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Cam swap, gas mileage, loppy idle

8K views 19 replies 11 participants last post by  BarnesGN 
#1 ·
I personally don't know what cam profiles achieve what outcome. I don't know how lift vs duration affects various characteristics of the engine. Don't know if what I want would be in a "pre made" cam vs having to get a custom ground cam.

I'd like to keep stock converter until I have to pull the transmission for whatever reason (rear main seal for example)

What is a good cam profile for a G8 GT to keep decent low 20s or 19ish gas mileage wise on the highway, still able to use stock converter, and will give a little bit of a loppy camped idle.
If it will make a difference I also plan on a having a 100-150 wet shot used every once and a while so doesn't need to be optimized for nitrous. Will almost never track the car. Stock heads/intake.

Don't have a G8 yet, just planning for when I do get mine when my current lease is up. This will be a daily driven car so I'm not looking for every possible HP out there at the expense of drivability and fuel economy. Just want a little bit more than a stock LS3 cam swap, and want the loppy idle while still being able to use a stock converter.

Does such a cam exist?
 
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#2 ·
This cam exists alright. It has been custom speced and there are off the shelf cams that fit this description. Easy to come by. Get a little lunati or a Pat G cam. So many of us have been there and done that with what you want to accomplish you will have no worries getting where you want to be.
 
#3 ·
Pretty much all shelf cams for the square port heads will result in 22 to 26 mpg on hwy. Youre going to lose city gas mileage though.

Stock stall id go no bigger than little lunati and even that takes patience tuning it to feel stock. If you want something that truly drives stock then get something with -10 degrees of overlap
 
#4 ·
I'm perfecly OK with losing city mileage... my lead foot does that enough. I do take the occasional road trip though and I usually mind my manners on the highway especially when the wife and kid are in the car. It was highway mileage that I was concerned about.

I'm not against changing the converter, just I'm hoping I won't have to drop the transmission any time soon. I have limited tools so don't know how difficult it would be dropping the tranny on a set of jack stands with nothing but a couple jacks and hand tools. I'd kill for a garage with a 2 post outside lift...

I plan on doing the DOD delete and cam swap myself, that I don't think I'll have any problem with. I've done plenty of head gaskets on DOHC V6 and V8 cars, so doing a pushrod motor should be a cake walk. I've done a few oil pans on LS motors though, and still haven't figured out the "trick" to not get them to leak. Used the feeler gauges when spacing from the bellhousing or whatever part it is and everything but still every one I did ended up leaking :( It's the only part I'm not looking forward to when doing the cam swap. My brothers in law however have alot more experience with LS motors so hopefully they can lend a helping hand.

I guess I need to do some reading on what the aspects of cam timing does.

I'd be fine with an off the shelf cam. I'll look into the little lunati. Since I'm in NC, I'd love to have Rick Crawford tune the car. But that's still a year away. I just like doing my research before hand as much as possible. Keeps me entertained until I get what I want :)

Thanks for the help!

-Jon
 
#5 ·
A good tuner can give you a Loppy idle with some tuning on your otherwise stock engine and be normal at cruising speed, thus allowing you to retain the city and highway gas mileage. Something to consider while you do some research for that right cam and other mods.
 
#6 ·
I am interested in the performance increase more so than the idle characteristics. Didn't mean to make it sound like I was after the show, without the go. If I'm going to delete the DOD (which I will, as I'll be buying a higher mileage G8 unless I find a stellar deal), then I'd like to put a performance cam in it instead of a stock ls3. Sure, I'd love for it to also have that "cammed idle" because it is cool. Not being childish about it, just is awesome. I'd love to wake the motor up at the same time.
 
#7 ·
The gen 4 idle tuning is involved. If you don't have a good tuner, I would be very conservative about what cam you put in. Most tuners increase spark and add some idle air and call it a day which allows it to idle, but will dip, surge and buck.

Absolute biggest I'd do with stock stall is the little lunati. You could also swap in a zl1 converter which will gain you another 500 stall rpm, which could help smooth out bigger cams.
 
#8 · (Edited)
I can chime in on the little lunati will make a pretty big difference with a stock stall.I know as it makes this car really pull & still be a DD.But if this car is driven more than 10,000 miles per year there is another option a cam 219/227 .612/.619 112+0 or 219/223 .612/.615 112+1
 
#9 ·
Just for general info - A loppy idle comes from more overlap between the opening and closing of the intake and exhaust valves when the cam is designed to make high HP numbers. High HP sounds nice except it comes at higher RPMs and at the expense of low end torque. So choose your cam with realistic goals in mind. For instance, installing a loppy high HP cam now without a higher stall and/or rear gears will result in s*&% daily driving.
 
#11 ·
I run a 219/232 on a 112 LSA with a stock converter and it runs awesome and sounds great at idle. No pushing at all, which is mostly in the RCR tune.
 
#12 ·
Thanks for the reply!

Do you have any videos of you car? Thanks
 
#14 ·
You would get some gains, but for the effort, I would just get with RCR for a custom grind for what your goals are and have him work his magic on the tune. You won't regret it.
 
#15 ·
How do I contact Rick?
 
#17 ·
I'm still trying to reach Rick
 
#19 ·
I've sent him five emails since October 4, no response.
 
#20 ·
Try calling Ace performance, Adam works with Rick.Adam can help you out.
 
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