The issue of concern (not a problem, just my concern) for me with the Thumpr series is a combination of three things, 1- A ton of exhaust duration, 2- not enough intake duration, and 3- not as much lift as most comparable cams.Īlthough I haven't build a street engine this way to compare back to back, for someone that wants the wicked idle, I think with the early cam timing, I'd rather run a little more lift on both sides, more intake duration and cut back on the exhaust (keeping similar overlap) and keep the lobe timing the same (tight and early). I'm a bit rebellious (if you haven't noticed) and I like to go against the grain so that's why I chose to run one.Nothing wrong with experimenting and there is no "right cam", but there sure are lots of wrong choices. The vacuum is basically non-existent but I run power nothing with a stick. It runs great, sounds evil (VERY EVIL) and I'm very happy with it. Initial timing at 20 total is 38 and it runs like a raped ape. I have a stroked 427 with the BMT cam in it.
I'm a bit rebellious (if you haven't noticed) and I like to go against the grain so that's why I chose to run one.
THUMPER CAM TRIAL
or do a little trial and error yourself, if you can afford it that is.
THUMPER CAM PROFESSIONAL
If you really want a PROFESSIONAL opinion listen to some of the real engine builders on here like Brent, Barry, etc. It comes down to choice so if you want to try one then go ahead and you make the decision instead of some internet commando. "What eye watering exhaust?"Īre there better cams? Absolutely! These are not racing cams by any means. I know holleys pretty well and once I got the timing and 4 corner idle set, other than toy with the power valves (cause of the shitty vacuum) I touched nothing, all I can say is. Hell, I even remember some guy commenting about th eye watering exhaust.
THUMPER CAM HOW TO
I think people are quick to judge on these considering 75% of the negative comments probably come from someone who has never ran one, probably never built an engine themselves and have no idea how to tune a carburetor or adjust timing properly. I don't race my car, I don't care about squeezing every ounce of horsepower out of my engine and I don't have it sitting as a dyno queen to show all my friends.
The truck runs as well as any low compression 390 could with any other reasonable cam and could easily be used as a daily driver. I can't say I would pick a Thumpr cam on my own, but it certainly wasn't nearly the enemy we generally make them out to be. Must be a whale of a lot of overlap there. That seems really low vacuum for a 226 intake cam.
THUMPER CAM DRIVER
It should be a lot stronger then, but for now it's a real nice driver and it sounds awesome. This winter, we are likely going to put a 3.98 crank in it to get the pistons up where they should be, potentially rock the cam back a couple of degrees and then tune again as 416.
In the end, this engine runs really well in a short box 2WD pickup. I put the spacer on initially to help keep the carb cool, but found that the carb also had very high float levels from the factory, so likely the boiling issue was due to that. Recurved the distributor to allow 38 total at 2800 with 20 initial and put a 4 hole Transdapt phenolic spacer on. I put a set of pink enrichment springs in the carb (was supposed to come with them stock, but didn't) to keep them from cycling at idle. Needless to say it was a little down on torque, good sized cam, big intake, big heads, but not as bad as you'd think. The engine is a truck 390 (low compression) with Edel heads, RPM intake, Accel dist, 650 Thunder series Edelbrock carb, FPAs, 3.50 gears and a CR 4 speed, cam was the smallest thumper, 226 intake, 241 exhaust, low 500s on lift, 107 LSA on 102. I can't remember who also had the small Thumpr cam in a 390 truck, but I finished tuning the one I was working on and it responded very well to minor tweaking.
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