Looking at the Thumpr series cam. I like the retro fit roller idea, the numbers seem good enough, but the lobe seperation of 107 worries me a bit. Has anybody run one yet? Like em?
I'd like to hear some feedback, too. I'm planning to put the mildest version in to a 302 Ford. cheers Ed N.
I think you answered your own question, the narrow lobe separation is what gives them that rough idle. Or in their advertising lingo, the thumper sound. I do not have any personal experience with them. But most old racing cams were ground on narrow separation to enhance higher rpm breathing, at expense of low-end idle quality.
The sound bite's on thier web site sound wild..i wouldn't mind running one myself.. My only question would be the maintenance of the lifters. I've heard that many after market roller's should be serviced/rebuilt after a couple year's of use..or in race application's more frequently than that. If you were to put say 5-8000 mile's a summer on your ride, some hard some not, should it be broke down or are they as reliable as the factory roller's used in modern ride's like the modern GM V8's? I know they are new to the market now, just wondering if anyone has read anything about this or not, i havn't found any info yet and would love to know.. Or, is it a wait and see thing because they are so new.. Breaking down the motor is no big deal in reality, but if it's running good who want's to have to do that if they don't have to. Tony
The reason i decided to use this cam was finalized after reading a article in super chevy mag.They said Zora Arkus- Duntov casually talked about this cam over dinner in 1986. Enter Joe Sherman Racing Engines, when Joe sherman was asked of his advice he said, he thought that if Zora were standing here today he'd much rather approve the comp cams " thumper " roller camshaft and beehive springs ( 0.510 intake/0.490 exhaust, 280 duration 107 lobe seperation angle) Anyway that encouraged me to try it.
I wouldn't worry about roller lifter durability with these cams. They're a hydraulic hot street cam, and as such, should have pretty good durability. You have to start checking rollers with agressive ramp solid race cams with 550+ open spring pressures.
There was a guy on ebay a while back selling a set of plans for using all factory GM stuff in an early block. Here's the link. I may drop 30 bucks out of curiousity. http://cgi.ebay.com/ebaymotors/Chev...004QQitemZ140178036765QQrdZ1QQsspagenameZWDVW
Too much money. IMO. The 303 Ford Racing Perf. Parts cams (except the E303) sound pretty good if you are doing a 302 or even a 351.
I have the Big Mutha Thumpr in the new engine for my A Truck, with a lift of .531 int./ .517 ex. Duration@.050 is .243 int./ .257 ex. and on top of that I went with a 1.6 ratio roller rocker, hee hee........with the 12 to 1 forged piston, it should run like a Banshee..nothing like a full roller engine......and I can not wait!!!...I still need to bolt on the new heads and do a push rod length check and get them.....getting close.....Littleman
Its just a 355, replacing the 327 thats in it, hoping it will burn the fuel better with the 6 x 2 setup.....The 327 did a real good job thou. The new engine should be an easy 100 or so HP gain over the old setup..........is it spring yet?..I am just waiting to find out, will up grade the truck in a few areas before blasting down the track.The truck will not be use to the extra power, so I will weed out the weak links and upgrade........Littleman
you mean replace the broken part's right? I'd be very interested in knowing how you think the new cam perform's when you do get it dialed in, especially with the multicarb's.. I'll be doing a similar set up just less comp..327, 4x2's and done right to run..your info may sway me toward one of these if it work's well for you.
The only thing that is keeping me from going with the Big Mutha Thumper is.....I'm planning on spinning my 327 higher than 6200 rpm. It sounds cool, but I need performance more than sound. The cam specs are respectable though, just not enough in the high rpm range for me.
I chose this cam , because I shifted at 6200 w/ my Isky cam in the 327 now, thats when it stops making power....not to mention theirs not too much to my truck and I could easily tear the thing up.....But it did run 12.20's-12.40's at the track and drive to work w/ the 327.......w/ the 4.88 gears that are in it...The Isky cam specs that is in it are only .464 lift and only .221 @ .050, so the new setup is much bigger than before...........Littleman
I forgot to add, another reason I chose this camshaft........running six carbs I want some kind of manifold vacuum still.....Littleman
I'm running this in my F100 with a mostly stock motor. .541 lift and narrow seperation make this thing idle like a monster. I did a lot of poking around before I dropped the dough on it, found nothing but good words. Only caveat from my wrench is that it may be tough to tune. I think the vacuum level is really low with it and that rough idle doesn't help. I've heard it run and liked it. Haven't driven it yet though. Soon though. Like real soon. I'll post any updates I have to offer when I get them.
When I tune this on my Truck, I set up each carb with a vacuum gage, so I will be able to offer that kind of info when the time comes, although each engine will be different...but it only helps you tune if you know what your dealing with..Keep us posted with your setup, Thanks Littleman
I've got a book (That I can't find right now) that has a sbc build up that is basically a bone stock 350 with iron vortec heads ($500) the cam is a chevy part # 12480002 HOT (thats what chevy calls it) it is a hydraulic roller with .492/.492 lift 218/228 dur and 112 lobe separation ....the kit comes with the cam, springs, retainers, locks, spring shims and roller rockers ($544) with an Edelbrock intake and a 800 cfm double pumper this motor made 422 hp @ 5800 rpm and it idles with 14 in vacuum.......all this can be put in an early block with aftermarket lifters (the valve parts are ava. separately).....I'm in the process of putting one of these mothers together.....They seem to be af good value for the money spent, for some reason it all works nicely, probably because of the heads.
You are correct, the heads are a big part of the majic......I do not dare tell everyone what kind of heads I bought for this engine, For I would have to put my head down, so I would not get hit by all the sharp objects thrown at me..........but I am a hotrodder in todays world, I like speed, and buy and build what ever will help me achieve speed, just as if I was born much earlier, I would be srapin my coins together to get the latest and greatest speed equipment available back then..........Littleman
For a more trad look your can buy some doo dads to use early model valve covers on this combo.....I'm with you, a relatively cheap motor that will just stomp the living shit out of everyone on the street is hard to pass up......and it will do this without loading the plugs up and shaken yore teeth out.....Oh yeah, an early block can be used if you remove the flanges on the cam retainer and use it as a spacer, then just use a cam button. That is the info the guy on Ebay is selling for 30 bucks
I am wanting a set of AFR's in a bad way....... I'm done with tradition. I have tried it for 4 years. Time to move on. I'm stepping up to the mid 60's.......I'm building a 301.
The Thumpr series are retrofit roller cams for the early non-roller blocks. There is a cheap lifter retainer kit from Comp to go with the cam, and then you can use OEM style roller lifters (this is on the Ford application anyway). But if you already have a roller block, then yes, another choice would probably make more sense dollar-wise. cheers Ed N.
I took my truck out for the first time tonight, drove up to Keller's for a burger. Just so you know what we're dealing with the vehicle has a 302 with Windsor block and Cleveland heads. Retro-fitted roller rockers and solid lifters. Holley carb. Other than that pretty much stock. Running the the Big Thumpr cam with lash caps. Automatic C6 transmission. It starts fine and idles like a top-fueler, really nasty sounding. It has good, smooth acceleration. It will definitely need a stall converter (probably a 1200) because it tries to die at idle in gear. Other than that I can report no issues with driveability. I've got 2.5 inch exhaust pipes with Flowmaster duals out the side just in front of the rear wheels. Sounds like a high-schoolers street rod. Too loud. I'm going to have to replace the things with something more mellow, for sure.
Thanks for the feed back........I can not wait for spring time!!!!! to unleesh the new little monster engine in my Model A Truck..Littleman
Rabid Atom, make sure you watch closely the valve lash. If you see one starting to gain more lash, pull the intake. The rollers are going south. I have a friend that is on his third set of solid roller lifters on the street. They won't live. These have less than 1000 miles on them. These were the redline lifters that were supposed to be heavy duty. The first set were Iskys. He's pulling the whole mess this time.
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