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Vortec 5.0 to 5.7 Swap


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Hey guys,

My truck came with a 305 from the factory, we replaced that engine a few months ago at 284,000 miles with a brand new 350 crate 2 bolt main

Before my truck was slow as hell with all those miles, but I never cared about performance, just cruising and straight pipes.

Anyways after we got the engine swap done we took it for a drive and ABSOLUTELY no difference in anything at all.

I'm thinking the PCM is throwing the 350 the same air/fuel/etc as the old 305 had, so it's running really lean (you definitely notice at WOT)

Was thinking about getting a stock 350 reflash but the dealership wants $600 for that shit...

Anyone have experience here on if it's the PCM or not?

And if it is, anyone know a good name that can do me a mail order tune?

Thanks

1997 Chevrolet Silverado Extended Cab, 350 Vortec

Things to come at some point...

Build Log: http://www.stevemead...2200ds-133-ohm/

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Oh and on the same subject, anyone have experience with these engines and upgrading the old poppet style injectors with the newer MPFI injection?

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1997 Chevrolet Silverado Extended Cab, 350 Vortec

Things to come at some point...

Build Log: http://www.stevemead...2200ds-133-ohm/

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What kind of vehicle is it? More info on the new engine?

1997 Silverado 4WD, vortec 305, the crate was vortec 5.7

edit: more detail, crate came with everything on lower end, we used my intake, injectors, exhaust manifolds etc

(305 and 350 vortecs were the same only bigger cylinders and bigger ports in the heads on 350)

1997 Chevrolet Silverado Extended Cab, 350 Vortec

Things to come at some point...

Build Log: http://www.stevemead...2200ds-133-ohm/

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  • 3 weeks later...

You might need to get your pcm re-flashed. I think its feeding your 350 with the amount of fuel intended for your old 305.You might also want to look into a aftermarket vortec intake and some headers for that lil extra hp.

Look for a performance shop around your area, they can prolly fix the problem or guide you in the right direction.

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i hope u didnt use heads from the old motor on the new one....

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all generation 1 small block heads are interchangeable. The 305 heads will work on the 350, however, the 305 heads have small 57cc - 60cc chambers which will raise the compression ratio on a 350 quite a bit, depending on what piston, possibly too much. they also have small 1.84 intake valves, which will give a 350 killer out of the hole power, but will lack upper RPM power, you`ll feel the power drop off past 4000 RPM. If your 350 has dish top pistons the compression ratio should be close to 10:1 and that will survive on pump gas, if it has flat tops then it might be a bit too far on the high side and the engine will detonate itself too death.

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Your gonna need a reflash or get a used ecu at a junk yard...or a custom black bear tune.

blackbear.. you might as well kill 2 birds with 1 stone, performance and the ecu flash you need. plus some better gas mileage.

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