Shift points using a factory short block

[dgoodhue]

I have a late model 4.3 V6 balance shaft motor with factory internals (2 bolt mains & cast pistons.) I have ported Vortec heads and a custom cam. I kind of know that I playing with fire on this build with not a lot of data of other owners pushing this motor. E-Rue is the only other person that I know who’s used a balance shaft motor and actually put some mods behinds it. I will try to track him down and find out more about what he used.

Currently my shift points are 5000rpm 1-2 & 5200rpm 2-3 and I am hitting about 5400rpm at the end of the track. I know the cam/heads that I have could easily spin up to 5800-6000 rpm. I have been thinking about at least upping my governor shift points 200rpm and maybe 400 rpm. The higher rpm shift points should increase my average hp. I saw that Tooky was shifting his stock motor (with vortecs and similar cam) at 5400 rpm (replacement gm motor, I can't remember if his replacement motor had the factory modular caps or not).

I would like to tune my truck to run mid 11's. It seems like the mph I would need is about 118-119mph, so that puts me at 5600 rpm going through the traps. Should I start thinking about shifting into OD the end of the track? I realize that using OD at the end of the track would probably lower my MPH, but it would only have a miniscule effect on ET. Is that harder on my built 4L60?

The more rpm I run, the less boost or timing I will need to run to hit my goal number. What is worse RPM, boost or timing? I am already planning on not running my motor on the ragged edge of timing or AFR, because I know that I don’t a have much of buffer for a tuning mistake.

 

[Sean Krupa]

Re: Shift points using a factory short block

Glad you made this post Dave. I to was wondering about this. I'd like to up the RPMs a tad to benefit from my Custom Cam, but still want it to be safe on stock internals.

I believe that if your still making power in the higher than stock RPMs that we should be fine becaue it's not struggling as much.

Not sure what the best route to go is, more Boost/Timing or RPMs. I'd think a Dyno would be one of the only ways to truely know if your making more Power with more revs. A governor change would also change part throttle shifts no? So for cruising around town might be odd.

I'll be checking back in this thread for sure, Rob and I are almost done Tuning my new setup and curious if its worth pushing more RPMs with my new Steve Morris cam.

 

[JSM]

Re: Shift points using a factory short block

You really need to figure out where you cam/combination is making peak torque. Just moving shift points up isn't always the answer. In fact when we ran the stock motor/turbo 11's, we found lowering them helped (probably due to turbo and cam restrictions).

Once you know where peak torque is, we can make a better judgement. As much as I hate chassis dyno's, you might consider getting a run at one (just be careful) and see where your torque curve lays.

 

[codename Bil Doe]

Re: Shift points using a factory short block

^This.

Same thing you see with LNF's (turbo 4 in Solstice GXP / Sky RL / Cobalt SS). People bump their redline up to 7k rpm. Why? Peak torque on those engines is ~3.1k rpm. The turbo chokes out around 6k rpm.

Bumping up revs just because you can't isn't necessarily a good thing.