[1967chevelle454]

What's your guys opinion on comp thumpr cams? I'm looking to use one in my combo: 781 heads-big valves,dual intake,holley 800 sr.bo., 10.5-1 compression,hooker headers,forged pistons.
Looked at biggest hydraulic flat but is only 520/507 lift. Maybe small for me.

Next is roller. SUPER expensive but they have 570/544 lift and 558/546 lifts. Just want good power and awesome sound for cheapest.
how much power would these flat tappet vs. roller ones?

[eric32]

Well getting more lift does not mean you will make more power unless your heads flow really well to utilize it. My opinion on the thumper cams is mixed at best. I have the biggest one that they make for a small block chevy and it was the roller version. They will make some decent power if matched with the proper heads,intake, carb, rear gears etc. I can only say from my experience your better off with something else if you want the most power your engine can make.

I got rid of mine and put in a lunati voodoo roller cam in place of it cause the thumper cams have a lot of overlap and trust me if you want your engine to be street able at all with out issues you have to have about the smallest one they offer. The middle one you could probably get away with.

The thumper cams are made for two things, first of all it was made for the sound thus the name of it and second it was designed to give you some basic horsepower and torque with out giving you the full potential your engine can make. Don't get me wrong they will make power and such but they are not made for all out power.

I would go for something from isky, comp extreme energy line, or the lunati voodoo line of cams. And to answer your question on the roller vs flat tappet, well a roller cam with same duration and similar specs of flat tappet cam you would make around 15 to 25 more horse power because of one less friction and two more overall duration and lift. Roller cams can have more lift and higher ramp rates then flat tappet cams.

Hope that helps out.
Eric

[cboy]

In addition to Eric's observations, the Thumper line appears to be relatively over priced. I'm no great engine expert but my capsule review of the Thumper would be, Big sound...small hat. And the company basically admits that in their advertising. The purpose of this cam was always to produce the "effect" of a big cam in terms of sound. It was never intended as a major player in the power department. A close inspection of grind specs will reveal many other cams which will produce more power for fewer bucks.

But then if all you are after is the sound and a bit of HP...the Thumper would be a good alternative.

[6sally6]

What THEY said........You need to realize its the LSA that makes the idle you want....in addition to the duration. Different cam comp. have different philosphies on how to make power. Isky have alway ground most of there cams with a tight LSA(small=tight) 108*.Lunati too I think. They have the rumpity-rump sound most guys like in a street rod. Other comp. like more LSA to get better vacuum(to run brakes and stuff) and spread the RPM range out abit. Different ideas to make power.
You can get a custom ground cam with THEIR expertise ground in for less than the Thmpr cam. AND make alot more power....customized for your engine combination. IMO
6sally6

[DoubleVision]

I don`t see the point in even making a cam like that when you can take a basic .224 duration cam and play with the idle and rocker adjustments to make it lope.

[6sally6]

Originally Posted by DoubleVision

I don`t see the point in even making a cam like that when you can take a basic .224 duration cam and play with the idle and rocker adjustments to make it lope.

Awwww DV...you're tooo young to think like MY dad! Sure you can"jerk a plug wire off" and richen up the carb and all that stuff,but........you know you break out in a big grin when somebody fires up a big-block...full-tilt...race-only...engine in their weekend play-purty at the local car show! Totally useless for a dailey driver but still.....THAT GUY always has a couple of "pals" hanging around and a small gang of old men (like me) loitering near by waiting to hear that really "bad'un" fire up.
Or do you really get into a nice Mercedes with their powerful engine whisper off down the road?!
Your a "good ole boy from Alabama"....I know you like them rad sounding machines!!
6sally6

[DoubleVision]

Sure, but I never had a problem with making a cam lope that had some duration to it. I never fooled with big blocks, I`m a poor man, poor man`s engine is a small block. I run roller cam 350`s and when you got small cubes, it`s easy to get it to lope. .224 duration @.050 in a 350, it`ll lope, even a comp cams .218 will. However years ago when we stuffed a .234 cam in a 400 small block it idled smooth. Of course we have to add in what kind of overlap it has, the exhaust system and other odds and ends. I`m by no means "old school" as far as that goes, I just never had much problem getting one to lope.