72 Olds daily driver best MPG carb?

[Seff]

Currently driving a '72 Olds Cutlass Supreme as a daily driver, 350 CID, low compression, stock in all aspects except after-market HEI and headers. 5 mile round trip to work. The current carb is a '71 Q-jet rebuilt with one of Cliff's kits, but has a dying vacuum choke pot, leaks/drains, and the engine pops at slow idle. Casting number 7041250. Current mileage highway is 14.8 MPG.

I have two 17057253 carbs lying around, apparently 1977 Olds manual trans Q-jets. Would it make sense from a mileage perspective to rebuild one of these instead of the '71? Given that they're born with HEI engines, and apparently have newer technology than the '71 carb, they COULD conceivably have better mileage characteristics. They're of the M4MC type.

[Shark Racer]

I like the M4MC carbs better as APT is easier to get at and the castings are a little sturdier over all.

I believe Cliff's opinion is similar.

I'd recommend building the carb with a good kit from Cliff as well as one of his choke pull-offs. I just received one and it's ready-to-rock for performance unloading.

How is the car currently geared? That mileage would be a little weak if you're running a tall gear like a 3.08 or 3.36, but is actually quite good for a lower gear...

[Seff]

It's running a 2.56 and a TH350. I was semi-expecting 20 MPG given that I'm not on all four barrels all the time.

Maybe I've just not tuned the carb correctly.

[Shark Racer]

Yes it should be a bit better, but bear in mind you are not running a lockup trans so that lops a few mpg right off the top.

[Seff]

Doesn't sound like a horrible idea to order a kit for it, then, and put one of those together.

[Cliff Ruggles]

The early carb can be made to work fine, with the correct tuning parts and accessing the APT system in the baseplate.

I still use and prefer the later carburetors for a variety of reasons, which are outlined in my book.....Cliff

[Seff]

I've decided to buy your book, since I'm tired of being fooled by a piece of alu with flaps, levers and hoses all over it. Before I do so, since shipping is expensive to Denmark, do you have any recommendations for jets and rods? Anything else apart from the HP kit off your webshop? The vacuum pods work very well, the choke pull-off and the one that attaches to the rear of the carb(not sure where that one should be drawing vacuum, actually).

I cleaned and reassembled the newer carb, and noticed that it has a bent choke housing (cover won't rotate), and is missing the whole hot idle compensator assembly. I'm assuming that either of those faults would result in the choke pull-off not being able to lower the idle, even when the pedal is applied a few times (which is how the old carb seems to work)?

[Cliff Ruggles]

Plug the hole in the rear of the carb and don't worry about the HIC.

The rear pull-off is not needed, just a back-up for the front one, we don't use them here.

I can supply the correct jets and rods when you place an order...thanks....Cliff

[Seff]

Excellent, I'll place an order and note my username and that I'd like jets and rods in the comments.

EDIT: Forgot to mention that I'd like the book as well in the order comment. >.>

[Cliff Ruggles]

Best to call the shop to place an order, we're here 8am-5pm M-F EST....thanks....Cliff

740-397-2921

[Seff]

What's that in GMT+1? I'm in Denmark.

[Shark Racer]

5-6 hour difference depending on daylight savings time.

[Seff]

I'm well aware, it was a failed attempt at suggesting email instead.

[Shark Racer]

Well worth a phone call to Cliff... fwiw.

[leeklm]

Another + for the newer carb.  I Have only built three qjets using Cliffs book, two from early 70's and then one from 79.  The 79 carb just seemed more friendly, and ran great right off the rebuild table.  Maybe it was because it was my 3rd carb, and not the 1st... but nonetheless, I like the newer model!