L30 PCM on a L31 engine

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BPR Speed

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Hello Everyone,

As I wrap up my engine build/swap a thought just occurred to me... I swapped my 305 engine for a 350 that I rebuilt for the truck but I just remembered I have a 305 black box PCM. Will the PCM have fuel and ignition maps that'll work for the 350?

I do have modifications on the truck:

Whipple side mount S/C on 6-8 psi, Whippletronics computer to control the two extra injectors, MSD 6AL ignition box, RAMJET 350 Cam on 1.6 crane cams true roller rockers. I do have the retainers for the cam lift being in the 0.480" area and I have PAC1218 LS springs for the heads. The engine has been bored 0.030" over with FM forged pistons. I've installed a Walbro 450 fuel pump to support the fuel needs if the injectors can keep up. I have a slew of engine monitors to keep an eye on things like Wideband 02, oil temps, air intake temps pre and post S/C, separate knock sensor and a lot of other misc. engine sensors from Just Race Parts.com

To not drag on... has anyone seen an issue between the PCM's? All tone wheels between the 305 and the 350 to include the distributor are original to the 350 and the dizzy is new out of the box. I'm just concerned the fuel maps and ignition maps may be different and cause a potential condition for knock if the 305 maps are too aggressive for the S/C even on pump 93. I'm also trying to avoid going the 0411 route at the moment as HP tuners is another $500 on-top of the $6K build so far. I'm not worried to do the swap or the software/tune but if I do commit to it, I'll put more down time on the truck as I already have a marine L31 intake and a set of LS1 injectors. Just trying to get it running for the summer so I can catch up on 3 other LS swaps I got going on.
 

Supercharged111

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Let me get this straight: you spent $6k on a build and now want to skimp on $500 to make it run right? Never ceases to amaze me. :whymewhyme: You don't need to put the marine intake on to do the 411, and HPT will work with the LS swaps so I'm not seeing a reason not to. With all the mods who knows how well the 5.0 PCM and Whippletronics will run the thing. A tune was the very first mod I ever did, I'll never understand why it's the most ignored mod out there.
 

BPR Speed

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It's not that I want to skimp at all, it's that I'll have to pull out the wiring harness to re-pin to the 0411 PCM and re-loom it to OEM looks for the first thought. I have a 0411 PCM on hand and the skill set is there but I've had no luck when reaching out to Lextech for the pin out. At this point it just more man hours to accommodate the need and it's crunch time with my ship going underway at the end of the month. I can probably decipher the pin outs between the two PCMs and get it close but that spread sheet saves time for sure and not mixing up a pinned location. I get what you're saying though. I most likely will have to go the 0411 route, but I'm just trying to ease the pain of stepping back a few steps and running more side jobs to gather the $$$ for the HP tuners and credits. I don't have the software just yet as most of my LS swaps went out to a local tuner but unfortunately he passed away in November so it'll be up to me to tune PCMs here soon to get the street tune right before driving it over to another dyno session site. Subsequent thoughts where the marine intake along with LS1 injectors I had laying around sufficiently covered the need of my calculated fuel requirements. It was just a preparation for the future once the truck was running and I wanted to twin charge it to 10-12 psi when I added the marine intake. I was only digging for solutions on if the PCMs have similar injector and timing maps, to include if the MAF sensor and O2 sensors would be able to adjust to the fuel requirements. I'm not looking to run wide open throttle pulls. Trying to keep it under 3,000 rpm to break the engine in for the first 3,000 miles. My S/C comes in a 2500 rpm so I may need to even cruise below that rpm threshold.
 

Supercharged111

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I wouldn't do it without the ability to log and have a wideband. It would be different if you were stock.
 

BPR Speed

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I do have the ability to log the wideband and various other sensors on my JRP engine monitor but I won't be able to log injector times and ignition in degrees. I also agree it is a risk so I'll make a decision once I get back to it tomorrow and lay it out on a plan. I think I can also go a grab a L31 PCM and see if I can get my vin flashed on it and run that. Anyone have any experience on that path? I'll also contact LT1SWAP.com and see what he can do for the vin issue as well.
 

BPR Speed

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It's the early 2000's whipple supercharger (side mounted above the driver side exhaust) but once I get the engine dressed back together I can snap some pictures. I just remembered that my buddies C1500 that I LS swapped had this 350 that went into this truck so I'll use that old PCM on this project until I 0411 swap for more control of the tune. I'll snap pictures of the do-dads that I've added along the way. It's still a work in progress and the truck still needs a refreshed paint job and another step side bed to replace this one. The previous owner drilled large quarter sized holes in the bed rails so that makes me want to keep the soft bed cover on until I get a donor and a paint job scheduled.
 

L31MaxExpress

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I ran my small cammed L30 on a L31 tune for about 3 miles before finding out it ran terribly.

Cannot just swap a 350 PCM over. The catalytic converter(s) and 02 sensor placement are different and require hybridizing a tune.

0411 or better yet P59 swap it, HP Tune it and be done. No need to pull the harness to make it look factory.
 
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