GM 5.3 swap into My 1976 GMC Jimmy

[chip cross]

Well, I figured I would start a build thread so y'all could all tell me what I was doing wrong... I have been kicking the idea of swapping a newer style LS motor such as a 5.3 or a 6.0 into my 1976 Jimmy for about two months now.

I have a good friend that said oh heck put an 8.1 in it and that got the gears in my head turning. I like big blocks, you don't have to spin them as hard to get horsepower and torque out of them which would only make sense they will last longer then a higher rpm small block. I did some checking around and talking with Kevin and Jason at Pacific Fabrication and I found just what I was looking for.

From my understanding the 8.1 will go right back into where a 454 came from. My Jimmy had a 454 in it before I bought it from the previous owner. I picked up some new motor mounts from DIY4X for 112.00 that are a lot better then the factory junk. I also picked up a fuel pump from FLeaBay. The only thing I have left is to figure out is what headers to use..... Any of you have any input ?

 

[The Violator]

Is they fit you might consider the stock exhaust manifolds. I am sure it will have lots of power with them, and they are free. Save a few bucks now, and later if you need more power, swap them out.

 

[chip cross]

Is they fit you might consider the stock exhaust manifolds. I am sure it will have lots of power with them, and they are free. Save a few bucks now, and later if you need more power, swap them out.

You have to cut the frame rails to make the factory manifolds work and that is not happening. "thumbsup"

 

[muddbogger]

I like the swap but i would have went with the lq4 or the lq9 to save weight and make more room for stuff like headers.And yes i know the 8.1 depending on which year made about 70-80lb-ft more but they give up that much in horse power and get worse mpg's than the smaller motor and you could use the stock manifolds with the smaller motor also. Im doing a 375ci(.60 over) lq4 swap in my 99 trans am and im shooting for 400hp and 400lb-ft to the tires should be a blast.Good luck on your swap and check ebay for headers they have off brand stainless steel long tubes for my car for 150 bucks.

 

[dkf]

I think the 8.1l is a good idea. With an overdrive trans and the proper gearing you may be surprised what mpg you can pull out of it, especially on the highway.

For the headers you'll probably have to modify a set to get them to fit. Would be nice if you could get lond tube headers to fit because they will give you the most HP and torque. I'm sure someone probably swapped the 8.1l in an older GM truck before so I'd hit the forums.

 

[Mr.Slave]

get a cummins.

 

[dezfan]

STFU!"thumbsup"

 

[thumper68]

I've never done a 8.1 swap but I have made several sets of custom headers useing these http://www.hedman.com/categories/?id=3505&rsku=0

If you don't have access to a tig welder you can tack them together and then take them to a local shop and have the finish welding done.

 

[dkf]

get a cummins.

No need to add an extra 500 lbs up front.

 

[skinner]

bb in a old jimmy hell yeah!! ive owned a 86 blazer with a 74' 454 mildly done and thump pumper they are.
headers shouldnt be a issue.

 

[Mr.Slave]

No need to add an extra 500 lbs up front.

**** yeah there is.

 

[Code454]

My buddy did the exact same swap in his 76 jimmy, its a nice combo

 

[2500hdon37s]

SAAAAAAWEEETTTTTT! ill be watching!

 

[untchabl]

I know they make a block hugger style manifold for the LSx motors. Look around and see if some are offered for the 8.1.

 

[Rckcrwlr]

You will love the BigBlock...I have it in my 2005 Avalanche...

 

[chip cross]

You will love the BigBlock...I have it in my 2005 Avalanche...

Ever had any problems out of it ?

 

[Rckcrwlr]

Not one...

I tow a 10K TT about 19 times throughout the summer with no issues.

They don't make the 8.1 Vortec anymore so you have a great find. Only 8.1 available now is the Crate 502.

 

[chip cross]

Let's try this again.....



Long story short Central Freight Lines trashed the 8.1 so I am going to go with a 5.3 from a 2006 Chevy truck. With CFL dropping the ball that has put this hole build up waaaaaaay behind. The 5.3 doesn't have the power of the 8.1 instock form but there is soooo much that can be done to the 5.3 to make it very nasty. Before everyone says you should have gone with a 6.0 there is a few reasons why I went with the 5.3 and the 1st is price for sure..... :ror: and weight, the 5.3 weighs 650lbs the 8.1 weighs 900lbs. :shock: Fuel mileage of the 5.3 will be pretty good. I know it will be better then the 8.1. 5.3 are a dime a dozen and a good 5.3 can be picked up for $500.00

Here is a few pictures from Saturday when we dropped in the motor.

Picking up the motor from the dock...

The Jimmy getting ready for the 5.3 swap.

Pulled out the old tank and put in a new 31 gallon EFI tank with a sump and a in the tank fuel pump. The pump I used is a Holly 255LPH which was dumb on my part because it is nothing but a $100.00 in the tank Walbro pump I guess you live and learn. I also replaced the old fuel sending unit with a new EFI sending unit. All the Fuel plumbing is going to be done in -06 Aeroquip Socketless hoes and -06 fittings. I am also using a Vette regulator and filter comb from Pace Performance with -06 fittings as well. I replace all the old straps to hold the tank in the truck and put on new anti squeak material.

We trashed all the old exhaust and I will be going with some mid length headers and a Magnaflow x pipe muffler.

My buddies 7 year and the head mechanic on this job. :lmao:

New home for the 5.3

Checking all the clearance

And it is in...

Specs on the Jimmy :

●Dana 60 front
●Lock Right going to replace with an ARB
●1/4 Diff Cover
●4:56 gears
●New rotors, calipers and studs
●New Wheel bearings
●King Pins reworked
●2.5 inch BDS front springs
●ORD HD grease able shackles
●ORD sway bar dico
●ORD Steering box brace

●14 Bolt rear
●Detroit locker
●4:56 gears
●1/4 Diff cover
●U joint / yoke rock guard
●Rear disc conversion
●New bearings and seals
●Shock mounts moved
●Axle perches moved
●4 inch BDS rear springs
●ORD HD grease able shackles

●Built TH400 with external cooler
●6 bolt round adapter
●6 bolt round NP 205 soon to be twin sticked
●New bearings, gaskets and seals in the NP 205
●1350 yokes on everything
●Thick wall drive shafts

●16X8 Factory Ford wheels :laughing:
Yea, I know Ford parts on a Chevy... but they make the truck look old
school with the GMC hub caps.

●Dual batteries

●Hydo boost brakes

●The inside of the tub has been Line X'ed

●3000 watt continuous 6000 watt max inverter

I am trying to make my mind up on what tires to run, I like the BFG KM2 but I also like the price and look of Pitbull Rockers. I am going to pick up some PRP seats and a Redneck ram Hydro assist from West Texas Offroad.

 

[Mr.Slave]

bfg km2 wear ridiculously fast on road. the ones on our work trucks are bald after 12000 miles.

 

[dezfan]

Hubba Hubba! :shock: