Making a '80 406 into a TBI thoughts..

[Twin Turbo Skylark]

Hi there, I have quite a bit of experience with the TBI engines, chips, upgrades and all that stuff and here is some info that may help:

1. It is the larger camshafts with changed vacuum readings that throws off the TBI
2. Plus it is a rudimentary setup that just cannot adapt on the fly like the new stuff can. It is pre-programmed with the chip and thats that.
3. I used a few custom chips in TBI 350s after I made upgrades and I never was happy with how it ran. I always went back to the stock chip.
4. The TBI system is low on CFM, about 470 CFM if I remember correctly, maybe 500 but no more. Yes you can use a 454 TBI but thats bunch of hassle for little gain I tried that just got worse fuel mileage.
5. Megasquirt works well, I had that on a TBI engine no problems... Paid a guy to dyno tune it and it was perfect, much better than the chips in the stock computer. Plus you can upgrade the EFI system and keep the megasquirt.
6. The TBI just isn't the best performance over 4000 RPM, under that it is great. It is simple, low cost, easy to troubleshoot, just 2 injectors, reliable, reliable, reliable.

I even had a 90s Chevy truck with a 383 and a Holley 670 TBI and it was using the stock computer and it actually ran better when I swapped a stock small cf. TBI back on it needed extensive tuning to run right and it was not worth the hassle to me.... Got the truck for $1200 because it ran like crap, swapped on a stock TBI, and it ran perfect and sold for $3000.

If it were me i would setup a run stand and try out that built engine you already have. And if you are not sure about the balance then just take it apart, clean it up and you may need a hone anyway if it sat that long. Try the engine out of the truck, and have a flywheel match balanced, or the assembly balanced whichever way you need to go. You say you have a balance sheet I am guessing that is your bob weight? Was the engine balanced internally or externally?

The NV3500 is a pretty stout trans, I would not swap that out for a 7004r no way! I understand the gains of an auto don't get me wrong but I would buy a different truck before I did a manual to auto swap.

Oh and one last thing... Fitech is a good setup, but there are lower cost options for aftermarket TBI and they all work really good. It is not like it is a race car, for a street driven truck even the low cost TBI setups are really good these days. 8 years ago when I was messing with GM TBI stuff we did not have an option for the low cost aftermarket stuff.