creepingdeath

Has anyone used this cam? or how would it drive? they say it has a "very rough idle" These are the specs..

Valve Setting: Intake - Hyd, Exhaust - Hyd
RPM Operating Range: 2500 to 6200
Cam Grind Number: 299THR7
Duration Advertised: Intake - 299, Exhaust - 319
Duration @ .050'': Intake - 243, Exhaust - 257
Valve Lift: Intake - .531, Exhaust - .517
Lobe Sep. Angle: 107°

Orr89RocZ

iTrader: (20)

that looks to be the muthathumpr or whatever. i wouldnt touch that cam on anything less than 383 inches

the base thumpr cam is more like 227/241.

tight lobe seperation and the overlap the cam has will make that rough idle. in fact it will be incredibly rough. choppy indeed. your talking about 95 degrees of overlap. cc306 cam is 230/244 on a 112, has 74.5 degrees of overlap and is a pretty rough idle cam in a 350.

But the duration split and valve events will give it a broad power curve. comp has said they took designs from endurance racing cam profiles and put it into this cam, to keep power curve broad/flat so you dont have to shift all the time.

creepingdeath

Ya thats there biggest the "big ***** thumpr" i was just wondering if they were actually good cams or if they were made to just sound good. Im thinking of getting the regular thumpr it has -283 -303 duration, Wich is still pretty big but i want to add some more power to my engine while i have it out this spring.
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I can't find the 227/241 you siad was there base thumpr though the lowest i could find was the one i posted.

Demon_Eater

mmm, its a good thing you asked this, cause I also a tad curious of this thumpr cam. I was gonna rebuild my engine and I was maybe thinking of putting one of these in my car, I love the rough idel, and I of course, I dont know all too much about cams, so is there really any disadvantages of this cam in a 305 (yes, I know its a dumb idea of messing with a 305, but im adding 150 hp to it, and later take these parts off and put them on a 350).

Kevin91Z

iTrader: (1)

You better be a hell of a tuner, carb and EFI, to put one of those cams in an engine. They're not for street vehicles.

creepingdeath

The smaller cams are streep/strip the bigger ones are race cams.

Orr89RocZ

iTrader: (20)

it will definately take some time tuning, especially EFI. a carb should handle it better as carbs tend to like tight lsa's. I think it can be done however.

the duration/overlap of the cam is what i dont like, its a large split and abit lazy lobes from the looks of it. should still make decent power. i think it would have been better if it was on a 109-110 lsa tho.

there are other cams out there that will make more power and give you good rough idle and are easier to tune.

Lucid

iTrader: (4)

The cam is the arguably the most important part for determining the powerband on that engine. This cam is for cars that are going to be raced, COMPcams even says that these were designed for racers that get tired and dont want to shift.

You are going to want to pick a duration that is going to be in the powerband that you are going to operate the car in. If this is going to be a street vehicle then this cam is going to have almost no torque coming from a stop.

If the car is computer controlled you will want to keep the LSA (lobe separation) closer to 112 or higher if possible.

There are better cams available for the 305 that will give it a power increase without killing torque or having to rev the engine to insane 7000RPM to get it to the powerband.

http://www.goingfaster.com/spo/325_h...chevrolet.html
http://www.hioutput.com/tech.html

Selecting the right camshaft for the vehicle is the key, so you might want to call one or all of the camshaft manufacturers and tell them what you have and what you want out of the engine. They have the tech experience to point you in the right direction on which cam to pick. Then you are going to have to decide whether to pick a flat tappet or a roller cam.

Demon_Eater

Thanks, that makes much sence to me now. I dont know much about cams and I have been doing alot of studing of rebuilding engines and adding more power to a 305.. the page Lucid posted was almost exactly what im doing to my engine, it is a TBI and it has alot of miles on it and want to put new parts in before I go to college. and hopefully a T56 6 speed tranny, cause I do know my stock transmission wont take the horsepower, and it would be nice to have a six speed then five.

creepingdeath

Actually the t5 can handle like 400 trq and even 500 they did it in high horsepower ford or whatever that magazine is.. its a '70 mustang with a 346 and 400 hp and they siad they have done about 100 drags with the car with big m/t slicks.

Demon_Eater

hmm, that also helps.. I was really afraid of my tranny going out if I rebuild the engine. my friend who rebuild two camaros and rebuild alot of engines.. like snowmobile, motorcycle, pickup, semi, etc engines all the time. the one camaro is a 1982 and he is putting like 340 hp and he broke his stock transmission but knowing him, he drives like a mad man from hell, so that probly explains it.

85z28guy

I put a retro fit roller setup in my 383 with the big ***** thumpr. Machine shop said they performed really well in a couple higher cubic inch motors they had done. They said at first they were hesitant, but once they saw the numbers were pleasantly suprised. As said it also had a really broad powerband, which is awesome in a street car. I can't tell yea how it perfroms in my 383 till the spring though

Orr89RocZ

iTrader: (20)

can you get any dyno numbers or track times for those motors that machine shop made? i'm curious as to what the power curves look like

creepingdeath

Thats why im wondering why everyone sias its a racing cam becuase comp sias that they were made for street cars going to car shows and stuff. i saw an advertisement for the thumpr cam and it was a guy driving into a car show in a street bel-air.

Orr89RocZ

iTrader: (20)

well it was taken from racing cam profiles and put into a cam that you can run on the street.

it will create a broad power band, because a similar type cam known as the CC306 has a 14 degree split in duration and 74.5 degrees of overlap and has a broad powerband. it will create peak power and hold that peak for awhile so you can stay in gear longer and dont need to shift alot.

It can be run on the street just fine i'm sure, but i would think there are other better suited grinds for a street car wanting a rough idle, but you have to match the cam to the heads/intake your using.

creepingdeath

I dont want to use it its too big for me... but it does sound really good and i was just wondering if it was made for just the sound. It would be nice if someone was using one and could chime in on this

neagan

iTrader: (7)

I JUST received my subscription to this month's Chevy High Performance. They have the Thumper's listed in the best article (for beginner's like me) on camshaft basics I've run into yet.

I'm quite interested in some of the above feedback regarding this cam being a REALLY BAD CHOICE for our EFI/TPI engines. Are you saying that ALL of these Thumper cams would raise hell on our PROM's or are you stating that this larger Thumper is an issue?

My engine builder has been dragging his feet for several months on my copy ZZ4 engine and did some sort of custom cam design for me. If he hadn't already done it, I would have asked him to use the smaller Thumper in my little torque monster 355. Since this magazine issue just hit my door, I havn't read the entire article in total, but I didn't notice a reference to it being a California smog compatible/L98 motor item.

Anyone with knowledge care to clear the issue up for those of us naive but wanting to learn members???? Nitro

Orr89RocZ

iTrader: (20)

the bigger cams would run like crap on our cars, for the most part unless you got BIG cubic inches. they are just mismatches for the cubes/intakes (tpi) we have. now they may work well with a miniram or hsr but they will want to spin VERY high.

but the main thing is the overlap and tight lsa. tighter lsa's like 110 and less usually have alot of overlap. the more overlap you have the more difficult it is to tune idle and low speed part throttle driving. too much overlap will allow some of the intake charge to be pulled thru the chamber and into the exhaust port and then into the exhaust stream. The o2 sensor will read this and think the motor is very lean and try to overly richen the mixture to correct this problem.

Now i do believe the small thumper cam can be tuned for 350-383 engines. Its got abit more overlap than the CC306 cam and that cam has been run on many of our cars with ok success. So it is possible to tune idle and such for that cam. Just would be harder to do and take alittle longer. Generally you want to keep overlap to around 50-65 degrees at advertised seat numbers. But it also helps to look at overlap at .050" and .200 if possible to see how the lobe profile looks. that will give you an idea on how the cam will work in the car and how hard to tune it will be.

HD4mula

They specifically state they don't recommend these thumpr cams for FI cars.

creepingdeath

neagan

iTrader: (7)

Hmmm, I'll have to go back to the article and see what's posted.

My engine builder hasnt shared with me what the custom grind that he did for my new long-block, but I was hoping for something with steeper/wide lobes.

Lucid

iTrader: (4)

The rest of us bought it and read it at the beginning of the month...


Engine builders usually have some experience building engines that work well. If you stick a Thumper in your car it wouldnt be a torque monster anymore.

Orr89RocZ

iTrader: (20)

If you can tune it, i dont see how it shouldnt be considered for FI. FI does like less overlap so the O2 sensor can work but there are ways to get around that. i know guys running lots of overlap on these GM ecms

neagan

iTrader: (7)

Thanx for reminding me that I live off in the sticks! My mailman dosn't even like to deliver here and sometimes gets pissy & refuses.....

Kevin91Z

iTrader: (1)

It depends on the engine builder. Most places build high horsepower carb race engines and know very little about street EFI engines.

If you dont have a way to do custom chips, then stick a ZZ4 cam in there. If you do, then the sky is the limit. Most of us are running cams similar to the LT4 hot cam in duration and lift.

I just stabbed a 226/232 .565/.565" 113 LSA Lunati cam in my car and and went thru some serious tuning to get it to idle at 800 rpms.