What makes an agressive cam "not streetable"?
07-18-2006, 07:27 AM
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What makes an agressive cam "not streetable"? I know everyones opinion of "streetable" is different - but what are some of the main factors that cause aggressive cams to give non streetable charateristics? I know tuning is a huge factor when running a large cam but I want to know what "most" people mean when they say that a cam is not very streetable.
For instance - I'm about to install a TR 231/234 .640/.590 112 LSA cam in my Z28. What kind of issues (if any) will I see if I drive it every day...
Thanks!
David
For instance - I'm about to install a TR 231/234 .640/.590 112 LSA cam in my Z28. What kind of issues (if any) will I see if I drive it every day...
Thanks!
David
07-18-2006, 08:53 AM
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Big cams make great numbers at high-rpm, but a the expense of torque and stability in the lower rpm's. That's great for the track where you never go below 4000rpm. But 99% of your daily driving occur between idle and 2500rpm.
With too much overlap at low rpm, you're bleeding a big part of your intake charge directly into the exhaust. And if your other mods are complementing the big cam (big headers, exhaust, etc...) you also loose gazes velocity, you got reversion, etc...
All of this mean a very choppy idle (some like it, some don't), surging problems, stalling issues, instable idle while running A/C, and less torque in the low rpm's. Big cammed cars can be a nightmare in a traffic jam.
Big cams also means high lift and (generally) more aggressive ramp rates. Now that does not really decrease street manners, but it means that you have to check and change your valvesprings more often.
I have a 224/224 .560/.560 112+4 in my Hawk and I really like it! No surging, no stalling, plenty of torque in the low an midrange rpm's, but the torque curve really start to drop quickly past 5500rpm. Since it's a daily driver that see the track 1 or 2 times a year only, I have no problem with that (best time so far 12.65@116, 1.905 60ft). On the other hand, one of my friend got a 238/242 .62x/.62x and he's running in the 11's at 121mph, but, to quote himself, "...forget it below 1800rpm!".
By today's standards, your 231/234 is not really considered a "big" cam. You should be ok with a good tuning. Just be sure to have good dual-valvesprings to handle the lift and check them every 10000 miles.
With too much overlap at low rpm, you're bleeding a big part of your intake charge directly into the exhaust. And if your other mods are complementing the big cam (big headers, exhaust, etc...) you also loose gazes velocity, you got reversion, etc...
All of this mean a very choppy idle (some like it, some don't), surging problems, stalling issues, instable idle while running A/C, and less torque in the low rpm's. Big cammed cars can be a nightmare in a traffic jam.
Big cams also means high lift and (generally) more aggressive ramp rates. Now that does not really decrease street manners, but it means that you have to check and change your valvesprings more often.
I have a 224/224 .560/.560 112+4 in my Hawk and I really like it! No surging, no stalling, plenty of torque in the low an midrange rpm's, but the torque curve really start to drop quickly past 5500rpm. Since it's a daily driver that see the track 1 or 2 times a year only, I have no problem with that (best time so far 12.65@116, 1.905 60ft). On the other hand, one of my friend got a 238/242 .62x/.62x and he's running in the 11's at 121mph, but, to quote himself, "...forget it below 1800rpm!".
By today's standards, your 231/234 is not really considered a "big" cam. You should be ok with a good tuning. Just be sure to have good dual-valvesprings to handle the lift and check them every 10000 miles.
