LM7 5.3 into a 84 C10 swap questions

I have a couple of swap questions. I am changing to an 87 gas tank with the baffles and going to run a Walbro in tank pump. My 87 sending unit has 3 lines 1/4", 5/16" and a 3/8" I was planning on using 3/8" for the feed, 5/16" for the return. Also I did away with the charcoal canister. Do I need to vent the tank ? If so, how would be the best way to do that ?....My 5.3 has a 2 wire plug connected to the alternator, a brown and a gray wire. My 84 has a 2 wire plug for the alternator, which has a red and a brown wire. The truck has gauges. Which wires do I need to connect to the 5.3 from the 84 plug, and where do they need to go ? Will my volt gauge read correctly ?

your gonna use the stock gauges? The 87 tank doesent have baffles, i was gonna use the same tank when i did my swap but ended up using the 82 tank. i believe the 87 tank has a tray in it... if you dont have a canister maybe you can put one of those little filters with a clamp on the metal line towward the front of the truck where the canister was.

yes I am going to use stock gauges, and speedometer from 88 Blazer

your gonna have to repin the wiring for the cluster or it wont work. i had the same problem i repined it but still didnt work because i have a gen4 motor if you have a gen3 motor think it should work for you. i dont have a working speedometer of tach. i dont remember using the wiring for the alt on the 82 harness. i sent the harness from the 5.3L to nelson performance and they reworked it. all i did was put power, ground, and switched power. everyting works except speedo and tach. i tapped in to the side of the pan where the filter is for the oil pressure gage

There should still be a large, red wire on you're current alternator (87), that runs to a fuseblock, or maybe even splices to the battery. The 5.3 should also have a place for the large, red charging wire. The two wires that connect to the stock alternator will not be used on the 5.3 alternator. The 5.3 alt gets its on/off signal from the pcm.

Also you are correct on the fuel lines. The largest are for feed and return (3/8 is feed). You don't need the charcoal canister; the tank will simply vent through the 1/4 inch line. However, when you have a full tank of fuel, or on a hot day, you'll get heavy fuel smells emitting from the truck. I would suggest reinstalling the charcoal canister, since it masks the smells, and doesn't cost you a thing.

Hello -

I am new to this forum, and I am also about to start my LM7 swap onto my 84 C10, I am building this truck for my daugther as her first car and sweet 16 present. sofar, I have ordered the engine mounts from Dirty Dingo, flex plate adapter and new flexplate to bolt to a 4L60e, like you, I will have a bunch of questions, specially when it comes to wiring, but I'm sure this forum will be able to help, not to mention the amount of information that is availble here!!!

The 84 that I am working on came with a 327 Small Block, heads and cam, headers and all the good stuff, but it is WAY to much motor for my girl, so that is why I'm going this route, I figured this should be more than enough power for her to drive to and from school, with no issues in a cold morning, not to mention a much modern AC system. GOOD LUCK with your swap.

Jose

The 5.3 is going to just as powerful or more than that 327.