I see where you are now. So while the cruising rpm is approached at 17-2200 Rpms, there's few few ears that can hear if a car has any type of performance cam in it. At the stop lights the owner can make rumpity rum pit titty rump noises and have a car that works and they can make the noise. The alternative it a car that makes noise at low rpms and the owner needs to compensate and deal with a car that doesn't do anything else very well.
Sum 1105 Vs Thumpr, now remember we are dependent on published specs. I used .050 because Summitt has really long advertised.
The cam was made to give " the idle" but keep reasonable driveabilty. Like all cams that have low idle vacuum the idle circuit needs to be richer. Sense the Idle circuit stays in play until about 2000 rpm you can expect lower fuel mileage.
A buddy of mine (a pro NHRA engine builder) has said he will not install a thumper cam in and engine. Claims its too hard on the bottom end. Personally I have never used one before, I have used the Summit brand cams with I would say good results. Never a breakage and good for basic cruises. I don't build all out race cars.
Quote: Originally Posted by jkeesey View Post A buddy of mine (a pro NHRA engine builder) has said he will not install a thumper cam in and engine. Claims its too hard on the bottom end. . I'd love to hear more on why he believes that Me too, here are the Gas Forces and BMEP for the Thumpr and XE274 __________________
He claims something about holding the charge puts un-needed stress on the bearings and leads to premature failure. I don't know, Im not a doctor. I just fix old cars.
In "theory" something harder on the bottom end/bearings (outside of detonation of course) is just about anything that's got potential of making more power, no?. So, if you want to protect the bottom end/bearings....no big compression/blowers/turbos/nitrous?
If I remember right he claimed it was similar to running with your timing too far advanced. I haven't talked to him in a long time, its been a while since I did any SBC work.
I have the Thumpr in my truck, like said before, the only thing I would have done different is go with a higher stall converter. I opted for a 2400 stall, and wish I would have gone with a 2800-3200. I am happy with my set up, it is a hydraulic roller in a 98 SBC. The motor is basically stock, except for a little port work on the heads, and of course better valve springs. Here is a video link. <iframe width="420" height="315" src="//www.youtube.com/embed/kpypBWBOCo8" frameborder="0" allowfullscreen></iframe>
I have one in my f-1 ford with a 5-speed , small block, and the original dana rear. Pulls good in second- 4th gear, shift into 5th and around 1900- 2300 rpms, you can really feel it, and gas milageis unreal with thisset up. I thought everyone onthe hamb were 3 pedal guys.
Great vid - sounds good. Are you running a vacuum advance? As to original question. Why not get one & try it? Get that 2 piece timing cover so it's easier to swap it out if you don't like it.
If you wonder what you are giving up compared to a conventional grind here is a Comp 280H vs The Small Thumpr. The 280H is slightly better up to 5500 then the big exhaust pays off.
Don, the Summit brand cams are built by Crane. Most of them are just Crane Cams in the same grinds Crane sells, but their are a few that are circle track cams that Crane grinds to Summit requirements. I've used numerous Summit/Crane cams, and never had any problems. Very nicely made, and durable. I had about 13 years of driving with one on my Camaro's 427 when I sold it last year. I wouldn't hesitate to use them; they're a real bargain!
I chuckle when someone says a certain cam is harder on the engine because of it's specs. I'm also running the middle Thumpr in the BBC in my Falcon in my avatar. It's got gobs of low end torque, and makes power well beyond where I should be running the engine! Revs quicker than most the SBC engines I've owned, and I really have to watch the shift light to make sure I don't over rev it! I'm running a 4 speed, but an automatic with this particular cam would need a 2500 stall converter, as it's got a pretty short 108 LSA. Click on picture to play the video:
I had a Thumpr in a .030 over 283 with a stock torque converter on a 700R4. It sounded like feeding time at the zoo but it had NO low end torque and burned more fuel that a four-motored air plane. I'm sure that, with the right combination of parts, they are fine cams but I wasn't happy with mine. The sound wasn't worth the absolutely shitty performance my set-up was delivering. JH
Harrison you have hit on something that most will never get. Unless you go with the absolute smallest or closest to stock performance thunmper cam you can find you are going to have to build the engine to support the cam shaft if you expect it to perform. Now for those of you who have not written me off as a hater and are still reading, that goes for about any camshaft. Close to stock cam stockish engine fine, lots of cam stockish engine, dawg. I gotta laugh, I was in a gas station a year or so back and this guy pulls in in a first gen effie. I thought he was running a diesel and I remarked that it was a novel idea. he said not diesel SBF and a Thumper. To each his own I guess.
^^^ Yeah but Comp says they're supposed to sound "cool" I was considering one for a 327 for my truck, but after researching the HAMB (of course) I'm choosing one of their Xtreme Energy grinds. Like someone else said here in another thread: "No one ever bought an L79 cam for the way it idled."
I guess there are Thumper Cams just like there are Gear Drives. Whats the point? I'm just not impressed by a bad ass idle.
I used Blue Racer cams in all my small blocks. My '57 Ford with a 406 sbc, 10.2-1 comp, World Prod. 200cc heads, RPM intake, 750 HolleyDP, Had a stock car grind, (something like 236/4.80), 700R4, 3.90 gears. Ran 12.90 and got 20mpg @ 60mph all day long.
nice car, nice sound, not sure I would have showed the secret switch that shows how to start w/o a key on the video though...
The entry level Thumpr I stuck in my buddy's 350 in his '48 Austin A40 is getting 20 mpg on the freeway at 70 mph the last road trip we made. That's with a TH350, and 3.73 rear gears too. I'd call that acceptable mileage for a rod without OD.
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