great vacuum? They don't go hand-in-hand. Positive overlap creates the 'wicked idle', it's fairly easy to figure out once you understand the formula;

(int dur + exh dur)/4 - LSA x 2

Any camshaft with around 60* of overlap will sound fairly good and run fine with power brakes (think Saturday Night Special at the strip), the wicked idle you're looking for is probably around 90+* overlap (think Super Stock Hemi..); which won't work well with power brakes.

Current Comp Cam:
262+270=532/4=133-110=23 x 2= 46* overlap
Just to fill you in, your current camshaft has less overlap than a factory 440 HP cam.

Now, here is the CL21-602-5 (Big Thumpr)
295+312=607/4=152-107=45 x 2= 90* overlap

Comparison:
Mopar .528 solid (good all-around solid, nice lope, good with power brakes, perfect cam for your combo if you want to go solid)
60* overlap
Lunati Voodoo 60304 (Part # 10230704, good cam but 'meh' against any solid)
60* overlap
Comp Cams XE275HL (2,500+ stall, good street friendly cam with healthy overlap)
61* overlap
Small Thumpr (Part # 21-600-5, terrible cam, not sure it will actually work with 2k converter, but will sound good)
74* overlap
Mopar .509 (great sounding cam, needs a 3k converter, manual brake territory)
76* overlap
Mopar .590 solid (most wicked sounding non-roller cam out their, 'window rattler') (3-4.5" of vacuum at idle, don't even think about it)
100* overlap

To give you an idea of how 'aggressive' the lobe is, subtract the advertised duration from the .050 duration, this gives you the 'ramp angle'. Knowing the ramp angle, you can make a good guess on how the camshaft will sound and perform. Generally, a tighter ramp-angle will mean you'll gain performance under the curve and for you, the cam will either lope faster or slower, depending on what you compare it to.

Example:
Comp Cams XE285HL (popular hyd. grind known for fast ramp rate)
44/50* difference
Thumpr listed above (gives you that slow-chug and wicked idle)
52/55* difference
Mopar 509 (known for it's great idle sound)
44/44*
Lunati Voodoo Solid (my custom w/ 115 LSA)
29/29*

 

[IQ52]

Remember too, the Thumper and Whiplash cams were designed for the lower compression engine. Overlap doesn't bleed off dynamic compression. Dynamic compression is controlled by the closing of the intake valve. The Thumper cams close the intake valve earlier and increase dynamic compression. Therefor, you may not only get wicked idle with your 10:1 383, you may also get wicked detonation.

 

[texas69bee]

Well I was impressed! Good info.

 

[IQ52]

Well I was impressed! Good info.

We all know you ment by Sweet5ltr. I was too.

 

[texas69bee]

IQ52... Lol, I've read plenty of your post and have been just as impressed. Keep up the good work guys.

 

[moper]

Figure out which is more important: idle sound or your brakes. You can't have both. To be honest the sound of the running engine is not a variable that should even be considered in that choice.

 

[Mike67]

You could enhance the note with some electric cutouts!!! Lol!
Great info by Sweets & IQ, thanks

 

[dieseldazzle]

I'd give up idle noise for the ability to do rolling burnouts and good running 383/440 should do that all day long.

 

[YY1]

Not sure how the MP 284/484 is with PB, but it idled like two Harley's.

 

[Sweet5ltr]

Not sure how the MP 284/484 is with PB, but it idled like two Harley's.

68* overlap will accomplish that, it's right above the sweet spot for power brakes IMHO. Anyone can have a very aggressive sounding, great performing camshaft and retain power brakes; just utilize some of the info I shared at the top to figure out which manufactures grind works the best for the intended application.

Another topic which is often 'voodoo' for guys like myself is, area under the curve. Harold (Ultradyne/Bullet/Lunati Voodoo camshaft wizard), stated you want as much duration at .020 that will retain your desired @ .050 duration. So when you've narrowed down your selection, make sure you're getting the full cam spec sheet to see the @ .020 number as well, compare it with similar grinds to see which one will actually make the most power.

 

[lewtot184]

i usually get **** about lobe profiles so i just get the old degree wheel out and map the lobe. use three numbers; advertised seat timing and at what lift, .050" number, and .200 number.

 

[Sweet5ltr]

i usually get **** about lobe profiles so i just get the old degree wheel out and map the lobe.

Some more good info from theturboforums

How To Figure The Timing Events On Any Cam

To do this you need the following information
1) The duration
2) The lobe Center – Lobe Separation
3) Intake or Exhaust Center-Line

The meaning of the cam lobe centerline is: The lobe as would be aligned with top dead center of the crank or piston

The meaning of the Lobe-Center (Lobe-Separation) is: The degrees between the exhaust lobe center-line and the intake lobe center-line

The meaning of overlap is the amount of degrees the intake and exhaust lobes hold the valves open during the 5th event cycle. (Exhaust is closing while the intake is opening)

To find the intake center-line: - Divide the duration in half & subtract the intake opening

To find the exhaust center-line: - Divide the duration in half & subtract the exhaust closing

To find the timing events for the intake: - Divide the duration in half and subtract the center-line from the remainder and that gives you the opening event. For the closing event subtract 180 from the duration and then subtract the opening number from that sum.

To find the exhaust timing events: - Divide the duration in half and subtract the center-line and the remainder and that gives you the closing event. For the opening event subtract 180 from the duration and then subtract the closing number from that sum.

To find the lobe center add the intake and the exhaust center-lines together and divide that in half.

To find the overlap add the intake opening to the exhaust closing

To find duration add the opening and closing figures to 180

To find the power stroke: - Add the intake closing to the exhaust opening and subtract that from 360

Intake opens BTDC before top dead center
Intake closes ABDC after bottom dead center
Exhaust opens BBDC before bottom dead center
Exhaust closes ATDC after top dead center

Dual pattern cam = A cam that has the exhaust lobe with more duration than the intake
Cam is advanced = The intake lobe center-line is less than the lobe-center and the exhaust center-line is more the the lobe-center

Cam timing is usually computed at .020 or .050 for mechanical cams and .006 or .050 for hydraulic cams.

More cam info at Harvey Crane Jr web-site

Denny@JDS Induction Products

 

[Swampdog]

MR. Sweet5ltr,

Small Thumpr (Part # 21-600-5, terrible cam, not sure it will actually work with 2k converter, but will sound good) 74* overlap
Is this close enough to use with Power Brakes?
Thanks I am Now overloaded with info, but I haven't ordered a cam yet.

 

[All4rocks]

Wow! all that cam stuff went right over my head. I got a 472 hemi 10.5 compression with this cam. Will it have enough vacuum for power brakes?

 

[Bee1971]

1971 Superbee - Factory Power Disc Brakes

I ran the Mopar 284/484 cam within my 383 Magnum for over twenty years - About 8" of vacuum at idle

Now same #s block , 432 Stroker - Running the Comp XE275 HL - About 12"-14" of vacuum at idle / 700 - 800 RPM Idle

10.58 to 1 Compression
Edelbrock E Street 75cc

Comp XE275 HL - Honestly feels like it has twice the Torque off idle through 4500 Rpms / Awesome shake the car idle within the 383

But so did the Mopar 284/484 at idle , but the cam itself ended there until about 3500/4000 RPMs

No issues with Power Brakes

 

[Bee1971]

Damn just saw this thread was a few years old

 

[Officer Higgins]

Wicked idle with great vacuum? They don't go hand-in-hand. Positive overlap creates the 'wicked idle', it's fairly easy to figure out once you understand the formula;

(int dur + exh dur)/4 - LSA x 2

Any camshaft with around 60* of overlap will sound fairly good and run fine with power brakes (think Saturday Night Special at the strip), the wicked idle you're looking for is probably around 90+* overlap (think Super Stock Hemi..); which won't work well with power brakes.

Current Comp Cam:
262+270=532/4=133-110=23 x 2= 46* overlap
Just to fill you in, your current camshaft has less overlap than a factory 440 HP cam.

Now, here is the CL21-602-5 (Big Thumpr)
295+312=607/4=152-107=45 x 2= 90* overlap

Comparison:
Mopar .528 solid (good all-around solid, nice lope, good with power brakes, perfect cam for your combo if you want to go solid)
60* overlap
Lunati Voodoo 60304 (Part # 10230704, good cam but 'meh' against any solid)
60* overlap
Comp Cams XE275HL (2,500+ stall, good street friendly cam with healthy overlap)
61* overlap
Small Thumpr (Part # 21-600-5, terrible cam, not sure it will actually work with 2k converter, but will sound good)
74* overlap
Mopar .509 (great sounding cam, needs a 3k converter, manual brake territory)
76* overlap
Mopar .590 solid (most wicked sounding non-roller cam out their, 'window rattler') (3-4.5" of vacuum at idle, don't even think about it)
100* overlap

To give you an idea of how 'aggressive' the lobe is, subtract the advertised duration from the .050 duration, this gives you the 'ramp angle'. Knowing the ramp angle, you can make a good guess on how the camshaft will sound and perform. Generally, a tighter ramp-angle will mean you'll gain performance under the curve and for you, the cam will either lope faster or slower, depending on what you compare it to.

Example:
Comp Cams XE285HL (popular hyd. grind known for fast ramp rate)
44/50* difference
Thumpr listed above (gives you that slow-chug and wicked idle)
52/55* difference
Mopar 509 (known for it's great idle sound)
44/44*
Lunati Voodoo Solid (my custom w/ 115 LSA)
29/29*

great information sir!

 

[Officer Higgins]

Damn me to old topic

 

[Sonny Black]

284/484...for that nostalgic sound....not my 1st choice....