5.7 vortec vs 5.3l or 6.0 swap

[MrPink]

I'm no environmentalist or nothin', but wasn't there something to do with CAFE? I mean sure the 5.7 doesn't drink much more than the 5.3, but when seen as a whole picture of all the trucks produced with a 5.7 vs. 5.3, those MPGs saved will definitely add up. My guess is even though the 5.7 might have been better suited for truck stuff (ik this statement is argumentative), the 5.3 drank a little less, so it was a better candidate?

Same reason we have these brand new heavy a** Silverados coming out with 4 cylinders in em, whatever will please the environmentalists on paper, and allow the company to produce ICE vehicles... you gotta do what you gotta do.

Also, please correct me if I'm wrong, but don't automotive manufacturers have to support a vehicle they produce for like 10 years or something at minimum? My guess to that second question quoted is that GM already met their minimum requirement and moved on to the more relevant stuff for them (i.e. LS-based engines and resources for future projects). No point in spending money to keep the operations running if the majority of people at the time are not buying the replacement parts being produced.

CAFE had everything to do with it as did the EPA, getting emissions reduced, and MPG improved, so yes the 5.3L was a better choice.. And yes we support most vehicles for 10yrs.

 

[618 Syndicate]

I must have missed something, but stock motor performance has no meaning to most of us as not even my cub cadet is left totally stock.

Carry on.

Agreed, but if we're evaluating platforms, comparing modified to stock is pointless, and modified to modified depends entirely on intended use and budget.

 

[RedneckWithPaychecks]

I must have missed something, but stock motor performance has no meaning to most of us as not even my cub cadet is left totally stock.

Carry on.

Even my waffle maker is modified...

 

[618 Syndicate]

Even my waffle maker is modified...

Boob job?

 

[tayto]

technically if you get a paint chip or replace the windshield your vehicle is no longer "stock". a 60s era numbers matching muscle car with a TH350 and you use modern frictions or a 700R4 sprag? sorry not stock. Oh your running DEX III? Sorry not stock. come on......

 

[618 Syndicate]

technically if you get a paint chip or replace the windshield your vehicle is no longer "stock". a 60s era numbers matching muscle car with a TH350 and you use modern frictions or a 700R4 sprag? sorry not stock. Oh your running DEX III? Sorry not stock. come on......

We're talking about motors, not entire vehicles. You tried though...

 

[tayto]

ok then, you replaced the original spark plugs. no longer stock

 

[618 Syndicate]

Only if the numbers we're using to compare stock motors were reported by the manufacturer after someone changed plugs. Which is highly unlikely.

 

[JeremyNH]

This thread really went off the rails. I have a 1998 Z71 with a marine intake, marine cam, and cpc so I've fixed some of the shortcomings the L31 had over the LS motors by adopting some of what the LS had that technology didn't allow when my truck was made. My take, and only mine, is that the LS is a superior engine no question. Better architecture means more power for displacement and better fuel economy. When comparing whether to upgrade the sbc or swap to LS depends on the starting platform. Leaving fuel efficiency aside (the sbc will never match no matter what you do) if you are starting from an L31 you can match the performance of an LM7 or even LQ4 for a little less money and a lot less effort than the cost to swap. But to beat LS performance without sacrificing drivability you need to spend a lot more. But then you can swap to an LS and spend on performance parts and outperform your built sbc but, again, at a premium over the built sbc. So which way you go depends on your aims and your pocketbook. Personally I have a block in the machine shop as of Monday being bored and clearance for a 390 stroker. I expect it will outperform stock motors even on the Gen5 trucks when done (except on fuel economy see above) but those with a built LS will beat my build. But it's just a personal preference (everyone has a LS swapped truck but fewer a stroker, and fewer still a 390 with marine intake and cpc). In truth the L31 is plenty truck as it is for what I use it for but has sentimental value as an inherited vehicle bought new by my dad. But on close I think it's a safe statement that whatever a sbc can be made to do a LS can be made to do better. Just depends on your aims, desires, and how much patience the CFO has. Common sense plays no part.

 

[L31MaxExpress]

This thread really went off the rails. I have a 1998 Z71 with a marine intake, marine cam, and cpc so I've fixed some of the shortcomings the L31 had over the LS motors by adopting some of what the LS had that technology didn't allow when my truck was made. My take, and only mine, is that the LS is a superior engine no question. Better architecture means more power for displacement and better fuel economy. When comparing whether to upgrade the sbc or swap to LS depends on the starting platform. Leaving fuel efficiency aside (the sbc will never match no matter what you do) if you are starting from an L31 you can match the performance of an LM7 or even LQ4 for a little less money and a lot less effort than the cost to swap. But to beat LS performance without sacrificing drivability you need to spend a lot more. But then you can swap to an LS and spend on performance parts and outperform your built sbc but, again, at a premium over the built sbc. So which way you go depends on your aims and your pocketbook. Personally I have a block in the machine shop as of Monday being bored and clearance for a 390 stroker. I expect it will outperform stock motors even on the Gen5 trucks when done (except on fuel economy see above) but those with a built LS will beat my build. But it's just a personal preference (everyone has a LS swapped truck but fewer a stroker, and fewer still a 390 with marine intake and cpc). In truth the L31 is plenty truck as it is for what I use it for but has sentimental value as an inherited vehicle bought new by my dad. But on close I think it's a safe statement that whatever a sbc can be made to do a LS can be made to do better. Just depends on your aims, desires, and how much patience the CFO has. Common sense plays no part.

I have zero complaints on fuel mileage. My moded L31 fuel mileage stayed the same as the EPA rating and sometimes it returned a full 1 mpg better. Fuel mileage on the 383 decreased less than 1 mpg despite it making over 100 hp more. On the highway it just stays in lean cruise more with the added torque and power. The 5.3L is EPA rated the same and the 6.0L worse. 6,200 lbs van still knocks on 18 mpg on the highway, which is what it got for 1,000s of miles with the stock L31.

With the 24x you should be at 16.5-17:1 afr and 48-52° of timing at 2,000-2,500 rpm. My L31 would still make 12-14 in/hg vacuum in lean cruise with 3.73s and the 4L85E cruising on flat road at 2,400 rpm at 70 mph. What I observed with the same intake and cam you have running the 24x system. I was even playing around with converter unlocked on slight grades for added torque multiplication and unlocking the converter kept it in lean cruise uphill at a lower engine load but about ~200 rpm higher. Unlocking the converter on slight grades gave me about 1 mpg better on trips with lots of hills.

Converter unlocked up about a 4% grade.

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