Which engine to get?

[jorgensensc]

Hey guys,
It's been awhile since I have been on here, you know, life took over. So here is my question:
I've got a 72 3/4 ton suburban with the big block. Runs great, but gas mileage sucks (6-9 mpg). Soon going to be my daily driver. So I'm looking into an Lsx swap. I've been trying to read as much as I can, but it's to a point now where there is so much info, I can't figure out what's what anymore. Here are my options:
2011 5.3 with 500 miles, already has stand alone harness and PCM with mag and pedal. Mated to a built th350. Price: 2500.00
2006 6.0 with 70k miles with harness and tranny and PCM and pedal for 2500.00
Which would you get if you had the choice? Should I get the overdrive tranny? Will the 3 speed really hurt mpg that much? Will the th350 hold up to the weight of the suburban?

Also, let me see of I understand everything else I need for the swap:
Fuel pump (walbro)
Fuel regulator (99+ c5 vette)
Motor stands ( which ones are the best, and will work with my 3/4 ton frame?$
Exhaust work
Which exhaust manifolds did we decide work?
Sanden AC compressor brackets (already have vintage air front and rear)
Power steering hose adapters (where to buy from)
Electric fans (I thought there were some that mounted to the stock '72 4 core radiator?)
Tranny mount ( buy new or adapt my th400 crossmember?)
Driveshaft modified
Anything else I'm missing?

Thanks for the help guys!!
Posted via Mobile Device

[nightmare]

Originally Posted by jorgensensc

Hey guys,
It's been awhile since I have been on here, you know, life took over. So here is my question:
I've got a 72 3/4 ton suburban with the big block. Runs great, but gas mileage sucks (6-9 mpg). Soon going to be my daily driver. So I'm looking into an Lsx swap. I've been trying to read as much as I can, but it's to a point now where there is so much info, I can't figure out what's what anymore. Here are my options:
2011 5.3 with 500 miles, already has stand alone harness and PCM with mag and pedal. Mated to a built th350. Price: 2500.00
2006 6.0 with 70k miles with harness and tranny and PCM and pedal for 2500.00
Which would you get if you had the choice? Should I get the overdrive tranny? Will the 3 speed really hurt mpg that much? Will the th350 hold up to the weight of the suburban?

Also, let me see of I understand everything else I need for the swap:
Fuel pump (walbro)
Fuel regulator (99+ c5 vette)
Motor stands ( which ones are the best, and will work with my 3/4 ton frame?$
Exhaust work
Which exhaust manifolds did we decide work?
Sanden AC compressor brackets (already have vintage air front and rear)
Power steering hose adapters (where to buy from)
Electric fans (I thought there were some that mounted to the stock '72 4 core radiator?)
Tranny mount ( buy new or adapt my th400 crossmember?)
Driveshaft modified
Anything else I'm missing?

Thanks for the help guys!!
Posted via Mobile Device

Not that I've done anything yet, but I'd go with the overdrive tranny. The TH350 would hold up, since it was what came in these trucks originally though. You should be able to just move the cross-member to accommodate for the changes. I think that it was decided that the Camaro LSX exhaust manifolds worked the best. As for the electric fans, I've mounted the one from a Jeep into the fan shroud. Works great. Others should be able to tell you better though.

[airdale94]

What rear end and gears do you have? With the right gears and tune you should be able to get 12-14 mpg out of that big block.

[jorgensensc]

If I recall correctly it is a Dana 60 with 3.54 ratio. It also has an edelbrock 750 which I know is running a little rich. Everything else is stock except for distributor. I think part of the problem is where I live is near the base of the mountains. Everywhere I drive has a slow steady grade up wards. I'm always driving up hills it seems. The suburban is also pretty heavy. I haven't heard of anyone getting 12-14 with one of these big blocks, but I haven't seen everything either.
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[luvbowties]

Originally Posted by jorgensensc

If I recall correctly it is a Dana 60 with 3.54 ratio. It also has an edelbrock 750 which I know is running a little rich. Everything else is stock except for distributor. I think part of the problem is where I live is near the base of the mountains. Everywhere I drive has a slow steady grade up wards. I'm always driving up hills it seems. The suburban is also pretty heavy. I haven't heard of anyone getting 12-14 with one of these big blocks, but I haven't seen everything either.
Posted via Mobile Device

I'm betting, that with the slow steady grades you face, an overdrive tranny will not see much overdrive time, and therefore you'd not see much, if any improvement in mpg from there. That said, I'd think the 5.3 with TH-350 should give better mpg for your use. It seems to be quite a torky little engine, as demonstrated by new pickups. And, that 6.0 setup probably has a 4L80E trans with same 1st 3 gears the same as TH400 which is only a tad different from the TH350. The lighter 4L60E has a much steeper 1st gear to help your heavy load to get moving. Oh, and I'd swap that Edelbrock for a properly-tuned quadrajet to increase mpg a tad.
Good luck, & keep us informed which way you decide.
sam

[derrickmanx1]

Originally Posted by jorgensensc

If I recall correctly it is a Dana 60 with 3.54 ratio. It also has an edelbrock 750 which I know is running a little rich. Everything else is stock except for distributor. I think part of the problem is where I live is near the base of the mountains. Everywhere I drive has a slow steady grade up wards. I'm always driving up hills it seems. The suburban is also pretty heavy. I haven't heard of anyone getting 12-14 with one of these big blocks, but I haven't seen everything either.
Posted via Mobile Device

Just some thoughts on MPG's. Two things I would do before I made a big swap like that. Especially if I was dreading it would be to: 1. Buy a wide band a/f sensor and install it so I could tune the carb while crusing for 14 or 15-1 a/f ratio. This is the best and most accurate way I know of for carb tuning. 2. If you could install a vaccum gauge in the cab it helps you to monitor the efficiency of the engine. The higher the vaccum the better economy. At 8-10 mpg's 15-20% increase in efficiency means $$$$ in the long run. IMHO I believe the 700r would be great but I think with the bbc they tend not to like the torque output. For the money a stock 4l80e would be great behind the bbc and last a lot longer stock for stock. Good luck with it.

[gearys 5600]

The 5.3 would be my choice.

All the 6.0's that I have had get horrible fuel mileage and rattle like a diesel.

I'm sure this will miff off the 6.0 fans on here, and I'm sure there is some 6.0 guru out there who gets 50 mpg. Out of a 500 h.p. 6.0

As the owner of an auto salvage for 23 years, I have sold lots of 5.3 and 6.0 engines. I am a huge fan of the 5.3 and not so much the 6.0
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[crazy longhorn]

Originally Posted by gearys 5600

The 5.3 would be my choice.

All the 6.0's that I have had get horrible fuel mileage and rattle like a diesel.

I'm sure this will miff off the 6.0 fans on here, and I'm sure there is some 6.0 guru out there who gets 50 mpg. Out of a 500 h.p. 6.0

As the owner of an auto salvage for 23 years, I have sold lots of 5.3 and 6.0 engines. I am a huge fan of the 5.3 and not so much the 6.0
Posted via Mobile Device

2nd that....5.3/4l60e, will probably show you the best mileage/decent power. The 6 liter, tends to be a gas hog....but most are running 3.73 or 4.10 gears & coupled to the 4l80 e (the trans takes a little more power to run also), just like the old 400 turbo. For heavy towing, the 6.0/ 4l80e, hands down. If you are just "family cruisin"...mileage counts That 5.3 has plenty of power....got 1 on the stand, to replace the gen 1 383 in my longhorn. I am looking for mileage this tripp crazyL

[Vintage Windmills]

Originally Posted by gearys 5600

The 5.3 would be my choice.

All the 6.0's that I have had get horrible fuel mileage and rattle like a diesel.

I'm sure this will miff off the 6.0 fans on here, and I'm sure there is some 6.0 guru out there who gets 50 mpg. Out of a 500 h.p. 6.0

As the owner of an auto salvage for 23 years, I have sold lots of 5.3 and 6.0 engines. I am a huge fan of the 5.3 and not so much the 6.0
Posted via Mobile Device

Are you comparing apples to apples? Most 6.0's are in front of 4l80es and 4.10 gears and lugging another 1000lbs of truck around than the 5.3's. Put a 6.0 in a 5.3 application and see what the difference is. I had a 5.3 in a 4.10 truck and it sucked gas too.

[BIGBLU 72]

6.0! I have one in my Silverado SS and its great never have a need for more power!
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[jorgensensc]

I'm partial to the 6.0 myself. We had a Trailblazer SS with the LS2. We loved it! The 5.3 is practically brand new though!
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[bk2life]

leave the burban alone and get your self a honda for a daily driver.

[jorgensensc]

Originally Posted by bk2life

leave the burban alone and get your self a honda for a daily driver.

Unfortunately that won't work with a wife and 3 kids, 2 of which are still in carseats, and one that's 10 years old.
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[Tom Vogel]

If I were making the decision for myself, I would buy a Holley projection and a gear vendors overdrive for that BB. The new Denali gets maybe 14 on the Highway with the 6.0 and multi speed electronic overdrive.

[derrickmanx1]

I went with the original 402 and built a .030 over hyd roller motor. I will be using the fast injection. I'm hoping for 14-16 mpg with my 4l80e and 3.73 gears but with 460-500 hp. I could have done the whole 468-496 I just thought it would be cool to make the 402 so people could see the potential they have due to the superior heads flow and strenght. I have set the engine up for NOS if need be but i'll have to change my fuel injection if I go that route. If I was set on swapping I would do the 6.0 with the overdrive.

[duallyjams]

No matter what engine you decide on for fuel mileage you will need a OD trans. You could do the trans now with the BB just to see how much better the mileage would be. IMOP

[OldCreek]

If you're doing this for mileage/money then find a 5.3/4l60e combo for about $1-1.5K. Make sure it is complete with all the accessories and wiring. All the ancillaries will add up.

All the things needed to get it done seem overwhelming at first but knock them out one at a time.

All the guys on here will help you through it!!!!


Think about this though....commuting in a car that gets 6-9 mpg will cost a fortune in gas. Buying a commuter or car that gets a modest 20mpg will save you a few thousand dollars in a years time.... It may be time for cheap commuter/import.

With an LS swap you might get close to 15-18mpg (maybe 20?).... This is the route I'm gonna try with my C10 LS 5.3... The thought of a cheap commuter/import gives me the shivers.

[jocko]

I think this comes down to money vs. goal. It seems you are considering 2 choices that both have their drawbacks (i.e. "New" 5.3, but with a TH350 - and - 70K 6.0, but with an o/d trans in the deal). Between the two, I'd choose the 6.0 simply because a built TH350 is, well, still just a built TH350. Barely 3/4 tonner big block (or LS) material, even if built. And it won't help your gas mileage at all as it has the exact same gearing as your current trans (i.e. ANY mpg improvement would be due to the 5.3 replacing the 402 only).

So, have you considered adding only an o/d trans to your 402/3.54 combo? You keep the originality, keep the highway gears, get an o/d trans, and keep the born-with torque of the 402. Now, having said that, you will not see as much of an mpg gain as an LS or LQ, but, the money you save by keeping the original motor would pay for gas for a long time...

However, if your heart is set on a modern motor conversion, I believe I'd scrap both of your options and look for a relatively low mileage 5.3+o/d trans combo and go from there. While a 6.0 is nice, if your goal is mpg improvement, you're swimmin against the stream with a 6.0 (vs. 5.3) or, for that matter, a TH350 (vs any o/d trans).

If the two motors mentioned are your ONLY options, I'd choose the 6.0+o/d combo, avoiding the TH350 like the plague. It's a good trans, but if your goal is improved mpg, it won't help much in the long run. And if you're always going up hill, well, mileage will suck in any combo.

[jorgensensc]

Hey guys! Thank you all for your opinions and advice thus far! It is nice being able to bounce some ideas off knowledgeable people. I live that everyone is approaching this from different angles and perspectives. Couple of things:
I love originality, but I'm trying to be realistic with this suburban. Even with a tune I truly believe the 402 is going to be a gas hog. I didn't really care When we lived in Texas (I generally got 10-12 mpg), but now that we are in California I'm having to actually think about gas mileage. I drove the burb daily when we first got here for a couple of months. With just driving around town taking kids to school and running errands and such I was getting about 6-8 mpg, spending about 150 a week on gas. I can't keep doing that. So the main idea behind the swap is to turn it into a daily driver again. The kids love it (they call it the "broooom broooom" because it's kinda loud) and I would love to get rid of another vehicle and pay some bills off. With that said, if I can't make it an easy to run daily driver with decent gas mileage then I will be forced to sell it, which I really don't want to do.
I initially was going towards a 5.3 w o/d from a junkyard, but for one with 80k they want around 2500, plus all the other expenses like harness and PCM program. I liked the low mileage 5.3, but wasn't in love with the th350 combo on it. I thought about doing the 5.3 to my th400, but again, no overdrive. I was only interested in the 6.0 combo because I was concerned about the weight of the 3/4 ton burb killing the mpg and being a slug with the 5.3. I thought maybe the 6.0 torque would offset the potential mpg loss of the 5.3, creating a wash between the two.
Adding an overdrive tranny to the big block ends up costing a little less than an engine swap, but i would still end up needing to tune the engine better, and potentially still not getting much mpg improvement.
I thought about doing a fuel injection system on the 402, but they are expensive.
I thought about used 454 tbi, but even those are getting more expensive.
I even considered a DIY fuel injection system. Seems simple enough, but somehow I don't see it being that simple.
If I do an engine swap I can sell the 402 and tranny and stands and recoup some of my expenditure on the swap.

Geary's 5600, what is the going price for a lower mileage 5.3 with overdrive combo with PCM, harness, pedal, etc in your area? Say about 70k miles, but no more than 100k?
Thanks for the responses so far guys! I appreciate them!
Shawn
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[crazy longhorn]

If you have the time to part the truck, you will be ahead of the game purchased a complete"wrecked' 2000 GMC.4wd, with a good running 5.3 (130,000 rounds). I gave 1700 for the old truck, & 80 bones to tow it home....after all the smoke cleared(parts sold ,ect), I have $80 in a good running 5.3/all accseries/harness /computer....pluss a few parts for my 02 Silverado crazyL

[BuiltwithIvy]

I bought an 04 5.3l/4l60e/computer/harness with 30k for 800 in Texas last year

[crazy longhorn]

The 6 liter engines, seem to command the big bucks.....as shown, you can pick that 5.3, for a lot better price. Your truck.....your call, do what makes you happyThat is the way I do it Big fun, crazyl

[OldCreek]

You should in no way pay more than $1500 for a 5.3/4l60e combo with all the wiring and accessories. At least, I wouldn't. I got my set up for $1300 local. There are guys who got theirs cheaper but I figured I could stay local, get a little guarantee from the salvage yard, etc.

I just can't imagine being disappointed with this combo once it's up and running.

If I remember correctly, LS1tech.com shows a lot of guys getting great numbers and cost starting with 5.3l and switching heads/cams/tunes. The 6.0L is not an absolute and neither is the LS1/LS2....

[gearys 5600]

We sell the 5.3/ 4l60 combo for 1200-2000 depending on miles..

[67ChevyRedneck]

Stay away from all 2007+ 5.3L engines. They have AFM and are having a lot of issues with oil consumption and the 4 AFM lifters going bad... I'd stick with the 06 and older 5.3L.