hey all I'm a newbie here!

I've been reading a lot of these forums and I have to say the "why LSA doesn't matter" thread is an outstanding resource for someone like me who is trying to better understand the fundamentals of valve events inside an engine.

I'm looking at two factory gm cams here for my 4.8 Lr4 engine and I can't decide which one to throw in there. I do plan at some point in the future to add a smaller turbo but not for a while so I want it to drive nice

I have searched multiple sites trying to find the exact specs on these cams and I'm pretty sure they are as follows,

"1721" LQ9-late LS1 dur@.050 196/207 .46x/.47x 117/115 timing (116 LSA)
or
"0965" 98-00 LS1 dur@.050 198/209 .500/.500 117/122 timing (119.5 LSA)

looking at these two cams the overlap @ .050 is -30 for the first cam and -35 for the second although it would appear the second cam is larger? based on the specs the only real significance appears to be the exhaust centerline.

I would imagine the first cam will have better midrange while the second will have better top end power?

I guess what I'm really asking is how bad is the 98-00 cam in the 4.8?

 

Go with the second cam it will make more power than the first plus if you go with a turbo set up it will work better than the first.

 

Thank you Kip! I'll go with the 98-00 cam then!

 

What are you putting it in? Call kip and have him spec you a cam for your application.

 

It's a 2002 z28 A4 2.73 car. I picked it up for $1000 bucks because the original LS1 had a hole in the block. I was going to use it as a parts car for my "nice" camaro but as I started to take it apart I realized I didn't have the heart to kill it lol. Being it's a little rough from sitting I decided to make a hellcat killing daily out of it. I've already got a low mile LR4 for it and I just wanted to know which of these stock cams I have lying around would work better with a small turbo. I realize a custom grind is what I need but that will probably be one of the last pieces of the puzzle. I need a turbo and plumbing first. Right now I just want to drive the car with the 4.8 swapped in... yes I know, I have HP tuners

 

I want to confess that I actually put the 1721 cam in my LR4 Camaro a few months before I started this thread and I've been thinking about valve events ever since... I've had it up to 7000rpm a few times and I really like how it growls up there.

I based this decision off the hot rod ls cam test article where they tested a bunch of factory cams on a 5.3L

since then I have been staring at the 98-00 cam on my shelf. I've been reading up in my spare time and I believe that I listed the specs for the early Ls1 cam incorrectly before. After some digging I think that I had the timing of the centerlines backwards but its difficult to find good info on the stock cam specs. As far as I can tell the 98-00 cam installed dot to dot is on at 122 centerline and the LQ9 cam would be at a 117 intake centerline. I had previously posted both cams as being ground on a 117 intake centerline. calculating the valve events for a 122icl I found that the 98-00 cam closes the intake valve six degrees later than the LQ9 cam! so that's it then. the real major differences between these two cams is the later intake valve closing and then that added lift.

I was trying to calculate the difference in dynamic compression between these two cams in the 4.8 but I'm not confident with my math as I can't find the #'s at 0.004-0.006 anywhere.

The car is a whole lot of fun to drive right now but for some reason I keep thinking I should put the other cam in there. I know there are better cams out there, even "perfect" custom ones but that's not what this car is about right now.

 

If you refer back to the Hot Rod article, the reason the LQ9 or late LS1 cam worked the best in a factory 9.5:1 five point three liter is it maintained the closest to stock cranking compression while adding @ .050" duration. Therefore it gave up nothing below 2500 rpms and only continued to gain as rpms increased. IIWY; I'd pop some blue LS3 springs in there and continue to relentlessly buzz that 3.268" arm to 7 grand !!!!!

 

I've already got a set of blue springs in there! I really like this little engine. This car is an absolute blast to drive!