I'm thinking about buying one of these "thumper" or Mutha Thumper" Valvetrain setups from Comp Cams.

From what I hear, they sound really good but have better drivablity than other lopey cams.

I'm wanting to rebulid the 350 in my 68 camaro and want it to sound like a drag car, but be drivable and not spill your beer when driving through a parking lot ;)

Imho, it's a money per cam kit vs real performance deal here.

pdq67

You want your insides to be dancing when your car is idling!!

I have a '68 RS/SS with a 350 cu.in. engine that I added a Comp Cams Thumper set-up too. It provides you with exactly what you want - deep big block lopy idle exhaust note- and driveability at the same time. I would highly recommend this set-up for your '68.

JP you have touched on a really hot topic, people will either say the cam is horrible you shouldn't pick a cam based on sound or others will point to the numerous articles siting good numbers various builders have gotten out of the Thumpr series.

I have a Thumpr in my big block, hope to get it dyno tested eventually, then the proof will be in the pudding.

If your ultimate goal is the sound at idle pick a cam that gives you that. You need a goal, drag racing, road racing, dyno HP, mileage, sound at idle...whatever it is pick the cam that meets your needs.

if your ultimate goal is the sound at idle pick a cam that gives you that. You need a goal, drag racing, road racing, dyno hp, mileage, sound at idle...whatever it is pick the cam that meets your needs.

x2

I talked to Comp Cams yesterday. They recommended if you are wanting performance based cam other than sound they suggested th XE or XR line. But the rep said Thumper cams do sound good and have a perfromace side, just not as much as other cams.

Comp's "Poser" line of cams did nothing to improve low speed driveability.
They have a tight LSA, which increases overlap, and they have a ton of exhaust duration for sound affect as well.
If you bought a cam of similar size, with a similar LSA, without all of the excessive exhaust duration you would get a cam that had better low RPM driveability, not worse.

Perhaps for a small block but in the case of a big block the increased exhaust duration and overlap really does help exhaust breath-ability which has always been a weakness of big blocks, "they can get it in, but not out".

Perhaps for a small block but in the case of a big block the increased exhaust duration and overlap really does help exhaust breath-ability which has always been a weakness of big blocks, "they can get it in, but not out".

That might help in the upper rpm's, but driveability will be worse, which is what the post was about.

STREET motor here up to about 10 to 1 CR. for starters...

If I was to want "cam cackle" as well as PERFORMANCE, I would go w/ a cheap roundy-round circle track 3/8 to a 1/4 mile track solid lifter cam that is spec'd like this!

268/228, 106/102, .430" NET lift.. (Something like a close centered Isky Z-20)...

Imho, it should "cackle" w/ the best of them and run like a "scalded-dog" and to me, should be relatively easy on the valve train like a hi-po stocker like the old 30-30...

You want more, then spec more lift and a "schosh" more duration, but watch valve-train wear.

Such as Isky's Z-25 and Z-27 on closer LCA/ICA's as long as your CR is up to them!!

And as always, jmho.

pdq67 and I'm talking street motors here is all.

I would just unhook a couple plug wires. The end result is the same, and it costs a lot less.

Or.....

Back off on the initial timing, mod the dist to make up the difference to get back your total.

Use ported vacuum advance to increase drivablity but still keep the idle advance low.

The lower lift on the exhaust side makes no sense to me for a performance aspect, it is easier to get it in than it is to get out.

Waste of money if your looking for performance. You can lope all you want but when someone in their wimpy import or v6 stang puts the hurt on you it's really going to damage your pride, and make them further the stereotype.

If your gonna sound good, mod the engine to perform, people tend to mess with you if your car sounds angry.

Isky makes a 268 Mega cam, part number 201268. Specs are 224-224 duration, .450 lift on a 107 lsa. Basically an oval track hydraulic that will give you the sound that you want but still provide lots of low and mid range and work with c.r. of 8.75-10.5 and not beat up your valve train. Will have better street manners than the Thumper 227-241 cam. I would also recommend the old Crane 274H06 but since Crane is out of business they are getting harder to find.

The comp cams magnum series have good all around power depending on how big you go, and I guess it's the lobe/ramp design but they all have a nice little lope to them, even with a 110lsa. The 272 would be a good choice for a some what modded engine. I personally would steer clear of the thumpr.

Comp Magnum cams are indeed good cams and as stated will give you the idle you are looking for. Comp also has a 268AH-8 cam 268-276 222-226 @ .050 .464 lift on a 108 lsa that has a very definate agressive idle to it. Had a friend with this cam in a mild 9.0 350 and it had very good low and mid range in his 62 Nova. The 108( as well as 106 and 107 ) lsa cams usually close the intake valve earlier which is good for a low c r motor. Comp also has the 268H-8 cam which is similar to the above cam but has 222-222 on a 108 lsa which is very close to the Isky 270 Mega cam at 221-221-.465 108 lsa. Lots of alternatives to the thumper cams if just do some searching. Maybe some of the thumper users could post a youtube sound clip of their 350 motors and let us know such things as vacuum readings at idle and the rest of their combo like c.r., type of trans., stall, rear gears, power brakes, etc. to get an idea of how the thumper would work and sound in other combos.

Hi
Will this cam sound just as good as a thumper cam.


http://www.competitionproducts.com/images/E1136thm.gif (http://www.competitionproducts.com/prodinfo.asp?number=E1135) Elgin, Hyd. Roller Cam, Chev 305-350, .480/.480, 230/230 (http://www.competitionproducts.com/prodinfo.asp?number=E1135)



Chev 305-350 ('87-'94 w/OE roller lifters)
Duration @ .050": 230/230
Adv. Duration: 306/306
Lift: .480/.480
Lobe Center: 108
2500-5800, Moderate idle, Street/Strip

they dont sound good at all

doesnt sound like a "true" lumpy cam.. it sounds way too lumpy for the idle that the cars are idiling at (like, it sounds the same idiling at 600rpm as a cam in a drag race car idiling at 1000rpm.. ust doesnt sound right IMO)

Hi
Will this cam sound just as good as a thumper cam.


http://www.competitionproducts.com/images/E1136thm.gif (http://www.competitionproducts.com/prodinfo.asp?number=E1135) Elgin, Hyd. Roller Cam, Chev 305-350, .480/.480, 230/230 (http://www.competitionproducts.com/prodinfo.asp?number=E1135)



Chev 305-350 ('87-'94 w/OE roller lifters)
Duration @ .050": 230/230
Adv. Duration: 306/306
Lift: .480/.480
Lobe Center: 108
2500-5800, Moderate idle, Street/Strip

what engine? that looks like a pretty healthy cam to me.. by no means would it be a moderate idle cam IMO

i have a 280h comp cam (same specs as above, only with a 280 adv. duration) in a 302, and that thing has a pretty radical idle

I have a thumpr in my 327, 9.5:1 with performer RPM heads. The sound is just incredible.

That being said its simply a street driven car. I am not overly impressed with the power, but im not unhappy either. Idle quality is rough as hell. The car shakes to much at a stop. But drivability is fine. It makes decent power for a low inch engine. I think it could use a bit more carb for real power. But i have a 650 on it for economy.

I should add that they say a 2500 converter is fine, i think a bit more would be better.

If you wanna hear it PM me and I'll call you if you think you can tell over the phone. The sound bits that have on line are soso.

Or.....

Back off on the initial timing, mod the dist to make up the difference to get back your total.

Use ported vacuum advance to increase drivablity but still keep the idle advance low.


Are you saying if I a person backs off the initial timimg the cam will sound lumpier? I wish my cam had a little more lump when it idles,

Only if i has a bit of a lump to it to start with. It makes a difference with mine (see sig). Probably not the best idea for ultimate all around performance but it has the effect of a bigger cam at idle. Remember if you don't mod the dist to get back your total (say 36deg as example) then you're screwing up peak performance. I have a MSD dist which makes it easy with the change of a bushing.

I feel some flames coming. :)

personally would steer clear of the thumpr.

Have you actually installed one or rode in a car with one in it?

The lower lift on the exhaust side makes no sense to me for a performance aspect, it is easier to get it in than it is to get out.



I think the reason for the lower lift on the exhaust side is to increase piston to valve clearance.Plus if you hold the valve open 10 or 15 degrees longer you don't have to lift it as high to get the same or better flow.If you look at solid roller cams .600 plus lift alot of them have more intake lift than exhaust.

Chev SB 262-400
Application: Max Oval
RPM Range: 4500-8200
Lift w/1.5 Rockers: .675/.624
Application: 296/306
Adv. Duration: 296/306
Duration @ .050": 264/272
Lobe Sep. Angle: 106

This cam has .051 less exhaust lift.

I say go for the thumpr. I have seen a lot of people ask about it only be immediately talked out of it. I haven't seen that many posts on this site with people that actually have the cam so there really isn't much info on here about it, other than it being bashed for its design purpose; to sound good.

Is the Thumpr cam for the same guy who buys the fake 12-bolt cover that's made for a 10-bolt? And the same guy who found some discarded 10" slicks and mounted them on his 7" rims? The guy with the big honking tach with a 8500 red-line and the glass-packs which sounded better after driving though water? You know, the guy with the B&M shifter on his stock powerglide?

Is that the Thumpr market?

For those that would like the Crane 274H06 218-218-.454 106 lsa cam and cannot find it then go to competitionproducts.com. Chad on this forum informs me that CP makes a clone of the 274H06. Has the same specs and is $99 with lifters. Part number is E1785PM. May not be as nasty sounding as a thumper but will get someone's attention and still be very streetable. Thanks Chad!!

Is the Thumpr cam for the same guy who buys the fake 12-bolt cover that's made for a 10-bolt? And the same guy who found some discarded 10" slicks and mounted them on his 7" rims? The guy with the big honking tach with a 8500 red-line and the glass-packs which sounded better after driving though water? You know, the guy with the B&M shifter on his stock powerglide?

Is that the Thumpr market?

Yes, unfortunately. I am truly amazed by the amount of people that don't choose a cam for its performance, but only care what it sounds like.

"I think the reason for the lower lift on the exhaust side is to increase piston to valve clearance.Plus if you hold the valve open 10 or 15 degrees longer you don't have to lift it as high to get the same or better flow."

Right, I too figure they shortened the exhAUST LIFT B/C IT'S DURATION HAS BEEN DRASTICALLY INCREASED AND IF THEY WOULD HAVE HELD THE SAME LIFT, IT WOULD PROBABLY OVER SCAVANGE IT!!

tHIS IS THE "OLD-SCHOOL" WAY OF MAKING CAMS IF YOU REALLY LOOK HARD!

PDQ67

Dam caps!!!!!!!!!!!!!!!!!!!!!!!!!

I have a comp XS 274S with 1.6 rollers on the intakes and 1.5s on the exh. It sounds NASTY in my little 350 and I'm happy with the performance. I looked at the Thumper line when I chose my cam it was just out at the time. I chose a solid cam because they sound better than a hydraulic, I don't like mushy lifters, it revs quicker and lashing valves once in a while is no big deal and I actually enjoy playing with my motor. In fact I have checked the lash a few times and it is still bang on. I think the 1.6 intakes helps performance and makes the engine (pop) sound better as well. I have more lift on the intakes than exh. With this cam I still have just enough vacuum for my power brakes.