The thumpr cam has been installed. The idle is affected alot. Those who have this cam I am looking for fine tuning points to start at. We have inceased the idle. The cam we have is the one that uses a stock converter. I have also installed a adjustible vac. advance What timing should I be looking at? I am sure the take off is sluggish at this point what should I do to correct that?
It's pretty normal in the baselines. Start with maybe 32-34 degrees when your all in. That should equate to 10-12 initial. You'll have to experiment from there. It may tolerate as much as 38, depending on compression and such. Tune your idle mixture a little higher than usual, then you can turn the idle way down, about 600 rpm.
I ran one these cams in my rock buggy for a couple of years. Just lean it out a bit at idle so it doesn't load up. I ran stock timing also. Other than that it performed really well with no issues. (except bending most of the stock push rods while racing) HA!
The usual suspects. Where is your timing set, how big is the engine, what kind of carburetor, what kind of intake, rear end gears, what kind of trans, did you put the cam in advanced, retarded, or straight up, and most important, what are YOUR expectations after the install? Are they realistic? Take the distributer to a shop that has a distributer machine. Tell them everything you have done to the car. DO NOT LIE !!! Have them set the vacuum advance also. Bring it home, install as directed (prob 12* BTDC, vac. adv. blocked). Test. Review results. Check drivability as far as carb. Test. Review results. John
Install a smaller cam...... Actually, the advice above is a good start, get your timing set, then start adjusting the idle circuit until you get a good idle that's not loading your cylinders up. From there, you can work on the jetting and the accelerator pump volume to help with off idle acceleration.... though depending on your transmission and final drive ratio, you still may have driveability issues because of the cam.
But isn't the whole point of a Thumpr cam to have crappy idle of a long duration cam without the pesky extra horsepower?
There's a good read about Thumper cams in TRJ no. 49. Yea the whole point is to have a rumpty bump idle and a mild streetable cam. Check it out here... www.compcams.com/thumpr
I have a thumper cam in my '55 chevy and it is the .480 lift version. I have a mild 350, 194cc heads, roller rockers and 10:5:1 compression motor .These Thumpr cams seem to like a little more advance timing. I set mine at 6-8 depgrees and it was sluggish. I then advanced it to 10-12 degrees at idle and it seems to really like it with good throttle response. I then hooked up a vacume gauge and played with the mixture screws until it made the most vacume. I am still a little rich, but at 7,000 ft elevation I have 30% less air so I need to jet it down some.
I've not seen the write up in TRJ, was it done by comp cans? Yea the whole point is to sound like you have a built motor correct? " Lets face it, nothing grabs attention at cruise night like a hard hitting ...... " first line from the link provided. The sound of a well tuned hi performance engine is better than music. Not everyone will agree but everyone on the hamb will agree to that. That lopey idle is a by product of an engine designed to run hard correct? That lopey idle was not the goal correct? Its lopey because its having a hard time idling smoothly because of the huge compromise made so that it will run extremely well at WOT. Marketing the sound track of a cam at idle is purely an exploitation of the human desire to get attention. Just like fake tits.
http://www.youtube.com/watch?v=eXr8h9AQGms Thumper cam says what? The thumper sounds like what? This is THE THUMPER CAM After all the discussion here is what we have...enjoy
This cam is truly great however it don't idle in drive worth nothing what do I need? A stall converter will that do the trick?
It does sound great! But that guy needs a higher stall so the engine doesn't "push"against the converter. I hate that. As for "look at me" parts on a hot rod, uh, that covers most of hobby, no?
best advice i have for tuning after a cam swap is to go straight to the company you purchased it from. know the specifics on your own personal application before calling, they will want to know everything. if you give them every detail, they will return the favor, by telling you everything they know from their own testing and product development.....its kinda their job! good luck man!
I'd tell you to run a looser converter and a bunch more initial, but then it wont idle like a sack of crap, PLUS, with the looser converter, then you may as well have just put a bigger cam in it, instead of one that just has more overlap and a delayed exhaust closing point to make it "rap" in the pipes. So that would kind of defeat the purpose. No, really, just having a little fun, "Thumpr" cams are kewl.
You guy's a tit on the wild side. Yeah I called the guy that I ordered the cam from. He said I may need a converter so I was kinda prepared. The other car I have a big cam in is my Dodge Charger. I have the Purple cam shaft in that. I had to use a converter in there as well. It is very radical however It idles very well and has great hole shot. It almost comes off the ground. I figure If you are going to have one of these street rods it should sound and look like a hot car. The car is so light launching it is not the problem it's the idle at the light or stop sign. If I can get it to idle like it does in park. I will have a great time at the cruz in. That's all I want. I don't have the nerve to race anymore I'm pretending! Ah ha.
Hey Fellas, Do anyone know who built the Thumpr Cams Red Hot Rod that I seen on the Thumpr Cams commercial? Jimmie
you must be a younger dude casue I'm thinking your way too fussy I did think of the thumper, and looked into it, but my engine deserved better, I can have the wild idle and the HP, don't see the point of noise and not the HP that's like a sock in your jocks, your going to get caught out!
I tell anyone who asks that I'm 29. Someday, everyone who owns a car will understand that a cadence/rough idle is an unintendend consequence of an engine that's built to run strong at high rpm range. That idle is actually caused by the engines struggle to stay running, as ear pleasing as it is. I don't care if anyone understands that or not, but is shines like the sun or a sore thumb if anyone does or doesn't. Going thru the effort of installing a cam and then discussing how it idles is about the same as buying a great set of hammers and talking about how nice they lay in and fill the tool drawer.
Buy a speed pro cam way less money and still get the idle. Low vacuum cams require a rich idle mixture, idle curcit stays in play to about 2000 rpm. A thumper cam is like those empty GMC blowers with a carb inside.
LOL the hype says tough sound good manners. If all things are correct I wouldn't think that you would need much more lead than stock if you can go by the hype. A stock converter cam shouldn't be that big muther cam that everyone is in love with. Be sure that your preload is correct if hydraulic or lash of not. Set your timing within a few degrees of stock and start tuning. What else have you changed?
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