What is it that gives the cam/motor more lump at idle I want my motor to sit and thump, my 360 has been rebuilt but we used a slightly above stock cam the block is a 1976 truck block I'm looking at a edy cam that's got a duration of 305
A little help on cams
- Thread starter mopardrt
- Start date
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nqkjw
Well-Known Member
It's the amount of overlap that gives it the lumpy sound.
Compression gives that solid thump out the exhaust.
305 duration is a bloody big cam and should give a sizeable thump.
Probably run like a pig unless you plan on $$$$ to buy the other parts necessary to make it work well.
However,if it's only the lumpy sound you're chasing and not the go then fine.
Comp makes a series of cams called "Thumpers" which are designed for maximum sound image and I've been told they work OK too.
Compression gives that solid thump out the exhaust.
305 duration is a bloody big cam and should give a sizeable thump.
Probably run like a pig unless you plan on $$$$ to buy the other parts necessary to make it work well.
However,if it's only the lumpy sound you're chasing and not the go then fine.
Comp makes a series of cams called "Thumpers" which are designed for maximum sound image and I've been told they work OK too.
Another member posted some info about the Thumper cams designed for just that.
You might find it with search ( good luck ) . If I remeber correctly, that grind delays opening the exhaust valve. Naturally it would have to open and close the valve faster.
You trade away some performance and fuel milage for the thump.
A radical cam that produces a lumpy and rough idle will not be as street friendly for around town driving and also reduce vacuum which effects power brakes. All of this stems from what I've read and not my personal experience.
You might find it with search ( good luck ) . If I remeber correctly, that grind delays opening the exhaust valve. Naturally it would have to open and close the valve faster.
You trade away some performance and fuel milage for the thump.
A radical cam that produces a lumpy and rough idle will not be as street friendly for around town driving and also reduce vacuum which effects power brakes. All of this stems from what I've read and not my personal experience.
You can easily get that cool sound without sacrificing power with careful camshaft selection. Overlap is a factor, but not the only thing. Overlap, duration at .050, the split between the intake and exhaust duration and lobe separation all play a role in how the camshaft sounds. Not to mention the engine's stroke and cubic inch displacement. Designs like the Comp Thumpr or Hughes Whiplash cams would be a good place to start.
afbill
FABO World Ambassador
A guy I work with runs a Hughs Whiplash and it sounds good. As a matter of fact I think they use his car for their on-line demo. It's a forest green '69 'cuda.
ir3333
Well-Known Member
.. long overlap cams give poor cylinder filling and burning at idle and low rpm and that is why they are usually lazy until the rpm is higher.
raw gas is actually burning/popping in your exhaust manifolds and pipes
the unburnt gas at lo rpm is also going to wash your cylinder walls and give poor mileage.
they are for racing...
all info i have read or been told, i have no first hand expertise.
raw gas is actually burning/popping in your exhaust manifolds and pipes
the unburnt gas at lo rpm is also going to wash your cylinder walls and give poor mileage.
they are for racing...
all info i have read or been told, i have no first hand expertise.
moper
Well-Known Member
While that can all be true, they have done some tweaking just like Storker metioned. The two lines mentioned are designed to be noisey and minimize the "downsides". IMO, still a foolish reason to buy a cam but there's a lot of people that just want the sound so those cam profiles were designed to make them happy.
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