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Need some Chevy guys to fill me in.

2K views 8 replies 4 participants last post by  Bo185 
#1 ·
Hey everyone,

First post and new here, but not an entire noob/moron to working on my own rigs and dd's. I hope I posted in the right spot, because I need some knowledge from you Chevy guys here.. mainly you fellas sportin both the 5.7 Vortec V8 as well as the newer 5.3 Vortec. In regards to my questions, please don't completely destroy me on my first post lol. If I posted in the wrong spot, please forgive and tell me how to go about getting it moved.

With that out of the way, my rig is a '91 XJ. Damn near stock (minus header/exhaust/ typical replacements) due to it being my DD for a while. Now I have an actual DD (07 Focus), so the Jeep gets the treatment.

One of the first things on my list when I have the cash is to swap in a GM V8. Now, here's where I need the help. Nearly every swap I find is either a 5.3L vortec, a carbed or TBI 350, or the 4.3L. I am yet to find anything on a Vortec 5.7. I understand the 5.3 is usually the 'modern' choice due to modern improvements and design, however I prefer older style (to an extent) with less of the crap (TAC module, Drive-by-Wire, etc..).

So, I plan to source a 5.7 Vortec and matching 4L60E trans from hopefully a '99 Tahoe, maybe a '98. If I have researched correctly, both year 4L60E's have the 6 bolt pattern for the transfercase, right? Hopefully so, because if it does I will be building a bastard t-case from a combo of my current NP231J, an NP231C, and possible a dodge unit (complete instruction was found on a 5.3 swap on NAXJA).

As for the 5.7, to be honest another few reasons I chose this over the 5.3 is because:

1) Vortec 5.7 assemblies run cheaper than 5.3 assemblies where I live.

2) The Vortec 5.7 uses a FPR mounted to that janked up lookin spider assembly, which means I can retain my factory fuel system to an extent (pump, gauge, filter, etc).

3) IIRC, the 5.7 is similiar to my current 4.0 in respect to gauges and their sending units. There is a spot for the ECM's coolant sensor, and another one for the gauge sender. Same for oil. Keeps is simple, however idk if the 5.3 is the same way.

4) After much review, the 5.7 seems to have much lower end torque, which is what I'd need more with 3.55 gears (for the time being [winter DD]) and for wheeling. In regards to horsepower, I think through bolt ons I can bring the 5.7 from 255hp to 290hp, near where the 5.3 sits.

5) There's just a cool factor associated with the badge for a 'Chevy 350' :D

6) The older setup should match up with my older systems (such as A/C and power steering) better.

Now, if I am wrong on any of those, PLEASE correct me. I don't want to wonder around like a retard with the wrong info. Also, to add to the q's, does the 5.7 vortec intake assembly sit about as tall as say a carbed 350 setup? I see guys running carbed 350's in their XJ's with no hood clearance issues, so I am hoping the vortec 350 sits about the same height intake wise.

Lastly, I understand when people swap 5.3 Vortecs into their XJ's, I think the alternator bracket and purge valve cause hood clearance issues, requiring a cowl hood. Does the 5.7 vortec assembly share this 'high accessory' setup? If so, can different brackets from a lower setup style be swapped in since the vortec 5.7 is still a Gen 1+?

I appreciate any and all help. And again, if I placed in the wrong spot, please correct me and tell me what steps to take to have it moved.
 
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#2 · (Edited)
I have a 1999 5.7 vortec sitting here waiting for installation into a 68 chevy, i wont be using the intake setup on it... and I know where the computer is, currently...

the air intake is not higher than a carb, but the air inlet will give it some height as well...

if you need a puter and intake and distributor, i can probably help you out...
 
#3 · (Edited)
I appreciate the offer, but honestly I'd hope you sold it and made some money for yourself before I was ready to buy anything. This swap will be a future project... let me rephrase.. this swap will be a "when money flies into my pockets" project lol. But I want to be knowledgible prior to the swap, so I'm not like a blind man diving into a raging sea. Thanks for the feedback also! By air inlet, what do you mean? The throttle body or the part of the intake that goes on the throttle body?
 
#4 · (Edited)
Hey everyone,

So, I plan to source a 5.7 Vortec and matching 4L60E trans from hopefully a '99 Tahoe, maybe a '98. If I have researched correctly, both year 4L60E's have the 6 bolt pattern for the transfercase, right? Hopefully so, because if it does I will be building a bastard t-case from a combo of my current NP231J, an NP231C, and possible a dodge unit (complete instruction was found on a 5.3 swap on NAXJA).

As for the 5.7, to be honest another few reasons I chose this over the 5.3 is because:

1) Vortec 5.7 assemblies run cheaper than 5.3 assemblies where I live.

2) The Vortec 5.7 uses a FPR mounted to that janked up lookin spider assembly, which means I can retain my factory fuel system to an extent (pump, gauge, filter, etc).

3) IIRC, the 5.7 is similiar to my current 4.0 in respect to gauges and their sending units. There is a spot for the ECM's coolant sensor, and another one for the gauge sender. Same for oil. Keeps is simple, however idk if the 5.3 is the same way.

4) After much review, the 5.7 seems to have much lower end torque, which is what I'd need more with 3.55 gears (for the time being [winter DD]) and for wheeling. In regards to horsepower, I think through bolt ons I can bring the 5.7 from 255hp to 290hp, near where the 5.3 sits.

5) There's just a cool factor associated with the badge for a 'Chevy 350' :D

6) The older setup should match up with my older systems (such as A/C and power steering) better.


Lastly, I understand when people swap 5.3 Vortecs into their XJ's, I think the alternator bracket and purge valve cause hood clearance issues, requiring a cowl hood. Does the 5.7 vortec assembly share this 'high accessory' setup? If so, can different brackets from a lower setup style be swapped in since the vortec 5.7 is still a Gen 1+?

I appreciate any and all help. And again, if I placed in the wrong spot, please correct me and tell me what steps to take to have it moved.
I have had both the L31 5.7L Vortec 350 and a 5.3L in my rig. The L31 had more lowend. The 5.3L loves to rev but still got the job done, and with a tune was even better.

I don't think its a bad choice even though what you listed (1-6) can be easily accomplished with a 5.3L as far as the FPR and sensors. But seems you are leaning toward the 350.

Now I doubt with bolt on's and tune you will see 290 HP at the wheels. Those truck made 200hp and 260ft lbs at the wheels stock IIR and 255 hp and 330 ft lbs at the crank. Now that said I would do a cam swap, but the stock vortec heads are limited in the amount of lift they will handle which really limits power. Stock heads w/stock retainers and valve guides will allow somewhere between 0.420" and 0.470" lift. If anything more than a stock cam is used new springs are required. So to much lift and problems and you'll spend at least $200 bucks just to get hte heads were they would take a good decent power cam. Also you want to swap to the "411" PCM goggle it! You might gain 50hp with the right cam. That said you still have to deal with the 19#/hr poppet injectors. I would just swap to a Marine or Ramjet 350 intake and ditch the CPI. Or at least upgrade to the newer injector spider assy. if keeping it. So spend all that money and it might make 300hp at the crank.


Now the good thing about the 5.3L is the Gen III's are very modular. Meaning you could buy a cheap 4.8/5.3 and later bolt a long block 6.0L right in its place and all you need to do is retune the PCM.

So the L31 5.7L really limits you power potential later if its just not enough. You can run the 5.3L and through in a decent cam and make some nice power numbers, you might just have to keep you foot in it more and rev it but it will get the job done.
 
#5 ·
Oh, I know 290 at the wheels woulda been a helluva alot more work. I was meaning 290 at the crank, because IIRC the mid year 5.3's had something like 295hp at the crank. The two biggest reasons I am straying from the 5.3L is because I lack the tools (and somewhat skill) to make a cowl hood as well as the fact that I am actually trying to avoid making serious horsepower. From what I've gathered, the stock XJ unibody can handle maybe a tad over 300 horses and I forget what amount of torque. And considering my 4.0 with a good high flowing exhaust and what not maybe puts down 200 +/- at the crank, a near 300 horse v8 would would be a very nice improvement in itself. Even a 290hp v8 gives me an extra 90 horses to play with. And I know 4.0 strokers can be built into the same power ranges stroked, but the v8 has mileage over them. 4.0 strokers use more gas. XJ's with V8's actually get better mileage, and considering late 90's Tahoes got 17-18 mpg highway at 5400 pounds, I can safely bet I'd get low 20's in my 3200 pound XJ. Plus, the 5.3's power really doesn't wake up until the mid to higher rpm ranges, which would basically mean a regear for me.

But hell, even with all that said, if I add up the cost of modifying the 5.7 to make close to stock 5.3 horsepower, and I can find a 5.3L assembly that's cheaper, I will probably jump on the 5.3. I would just hope to find a pre-03 LM7... I really don't like all that DBW bull. But I've heard the earlier 5.3's had piston slap issues. Lol, which way do I go? Thank God I have a good amount of time to figure it out completely.

Thanks for the help!
 
#6 ·
Also, can someone fill me in as to whether or not the A/C system is controlled entirely by the Chevy PCM?

Reason I ask, I am pretty sure my '91 XJ's HVAC controls are all closed circuits and vacuum controlled with no interface directly with the computer. The e-fan is an override in the PDC if I am I correct as well. If this is the case, I am guessing I would just go ahead and have my tuner remove any HCAV programs from the PCM, and then splice the wires for the compressor?

I have also been made aware that the PCM can be tuned to control e-fans. If I had this done, would I just reuse the existing override switch for the a/c?
 
#7 ·
I appreciate the searching and while I have no answers for you, all i can add is:

Gay thread title is gay. :flipoff2:

I LOL'd when I first read it. Immature? I know. Still funny.

Carry on.
 
#9 ·
The later pistons have coating on the side to help deal with the slap. You can get an 03 up and swap to DBC as well as run a car intake on it and leave the truck accessories.

Youcan just hook the compressor up to the HVAC system as all it needs too do is turn the compressor off and on.


Search on the XJ section here for more details on the swap.
 
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