Originally Posted By: OVERKILL
Originally Posted By: BlueOvalFitter
Originally Posted By: OVERKILL
Actually, the good blower cams have little to no overlap and don't sound very nasty at all.
Honestly, I don't know how to approach that reply. Can you elaborate just bit more on that?
I do know that the camshaft is the heartbeat of an engine. When I was building engines and racing I would put a lot of thought into my camshaft selection. (Lift/Duration-Solid/Hydraulic)
When you are running an engine with a blower, you don't want the boost going out the exhaust valve, which happens when you have overlap (both valves open at the same time).
This means that LSA (lobe separation angle) is an important item, because the wider the LSA, the more duration that can be run whilst minimizing overlap.
A narrow LSA, lots of duration and subsequently, overlap, is what gives engines that "nasty" sound. The intake and exhaust valves are open at the same time, so some of the intake charge ends up being drawn in while the exhaust charge is still exiting the chamber. You lose a bit of compression, and get that nasty snappy lope. This promotes scavenging at higher RPM's (the exhaust charge exiting literally draws the intake charge into the chamber) and results in more power.
However, on a boosted engine, there's no benefit to the overlap. The intake charge is already pressurized. So a wide LSA, lots of duration and lift (within reason of course) to maximize cylinder fill, and you end up with an engine that certainly sounds aggressive, but likely milder than you'd expect it to.
There are a bunch of guys that leave the stock HO cam in their 5.0L's for the true "sleeper" approach. They do heads and intake, put on a blower, and leave the stock cam in (though they often use 1.7 ratio rockers for more lift). The engine sounds almost stock, but can make close to 500RWHP
The TFS #1 (which is a cam I ran) is a popular choice for an "off the shelf" camshaft for the 302 Windsor:
http://www.trickflow.com/partdetail.asp?part=TFS-51403001&autoview=sku
221/225 duration, .499/.510 lift (I ran it with 1.7's, so my lift was .530/.542) and has IIRC, -2 degrees of overlap on a 112LSA (it has been a few years since I did the math, so that figure might be off).
My custom replacement was ~230/240 .549/.552 on a 113.8LSA and had negative overlap as well, as I had mentioned to the grinder that I may be putting an S-trim on the car.
Um, yeah.......that was it to a tee!
I respect your knowledge very much. I bet you have built some very "mean" engines, huh?
I can't say that my knowledge compared to yours in that vast. I learned all my building techniques from watching my dad, friends, and OTJT. (Hands On)
But, I can say I have built some "nice" engines that I am proud of.
Originally Posted By: BlueOvalFitter
Originally Posted By: OVERKILL
Actually, the good blower cams have little to no overlap and don't sound very nasty at all.
Honestly, I don't know how to approach that reply. Can you elaborate just bit more on that?
I do know that the camshaft is the heartbeat of an engine. When I was building engines and racing I would put a lot of thought into my camshaft selection. (Lift/Duration-Solid/Hydraulic)
When you are running an engine with a blower, you don't want the boost going out the exhaust valve, which happens when you have overlap (both valves open at the same time).
This means that LSA (lobe separation angle) is an important item, because the wider the LSA, the more duration that can be run whilst minimizing overlap.
A narrow LSA, lots of duration and subsequently, overlap, is what gives engines that "nasty" sound. The intake and exhaust valves are open at the same time, so some of the intake charge ends up being drawn in while the exhaust charge is still exiting the chamber. You lose a bit of compression, and get that nasty snappy lope. This promotes scavenging at higher RPM's (the exhaust charge exiting literally draws the intake charge into the chamber) and results in more power.
However, on a boosted engine, there's no benefit to the overlap. The intake charge is already pressurized. So a wide LSA, lots of duration and lift (within reason of course) to maximize cylinder fill, and you end up with an engine that certainly sounds aggressive, but likely milder than you'd expect it to.
There are a bunch of guys that leave the stock HO cam in their 5.0L's for the true "sleeper" approach. They do heads and intake, put on a blower, and leave the stock cam in (though they often use 1.7 ratio rockers for more lift). The engine sounds almost stock, but can make close to 500RWHP
The TFS #1 (which is a cam I ran) is a popular choice for an "off the shelf" camshaft for the 302 Windsor:
http://www.trickflow.com/partdetail.asp?part=TFS-51403001&autoview=sku
221/225 duration, .499/.510 lift (I ran it with 1.7's, so my lift was .530/.542) and has IIRC, -2 degrees of overlap on a 112LSA (it has been a few years since I did the math, so that figure might be off).
My custom replacement was ~230/240 .549/.552 on a 113.8LSA and had negative overlap as well, as I had mentioned to the grinder that I may be putting an S-trim on the car.
Um, yeah.......that was it to a tee!
I respect your knowledge very much. I bet you have built some very "mean" engines, huh?
I can't say that my knowledge compared to yours in that vast. I learned all my building techniques from watching my dad, friends, and OTJT. (Hands On)
But, I can say I have built some "nice" engines that I am proud of.
