B2 Motorsports Custom Cams....

[blykins]

There has been a lot of talk about the "Thumpr" cams that are available. The most recent discussions have been over on the FE forum.

The Thumpr cams are known for their radical sound, which is what most guys want. The desire to pull into a cruise-in spot with a thumping camshaft will usually overwhelm the desires to have a clean idle, good throttle response, vacuum for power brakes, etc.

One of the camshafts that was discussed on the other forum was a "Big Mutha Thumpr" cam for a Ford FE. With a 242/257, 294/312 duration layout (lazy lobes), there is a huge span between the intake and exhaust durations. We're often used to seeing a little bit of a span between the two, on the order of around 4-6°. On a race engine, the extra exhaust duration helps to "hang on" up top as it can make up for poor exhaust flow. On a dyno, this split duration will often produce better results as well.

A split duration of 15° combined with a tight LSA does a lot of things. One of those things is it increases valve overlap. On this particular camshaft, you have 89° of overlap. That's 89° of overlap where most street cams of this magnitude have 65-70° of overlap. It would definitely sound good, but that's where the "pros" end. The "cons" would be a great amount of reversion (exhaust backing up into the intake), a poor signal to the carburetor, fussy idle and off-idle performance, etc.

These cams are really talked up, but there are some other engine builders who have put these up against the Comp Xtreme Energy lobes with no discernable increase in power. No increase in power along with a lot of horrible manners elsewhere doesn't sound like a very good sacrifice just for sound.

I'm offering some custom camshafts based on different Comp Cams lobes that will be in competition to the Thumpr cams. These are available for the FE, Windsor & Cleveland, and the 385 series stuff. Custom flat tappet camshafts are $200 and custom hydraulic roller camshafts are $350. The purpose of this is to put some cams out there that not only will sound great but will still have great manners and performance down low, where you spend the most time. Instead of a 15° spread on durations, these cams will either be a single pattern camshaft, or a few degrees apart. These will be ground on a 108° LSA to help out with "the sound."

All of these will be custom ordered depending on the vehicle and engine components. The list of specifications needed to determine an optimal cam is very long and it takes a good amount of time to qualify an owner/engine for a new cam purchase. Depending on these specifications, lobes can be chosen from the Magnum series, Xtreme Energy, or XFI series. These are all more aggressive lobes, which help to make more horsepower.

The cam is one of the most important pieces in your engine. It can make or break the driving experience. An engine where each component is methodically chosen based on a specific application/purpose will exceed the owner's expectations in all aspects. An engine where each component is chosen based on unrealistic goals or "wants" could very well disappoint you in maintenance and performance.

My cams are ground by Comp Cams and in most cases can be ground and shipped out within 2-3 days.

[DAVID GAGNARD]

The cam is one of the most important pieces in your engine. It can make or break the driving experience. An engine where each component is methodically chosen based on a specific application/purpose will exceed the owner's expectations in all aspects. An engine where each component is chosen based on unrealistic goals or "wants" could very well disappoint you in maintenance and performance

Totally agree......... a while back I was helping out my neice's husband on his 1988 Bronco with a basically stock 351-W....He had the bright idea to put in the "big mutha" thumpr cam, as he told me, "he likes to "hear" the cam"....well, that lasted less than 100 miles, no low end power, no vacum for his power brakes, and pi$$ poor performance all around.....I finally talked him into a cam that would work for his engine and application and we did the swap. Afterwards, I took the POS thumpr cam and put in on the concrete floor and hit it as hard as I could with a 17 pound sledge, then gave it back to him....he had the WFT look on his face and I told him now NO ONE would ever have those problems again with that camshaft........

David

[blykins]

Too bad it wasn't a billet cam....you could have smacked it against the floor and it would have shattered.