I'm swapping my LSJ to the L61 thermostat setup and ditching the external oil cooler.

another issue I resolved today was the clutch actuator. turns out the backside of the actuator assembly is a seal for the input shaft's bearing. no way to put a spacer there unless you machine a perfect mate for the seal on the back.. in the end not worth it.

so the plan is LSJ + L61 coolant pipe/t-housing and the F23 trans with the F23 jbody clutch actuator. no spacer required.

 

Okay, let me know how it all goes. I still really want to do this, but at this point, I'm starting to get a little discouraged. But it sounds like you still have everything under control. So keep us(me especially) posted.

I will probably be the first cobalt ss to actually perform the swap. I won't be doing it until I return from my deployment though.

 

ummmm.......

take another look at the gear ratios in the original post. the difference between 1st and 2nd is less with the F23, but other than that, the F35 gears are closer together.
if you go with the F23, your 2-3, 3-4, and 4-5 shifts will put you at lower revs--further out of the power band-- after shifting than with the stock F35.

 

the 1-2 is the biggest improvement by swapping to the f23. The 2-3 is the same drop in both trans and the 3-4 is like 200rpms lower drop in the f23.

The biggest advantage is how fast you will move through the gears. since the f35 gears are so long, the boost takes longer to build and so the acceleration in gear is a tad slower. While with the f23, the gears are shorter so the boost builds quicker and the acceleration is a tad quicker.


DaFlyinSwirl: any new updates?

 

Sounds like you need to change out your pulley if you wanna build boost quicker, changing to an F23 is SOOO not worth it for an SS/SC, if you want a little lower gear ratios just change your final drive over to the 4.15(or other ratio) that road race guys use.

F23 with 235/45-17(closest tire I had specs for) and 7000rpm gear change:

Top Speed in 1 gear = 36.259 MPH
And changes into 2 gear at 3950 RPM dropping 3050 RPM
Top Speed in 2 gear = 64.261 MPH
And changes into 3 gear at 4678 RPM dropping 2322 RPM
Top Speed in 3 gear = 96.154 MPH
And changes into 4 gear at 5081 RPM dropping 1919 RPM
Top Speed in 4 gear = 132.457 MPH
And changes into 5 gear at 4929 RPM dropping 2071 RPM
Top Speed in 5 gear = 188.127 MPH


F35 with same:

Top Speed in 1 gear = 37.362 MPH
And changes into 2 gear at 3645 RPM dropping 3355 RPM
Top Speed in 2 gear = 71.751 MPH
And changes into 3 gear at 4693 RPM dropping 2307 RPM
Top Speed in 3 gear = 107.019 MPH
And changes into 4 gear at 5280 RPM dropping 1720 RPM
Top Speed in 4 gear = 141.890 MPH
And changes into 5 gear at 5584 RPM dropping 1416 RPM
Top Speed in 5 gear = 177.862 MPH

Not even discusing the fitment or durability issues, or the previously mentioned fact that the F23 is a 3axis trans and the F35 is a 2axis(2 shaft versus 3 shaft intenral layout, more power robbing pieces, AND they are smaller), This should make it clear that the the F23 has no real advantage in a drag race, first of all: youre only losing 305rpm on the 1-2 shift on the F35 compared to the F23. {does this even drop you out of your power band significantly? where does your engine make peak torque?? what the curve look like?} Not what I(or most amateurs) would consider a huge difference, or worth taking on such a massive and potentially fruitless endeavour. Second you can see that you actually lose MORE revs with the F23 on all subsequent shifts, therefore according to your argument taking you out of boost in the most crucial area of the race where you would actually be able to put down the power. Lastly and easiest to see, is that an F23 will REQUIRE A SHIFT TO FOURTH, whereas the F35 would not. A shift is an extra action, its an interruption in power flow, its lost time no matter how you slice it.

 

maven makes some good points. anyway, here's an update on my project:



charge pipe mock-up:


I expect to have the engine running in about a month or so... finally going to find out if the F23 works with the LSJ bottom end.

If it doesn't.. I may be looking into swap an F35 into my car instead.

 

Damn man looks good,i was following your n/a build when i was a member on jbody.org

 

yea n/a no more. this engine is getting tested and the spectre is going through its paces without the turbo bolted on, but once that initial phase is over, I'm bolting on a turbo with a vulcan manifold and external gate. the goal is 450whp on the stock engine.

but diamonds, a ported head, and a cam upgrade may be in store as well. still undecided.

the car has a 12 gallon fuel cell w/2in" drop sump mounted where the spare tire well used to be, and an aeromotive A1000 fuel pump, 750cc injectors

 

damn, sounds bad ass. I still think the f23 is better geared. That 1-2 shift being the biggest improvement. The f35 1-2 shift just falls flat on it's face.

 

it appears to me that the f23 only has the advantage in the 1-2 shift...but otherwise the f35 is superior. and I'm sure having to shift into 4th as mentioned should be a big downfall given your track goals...

I would love to be able to make a pass in 3rd gear...i have to shift to 4th and i only trap 96ish mph

on topic though skwirl you're shooting for 450whp on stock bottom end? what exactly do you mean by that?

 

pistons, rods, crank are stock

balance shafts are removed but I've seen at least one other turbo LSJ making 415whp

no reason I can't duplicate it at the least.

 

oh nevermind, for some reason I was thinking l61 bottom end

 

So what r the gear ratios for a lsj with a redline of 7k?

 

LSJ F35 MU3 Gear ratios:

First : 3.38 - 39Mph @ 7000 RPM (with stock tire size)
Second: 1.76 - 75Mph @ 7000 RPM (with stock tire size)
Third : 1.18 - 112Mph @ 7000 RPM (with stock tire size)
Fourth : .89 - 148Mph @ 7000 RPM (with stock tire size)
Fifth : .70 - 188Mph @ 7000 RPM (with stock tire size)

Final Drive: 4.05:1

 

When it comes to drag racing it's all about what part of the gear you're finishing in, and you want to finish it at the end of a gear. That's where you make the most power. To do that you either increase the power or change the gearing. So it's going to depend on how much power you're putting down for most people. Most SS/SCs are better leaving the gearing alone because most can finish at the end of third. If you had to shift into 4th I would rather do the valvetrain and get another 1200 rpm out of the car before switching trans.

 

i need to do this.. i have to shift into 4th right before i cross the traps

 

if anyone was still interested in this, I did a test on my car last night.

if you want to use an F23 transmission with the LSJ, you NEED to have the spacer in place. If not, the pressure plate rubs on the inside of the bellhousing, and will not allow the engine to turn.

This, of course, is with a jbody F23. I know the cobalt F23 has some changes, but I don't think any of them were to the bellhousing.

 

hmm you have any pics of the build?

 

a couple revisions to the engine here and there since last I posted a shot of it.


a look at the front mount oil cooler


LSJ oil cooler adapter


electronics mount plate (bolts in place of the HVAC unit)
silver box is ECU, red box is MSD ignition, black box is FPSC (fuel pump speed controller) and the long black box on the right is the relay box. The wires are still a mess because I haven't trimmed and loomed them yet.


the gauge cluster i fabricated


Video of the first successful start of the LS61 on the stand alone setup.. world's first naturally aspirated LSJ??
http://www.youtube.com/watch?v=H7L13cTv0tI

 

nope blown 4 banger went NA a long time ago lol

 

My swap is now complete. I have successfully swapped in a F23 into my LSJ. Been running on it for a good month now with no problems.

 

That's an lsj motor? That's a good build you got there

 

any comparisons or data that you can provide that the swap was worth it?

 

i got all the data i need. I can now do a 3rd gear pull without it exploding. And i no longer fall out of boost during the 1-2 shift.

 

any concrete info though? Not just opinion?