Sorry, hope this doesn't rub the wrong way, I have known 2 people that tried the 'thunper', I know 2 people that gave up trying to get the motor tuned and took the Thumper out and put it in the scrap heap.
I'm sure I'll have to adjust the secondary butterflies, accelerator pump cam, squirter size and the spring for the vacuum secondaries too. I've already bought 3.5 and 4.5 power valves for my holley and I'll be tuning on it next. I haven't checked idle vacuum yet, however I'm sure it will be about 8-9" based upon research. Basically I wrapped up the install today, broke the cam in and drove it around the block. I'm sure the tight stock converter is keeping it from idling the way I want when it's in gear. I've got about 18-20 degrees of initial timing in it(w/vacuum advance hooked up) and 33 degrees total by about 2300 rpm. The cams perform well when tuned and I'm starting that next. The 350 in the truck is stock and I primarily wanted a cam that had that big cam sound but wasn't super aggressive on lift. Oh and have you measured vacuum? What is it at idle? Are you sure you have no intake leaks? Did you try playing with the timing to see if you can get better idle performance? Last time I helped someone with a Thumpr, we had to dial in quite a bit of initial timing to prevent it from stalling all the time. If you get too aggressive with the stall without knowing the gearing, that creates problems of their own too. 2300-2500 should be OK, but tell us what rear gears you have and tire size. Yes, you will need a high stall to reign it in a bit. They tend to be all show, and no go, and hard as heck to tune properly for good street manners. I don't know anybody who really likes the Thumpr cam. I like the cam, even with the 3:08 gears in my Corvette (3100 lbs).A little too late, but perhaps you should have asked us what cam/converter combo would work together BEFORE you bought that cam. It also kills vacuum, I think on its best day it might make 9 inches.Ĥ) Everyone, and I mean everyone, gets that stupid grin on their face when they hear it run. stock 4 bolt main truck 350 with Vortec heads, air gap intake, CR is 10.5:1 and it sounds excellentģ) It's an 108 centerline cam, you expect cadillac torque? I honestly don't think it gives up that much bottom end, but oh good heavens, when it hits 2800 rpm, hang onto your girdle, it'll pull your panties right off all the way up to redline. now my problem is keeping clutches in the car.Ģ) I have the next-to bottom of the page cam. it sucked, it was like a light switch, and idling down the freeway, it wouldn't make enough pressure (tc) to keep it in 3rd gear. That said, the first itineration of this set up was with a turbo 3 stall. I have a 4 speed, so I couldn't care less.
sounds like I'm the only on running their Thumpr cam.ġ) stall depends on which cam you buy (there's like 5).
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