Well, first, as lsa is decreased, the lumpier the idle. 117lsa= stock like idle, 110 lsa, very choppy idle. What other considerations come into play? 3 cams to examine:
230/224 .575/.563 111 Thunder Racing Cam

242/248 - .608/.612 - 110 lsa T-Rex

226/236 .525/.525 110 lsa GMPP ASA cam

Would all of these have a very similar idle, or is one more noticebaly extreme than the other? Does larger intake and exhaust duration differences have anything to do with lope? From what I heard in person, and the big lift and i/e duration, it would seem the TRex would have the lumpiest idle. Or, the ASA has the same lsa, but a larger difference in duration. Or even the TR cam, where intake duration is greater than exhaust.
Or are they just the same, or barely noticeable from each other? I hope someone is able to clear this up.

 

Your roughest idle will be that t rex cam. Exhaust and durations have a big deal of it. The higher the duration, the lumper the idle

 

The amount of overlap is what causes your "rough idle". You can figure this with this equation: Intake duration + Exaust duration, divided by 4, - LSA, x 2. The more overlap, the rougher the idle. For the cams listed you have 5 degrees for the 230/224, 25 for the T-rex, and 11 for the ASA.

 

Overlap is what causes lopey idle, NOT lsa. Lsa is only a FACTOR in CALCULATING overlap.

 

good info

 

Will my TR224/224 .562 112LSA be lopey at all? I'm hoping it won't sound near stock. I was hoping for some good lope, but now after reading this, I don't know.

 

a 224 doesnt sound stock at all ...

 

After reading this, you should be convinced that until you calculate overlap, you won't know if your cam will lope or not. The TR224 on 112 is known to lope. There's a vid of it loping in the dyno section.

 

i have 15.3* overlap @ .050 and 78* @.004

 

Here check this out same cam you mentioned.


http://www.mainstreamtopics.com/memb...paolinows6.mov

 

I have a TR220 on a 112 and it lopes pretty nice ... just enough to make it sound good when I'm sitting at a red light. I didn't want a lot of lope, but, just enough to fit what I wanted. This said, I would imagine a TR224 on a 114 would lope less or about the same. I can't speak to this subject like some of these other guys ... just my $.02 worth from what I already have.

 

Overlap causes misfires at idle and that makes the lope or choppy idle. It causes a lot of intake reversion which causes the engine to basically choke on it's own exhaust during idle. The more the overlap the more the lope will be.

 

Sounds good to me! You guys have great information!!

 

Mine has 24.

 

mines at 9 degrees overlap. i did a tr224 on a 114 and ended up with less than zero. is that right?

 

Yes, -4 to be exact. Hence the reason it passes emmisions....

 

Great info, that formula was just what I was looking for. At the top, overlap rates of the 3 cams were 25, 11, and 5. How discerning to the ears are they? I mean, if you lined all three up in 3 different cars, would there really be THAT much difference?
And where can you get a freakin' cam that has less than 600 lift that can "whump whump" like a larger cam. I don't know how some of you can run these gigantic cams, especially in an auto. I knew I should've gotten a 6 speed! damn! I just went to an fbody meet, and there were some sweet sounding rides. The Trex was music to my ears!

 

J-Rods "Cam Discussion Part II" thread has a link to his "Quick and Dirty Valve Events" xls. It's great for quick checks on overlap, IV opening, IV closing etc.

 

damn this is helpful.. a f13 on a 112lsa only has 7 overlap...
the rest of futral are as follows below
f9-only has 6
f11- 5 on a 112lsa

damn no wonder there cams really dont lope..
tsp
tq'er - 9
233/239- 12

so how are these cams so low but they all have very choppy idles? i think if the cam is a split it also helps it lope, for example.. ive heard hotcams that sound better then f11's..

 

i like my lil cam, it has some overlap
243/249 on a 109lsa