98 C1500 5.0 TO 5.7 SWAP

[df2x4]

Its the same PCM, just has to segment swap the engine files from 305 to 350.

Yes, I'm aware. Was just describing how the process works with BBP.

 

[Supercharged111]

If it were my money, I'd either send Blackbear the current blackbox or have them flash a 411 if you're willing to swap. The tune is gonna unleash about as much power as the 350 would on its own.

 

[badco]

I recently did the swap, the throttle body was bigger on the 350 than the 305. The 350 has two catalytic converters but the maf will adjust for the extra cfm. Can't think of anything else.

The throttle body size was exactly same from 305 to 350. The tail thing thats rivited to the blade was bigger on 305 to restrict the flow. I always take those off anyway and if intake is off i pull those pipes for egr out and plug those also.

 

[badco]

I replaced the 5.0 in my '97 C1500 with a 5.7 from a '99 Escalade about 8 years ago direct swap and I never flashed the ECM cause the '97 black box isn't compatible with the flasher I have and I didn't change the exhaust, the 5.7 tune will be looking for a different o2 sensor layout due to dual cats, but its been fine and even passes Commifornia emissions testing as is. MPGs dropped from average of 15 to 13 though.

I actually gained mpg in mine. I haven't had cats on anything i own more than a couple weeks. Not all the 350s had duals to the muffler, had a 97 and a 98 i worked on that had single but my 98 k1500 parts truck is dual. Had a 97-98 c2500 5.7 i parted out that had big dual exhaust 2 7/8 and cats to muffler so if you want big exhaust hit local pull a part for 3/4 tons

 

[L31MaxExpress]

I actually gained mpg in mine. I haven't had cats on anything i own more than a couple weeks. Not all the 350s had duals to the muffler, had a 97 and a 98 i worked on that had single but my 98 k1500 parts truck is dual. Had a 97-98 c2500 5.7 i parted out that had big dual exhaust 2 7/8 and cats to muffler so if you want big exhaust hit local pull a part for 3/4 tons

Alot of the vans have 3" dual to the muffler.

 

[badco]

Alot of the vans have 3" dual to the muffler.

Never noticed that. Was looking at scrap tickets the truck was a 97 3500 work truck. Long bed 4 door single wheel with a 5.7 that was a 4 bolt and steel crank.

 

[mrvsfriend]

The throttle body size was exactly same from 305 to 350. The tail thing thats rivited to the blade was bigger on 305 to restrict the flow. I always take those off anyway and if intake is off i pull those pipes for egr out and plug those also.

The entire butterfly valve was bigger on mine, I caught it when trying to swap over parts from the 350 tb to the 305 one since my 305 tb was in nicer shape. Idk maybe one of the many previous owners used a throttle body from a v6? Either way, worth looking into.

 

[Supercharged111]

The entire butterfly valve was bigger on mine, I caught it when trying to swap over parts from the 350 tb to the 305 one since my 305 tb was in nicer shape. Idk maybe one of the many previous owners used a throttle body from a v6? Either way, worth looking into.

I think even the V6 had the same butterfly, but with a massive lip.

 

[badco]

I think even the V6 had the same butterfly, but with a massive lip.

Yup

 

[L31MaxExpress]

I think even the V6 had the same butterfly, but with a massive lip.

My 99 Tahoe had the same lip as the 4.3. My 97 Express van had a much smaller lip. The 454 even has the same blade, although the housing is the same size all the way through.

The 99 Tahoe had alot less timing in the lower rpm/high map area than the van. As much as 8° less than the Express van.

Almost seems as if GM was trying to make the Tahoe feel less torquey, possibly to push the new 5.3s.