327 + 700 R4 + Big Tires
 

I completed a build about 100 miles ago and I'm finding out that things won't be as I expected.
I built a 327 because I had all the parts on my shelves and didn't have to spend much.
The engine has flat top pistons .060" overbore, a small cam... one of the 204deg @ .050 kind like everyone makes
Smog heads, zero decked for about 8.5:1 CR.
Shorty headers... Q-Jet / Performer... Nothing too extensive
Behind that I put a 700 R4
3.73 gears and 31" tires
I pictured in my mind that I'd be turning about 2000 rpm at 55 mph with the TC clutch in lockup in overdrive
It ended up that in OD with the TCC locked up @ 60 I'm turning 1800 rpm, And the 327 is barely awake at that speed.
I thought that with a cam that small, the power curve would be fairly flat below 2000
But - IT WILL BARELY PULL OVERDRIVE ON LEVEL GROUND
If I switch the TC clutch on @ 60 mph, the vacuum ga drops from 15" to 10 or 11 and the engine needs help just to hold a steady speed
If I go 70 or 75, it's waking up a bit.

I've tried tuning the carb and ign timing, but it's apparently just something that's inherent to the design
The engine BEGINS to come to life at about 1800
I can downshift, no problem, but my fuel economy isn't what I'd hoped it would be.

I'm not unhappy with it. The 327 runs smooth and it's fresh, but it's not what I expected.
I thought I'd be able to cruise at about 2000 rpm @ 60 and get 18 - 19 mpg

It's over-geared
What to do?

If I get smaller tires maybe that will help
A 350? ... I have a 350 that needs to be put together
A 383?
I also have some Dart 165 heads with 72cc chambers and 2.02" valves That would raise the CR to about 9:1
I have parts for a TPI also, but no wiring harness

I'm just looking to compare notes and get some feedback

Looking forward to hearing what other guys have done

Thanks

Instead of swapping engines, and all that, why not just put a set of 4.10 or even 4.30 gears in it? Bump the RPM up just a little so you can cruise more comfortably

I'd do that, but it's a 4WD with IFS front axle and gear changes aren't as easy

They make different ratios for the front, as well. I plan on regearing mine to 4.56 at some point. My 3.73 don't really turn the 33"s as well as I hoped, lol

Well - For anyone else who's been thinking about doing what I did - It'll work, but the engine will be below the range where optimal V.E. is happening, when you're in OD on the freeway, so things will need to be changed if you expect to get acceptable MPG at highway speeds.
This same rig with a 350 in it got 19 mpg on the freeway - 29" Dia tires instead of 31.5"
That was with a Quqdrajet.