I figured I'd start this thread up now that the overhauling of the Series II L67 is about complete. It might be a little premature, but I'd figure I'd share my thoughts on some of this stuff before it actually happens (and y'all get to giggle at my mistakes when I make them )

Recap of the basic plan goes like this:

Car is currently a 1990 Bonneville LE, LN3 motor, 440T4 transmission, stock 253 ECM with ASSK prom. Mods that will carry over are the intake with K&N filter. While the car is equipped with a Fogger NOS system, that'* a secondary consideration to what I will be doing. I'm not going to tune the car for the NOS, I'm going to tune it to the new motor and then tune the NOS system at a later date using new jet sizes.

The new motor is a Series II L67, bored 0.030 over, with M90 Blower, 1994 Throttle Body adapted to use a TV cable to the transmission.

Based on yesterday'* data collection run up I-95, the stock LN3 has the following state of tune with the stock ASSK prom:

BLM is averaging 127, Integrator hovers in the 120 to 130 range.
KR is 0 on 87 octane with brief jumps to 3 if I lug it up-hill on throttle light enough to not unlock TCC.
O2 values at WOT through all the gears are 0.888 to 0.905 vdc
No codes.

This is about the state of tune I'm going to try to achieve on the new motor, using mid-grade gas.

Tools in use: Actron scanner to monitor the ECM while it is running. TunerCat 2.11 software with type $5B config to edit the prom. And an old JDR Micro-devices EPROM reader/burner to generate new proms.

I can also confirm the presence of a speed limiter on the LN3. I found it in the ECM constants table set to 115mph. That, along with the RPM fuel cutoff values are going to get moved to their maximums as the first test, to make sure the software is decoding the eprom correctly. (In other words, I'm going to alter a few values in the stock PROM and try them out on the stock motor before the swap, just to confirm that the software is working correctly.)

That'* about it for starters. I'll post some shots of the process as I go along.

If there is any real interest, I'll post the PROM bin files along with dumps of the tables so any of you LN3 folks can follow along...or mess around with your own 87-91 H-Body.

Sounds like a pretty sweet project, I hope you have good luck with the Torque Axis mount like randman1 did with his SSE.

What PCM and Tranny are you running with the swap??

My '90 has the holes in the frame for the torque axis mount, so I went ahead and set up the Series II 3800 L67 to also employ a torque axis mount. I'm undecided if I will retain the underslug stock LN3 mount as well. I think I will.

The transmission is the same 440T4 that is in the car now. The ECM will also be the same Type 253 that is currently used. The rational for this is pretty simple...the '90 ECM is MAF based and does not try to control the transmission shift points. Only the TCC solenoid. In other words, the motor will mecanically be a supercharged series II, electrically it will be an LN3.

I thought a 440T4 would get chewed up by a SII L67? :( , dont they use 4t65e and 4t65hd , i believe those are the correct names. possibly if it'* built real good it could handle th power . That is the trans I have also, and I was told this is not a good idea because of the reliability issue, WILL a good built 440T4 do the trick? This topic should be in Performance & Brainstorming

Woah ok. So you've got a custom rebuilt L36, overbored, blown. You're going to use the 440T4 and control the engine with all the stock wires and equipment except for a ECM with modified values. So are you planning on any mods to the trans then? Ok, so bored 0.030 over...how much does that change the displacement of the engine and how much power do you expect from it. This is quite some feat you're attempting. Sounds amazing!

.030 over will take it from 231cubic" to 235 or from 3785 to 3850 cc'*.

At present no. The transmission, with 73k miles on it, is in great shape. Nothing amiss with it as of the last fluid change (dumped the pan and changed the filter a few weeks ago.) Only modification thus far has been a cooler added to the system.

Now, is it advisable to use a 440T4 with a supercharged motor. The consensus of this list has been No. However, hitting the motor with nitrous shots over the past few months hasn't hurt it yet...no slipping, no rattles or clunks, no snapped CV'*. With that in mind, I'm going to keep rolling the dice on this one.

If it breaks the transmission, then I'll cross that bridge when I get to it.

Actually, I would perfer that it remains here in the '87 to 91 area. Most of the tuning I'll be doing and problems to be addressed are relevent to the type 253 ECM and the 87 to 91 chassis. 92 on up uses a different ECM and the addition of the transmission to the powertrain programming is a topic I'm not getting into.

Now, as far as differences between the LN3, L27, L67 (series I), L36, and L67 (series II) there'* not a whole lot of difference with the sensor suite that runs them. The blown engines are different internally and, of course, carry a supercharger on top. The major difference in control circuits are the EGR and the Boost Control module..which I'll have to work around in my swap.

If I can't get it to work, then I'm not stuck. There'* always the option of switching to the more expensive to tune PCM from a more recent model year.

I imagine the shop would be able to beef the converter up, or you could, possibly? Along with a shift kit and a adjustable modulator. They did use the same tranny in a caddy with a beefier converter. If you found that converter it would back up your blown v6 I think also, seeing as it was on a V8 in a heavy car. You could possibly even you some internals from one if you found the whole trans, you would be able to some internals from it? possibly they are beefier? I know it'* a RWD trans from the Caddy correct? but its still a 400T4 so it would have some matching internals I do believe.