1985 6.2L Turbo?

[eagle mark]

I've been a gas guy all my life but have an opertunity to convert to a 6.2L. I've driven one before and pretty gutles but think the fuel milage was good?

How about a turbo on this?

Motor has 63K so how long do they last? Maintence problems or known issues on these?

 

[kennyw]

The fuel mileage is typically about double that of a small block setup otherwise identical. They can last a long time or a short time depending on how well they are cared for. Even if your motor has only 63K miles, you don't know how many hours it sat idling in a parking lot.

You will want to check the bottom end for signs of the block and crank cracking. Check the harmonic balancer for signs of deterioration (rubber breaking down or coming out). If it is still in running condition, getting a compression check is a good idea too.

 

[eagle mark]

Thanks Kenny.

Been doing some searching and not finding much on adding turbos or pump tuning, fuel presure and such...

How is the idle and off idle on these engines? I found the tech data but low end ratings were all from 1200 rpm. Is that bottom operaing rpm?

How do they run on the highway? Planning on my 700r4... dsns 44 front with 5:13, lock right and 36inch tires...

 

[6.2 man]

Mine does great on the highway ....I did switch intakes and installed one without the egr valve in it . Made a big differance and also I have over 230,000 mile on her and have only had glow plug problems and a water pump .

 

[Russell]

These engines have crazy good torque right off idle. I rarely touch the throttle in technical parts of the trail, even if it is a decent uphill climb. If the tires will catch traction, she will go up the side.

 

[kennyw]

These engines have crazy good torque right off idle. I rarely touch the throttle in technical parts of the trail, even if it is a decent uphill climb. If the tires will catch traction, she will go up the side.

And with the motor being governed, you don't have to worry about it stalling on most obstacles.

 

[eagle mark]

These engines have crazy good torque right off idle. I rarely touch the throttle in technical parts of the trail, even if it is a decent uphill climb. If the tires will catch traction, she will go up the side.

Tha'ts great! I'm assuming the engine is designed to operate at low RPM? Oil pressure wise? I know some engines will run great very low RPM but should really be kept at like 1200 RPM for proper oiling and cooling...

 

[tRustyK5]

My 6.2 makes 40-45 psi at idle. Good luck pulling it down under the idle rpm it's governed for...the more you try to pull it down, the more fuel it'll add to try to maintain idle speed.

That is one of the reasons they work so well off road with a manual tranny. I wheeled about half of Pritchett at BB '03 before nuking my rear driveshaft. Everything even remotely technical I did with my feet flat on the floor, at idle. If it could find traction it was gonna climb it. It made wheeling elegantly ridiculously easy.

About the only time you gotta worry about oiling issues is in an extreme nose down situation, but you have the same worry with about anything GM put in these trucks due to the rear sump.

Rene

 

[eagle mark]

My 6.2 makes 40-45 psi at idle. Good luck pulling it down under the idle rpm it's governed for...the more you try to pull it down, the more fuel it'll add to try to maintain idle speed.

That is one of the reasons they work so well off road with a manual tranny. I wheeled about half of Pritchett at BB '03 before nuking my rear driveshaft. Everything even remotely technical I did with my feet flat on the floor, at idle. If it could find traction it was gonna climb it. It made wheeling elegantly ridiculously easy.

About the only time you gotta worry about oiling issues is in an extreme nose down situation, but you have the same worry with about anything GM put in these trucks due to the rear sump.

Rene

That's all good news! Thanks!

 

[eagle mark]

So how goes the 6.2L with a turbo?

What kind of RPM do you guys turn on the freeway? I'll probably end up with a manual trans and 36 inch tires.... reason I ask is I have a set of 3/4 ton Dana 44 front flat top knukle and 14 bolt with 4:11 and one with 5:13...

 

[Russell]

Goes a similar to, if not a bit better than a healthy bone stock TBI 350 from the early 90s IMO Sounds way cooler doing it (I love that turbo whistle at speed!), and gets better than 20mpg on the highway to boot.

Mine runs around 2000 rpm at 60mph (4:56 gears with 34" tires and a .73:1 overdrive). The sweet spot for the non turbo engines is around 1800 rpm or so, but with oversize tires and heavy duty drivelines, I feel that turning the engine a bit faster is a good thing. I do have to downshift to 4th gear on some larger hills, but that is more due to rapidly climbing exhaust temps with the boost it builds than anything.

With your 36s and frequent freeway travel, I'd go with the 5:13s only if you are putting an overdrive transmission in. Definitely run the 4.10s with a non-overdrive transmission like an SM465 or SM420. The 5.13s would have you running nearly wound out spinning 2900 rpm at only 60 mph. The 4.10s would have you at 2200 rpm at the same speed. If this is a trail rig only, then the 5.13s wouldn't be a bad choice, however, your 1st and 2nd gears on an older 4 speed would be pretty much useless. Start in 3rd, and catch 4th shortly afterward!

 

[tRustyK5]

OK, for best economy aim for ~1800 rpm at cruise speed on the highway. Without OD you're never gonna see numbers near that low so just keep it in mind for the future.

My combo was 4.56's, SM465 and 39.5's ... 2550 rpm at 65 mph

4.10's, SM 465 and 36's ... 2484 rpm at 65 mph.

Near enough to the same. As long as it's not a commuter you'll be more than fine with that. I was for many years, including the trip down to Moab and back home to Vancouver BC. That's roughly 2500 miles of straight highway driving.

The 6.2 is governed to a max rpm of 3600 rpm, and being a V-8 it doesn't mind revving. You 'may' have seal issues like I did though if it spins those R's for extended periods of time. I came home to a rear main seal that was in need of replacing after BB '03. It may have gone anyways, but I don't think turning ~2600 rpm for 2500 miles helped any.

A turbo on a 6.2 is fine, Banks has had a kit available since the 6.2 was intro'd...in fact GM used the Banks kit as a dealer option before the 6.5 TD was offered. You can't run crazy boost, because the 6.2 has relatively high 21.X:1 CR. Seems 7-12 psi is about it...but that does a lot to wake these up.

I found as long as they're geared a little agressively they move out decently even without the turbo. However, most stock 6.2 rigs got craptastic gearing too.

Rene

 

[eagle mark]

You guys seem happy with them. Would you do it again?

Also anyone have a photo of where the exhaust routes? I'm looking to put this in my 73 Scout II. May have to look for real estate for the radiator... and turbo pipe... and innercooler...

 

[Russell]

I'm not running an intercooler yet, and I ran my exhaust down the outside of the frame rail. I'm running a GM-3 turbo which dumps directly above the rail, I could easily have inside the frame rails with any other transmission, but my slave cylinder makes clearance too tight for a 3" pipe

 

[AJMBLAZER]

I found as long as they're geared a little agressively they move out decently even without the turbo. However, most stock 6.2 rigs got craptastic gearing too.

Rene

Amen. Both of mine have deep gearing (4.56's in Big Ugly and 3.73's in The Blazer) and they drive just fine.

I've also found most folks who say they're slow have only ever driven either a heavy truck (C/K30 work truck) or a half ton with 3.08 gears.

 

[6.2Blazer]

I've owned my 6.2 Blazer since '94 and it spent many years as stock to mild build daily driver with decent gears (3.73 with 32's, and then 4.10's with 33's). Even after driving my 300 HP 2500HD for several years I would not hesitate to daily drive another 6.2 powered vehicle.

 

[tRustyK5]

My C10 pick-up has 3.42's and 28" tires...and it moves out very well for a NA 6.2. Someone has turned the pump up in the past though, it smokes like a modded 12 valve at WOT. In fact I start getting noticeable smoke at under 1/2 throttle.

I'd do it again, although i might go big block with the Crew Cab. Haven't decided yet. The big decider for me last time was that my Jimmy was also my DD...so the 6.2 solved the most issues. Good off road, good road manners, cheap to swap to, double the fuel mileage I had been getting with the 355.

Rene

 

[MaxPF]

You guys seem happy with them. Would you do it again?

Also anyone have a photo of where the exhaust routes? I'm looking to put this in my 73 Scout II. May have to look for real estate for the radiator... and turbo pipe... and innercooler...

My 91 K5 originally had a TBI350 in it, and got a stellar 11MPG tops with a 4L60, 4.56's, and 37's. I swapped in a 165HP J-code 6.2 (you will find that HP J-code in the 91-92 3/4 and 1 ton trucks) and I haven't looked back. I get 16MPG MINIMUM in town. Highway I can do 18 or a bit more. Keep in mind lifted trucks with deep gears and big tires are never going to get the high mileage figures some claim. Anyway, power is close to if not equal to the TBI 350, despite the 45HP difference on paper. Low end torque is great - if I step on it I can squirt my way into traffic no problem. I actually like it so much that I abandoned a Cummins swap (besides the fact a Cummins is awfully porky for a K5, and the swap was going to be $$$).

My only recommendation is to look for a good low-mile CIVILIAN engine. Military engines have been beat on more than Tiger Woods and by the time they are retired they are usually either worn out or plain broken.