Early 4.3 upgrade?

[Scruffy49]

The original issue 4.3 in my 85 swb is tired. Smokes like a 2 stroke tired. IF there is enough wall thickness left, going to rebuild it.
RV cam? Retrofit roller cam? Thermostat temperature? Exhaust w/o egr or smog pump provisions?
Already installed a non-ESC distributor (Jegs with 4 pin icm).
Swapping to a 500cfm capable Holley 2bbl on an adapter, 1/2” spacer, stock iron Qjet high rise intake.
Truck has a Th400 that will also get refreshed. Deep finned aluminum pan, higher flow rate filter, stand alone cooler, new cooler lines.
Rear axle is open 2.73s. Finned aluminum cover, getting new axle seals, internals all look factory new other than the leaking axle seals, pinion seal and tubes. Weld the tube/housing seams fully? Add a truss? Best brand for seals? Used to Mopar 8.75, Ford 9” and Danas, an 8.5” 10 bolt is a bit different.

I’m sure the long term GM guys are rolling their eyes, but, grew up building/driving flatheads and FEs. Not much translates…

Thanks for any parts/building reccomendations and/or tricks.

 

[Scruffy49]

And please don’t say LS swap it. I’d rather scrap it than run a computer controlled engine in it.

 

[Ricko1966]

Seriously with all the people doing LS swaps you should be able to find a usable as is SBC cheaper than you can buy a stock rebuild kit,more power,easiest swap ever and if mpg is your concern use a 305. My 2 cents

 

[bucket]

If I were to stick with the V6, I'd start with a 4.3 from a '96+ truck. They have much better heads, a balance shaft and a factory roller cam. You can find them used with fairly low miles still. With the money saved from not having to rebuild, there will be money left over for an aluminum intake and an electric fuel pump swap.

Then I'd swap in a transmission with overdrive. A 700r4 would work nicely here and it has a steeper 1st gear too.

Out back, don't worry about welding the tubes or any kind of truss. That's not needed at the power levels of a V6. However, I would swap to a 3.73 or 4.10 gear, depending on tire size. It will make the biggest difference for acceleration than any other modification to the 4.3l. Aside from boost.

 

[Scruffy49]

As long as it stays 4.3 and carbed. Not a mpg issue, the truck is mainly cruise nights toy and back up vehicle. I love the WTF factor when I pop the hood…

700r4? I have been turned against them by a 92 K1500 that eats them like a toddler eats cookies. But maybe would survive in a 2wd.

Truck runs P235/75r-15 all terrains out back on stock 6” rally wheels. Dropping the front tire back down to the as built P205/75r15, with st minimum a 3/5 static drop. Again, this is a toy, but if it gets a 700r4 swap, want the correct gear ratio.

Even at a never opened up 40 years old, sparkplugs are a perfect tan, just badly glazed by modern fuel blends. I change them at 24,000 miles, plugs are usually R44 or the Autolite equivalent. Truck got 12-14mpg in town, longer road trips once the carbon thins has seen 22-24mpg. Drive from Memphis to the MS Gulf Coast, 14-18mpg, coming home 22-24mpg. With the 400 and 2.73s. Original owner spec’d it to survive long highway road trips, in Texas.

 

[bucket]

The "correct" gear ratio isn't determined my keeping the speedometer accurate. The correct gear ratio is determined by the desired mix of power vs. economy. Then the correct speedo drive and driven gears are chosen to make the speedo accurate. The 700r4 can allow for much better acceleration when combined with steeper rear axle gearing, but continue with your current level of economy.

The stock 80's 700r4 used in a 4x4 would often fail at around 125k. They can be made to hold up much better than that. Imho, if your '92 truck is eating them then you are either installing used ones that are failure prone, or they are being poorly rebuilt.

 

[Ricko1966]

The "correct" gear ratio isn't determined my keeping the speedometer accurate. The correct gear ratio is determined by the desired mix of power vs. economy. Then the correct speedo drive and driven gears are chosen to make the speedo accurate. The 700r4 can allow for much better acceleration when combined with steeper rear axle gearing, but continue with your current level of economy.

The stock 80's 700r4 used in a 4x4 would often fail at around 125k. They can be made to hold up much better than that. Imho, if your '92 truck is eating them then you are either installing used ones that are failure prone, or they are being poorly rebuilt.

Or the TV geometry is incorrect or the cable adjusted incorrectly.

 

[legopnuematic]

I’ll add that the 700r4 or even a TH350c would likely increase economy by the addition of a lockup torque converter.

they are being poorly rebuilt

Or improper TV cable adjustment (I see Rick beat me too it) or any reused parts are not being cleaned properly or replaced at the time of overhaul. Things like cooler lines, cooler itself.

 

[Vbb199]

Make sure its a 87-91 700r4