SMOG LEGAL ENGINE SWAP TO LS yesterday passed!

[Steve Van Gent]

My son just got his CA smog cert motor swap approved yesterday from referee on his 90 GMC Jimmy. I am writing this up as still fairly fresh in my mind and don’t want to lose knowledge. We were also told his rig is first smog legal GM 90s truck engine swap to LS in Northern California. ALL BELOW IS GOOD FOR TRUCKS, SUVs.

This was almost year long process (although could have been done in month if really serious) and surprising amount of money involved. The result is he now has 2001 5.3L Tahoe motor in his Blazer he can play with. Also, better fuel mileage (16-20MPG vs 8-10MPG) and more stock HP. Once in, lots of fun things can be done with respect to tunes and add on’s (not CA legal, but a person could do between smog visits).

Choosing donor vehicle was not arbitrary; If you choose too modern, gets harder. If you choose too old, no point. He decided to shoot for 2000-2004 series motors as they represent decent version of LS motor and straight forward for smog reasons. He landed on a 2001 49 state Tahoe with 5.3L and 4L60E trans. The motor had 862 heads, make sure to look if you choose 5.3L. In retrospect, he thinks the sweet spot swap is 2002 Tahoe.

CA RULES:

Must be newer vehicle than your current one.

Must be same CLASS of vehicle (you cannot put car motor in truck or vice versa). GVWR is considered, motor must be designed to push similar vehicle (originally they said must be LARGER MOTOR, but turned out not to be true).

Any item associated with smog control MUST be from donor vehicle (trick is know what they truly are!).

IMPORTANT POINT!
You must know what version your squarebody is before you buy donor!!! California dealers, in his year, sold BOTH CA only versions and FEDERAL emissions versions of Square body. The donor vehicle MUST MATCH!!!! If you are forced into CA version of squarebody, the CA version of Tahoe had air injection that must be moved over. My son had federal Blazer/Jimmy, so he found federal (49 state) version of Tahoe in Nevada. Vehicles we considered were Tahoe, Denali, Suburban, Yukon.

To keep your life simple, GET AS A SET FROM DONOR CAR; ENGINE, ECU, TRANS, BODY CONTROL MODULE (YOU WILL NEED), AIR INJECTION (for CA version), CROSS OVER PIPE WITH O2 SENSORS MOUNTED IN CORRECT PLACES before and after each catalytic converter x2 (you will need different cats), ALL EVAP ITEMS (charcoal canister, OEM tank that will not be used, pressure sensor, purge valve), engine and transmission wiring harness all the way back to gas tank, no exceptions. ECU serial number drives everything else requirement wise, get all parts or you will play scavenger hunt hell!
All systems dealing any form with smog must be intact. In my sons case, the Tahoe had VATS system that cuts off fuel as part of theft deterrent. THIS MUST BE INTACT!. That does not mean column must be there, but the body control module will need to exist. This should come from donor car. Be advised, it will need to be hacked to satisfy all inputs including VATS, as it will throw check engine light and you will fail! My son stuffed unit under dash and installed VATS resistor and bypassed other necessary items to prevent error code. 1-wire bus must be connected back to ECU.

NEEDED ITEMS;

TIME! See my note about passing current smog before starting swap.
RESEARCH! COMMITMENT! This is far more work than typical engine swap. Make sure you know your rig and rig you are getting parts from. Take your time!

AC DELCO EP381 FUEL PUMP
VCX NANO TECH 2 SOFTWARE KIT
DIRTY DINGO AC BRACKET (allows use of R4 90s compressor), DIRTY DINGO MOTOR MOUNT KIT
4L60E TRANS from donor truck.
SPECTRE BRAND COLD AIR INTAKE CARB APPROVED
CARB APPROVED headers (will need as stock manifolds will NOT fit between frame rails).
Adaptor to connect your 4l60E to your transfer case (he had NP241C TRNSFR CASE).
New CARB approved CATS, Small enough to fit application. Lots of options, look at your actual requirements.
Fuel line converter connectors to mount old tank lines to new fuel lines.

Save yourself headache, buy new aluminum radiator! Will need extra cooling anyway!

KEEP ALL CARB APPROVED PARTS RECEIPTS AND PRINT OUT CARB APPROVED DOCUMENTS FOR EACH PART! HAVE ON HAND!
SERIAL NUMBER OF DONOR CAR!
GOOD AT WELDING EXHAUST PIPES. In the end, I hacked exhaust in just enough to drive to exhaust shop, then paid tech to piece new system together.

STEPS-

STEP 1: WAIT UNTIL YOU PASS AN ANNUAL SMOG TEST! You will want the time to ferry your rig around and time to work on nuisance issues.
STEP 2: PLAN, then buy.

NOTES:

YOU CANNOT HAVE CHK ENGINE LIGHT FOR ANY REASON!!
USE CA FUEL LINE FOR ALL FUEL RELATED ITEMS. Almost failed last run due to using vacuum line instead of fuel line for pressure sensor.

IMPORTANT NOTE ON EVAP TEST!!!! It seems that GM might have had issues with evap software in ECU for that generation; it is VERY common for evap to fail on that gen vehicle. Once can run test 10X times, get only 1 pass, and nothing be wrong. In the CA smog reference guide, evap test is not required for annual test, BUT MUST PASS FOR ENGINE SWAP!!!

ECU MUST BE FLASHED BY DEALER WITH LATEST VERSION FW, CHECKSUM MUST MATCH AND VERIFIED BY REFEREE. No cheating, it must be stock with no bypass. None.

You will need to know your engine wiring harness, wire by wire. You will need to know each pin on your ECU, function of each pin and how it connects. You will need to put power and ground on dozens of pins on your ECU.

O2 SENSORS IN EXHAUST; these must be mounted in similar location to OEM, and MUST be same distance from engine as OEM. 4 total, there are 2 on each side of engine, before and after each CAT.

The OEM crossover will not fit on your squarebody, too wide. Have exhaust shop put whole system together. Cost me $200 to have all done for me (not including parts I bought), not worth my time.

Cold Air intake: Rules say that intake must be for donor vehicle. OEM air box simply will not fit! He found SPectre CARB APPROVED version cold air intake, we found would not fit on passengers side. After anguishing about it for hours, we found we could mount it up-side down and fit on drivers side. Had to weld bracket to make it work. Referee examined this quite a bit and called supervisor, ruled to be OK. You may not modify ANYTHING AT ALL FROM ORIGINAL CONFIG.

Frame rail will need to be notched slightly to fit header in; right around EGR mounting point on passenger side.

Lots more detail, will post as time permits…

If you get into this and find yourself in trouble, you can email me. steve.vangent@att.net