"thumper cam"

[crushermechanic]

no it doesnt load up or die in traffic. hard stops are fine too. if i had to do it over i probably would have gone with a different cam. it runs good and sounds wicked but i think there were better choices.

[pockets]

There is a similar thread on here with a few thumpr haters. I have seen at least 3 different magazine builds all with 496's that made between 550hp with summit branded iron heads to well over 600hp with aluminum heads. PHR built one for a chevelle a while back called the howitzer that made 625hp and 635lb. The torque curve on it was incredible. Almost 600lbs at 3100 rpm (the lowest they started the run at) Google "496 howitzer" and you can see the dyno chart.

Does it sound good, yes. Lots of YouTube vids to watch and listen
Does it make power, yes. Dynos don't lie too much.

Will it make the best power for your application? Depends greatly. But hey if you like the sound go for it. Besides, "best" power is rather vague anyways. Peak hp means nothing for a street vehicle. If you aren't sure call comp cams and ask. I'm sure they'll be glad to tell you if your combo is right with that cam.
Posted via Mobile Device

[wwotr]

Originally Posted by pockets

There is a similar thread on here with a few thumpr haters. I have seen at least 3 different magazine builds all with 496's that made between 550hp with summit branded iron heads to well over 600hp with aluminum heads. PHR built one for a chevelle a while back called the howitzer that made 625hp and 635lb. The torque curve on it was incredible. Almost 600lbs at 3100 rpm (the lowest they started the run at) Google "496 howitzer" and you can see the dyno chart.

Does it sound good, yes. Lots of YouTube vids to watch and listen
Does it make power, yes. Dynos don't lie too much.

Will it make the best power for your application? Depends greatly. But hey if you like the sound go for it. Besides, "best" power is rather vague anyways. Peak hp means nothing for a street vehicle. If you aren't sure call comp cams and ask. I'm sure they'll be glad to tell you if your combo is right with that cam.
Posted via Mobile Device

Thanks Pockets(and everyone else).
Heres an email that I sent to the company outlinging what I have and my Driving Habits. Any additional info you guys have is still much appreciated.

I was looking into one of these for my 72 GMC Truck.
The previous Owner put in a 1994 350 Engine out of a GMC Sierra in it.
I'm running HEI ignition, Headers and an Edelbrock 4 bbl Carb.
The engine is by no means "pumped", and will probably be changed out in a couple of years. I'm currently having my mechanic put on some Electric Exhaust Cut-Outs and your Thumper Cam would be a welcomed addition.
I'm really not concerned with HP, and I rarely rev over 3000-3500 RPMs.
I just like cruising and don't race. What all do I need (besides your Cam),
to have my Mechanic complete the install, (as far as Lifters, Push Rods)? What stage Thumper Cam would you recommend, based on my,
Engine Info/Driving habits? Is there anything else I have to change in order to install this, (i.e. timing, Carb ect)? I'm hoping that you just install the cam and drive on down the road. Any info you can provide would be appreciated, along with prices and/or Dealers, Links, Websites, Part Numbers and where I can purchase everything.

[Bad70sbchevy]

I always heard the rule of thumb was no more than 300 duration for on the street. I'm running a 292 with .501 lift flat tappet cam (Comp Cam) with roller rockers and I drive my truck every day in traffic and on the highway and have had no problems at all. The only thing I ever had was the carb loading up, but its from running a holley double pumper which are notorious for running rich (for power) and not from the cam. The only issue you run into with running a cam with a low lobe separation angle like the thumper cams is it doesn't produce enough vacuum to run power brakes properly by itself without the help of a vacuum canister or a pump which a friend of mine uses on his 383 Nova. Sound wise it sounds awesome, you got to love that lope. Performance wise, these kind of cams will make power at higher rpms, but will usually make more power "IF" your heads and exhaust can flow well enough to take advantage of the added Volumetric efficiency caused by scavenging due to the valve overlap.
IMO you can never go wrong with Competition Cams.

[wwotr]

Do any of you run the "Thumpr Cam",
(not the Big Thumpr or the Muther Thumpr).

If so, how do you like it, and can you post any Video/Audio,
you may have of it idiliong.
Also if you are running this Cam, what Stall Speed is your Torque Converter,
if different from OEM?

[Bennett68C10]

I have thought about this cam alot myself, just go to youtube there are a ton of videos of small block chevys with thumper cams in them. I would also run a different stall as comp says that you can use stock converter but works better with 2000+ stall. I don't know about you but i read that as this cam needs 2000+ stall.

[Dark Knight]

I'm running it and LOVE it. This was my first time at building an engine, so I really didn't know what to expect. I went with 72cc combustion chamber heads with 2.02/1.94 valves on a 355. Stock intake and Q-Jet. It is a torque monster! Plenty of power and great acceleration. It sounds pretty mean too. The only problem I had was tuning the carb, but I just had to change to an orange power piston spring and fiddle with it a little. It will soon be replaced by an Edelbrock though...

Oh yeah, plenty of vacuum for power brakes too.

[oldblue1968chevy]

dark knight, whats your timing at (total/initial)

Im not all that happy with mine, but I never got the timing squared away

[Dark Knight]

I'm running the initial timing at 12* BTDC. As for the total, I haven't checked. I really don't have a way to. I've got a stock balancer w/o timing tape. I'm using a stock HEI distributor and have the vacuum advance connected to straight manifold vacuum. Yeah, they're pretty particular about timing. Mine diesels with 89 octane, but just every once in awhile with 93. Of course, the compression comes into play with that as well. I know it's somewhere between 9-9.5:1. Think I might try some octane booster next. Premium is up to $4.08 around here.

[benoit454]

retard the timing some or put that advance to a ported vac. source. ping or spark knock can be lowered by retarding the timing. it will also cause your idle speed to lower and give you more of a thumpr idle as well.

[wwotr]

Originally Posted by Dark Knight

I'm running the initial timing at 12* BTDC. As for the total, I haven't checked. I really don't have a way to. I've got a stock balancer w/o timing tape. I'm using a stock HEI distributor and have the vacuum advance connected to straight manifold vacuum. Yeah, they're pretty particular about timing. Mine diesels with 89 octane, but just every once in awhile with 93. Of course, the compression comes into play with that as well. I know it's somewhere between 9-9.5:1. Think I might try some octane booster next. Premium is up to $4.08 around here.

Now this is good info being passed around here.
I have been in touch with Brad (Comp Cam Tech), and have gotten info from him, but now I want to get real world input from exceptional people (such as yourselves) that have installed/used this Camshaft.

I'm trying to "cover all the bases" before I delve into this,
so I'll post some of my concerns/questions.

1) On the "Thumpr Cam", it says you can use it with a "Stock Torque Converter", but one with a 2200 Stall Speed would give better results.
Are those of you running this, using a Stock Torque Converter?

2) My current 350 is out of a 94 GMC.
It runs flawlessly on 87 Octane with no pinging/run-on whatsoever.
If I go to the "Thumpr Series" cam, am I going to have to go to a higher grade gas?

Not that the above would be "Deal Breakers" because I'm having my Shop do all the work, and he has installed a few Thumpr Cams.
My Mechanic is wanting me to go to the "Muthar Cam" (the 2nd one up) and go with a 2200 Stall Speed Torque Converter.
If I had bottomless pockets, this would be no problem, hence question #1.

Any help/input/advice/stories would be welcome.

[oldblue1968chevy]

So ported vacumn or manifold vacumn?

[benoit454]

I run mine ported. or timed, not full/manifold.

Having to run higher octane fuel because of a cam swap is wrong, if you need to do this the timing is off, yea it might work better with it more advanced, but on the other hand they have advance curve kits and adjustable vac. pods to bring the advance in faster if need be but less base timing to try and stop the ping/spark knock.

Now if you done some higher compression, like heads or pistons yea that's cause a need for higher octane.

I guess what I'm trying to say is to the bst of my knowledge cams don't change compression ratios so there should be no need for higher octane fuel.

if you retard the timing it may cause you to loose some power, noticeable amount? maybe, but to avoid the spark knock or ping, sometimes you just gotta do what ya gotta do, run higher octane to avoid timing retard and possible power lose, or retard it and save a couple bucks at the pump.

[oldblue1968chevy]

Ok, im running on full manifold vacumn, initial timing set @ 8* btdc, no idea what total timing is (never really go that..).

If I give it more advance it has more power, but it doesnt start/doesnt start very well. Does it need the curve kit or whatever? I never really learned that aspect of it all..

Im running 93 octane btw

[fleetsidelarry]

Oldblue, if you are pinging at 8° with 93 octane and it gets hard to start/stop beyond that, you really need to sort out your timing. A SBC should be perfectly fine at 8-10° initial on full manifold vacuum. Either your distributor has too much advance in it or the damper is not accurate, both are quite possible.

Most performance guys (but not all, as evidenced by benoit454 above) would recommend full manifold.

But give the ported source a try, if it cures your problem, good, if not, switch it back.

for a more definitive discussion you may want to start another thread on the ported vrs full topic.

[oldblue1968chevy]

It starts good and doesnt ping at 8* it just has more power etc if I give it alot more advance

Its a new dampner the old one had the rubber ring worn out on it

[Bennett68C10]

Originally Posted by wwotr

Now this is good info being passed around here.
I have been in touch with Brad (Comp Cam Tech), and have gotten info from him, but now I want to get real world input from exceptional people (such as yourselves) that have installed/used this Camshaft.

I'm trying to "cover all the bases" before I delve into this,
so I'll post some of my concerns/questions.

1) On the "Thumpr Cam", it says you can use it with a "Stock Torque Converter", but one with a 2200 Stall Speed would give better results.
Are those of you running this, using a Stock Torque Converter?

2) My current 350 is out of a 94 GMC.
It runs flawlessly on 87 Octane with no pinging/run-on whatsoever.
If I go to the "Thumpr Series" cam, am I going to have to go to a higher grade gas?

Not that the above would be "Deal Breakers" because I'm having my Shop do all the work, and he has installed a few Thumpr Cams.
My Mechanic is wanting me to go to the "Muthar Cam" (the 2nd one up) and go with a 2200 Stall Speed Torque Converter.
If I had bottomless pockets, this would be no problem, hence question #1.

Any help/input/advice/stories would be welcome.

Also don't forget that if your running stock heads it is recommended that you also change out your springs to match the cam. If i were you in a stock motor with stock heads i would just run the thumpr not the mutha thumpr. I think you would be very happy with it.

[benoit454]

I ran into the same problem with our comp 268h cam kit. The thing didn't have much of a choppy idle at 8-10 nor did it have much power at all. I had to advance it up kinda far, and it had good power, but started to have starter drag/hard starting so I had to retard it. Ours needs a curve kit but I haven't done it. Basically from what I understand ported or timed comes in just off idle so basically you are getting full vac. all the time except on idle.

I would agree though, do what I did try it on a full vac. then try it on ported. I did and mine just seemed to work better on timed.

8-10 should definately be fine, when you get into like 12 and above things start getting hard to start etc. I usually just go by the old school way of timing, advance it until it starts to ping and WOT then retard it to stop it, see if it drags on startup, if so retard it til it stops, if not then lock it down.

[oldblue1968chevy]

Im running vortec heads with stocks springs with the small thumpr.

I think i'll bring my timing back up, it more power than it does now @ 18* btdc

[fleetsidelarry]

Originally Posted by oldblue1968chevy

I think i'll bring my timing back up, it more power than it does now @ 18* btdc

now you're scaring me, 18° is way too much initial. you're going to hurt something

1. is this the setting where you were hard-to-start and pinging?
(I mean, indeed you should be experiencing those problems at that setting)

2. initial timing set with vacuum advance disconnected and port plugged at carb--correct?

[oldblue1968chevy]

Never was pinging, but it was running great (to me) @ 18* initial...?

Yeah at operating temps with vacumn adv. plugged going to carb (I forgot if it was manifold or ported vacumn though, its around 8* now)

[Captainfab]

Have you verified that your timing pointer is the correct one for the balancer? Just because it is new doesn't mean that your timing mark couldn't be off.

Originally Posted by oldblue1968chevy

It starts good and doesnt ping at 8* it just has more power etc if I give it alot more advance

Its a new dampner the old one had the rubber ring worn out on it

[wwotr]

Originally Posted by Bennett--G4L

Also don't forget that if your running stock heads it is recommended that you also change out your springs to match the cam. If i were you in a stock motor with stock heads i would just run the thumpr not the mutha thumpr. I think you would be very happy with it.

Thanks Benett, I'll take that under advisment
Yea I was going to buy the Cam/Springs/Keepers,
(that is what the Comp Tech suggested also).

[oldblue1968chevy]

The mark on the OE timing cover, or the slot on the balancer?

No I havent checked either

Edit, how would I?

[fleetsidelarry]

Originally Posted by oldblue1968chevy

The mark on the OE timing cover, or the slot on the balancer?

No I havent checked either

Edit, how would I?

What I (and Captainfab, I think, though I don't want to put words in his mouth) was alluding to is: there is no guarantee that the damper slot is lining up with the timing tab 0° mark, even though you've replaced the damper. some dampers have the slot more counter-clockwise from the crank key, requiring a different timing tab and placing the tab 0°/damper slot matchup at almost the 12 o'clock position.

This might be worthy of checking if you are indicating odd timing mark match-ups (which to me, 18° is). I believe you said that if you went beyond that for an initial setting you got into hard start/dieseling. But I would think that at 18° you'd already be in that realm. Perhaps not.

I don't know where I got the idea you were experiencing pinging, I guess I read the word in someone else's post. If you are running a common HEI with no tweaking, you might be somewhere around or over 50° total, starting with a true 18° initial.

you need a piston stop and a means of turning the engine over by hand to check your damper indexing.