LS Swap, 71 GMC

[biohazardbill]

Picked up this little guy not to long ago



Plan on doing an LS swap.

What all is needed to make this as seamless as possible? Currently there is a 250 I6.

I plan on using 6.0 woth truck accessories, 4l80 trans and boyd tank for the rear. Debating on truck vs ls6 intake.

So what will be needed as far as conversion mounts, fuel lines etc?

Thanks in advance.

[Lees68GMC]

Love my LSX GMC

[biohazardbill]

What mounts etc did you use?

[Lees68GMC]

The Hooker header mounts from Speedway about $79.00. Don't be confused they are available in several set back dimensions, I used the Stock location ones and they worked great, either way you have to deal with tranny cross member location and have a correct drive-shaft built. Nice Truck by the way. To use an LS6 intake you sacrifice bottom end torque and move torque and HP higher up the RPM range. Not a particularly good application in a truck unless you expect to be up around 5500 RPMs a lot, does Look better though.

[Matt Cramer]

For conversion mounts, you can fab up a set yourself using dimensions given in the LS swap forum, or there's a ton of bolt on options as well. I cut a set out of 1/4" steel stock myself - see my build thread for details.

Most factory truck LS manifolds have a few frame clearance issues. If you want manifolds, Trailblazer SS or 2010 and later Camaro manifolds have good clearance. There's also a couple headers.

For radiator hoses, I used a set intended for a 2005 Silverado. Had to trim a little off the lower hose, and put dish soap on the ends to get them to slide over the (somewhat larger) fittings on my stock '72 radiator.

I just used a tubing bender and made my own fuel lines.

[Lees68GMC]

Yup he's right the truck manifolds hit the frame, I used 2014 Camaro LS3 manifolds because Camaro guys put headers on all the time and the manifolds are available cheap, they fit well and made 436 HP in the stock Camaro SS.

[boraxman]

Hey Lees, where is your air intake pulling air from? Did you cut into the rad support? Where did you get that intake?

Im looking for something better, im getting high IAT as my cone sits between the engine and radiator/

[brushbuggy]

i agree with Lee, love my 68 chevy with a 03 5.3 .I did mine and helped Lee with his. I used a aftermarket air intake from a 03 truck ,sorry no pic

[Lees68GMC]

Your Truck looks great Tim! Actually Tim did mine and I helped

[Lees68GMC]

The intake is just the production K&N for a 2005 Suburban and that's the stock enclosure around the filter on mine, Problem is the 2005 Suburban OEM has Electric fan and we used a Mechanical fan, more efficient but bigger diameter rubbed the underside of the plastic intake tube. We heated the under side and pushed a "dent" in it to clear the fan. The LSX is just an e-bay stick on where we sanded the K&N logo off.

Heres a picture of Tims intake

[brushbuggy]

Thanks Lee