'71 Burb "Earl" drivetrain

[RyanAK]

Hey, gang. As I'm getting the suspension plan in order for Earl, (see http://67-72chevytrucks.com/vboard/s...d.php?t=593384) I thought I'd start a discussion to gather thoughts on some possible upgrades to the heart of the beast.

Earl has about 48K on the original 350/350TH and 3.73 rear. Runs like a champ, if somewhat leisurely. I'm looking for ideas on a nice balance between snappy performance and reasonable economy. Fun to drive, but won't kill me at the pump. The '04 Z71 Burb with 5.3 gets 18mph, and I'm ok with that. Most miles that Earl sees will be highway miles.

Engine-wise, I'd like to keep the original 350 and go with bolt-on upgrades. Headers, carb, intake, heads, etc. 48K on it, after all! I'd be interested in eventually going with a transmission swap to gain overdrive. Or a shift kit if it will gain me something. Rear gears... I actually think the 3.73 is a good compromise, as Earl may very rarely get the call to tow a 3800 lb (dry) Airstream. But highway driving gets priority.

So whatcha think? What are some reasonable upgrades that work well in combination to get me that performance/economy ratio I'm looking for?



Thanks guys.

Ryan
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[Average Joe]

Hey Ryan i'll throw in my 2cents for what its worth. Id start with a good HEI ignition if it doesnt already have it. Try for 36 degrees total timing all in by 2800ish rpm not counting vacuum advance.
Next I would consider a rebuild on your qjet. S.M.I. or Cliff Ruggles can do a quality rebuild and custom build it to your specs.
I'd also get a full length 2 1/2 exhaust with low restriction mufflers. Headers generally require more maintenance than manifolds and your existing ramhorns are pretty good as manifolds go.
If you dont already have a clutch fan you might want to consider one or go dual electric fans.
If after all this you still want to do a head swap grab some vortec heads with a intake manifold that fits these heads ie edelbrock performer with a spreadbore carb pattern soyou can utilize your qjet. Swap in a mild cam keep duration under 218 at .050 and lift under .460 and youd be set. Oh btw vortecs like less timing like 32 max.

[RyanAK]

Right on. A lot of what I'll do depends on the current state of the 350. She's running good now, but won't know it's potential until I get home to PA and do a compression check and some other snooping around.

Assuming the motor is basically good, my initial plans are for:

HEI, plugs, wires. Need to do some research here.

Electric fans.

Q-Jet rebuild (thanks for the names!) I like the power/efficiency potential with this carb due to the small primaries backed by respectable secondaries. Should get decent mpg if I keep my foot out of it, but have some snot when I want to play.

Better air filter to let 'er breathe.

Bigger dual exhaust with high flow mufflers to let 'er exhale.

This should give a little more pep to an otherwise stock SBC. All that can be done without pulling the motor. Honestly, if I go down the heads, intake, cam, etc. road, I'll probably go crate 350/700R4. Whatcha think?

One thing I've been pondering is getting the RPMs down at highway speeds. I don't have a tach, but the TH350, 255/70R15s, and 3.73 sounds wound up. An RPM calculator over at chevellestuff.net shows 3020 RPMs at 70 MPH. That sounds about right...

The same calculator shows these interesting numbers. 255/70R15s at 70 mph.

TH350 with 3.73 rear = 3020 RPMs.
700R4 with 3.73 rear = 2141 RPMs.
TH350 with 3.07 rear = 2486 RPMs.

An OD tranny is obviously the preferred swap, but what would switching to a 3.07 rear end be like with a 350 with the above bolt-on upgrades? Better mpg with acceptable spunk, or a chugging small block with neither efficiency nor power? Hmmm....

R
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