Thread: COMP Thumpr Cam is in

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Finally, the Thumpr is in the 350 and I have the 34 fired after much frustration with the new chrome Weiand intake manifold. Part of the problem is the tight fit of everything under the hood, but Weiand moved some ports around on this new manifold, causing me mucho grief getting the heater hose and temp sending unit fittings to clear the AC condensor and the alternator. I think I now have half a hardware store on my garage floor. Got the big thump I wanted, but having run-on when turning it off. Have some more tuning to do, and hopefully that will solve that problem.

Those Thumpers have a great idle from what I've heard on YouTube. I guess they figured out most of us have enough performance in our rods to suit us, we just want them to sound like a fuel dragster to complete the picture.

Don

Ain't Nothing like a good sounding old school cam to me.
Ya gotta love that big lopy sound of a good motor.
But that's just the way I see it. Kurt

I just do cruising with it and don't care if I can spin the tires, or how fast I can get to the next stop light. I do at least 25 Wednesday night cruise-ins in my area every summer. This cam is the lower level Thumpr, made mostly for the thump, while maintaining good driveability. I certainly got the awesome idle I was looking for. With the bigger Thumprs, I would have to deal with more mods, like the torque converter, etc.

I'm considering a thumper for my ZZ4. The engine is less than 5000 miles old and runs fine....just needs a lumpyer idle. Can anyone tell me if I should be worried about valve springs?

My ZZ4 350 had 4,500 miles on it when I did the change. I had several good mechanics tell me that I could use my existing springs with my Thumpr in the ZZ4, particularly since I don't race it or get into the real high RPMs. I bought the COMP beehive springs anyway. You should replace the pushrods, and if you do the springs, will also need the spring retainers (#787) and the spring seats/locators (#4693). If you buy the COMP Thumpr, you can get it from it from Summit for about $40 less than from COMP. One more thing, if you change the springs you will need new valve stem seals.

As far as putting this cam into a daily driver (63 Chevy II Wagon) with a 327 in it, would you recommend this cam? I want a streetable cam but not stock or anything. I want more power out of it but was concerned that with the lumpy idle cam like this (even though it's for street use) that I will have to sacrafice some power and possibly fuel milage? What do you guys think on this?

That is the cam I'll be going with as well. Glad to hear that the idle is as rough as they say.

I put the Mutha Thumper in my 350. Basic rebuilt 350 4 bolt block with nothing special just the normal bored out, forged flat top pistons, ballanced. Rebuilt heads with stock springs. Runs good, sounds, mean. Had to install a 2000 stall in the TH 350 trans with 3.7 gears. Even power brakes works good. Vey streetable. Almost willing to try the BIG Mutha Thumper in my ZZ Fastburn. Ken