ScaryFast

Where do you guys set your rev limit on stock LS6 motor and heads?

My understanding is that keeping it below 7000 RPM is fine, so I set mine to 6800.

However, I've recently heard that with stock 243 valvetrain that's asking for trouble. Those of you that have track experience and not internet experience please confirm which is correct...

The motor is a stock 2005 LS6 out of a CTS-V. About 25k miles.

Cobra4B

It depends on the components you're using. Lots of guys bump the rev limiter to 7000 on stock motors and use the extra RPM as needed. Personally, I left mine at 6600 for longevity, but I have been on track with Sperkins/Drivinhard/Jason/etc. where the extra RPM comes in handy in a few places.

The main issue is the timing chain. If I were going to spin the extra RPM I'd want a better chain and the OEM chain damper. I put a LS2 chain on my engine which is much beefier than the old LS6 chain. You can't even buy the old LS1/6 chain as the LS2+ chain has superseded it. My block wasn't drilled for the chain damper so I didn't bother, but yours probably is. You can't buy the LS1/6 damper new from GM anymore, but there are places on Ebay that sell the LS2+ damper with new holes drilled to accommodate the LS1/6 bolt spacing (for some reason the LS2 block got narrower bolt holes for this).

AU N EGL

You should be OK, but may experience some valve float above 6500 with stock springs

RX-Ben

Realize that there are bad lower end harmonics starting at 6900.

A spring and pushrod upgrade is cheap insurance.

CHJ In Virginia

Others may disagree, but I limit my max RPM to 6250. HP and Torque start to fall off quickly after 6000 on a stock LS6. So why push it any higher ? The motor will last longer too !

redtopz

Many T1 guys are reving over 7000 and getting pretty good engine life. It comes in handy not having to shift/downshift in some areas especially in 3rd gear with the mn12 tranny. That said, I set my rev limiter to 6900 and change valve springs annually assuming my engine lasts that long.

AU N EGL

7000 with regular spring changes should not be an issue

redtopz

Most dyno curves I've seen show hp remaining pretty flat up to 6800 rpm or so. At least with longtube headers.

GettReal

Get a dyno done and you'll know exactly where to set your limiter and also where to shift. For me basically trq and hp start to drop off around 5900-6100 so I pretty much shift at 6000, that way I fall back into peak try and hp of the next gear. There is no point going to 7000 just to get "extra revs" you'll be harder on your drivetrain for no reason..

my 2 cents.

Jaymz

I rev mine 7250 all the time.. just make sure you replace the valve springs and timing chain yearly or so.

My old original motor had 25,000 miles on it. 5,000 miles of 7250 RPM shifts.

Cobra4B

Do you have a LS1 or LS6? If you've got an LS6 then you're leaving a bunch of speed on the table. Also, there are instanced where being able to keep it in a lower gear i.e. at the end of a straight pay off vs. having to shift to 5th. This can also apply to other situations on track where you can be faster by not having to shift or getting into the limiter.

sothpaw2

Are you shifting to 5th at Summit on the Main straight and at VIR on the back?

I've noticed this year as my corner exit speeds are better that I'm up on the stock rev limit in 4th as I approach these braking zones. I don't like spending even a second up there(6500) but otherwise I have to add a shift to 5th just prior to the braking zone only to downshift to 3rd at the end of the braking zone.

Curious what folks w/stock gearing do about this.

spazegun2213

Wally and I raised it to 7k for years, and never had a problem. I'm keeping mine there

moespeeds

Damn I've been short shifting mine at 5k, but my motor has 112k on it and I want it to last. As I get faster I'm starting to see how it hampers me though, especially places where I gotta upshift right before a corner.

ScaryFast

I should have been more clear, I do have the ATI damper and LS2 chain (the 2005 LS6's had the better chain from the LS2 already).

So, specifically, valve float was my concern. I'm fine changing springs once a year, I just don't want to lose a motor. right out of the gate. That's been happening to me too often lately.

So the consencus is that 6800 will be fine if I maintain my equipment...

Thanks for the responses.

brkntrxn

I have my limiter set to 6850 for four reasons:

- stay in 3rd coming into T4 at CMP
- stay in 3rd coming into T14 at CMP
- stay in 4th on the back straight of VIR
-stay in 4th on the back straight of Charlotte

If there is no pressure or no time to be had, I shift at 6k and use 5th if needed. But the extra couple hundred rpm make a difference when you need it.

rasrboy

I ran my old T1 LS6 at 6800 for longevity since my wallet was pretty
thin. I May have not been Mario Andretti out there, but I sure had fun and loaded the car up with no engine problems.

James and others are right though, in this sport no matter what your
spinning it to, you should all replace springs yearly. There cheap!

Aaron

96CollectorSport

Short shifting is definatly the way to more longevity on any motor and I will never argue about that. However if you say shift at 6300 because your hp and tq are falling off then you may want to learn a little about torque multiplication. Through the gear ratios in the transmission and differential you will actually make more power to the ground staying in the lower gear and reving the snot out of it. Here is a graph I made off of a dyno off a stock LS6 with intake and headers.

Torque Multiplication / Shift Points

RPM Torque/HP 2.97 2.07 1.43 1.00 .84
2500 320 150 3249 2264 1563 1094 920
3000 325 180 3300 2302 1590 1112 934
3500 340 220 3454 2408 1662 1163 978
4000 360 275 3656 2548 1761 1231 1033
4500 370 320 3762 2620 1813 1265 1064
5000 380 360 3861 2692 1857 1300 1091
5500 360 380 3659 2548 1761 1231 1033
6000 340 385 3454 2408 1662 1163 975
6500 310 385 3150 2196 1515 1060 889
7000 280 380 2845 1984 1368 958 804

RPM Drop Shift Point
1-2 2200 7000
2-3 2100 7000
3-4 2100 7000
4-5 1100 6000

As you can see with my little chart above you are actually better off - torque wise - to leave it in the lower gear even longer than 7000 - probably more like 7200 or 7400 to get the best torque availible.

Jaymz is pretty fast and does it so does Buttermore, again for longevity short shift is best, but you are leaving something on the table if you are short shifting at 6000 rpm.

wtb-z

You don't necessarily need to run the torque numbers - if you just look at flywheel horsepower before and after the shift you will reach the same decision points regarding shifting. Which shouldn't be that surprising - car accelerates the fastest when the motor is making best possible power.

The LS6 is a pretty peaky motor, gotta keep those RPMs up.

GettReal

I have a 383 stroker in mine now and my LS6 heads just got swapped out for my AFR's so I couldn't be specific on what rpm to run it up to, but my suggestion was to let a dyno help you understand where you a good shift point is..

I agree with you though that depending on the section of a particular track it makes sense to extend the rpm range a little to save from needing to do a non useful shift.