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Discussion Starter · #1 ·
I am building a 355 for my ‘85 El Camino. Does anyone here know what the difference is between the Thumpr and the Mutha Thumpr? Any advantages or disadvantages between them or sound differences. Thank you I’m advance.
 

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Mutha Thumpr Cam (PN 12.601-4)


  • 287/305 Duration
  • 2200-6100 RPM Range
  • Lift: 0.489 Intake/0.476 Exhaust

Big Mutha Thumpr Cam (#PN 12-602-4)


  • 295/313 Duration
  • 2500-6500 RPM Range
  • Lift: 0.500 Intake/0.486 Exhaust
Both are too long and too slow. Probably okay for show, not much go.
 

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Discussion Starter · #7 ·
Well, everyone has an opinion. If you dig the sound of the Thumpr cams, then I say go for it. All the advice about gearing and valve train still apply when selecting any cam, but the Thumpr has some good qualities. Check out the article linked here:

COMP Tech: 4-Way Camshaft Dyno Shootout! (chevyhardcore.com)
Does my transmission make much of a difference? My original plan was to go with the mid option, the Mutha Thumpr. But I was told that I can’t do that with an automatic transmission, is that true?
 

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As others have said, they are a poor choice for using on the street other then the sound.

If you want a good recommendation, provide all the info needed for a solid answer.

Need to know:
Car or truck? I see it’s both, it’s an Elcamino
Engine: a new build, roller block or flat tapped?
Do you know compression, heads and intake.
What are you looking to do with this car?
What transmission and rear gears?
 

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The thumper cams get more radical as you move up the list and the more rough the idle will be and the more rump rump sound it will have but also will have less vacuum and more overlap. I have used the Big Mother Thumper cam roller version and all I can say is they all can be used with an automatic transmission as long as you have enough of a stall convertor for a size of what cam you use and also a proper rear end gear ratio to keep your engine in the proper range to work with the cam you choose. All I can say is they can make power but there are better grinds that will give a nice sound on the idle but will also perform better and is made for performance and not a idle sound.

The one I had was only in my build for about three months and it was just too much in my opinion and did not like the way it ran and hated the street manors with it and it was a nice sounding cam and did perform but not what I liked and I swapped it out for a slightly smaller Lunati hydraulic roller voodoo cam and it ran way better and it still had a nice racy idle but way more vacuum and less overlap and ran and performed in all situations way better. I recommend you read up on camshafts and the numbers they advertise such as duration and lobe separation angle effect and also what the effects of overlap is and get to understand the tech on them when looking at the seat to seat duration and the @ 50 duration and the effects of lobe separation angle as they all have a pro versus con effect on how it will run with your build.
 

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The problem with these cams is they really work best with a lot of compression like a ratio to a ratio and a half above the manufacturer’s recommendation. That requires running aluminum head’s which requires either a zero deck block or raised compression heigh pistons. This is necessary to get compression ratio up to what these cams really need to have and at the same time to get the chamber activity up of squish and quench which along with the fast heat transfer of aluminum head’s let’s you run old time 10.5 to 11.5 compression ratios that these cams really need to have to operate effectivly and do it on 91/93 octane corner station E10. Otherwise these cams just bring a rough idle to the party. So to really get what they should deliver you really need to build the engine into their needs rather than just stick them into any engine laying around.

These cams really work best with a stick transmission, especially if your not building as described above. The need is to use the transmission to keep the revs in useful areas of the power band. Automatics get you into gigs stall converters and a lot of manual gear changes that unless you buy or build a beefed tranny, automatics are not built around manual shifting from the factory as this dumps a lot of load primarily on the one way roller clutch which is st best designed for occasional use for engine braking not holding acceleration loads of banging through the gears while getting on the go pedal.

So you can short cut all of this and just run one of these cams but be aware without treating them in concert with everything else they need as supporting cast characters there are problems with them.

Bogie
 
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