93 6.5 into 86 crew cab

[campfire]

Hey there. Hate to thread jack. But do you have any experience with running a 6.5 with a small tire..say 29 or 30 and a 3.07 or 3.42.

Everyone i dove was a 4.11 tall tire 4L80 truck. Im trying to find optimum highway rpm for a little 6.5 in a 2wd im going

I don't see a specific question here, but I'll share my experience.

My '83 K10 has a nearly-stock 6.2/700R4/3.08/29" combination.
My '84 Suburban has a stock 6.2/700R4/3.73/31" combination.
My family's '93 K10 has a stock 6.5/NV4500/4.10/33" combination.

The K10 is close to what you're describing. It is a great combination for light loads, sporting really nice fuel mileage numbers. It does require some patience compared to modern vehicles, but it does not seem any slower than a stock sbc. I'm not one to race down the road, but I don't lag behind traffic, either. It's worth noting that I live at <1000' elevation and have never taken it up anything steeper than 7% grade. The low-end torque makes up for the anemic gearing at low speeds. At high engine speed the power availability drops off, but running the turbine setup should rectify that. At 65 with light loading I can take up to about a 4% hill without it downshifting (and I'm sure that having a stick would improve the control of this aspect). With a trailer, it gets kinda slow, and there isn't a gear on the 700R4 that makes it happy clawing up a steep hill under heavy load (perhaps with the shallower O/D that the 3500/4500 have). But if you aren't trailering the combination is just peachy.

Mileage is great for the class. In town I expect 19-20MPG. OTR, I expect 21-22MPG @ 65MPH and 23-24MPG @ 55MPH. My one modification is swapping the c-code manifold for a 6.5 intake manifold (stock airfilter). Before that swap mileage was slightly lower. Running a stick might improve this.


The Suburban gets much more power to the wheels, but it just spins too fast at highway speed (compounded by the TC failing to lock up). The M1009 Blazers (6.2/TH400/3.08/31") that I have driven had the same problem. 1800RPM is fast for a 6.2 engine. 2500RPM is just too fast. At 55MPH the K10 spins 1375RPM. At 65MPH I calculate 1625RPM. This will comfortably take most midwestern hills without downshifting. The Suburban has taken every hill yet without downshifting (Even when I tipped the scales at >11,000# while trailering scrap). It is overgeared in its current condition.

The 6.5/4.10/33" truck is set up for heavy trailering, and it does a good job hauling. It's fun to watch the boost gauge rise and feel the accompanying surge of power. Maybe someday my trucks will do the same.

1800 RPM is a common target speed. This will give you more power than I have without sacrificing too much economy. How heavy a load are you planning to haul? I'm guessing this is a 2WD street truck. In which case you may find that my gearing + the 6.5 turbo setup is exactly what you want.

Do you have any specific questions about the setup?

 

[63chevyll]

Campfire.

This is all great. Thanks. I remember reading somewhere thats 1800-1900rpm is a good target for no load and highway speeds.
I like your suburban gearing the best. Im shooting for a lower RPM at highway speeds. I wont be towing anyting and at this point im trying to pick my trans and rear ratio. Yes its a light street truck.

I have some pictures of my contraption in the GM diesel thread. I was asking some questions.

 

[campfire]

Campfire.

This is all great. Thanks. I remember reading somewhere thats 1800-1900rpm is a good target for no load and highway speeds.
I like your suburban gearing the best. Im shooting for a lower RPM at highway speeds. I wont be towing anyting and at this point im trying to pick my trans and rear ratio. Yes its a light street truck.

I have some pictures of my contraption in the GM diesel thread. I was asking some questions.

Ok. I think the Suburban is ridiculously overgeared for a non-trailering street rig with 31" tires. Swapping down to 29" and adding a turbine like you suggested may be overkill. I did try 29" tires last summer for a short time and found it downright irritating. FWIW, the Suburban is tagged as a high-altitude model. Not sure if that impacted the original gearing choice or not.


What tranny are you wanting to run? The different O/D ratios can make a noticeable impact on the engine speed. All of the non-700R4/4L60 GM tranny options that I'm aware of will have a shallower top gear than what I'm running. The final ratio on a 4L80 will make my 3.08 feel like a 3.30 ratio and my 3.73 feel like a 3.99 ratio (.75 vs .70 for 4th gear ratio). Definitely something to keep in mind as you pick your numbers.



I found some engine/turbo pictures in your turbine thread. You have any truck pictures yet?

 

[63chevyll]

No pics on my phone and i should keep this thread on topic (sorry)
But... turbo 6.5 4L80 or 700r4, 2.73, 3.07, 3.42, 3.73 or a 4.11 is what i have with a 29 inch time. Weight around 2000lbs

 

[blazinzuk]

No pics on my phone and i should keep this thread on topic (sorry)
But... turbo 6.5 4L80 or 700r4, 2.73, 3.07, 3.42, 3.73 or a 4.11 is what i have with a 29 inch time. Weight around 2000lbs

Your stuff is more interesting than mine. I just posted mostly cause I am happy I finally have a plan and all the parts to make this happen

 

[82355]

When do you expect to actually start working on it? Seeing as you are buying the house, fixing up the shop, etc.

(Just curious, not mocking, the written word is so easy to take out of context.....)

Martin

 

[blazinzuk]

When do you expect to actually start working on it? Seeing as you are buying the house, fixing up the shop, etc.

(Just curious, not mocking, the written word is so easy to take out of context.....)

Martin

The plan is in about 2 weeks. The only trailers that were big enough to haul the 2 trucks have all been pressed into service doing other things. So helping my buddy put together his newest aquisition is needed before the trucks get up to my place.

So lots to do but first thing will be to disassemble the 93. Then rebuild the 4l80. By then I should know what parts I need that one would not expect.

I don't move fast unfortunately on these things due to my health but I need to get this in and running sooner than later

 

[campfire]

No pics on my phone and i should keep this thread on topic (sorry)
But... turbo 6.5 4L80 or 700r4, 2.73, 3.07, 3.42, 3.73 or a 4.11 is what i have with a 29 inch time. Weight around 2000lbs

That's quite a wide range of gear options.

You have access to any similar trucks so you can test drive some of these gear combinations? Or have you had something like this in the past?

And what are you driving that will give you a 2000lb weight?

 

[speed_deed]

My k5 with 6.2 700 and 3.42 got amaizng mileage in town and on the highway. It went down the road great maybe too good blow the bottom end out of it and had to rebuild.

My 96 6.5 4l80 4x4 suburban with 4.56 is retarded low. I put 285 75 16 on it and it can get down the highway anything smaller is so stupid on it.


I think 3.42s or 3.73s is about ideal for a daily driver that isnt tugging HEAVY loads often

 

[blazinzuk]

My k5 with 6.2 700 and 3.42 got amaizng mileage in town and on the highway. It went down the road great maybe too good blow the bottom end out of it and had to rebuild.

My 96 6.5 4l80 4x4 suburban with 4.56 is retarded low. I put 285 75 16 on it and it can get down the highway anything smaller is so stupid on it.


I think 3.42s or 3.73s is about ideal for a daily driver that isnt tugging HEAVY loads often

Well the eventuality of it is that it will in fact get bigger tires. So I will just go slow until then. Gonna be alot better than with no overdrive though