Thread: Whats The Total Camshaft Lift You Can Run?'s

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Originally posted by Streets
You kin get that "Lopey" feelin' by leavin a plug wire off too... hahahaha

OMG!




Streets open your PMs for a bit and I'll give you my new Addy.

Gyva, I hate to stick my nose into this conversation at this late in the game but.....you asked about how much lift to get a lope in your idle. This question in... in and of itself.... screams that you dont know much about engine theory, or you that as well as your young and going for the sound to impress your lady friends. Now, time for a bit of schooling.

A lope in your idle is a product of a larger valve overlap. Overlap is the time that the intake and exhaust valve are open at the same time. At lower RPMs this causes severe contamination of the intake charge because of ex gas reversion, but the magic comes to play at higher speed. Just like water, or a train, or a car... air has momentum. It has mass, therefor it can gain energy from moving mass at speed. This fact is what allows 2 magical things to happen in a RACE engine. (Not a low compression street engine) It allows the ex gasses to run out the port leaving behind it a negative pressure pulse to actually suck the intake charge into the cylinder and a bit of it out the ex port. THis creates a very clean and full charge of intake gasses. The second part of the magic is the fact that because of the velocity in the port during this fantastic rush into the negative charged chamber, when the ex valve does close and the intake valve is still open a while, you get a wonderfull ram effect where you actually overfill the clylinder with oxygen and gasoline! If the RPM's are high enough and the cam overlap and valve timing is just right this can make magic! THink NHRA Pro-Stock drag racing.

THere are many steps in camshaft lift/duration/overlap between what the factory put in and what a Pro-Stock engine uses, but the fact is that if all else remains the same and you start swapping camshafts up that ladder of cams you will notice that the further from the stock type cam you got the worse things are getting. You may improve over the factory cam for a few cam steps, but these will be mild cams that maximize cylinder pressures and are designed for lower RPM use. Until your running a combination that requires a lope in the idle (Pain in the asz) run a cam that makes the most power in the range your most going to put the power to use. Usually in the range of 1000 to 4000 RPM for a street use engine.

I run a engine with a lope in the idle, its a BBF. Its a stroker race only engine with 14:1 compression, my heads flow nearly 480cfm on the intake and 345cfm on the ex. I run all titanium valve train and jesel shaft rocker system with a solid roller that has 0.920" lift and 328 duration at 0.050" It has a lobe sep of 112. It also has spring pressures of 370 lbs on the seat and 1170 lbs open. I carry extra springs with me at $90 each to swap in. Each time I use the engine I test the seat pressure of the springs and replace any that are low, I yank the dizzy and pre-lube the engine, put dizzy back in, bolt the Jesel's back on, replace the valve covers and start the beast. My fuel is almost $9 a gallon, I change the Royal Purple synthetic oil each run, or every 30-45 seconds of use. It lopes, and its a beast to get this thing moving in a polite way. Its a light switch engine, ease into the throttle to get it moving and it will suddenly find its burn and take off. Its in a pulling truck, so once I am chained down thats fine, moving in the pits has become such a chore I now use a 4x4 atv to pull it around. My idle is set as low as I can go and keep it running, this is about 1450 RPM. Why, Overlap and lobe sep angle.

I would ask that you read some of the "Tech files" on my site, it will help you talk smarter and make better decisions later.

http://www.truckpulls.com/Tech%20Fil...%20Effects.htm

http://www.truckpulls.com/Tech%20Fil...erformance.htm

http://www.truckpulls.com/Tech%20Fil...ain%20Tech.htm

That should teach you more than you ever planned on knowing about camshafts.

I hope I did not come off as ignorant, I meant to be helpfull and detailed in explaining things. Good luck man!

Thanks a lot larry I'm glad you took the time to teach me. I did believe this was the place to come for that. I guess if you had a forum called "you can only post in here if you know what your talking about ONLY!" it would be a pretty boreing forum since you'd only be talkin to yourself. Thanks again for the help I'll read your links.



Till then ridein with one plug wire pulled.....


Mike....

I still read it trice but I get it .............

thank U .....