[john5670]

I think a lot of people love the sound of a nasty, rough idle cam. But what causes this? In most cases your air and fuel are not properly mixing. This is fine and expected if you have a drag car that creates its power at high RPMs. I think its important to find that balance though for a street car. A rough idle creates cylinder wash at low RPMs until the motor start reaching the proper mixture. Cylinder wash will cause premature engine ware and poor street ability. My 2 cents is find the right balance between sound, power, and longevity.

[performerrpm]

Originally Posted by john5670

I think a lot of people love the sound of a nasty, rough idle cam. But what causes this? In most cases your air and fuel are not properly mixing. This is fine and expected if you have a drag car that creates its power at high RPMs. I think its important to find that balance though for a street car. A rough idle creates cylinder wash at low RPMs until the motor start reaching the proper mixture. Cylinder wash will cause premature engine ware and poor street ability. My 2 cents is find the right balance between sound, power, and longevity.

i dont think thats altogether right??? sure that causes a nasty idle so does unplugging a vacuum line, i think those cause the other nasty idle. theres plenty of cammed street cars running around without that problem, i think it really depends on how obnoxious a cam you cal tolerate on the street

[john5670]

Originally Posted by performerrpm

i dont think thats altogether right??? sure that causes a nasty idle so does unplugging a vacuum line, i think those cause the other nasty idle. theres plenty of cammed street cars running around without that problem, i think it really depends on how obnoxious a cam you cal tolerate on the street

A properly tuned engine that has a rough idle does not have the correct fuel and air mixture at low RPMs. The rough idle is cause by poor burning of the air fuel mixture. If you cause your car to run rough to look like you have a lot of horse power, your foolish. Your giving up what your trying to advertise. Yes there are plenty of large cam street cars running around, but if they are not properly tuned to have the correct air/fuel mixture for the used power range, its only a matter of time before they need to be rebuilt. It may be 2,000, 10,000 or 50,000 miles. It won't be the optimal engine life though. Ask a reputable engine builder. I would be surprised if he recommends a poor tuned engine for a cool sound.

[performerrpm]

Originally Posted by john5670

A properly tuned engine that has a rough idle does not have the correct fuel and air mixture at low RPMs. The rough idle is cause by poor burning of the air fuel mixture. If you cause your car to run rough to look like you have a lot of horse power, your foolish. Your giving up what your trying to advertise. Yes there are plenty of large cam street cars running around, but if they are not properly tuned to have the correct air/fuel mixture for the used power range, its only a matter of time before they need to be rebuilt. It may be 2,000, 10,000 or 50,000 miles. It won't be the optimal engine life though. Ask a reputable engine builder. I would be surprised if he recommends a poor tuned engine for a cool sound.

im no professional but, theres alot more to the rough idle than just bad a/f ratio. sure if i take a stock 400 with stock cam and fatten up the tune for a nastier sounding idle it would be foolish, but if i take that same 400 put a lil bigger lopier cam in, after fine tuning it is still gonna have a rough idle and it wont having anything to do with air mixture it will be more due to the reversion caused by the bigger cams duration and overlap. as long as you use the right gears and converter the only real sacrafice poor life expectancy of tires poor gas mileage, and some times it could get to be a pain to drive if you were gonna try and drive it all the time. the only thing that i really see being a factor of how long will the motor last is, most people with these types of motors dont just wussy foot around in them, they run the piss out of them

[john5670]

Originally Posted by performerrpm

im no professional but, theres alot more to the rough idle than just bad a/f ratio. sure if i take a stock 400 with stock cam and fatten up the tune for a nastier sounding idle it would be foolish, but if i take that same 400 put a lil bigger lopier cam in, after fine tuning it is still gonna have a rough idle and it wont having anything to do with air mixture it will be more due to the reversion caused by the bigger cams duration and overlap. as long as you use the right gears and converter the only real sacrafice poor life expectancy of tires poor gas mileage, and some times it could get to be a pain to drive if you were gonna try and drive it all the time. the only thing that i really see being a factor of how long will the motor last is, most people with these types of motors dont just wussy foot around in them, they run the piss out of them

Like I said, it needs to be properly tuned to have the correct air/fuel ratio. I am not saying all large cams are bad. I have a 462 stroker with 585 hp at 6000 RPMs. It has a very large cam for a street car. I am only suggesting to the member that he does not sacrifice longevity for a cool sound. As long as he can maintain the correct air/fuel ratio for the RPM range that is used the most he is good to go. As far has him dirving the piss out of the car. That is hard to do when you are cruising the highway at 75 mph. A lot of damage can be done even at cruising speeds if you do not tune the engine correctly. Although there are many contributers to a rough idle, a poor tune should never be one of them. Why put thousands into a motor for poor performance.

[ta man]

When guys say they have a large or big cam they always refer to duration it seems.My car has large lift for a street cam in the .650's but smaller duration compared to many at around a 230/240 @.050.I wouldn't say it has a nasty idle as in rough but it sure trumpets out the back especially if its idling in park.

[SPEEDZONE]

An Idle more than this? Its not a Pontiac, but its my 74 Pantera....... Check Vids

http://www.youtube.com/watch?v=eNn1u9EDLEI

http://www.youtube.com/watch?v=9ECF59WNZqA