Upgrade my 350

i have a 94 silverado. it has a the stock 350 with tbi. i have a chance of getting a rebuilt vortec 350 from a 97. the block is the same but the heads and intake are diff. my question… do i have to change the eng computer? will the comp from a 97 truck fit the stock connector on the 94? what other electronics have to be changed?

Yes it requires a different computer and wiring. I’d just get a newer truck.

a new motor is nice. maybe your current motor is tired. rebuilding it is pricey. lots of labor. swapping out motors is also a lot of work. none just gives away a good vortec motor. maybe you are paying close to retail for it. you would be better off redoing your motor.

There are also probably more aftermarket performance parts for the venerable Chevy 350 than any other engine ever produced.

i already have the bottom end done. i now have a choice, continue with the stock tbi heads, intake or go change to vortec and try to get computer upgraded.

Well, just theorizing here but,
U removed ur motor, rebuilt short block, $$
U have not done heads yet?
U found newer vortec motor which IS rebuilt
So, buy vortec, sell ur shortblock,
And mess around with computer issues?

I think it’s more than just ‘upgrading’ the computer. It’ll need to be replaced, along with a new wiring harness . And I wonder how it’ll work with the transmission. It can be done, but there could be a number of problems to sort out.

If you are subject to emission testing, forget it, you will NEVER get that CEL to go out, unless you take it out…If the '97 Vortec is multi-port injected, you will have to change the entire fuel system…

Just stick with your stock heads and short block. The '97 heads may or may not work, I honestly don’t know. The intake and fuel system from the '97 would definitely not work since the '97 was SCFI. You would have to swap the computer, wiring harness, fuel pump, fuel lines, air cleaner, and all other sensors and controls from the '97 truck into your '94. Technically, it could be done but would be impractical to attempt it and probably cheaper to buy a newer truck. Besides, if you bought a '96-'98 (when the '97 engine was used, and also in some '99s), you also get a much nicer interior than is in your '94.

Your 94 has a 14psi fuel pump. The 97 needs 60psi. I believe the fuel tanks themselves may be different, though I’m not sure. But certainly the fuel lines to and from the engine are. I also think the A/C lines and heater hoses are different, as are the mounting brackets. I think the air cleaner and intake duct work from a 97 won’t fit on a 94.

The block is not the same. The 97 uses the LT1 block, different cooling passages, different oil passages, etc.

You will certainly have to changed the ECU, the 97 will have multi-port injection, and a host of other sensors (it’s OBD-II) that your 94 won’t have. You’ll probably have to get a custom tune written for it. This is not going to be nearly as easy as you think it is.

As others have said, a new fuel pump and possible fuel lines will be needed, you’ll need the exhaust manifolds off the 97 as well as the exhaust ports on the LT1’s are a different size.

Weighing the aggravation and expense of adapting an engine with a completely different fuel and emission system against the proper engine setup for the truck, you will find that it’s faster and much cheaper to go with the proper engine.

ok, thanks. i did not know all of the work involved in the change. … how can i get the most power out of my 94 350. i have a better than stock cam, roller rockers, i will be doing a some work on the heads so they flow better, will a accel super coil make any diff.?

A coil will not help much if any at all except at the upper limits of the RPM range and will certainly not be noticeable to the driver. A coil will only put out what is asked of it (usually 7 to 15k volts, all depending) so any references to 50k volts and so on is mostly hype to sell the coils.

There are a number of things that could be done to increase horsepower but most depend upon the tolerance to spending money.
Larger valves in the cylinder head, timing tweaks, exhaust modifications with long tube headers and a true dual exhaust, underdrive pulleys, rear axle ratio change, etc, etc can all help.

One freebie that will actually help is to index the spark plugs and round the tip of the side electrodes on the spark plugs. Once upon a time, I saw a dyno printout on a small block Chevy that picked up almost 5 horsepower just on that tweak alone.
Gasket matching the intake manifold and cylinder head ports can also help a bit as that serves to smooth out any airflow disruptions and while it can be a bit time consuming it’s free if you’re DIY.

@ok4450: "A coil will only put out what is asked of it (usually 7 to 15k volts, all depending) so any references to 50k volts and so on is mostly hype to sell the coils."

I think you may be mixing up voltage and current. This may be a poor analogy, but If you have 100 amps available, but plug in your cell phone to charge, it will only draw the amount of current it needs (a fraction of an amp), while the voltage supplied will remain constant.

The same applies to ignition coils. While it may not take 40,000 volts to jump the gap on your spark plugs, the (up to) 40K volts is available and will yield a hotter spark, while the current that runs through this system is small, and is intentionally limited. (Your spark plugs wouldn’t last very long if a heavy current was flowing through that spark) The 40K volts will only not be available if you have a short to ground somewhere in the system before the spark plug, or if the system is damaged or under performing. The voltage will never be in the 7-15 KV range unless there is something seriously wrong with the ignition system.

GM’s ignition systems since the early 70s when they came up with HEI (high energy ignition) have supplied around 30-40K volts. Older stock points ignitions topped out at around 18KV I think.

Indexing the plugs is a good idea though that I wouldn’t have thought to mention.

Ur motor is tore down? U r rebuilding heads? Don’t really know what upgrade heads will work with older Tbi fuel systems? Can u put in a slightly hotter cam? Better flowing exhaust? Since there are millions of these trucks out there, I gotta think u can pick up a little power. I bet a 4x4 website might have some Tbi motor info

Have you seen what Jegs and Summit Racing have to offer?