Harbor city, CA
Elevation 49ft
CylinderPressure, unspecified
transmission, unspecified
stall speed, unspecified
cruise-timing, unspecified
IDK how anyone can give you accurate advice.
But yeah, as I said earlier, 67PMJs are gonna be lean, requiring extra throttle to get to 65mph, and possibly to maintain it.
Put some 70s in there and 78s in the back, and a 10.5 PV. Sync the Transfer ports, reset your pumps, Modify your VA and Mechanical Timing Curve to, together, generate at least 48* of Cruise timing.
Here's how to set your cruise timing exactly right.
1) check your timing at cruise-rpm
2) rev your engine up to cruise rpm, Set your cruise timing to 48*, then
3) keep it there for the rest of this test.
4) without regard to the actual timing number, advance the timing a small amount. If the rpm goes up, bring it back to the reference rpm. Then repeat until additional timing produces no additional rpm.
5) but if additional timing from 48* does not produce additional rpm, then go the other way, taking out timing, looking for the whatever timing makes the rpm to peak.
6) after the max cruise timing is found; determine if the AFR is rich or lean, at that rpm, and fix it.
7) finally, take out 3 degrees of advance, to compensate for the lack of cruise load. Read the timing; Whatever you get now, at cruise rpm, that is what your engine combo needs and wants, and that is your target.
8) reset your cruise-timing to what it was in step one above; then return the engine to idle and let it cool before shutting it off.
9) now you gotta figure out how to get to that target.
Notes.
1) what you are hunting for is the magic timing number required at cruise-rpm, at the smallest throttle opening, that the engine combo is able to produce. Then lean it out to the minimum amount of fuel to maintain that rpm, at that throttle opening.
This is so easy, and it works for any cruise-rpm.
2) I once had a combo that cruised 75@ 1840 rpm, in double-overdrive. I used this method, and she gave me back 32 mpgUSg. I'm certain that if I had been cruising in direct at 3300, the results would have been very different.
3) Another thing I did was to, at cruise rpm/speed, put the trans into neutral and see how much distance it took to slow down to about 20 mph.
Then I checked the cars mechanicals to see what could be done to increase this distance. Things like adjusting the wheelbearings , the brakes, installing new U-joints, adjusting the front-end height, the attack-angle of the rear spoiler, and of course, the tire pressures and the alignment.
4) I don't run that combo any more. That cam lost lobes, and I replaced it with the next bigger size from the same manufacturer. This new cam lost bottom-end, big-time, relatively speaking, leading to a different transmission, and the loss of Second overdrive.
I took the engine apart, and increased the Scr some more, with slight loss of Quench.
The new combo cruises at 65=2240, and forget about 32mpgs. But it's still pretty good. But she now likes 56* or more, of cruize-timing. and I leaned her out a bit more, lol.
5) At cruise rpm the engine doesn't care about how many accelerator pumps are on the carb, and it doesn't care if it has vacuum-secondaries nor what size MJs are in it unless the PMJs are just too small, to even get to the desired cruising speed. It doesn't even care about the Transfer slot sync. unless the idle-mixture screws are cranked right out.
6) at cruize rpm, the engine only cares about maximum cruise-timing and minimum fueling, for the load it is pulling, which can change quite a bit with the engine's running temperature.
Addition concerns are; the inlet air temp, and of course the air density and humidity.
Some things cannot be easily compensated for, like the amount and strength of the overlap cycle, and most especially with the amount of power extraction degrees.
In your case I grossed your cam up to guess at the zero-lash numbers and the formula spit out just 106 degrees. This makes your compression degrees and your extraction degrees nearly identical to mine, with the exception that you overlap is about 67* to my 61*.
I see almost no reason that your combo, being roughly 600 pounds lighter than mine, couldn't out-perform mine in the fuel-economy arena, if we both ran at the same rpm. At that point, the only advantages that I might have is the 3.58 stroke, maybe a slipperier body, and the fact that I run a minimum coolant temp of 207, with fresh cold, above-the-hood inlet air.
And BTW, I run an ancient 750DP Holley that I bought used in about 1977. Notta chance would I, if I had your carb, give it up, no way.
7) Just to give you food for thought;
My previous cam was
276int/115comp/112Power/276 exh/53*o-lap
As you can see the extraction was 112* to your estimated by me, 106*
This cam was 223/230 @050; and it was way more fun than the cam that followed, namely,
276/114/105/286/61* overlap 230/237@050
Your 234/244 has at least 4* more exhaust duration than it needs, and for the lightweight car probably 8 or 10 too much. which at WOT is a maybe a good thing, but those extra degrees are stolen from the extraction cycle, which means, that at cruise rpm, a lotta pressure is going right out the tailpipe.
If I had your cam, I would retime it to 2* retarded, in at 110; But, this will reduce your CCP, which is why I asked for your current compression test results. If you are in at 104 now, going to 110, that represents a pressure loss of perhaps as much as 12psi, which with 3.91s and a 3500TC you won't hardly notice. But with 3.23s and a manual trans, I know is gonna suck.
However the 110 degrees of resulting Power extraction versus my estmated 106, is gonna make a huge difference in the potential to make fuel-economy, after the carb and timing is cleaned up.
I'm pretty sure your combo can't ever make 32mpgs, but I'll bet 20 in steady-state at 65=2400 is doable, and with any 750, and more with a spreadbore with triple boosters.