Opinions on touring enging options...

[TIE_Fightertk06]

On the last trip out with my R2500 Suburban, I had some time to think about what's next for that truck. With the 700R4, and the 3.73 rear end sorted, I think next year's big work will be an engine overhaul or replacement. I think by the time I get done with this summer's road trip, I'll be fed up with cruising at 65 mph just to eek out the best MPG.

So here's my question:

What do you think the best option would be for a proper grand touring engine? I want more power than the 5.7 TBI is putting out, as it is pretty lethargic. But I also want fuel mileage at least in the 20s like I have right now (20.5 avg on this last trip)... Better is always, well, better.

My gut says a 383 with good heads and a simple programmable/learning fuel injection setup would get me to where I want to be.

I'm not feeling an LM7 swap for this truck, but I suppose it should be considered given the performance and MPG they can get for the money.

Let me hear what you think, and why, if you can spare the time.

Thanks!

 

[Adam G]

I would go with an LS swap they make good power and can get good gas miliage

 

[1987 GMC Jimmy]

I think in terms of power vs. economy, you're going to have to pick your poison and mitigate your loss in the other area. It's clear that power is the priority over economy, but you can certainly build something that won't be a fuel hog. I'm not a big fan of an LM7 swap, myself. However, I am starting to warm up to Gen III swaps that utilize a carb and distributor conversion kit. What I'd like to do someday to my Jimmy, which has the same setup as you do, is build a Vortec 350 using the factory TBI system. You already have the self-learning fuel system. It's more primitive, yes, and the actual air/fuel delivery was anemic from the factory, but that can be overcome. Let's say we're using the 350 that's already in yours. Here's what would likely need to go down to make that thing really sing. Exhaust. Ditch the manifolds, and get some long tube headers. You can do a nice, simple dual exhaust, which will be especially easy if no emissions constraints in your area. You'd need to do a heated O2 sensor, but that's like five minutes and done. Cam. I'm really looking at the Comp 08-300-8. It's a fairly mild roller cam that takes advantage of the fact that you have a later model SBC. You'd have to upgrade valve springs on Vortec heads, but overall it'd be a definite upgrade over whatever flat tappet cam GM put in there. Heads would be Vortec, of course. Keeping TBI, the only Vortec intake out there is Chevy Performance 12496821. Fuel delivery. You could send your current TBI to be worked at SPR performance from a 450 CFM unit to a 650 CFM unit, and you'd need a 1994-95 454 TBI or Walbro aftermarket pump to push the requisite fuel pressure if I'm not mistaken. Finally, the PROM. I don't really know what has to happen here. In this hypothetical build, you didn't disturb any of your sensors. Your cam is also a computer friendly model... That being said, I don't see how all the stock parameters will line up with your much better engine, but it's not like you're completely reinventing the wheel on this one. When I went out and looked for my vehicle, I wanted a 1987-88 Jimmy because of the TBI. I was tired of pissing around with carburetors and wanted something more modern that wouldn't, at least in my eyes, destroy the identity of the vehicle - in this case a square body. Little did I know then that TBI, while economical, reliable, simple, and very turn key, isn't very good in terms of power potential. It is fixable, though. You've already got an engine. I think it'd be cool to give it a second life. Even though I probably missed a couple points, and there maybe a few bugs in my theory here, I think it's a fairly solid roadmap. You wouldn't kill your economy, and you should have a motor that's putting out 360-400 HP. Besides, wouldn't it be cool to smoke some kid who thinks he's got himself some little hotrod in a regular old TBI 350?

 

[Honky Kong jr]

Depending on budget and technical restraints 6.0 6L80 swap. Would be good power and economy.

 

[4WDKC]

I think in terms of power vs. economy, you're going to have to pick your poison and mitigate your loss in the other area. It's clear that power is the priority over economy, but you can certainly build something that won't be a fuel hog. I'm not a big fan of an LM7 swap, myself. However, I am starting to warm up to Gen III swaps that utilize a carb and distributor conversion kit. What I'd like to do someday to my Jimmy, which has the same setup as you do, is build a Vortec 350 using the factory TBI system. You already have the self-learning fuel system. It's more primitive, yes, and the actual air/fuel delivery was anemic from the factory, but that can be overcome. Let's say we're using the 350 that's already in yours. Here's what would likely need to go down to make that thing really sing. Exhaust. Ditch the manifolds, and get some long tube headers. You can do a nice, simple dual exhaust, which will be especially easy if no emissions constraints in your area. You'd need to do a heated O2 sensor, but that's like five minutes and done. Cam. I'm really looking at the Comp 08-300-8. It's a fairly mild roller cam that takes advantage of the fact that you have a later model SBC. You'd have to upgrade valve springs on Vortec heads, but overall it'd be a definite upgrade over whatever flat tappet cam GM put in there. Heads would be Vortec, of course. Keeping TBI, the only Vortec intake out there is Chevy Performance 12496821. Fuel delivery. You could send your current TBI to be worked at SPR performance from a 450 CFM unit to a 650 CFM unit, and you'd need a 1994-95 454 TBI or Walbro aftermarket pump to push the requisite fuel pressure if I'm not mistaken. Finally, the PROM. I don't really know what has to happen here. In this hypothetical build, you didn't disturb any of your sensors. Your cam is also a computer friendly model... That being said, I don't see how all the stock parameters will line up with your much better engine, but it's not like you're completely reinventing the wheel on this one. When I went out and looked for my vehicle, I wanted a 1987-88 Jimmy because of the TBI. I was tired of pissing around with carburetors and wanted something more modern that wouldn't, at least in my eyes, destroy the identity of the vehicle - in this case a square body. Little did I know then that TBI, while economical, reliable, simple, and very turn key, isn't very good in terms of power potential. It is fixable, though. You've already got an engine. I think it'd be cool to give it a second life. Even though I probably missed a couple points, and there maybe a few bugs in my theory here, I think it's a fairly solid roadmap. You wouldn't kill your economy, and you should have a motor that's putting out 360-400 HP. Besides, wouldn't it be cool to smoke some kid who thinks he's got himself some little hotrod in a regular old TBI 350?

The vortec build is an easy swap, not sure on what mileage will be as mine is not done. I have everything except accessory brackets to do the swap from my vbelt config. The ecm can be modified to use a new chip that is faster to burn, guaranteed to erase and cheaper. The ecm isnt that good at self tuning so you would need to learn to do it or work with someone remotely. Vortec swap needs more fuel than TBI so you would need to pick up a ep241 or ep387(?) Delco or Delphi pump, the 241 is from a tpi fbody and will handle the swap, if you think you may ever do a ls swap, a full vortec swap you will need the ep387(?). It is a stock vortec replacement pump and will support the ls swap also, If you don't have emissions you dont need the expensive gm TBI/vortec manifold with EGR. I am going to use a carb manifold for vortec with an adapter for TBI.