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Fuel Mileage?

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Poll Question: Whats you mileage with an Inliner?
Poll Choice Votes Poll Statistics
7 [25.00%]
21 [75.00%]
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pdok Quote  Post ReplyReply Direct Link To This Post Posted: Feb/27/2012 at 6:16pm
Mine is the low number.  I'm getting around 14 with the 38 Weber and all the Clifford fixin's.  I'm actually disappointed it's so low, but I've since read that "standard" mileage was around 15-17 for the 258 back in the day, so maybe I'm not far off.  That sounded a bit low, however.

The 38 carb undoubtedly contributes to the lower number, because the 32/36 is a thrifty design by comparison with its progressive linkage.  With both barrels opening on mine, it's going to suck more gas outta the tank.

If anybody has any other thoughts, I'd love to hear them.  I've got solid idle tuning, HEI, good overall timing curve, 3.08 open diff gears, and the 904.  Can't think of anything else but the carb choice.

Honestly, I didn't get it for the economy, and it's a blast to drive, so I'd probably still do the same combo.  If there were a way to swap a 518 tranny in there without surgery, I would be doing it right now instead of typing this....
76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thikstik Quote  Post ReplyReply Direct Link To This Post Posted: Feb/27/2012 at 9:59pm
Mine was 19.8 at 75-90 mph with ac on...that was with 2:73.  Put in 3:15 and it went to 15.5.   258 is like a v-8, it needs overdrive.  3300rpm at 75mph is a waste.  I do have a little bit of stall.  Things got worse..I dynoed and found 11 more ftlbs of tork going from 53 jets to 58.  And, on the way home , i couldnt pass a gas station. City mpg is excellent, but over 50mph is abject squalor.   So im trying to find a way to add more fuel on takeoff w/o using the big primary jets.  I dont like the holley 390, as the open jets (no metering rods) cant yeild a lean cruise mixture/and a good load mixture.   The 4.0 proves itself in performance and economy #'s ala turbo rambler's experience with 24 mpg.  How much of that is fi?  Serious carb tuners dont like the 'dump it" style of performance carbs.  I would like to try a quadrajet someday. This topic is serious....expensive gas is coming for good.  
75 gremlin x, jeep 4.0 headed 258,
264H Cliff cam, intake,header. 390 holley. I want a 282 VAM motor!

AC/PS/PDB.

72 AMX , 304 2bbl, 3speed, now disks...probably will sell, want an automatic /AC.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pdok Quote  Post ReplyReply Direct Link To This Post Posted: Feb/27/2012 at 11:21pm
That's always been Holley's solution to everything, it seems.  They have some tuning there, but there's so much sloppy overlap with transitions that it will never be really efficient no matter how hard you try.  I'm speaking more from my experience with my 4160 Holley than anything else.

There are some benefits to the FI, but danged if you can't buy a lot of extra gas for the price of all that.

There's some good sense in an overdrive trans, but the thing that kills it is having to fit the extra large tailshaft area into the tunnel.  I've looked into guys putting 200r4's behind these things, and it's a large hassle, to say the least.

The 4.0 swap, complete from a FI Jeep would be fun to try, but I just don't have the heart to go that extensive at the moment.

So, that leaves stuff like the Gearvendor unit, which I can't really justify the cost, either.  Looks like 1976 technology is here to stay...
76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thikstik Quote  Post ReplyReply Direct Link To This Post Posted: Feb/28/2012 at 12:19am
All true...and sadly, the A500 is a huge horsepower sapper.  I wish the 700 r4 was ok to try, but im afraid the gearing is too deep in 1 and 2 to be ok.  That said, id rather have it than no OD at all.  I think im gonna do an AW4 or a 2004r...or maybe just never go more than 50 miles from home.
75 gremlin x, jeep 4.0 headed 258,
264H Cliff cam, intake,header. 390 holley. I want a 282 VAM motor!

AC/PS/PDB.

72 AMX , 304 2bbl, 3speed, now disks...probably will sell, want an automatic /AC.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bryan G Quote  Post ReplyReply Direct Link To This Post Posted: Feb/28/2012 at 10:12am
Mine is in a heavy '74 IH pickup with a 3 spd manual and a stock 1bbl Holley. I have a pretty consistent average of 13.5 but have hit 14.5 under ideal circumstances. I've often wondered what I could eek out with a 2bbl Motorcraft and electronic ignition. If I could consistently get above 15 I'd be elated.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Feb/28/2012 at 10:33am
When you have only "adequate" power, even a little more is noticeable both in feel and economy. You should be able to pick up at least 1 mpg with electronic ignition and a 2V carb... might even pick up 2 mpg. As others have said, the electronic ignition alone doesn't help IF the points are in perfect shape and kept close to perfect. So tune up every 500 miles and you might be able to keep close to a consistent spark. With electronic ignition you tune up every 5K or so and it should be consistent the whole time. THAT is where the extra power and economy comes in. Not a lot of extra power at first, but performance fall off with miles with points, shouldn't with electronic. 
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thikstik Quote  Post ReplyReply Direct Link To This Post Posted: Feb/28/2012 at 6:37pm
I am experimenting with my holley390 trying to get a "lea n cruise mode" without cutting down takeoff power..  If car can cruise on 52 jets just fine, that's what id like it to have.  But , it hurts tork. On the dyno, i drove in with 54 jets and got 11 more ft lbs with 58's.  actually all they had to try were 60's so I drove home with those and mpg was horrendous.  After getting home i got them down to 58.  I then try 57's and thats when i feel the tork is falling.  So my strategy is to try to run smallest jets for cruise and have enrichment start early.  So if 57 is point that is too lean for performance, i need an earlier power valve.  I went from a 6.5 to a 8.5 and it did help, but still not as nice as the 58 or up jets.  So next step will be to open up pv channels.  This will allow more gas when pv does "crack".   I have an Innovate AF tool, but my o2 bungs plugs are frozen...I dont really care, because i have shown car can cruise alot leaner.  I doubt ill get very far with this strategy...bottom line, im surprised how bad a non metering rod carb is on cruise mpg.  Going from a Qjet to a 4150 850 carb on my gto was about 1.6 mpg on hiway.  
75 gremlin x, jeep 4.0 headed 258,
264H Cliff cam, intake,header. 390 holley. I want a 282 VAM motor!

AC/PS/PDB.

72 AMX , 304 2bbl, 3speed, now disks...probably will sell, want an automatic /AC.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pdok Quote  Post ReplyReply Direct Link To This Post Posted: Feb/28/2012 at 7:12pm
Send that old Q-Jet to Cliff's with your cam/gearing specs and see how it does!  I'm about to do that swap onto my 350 chevy truck, hoping a top quality rebuilder can put the right combination of jets/rods and tubes.  Options you just don't get with a Holley, and a great QJet can be simply phenomenal.  And expensive...
76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thikstik Quote  Post ReplyReply Direct Link To This Post Posted: Feb/28/2012 at 10:57pm
Yea, id do it myself as some rebuilder would short build one if he knew it was going on an amc.  The thing?  Could the i6 take a 750?  Almost all qjets are 750-800 cfm, with 800 the rare bird and 750's almost everywhere.  There were a few years qjet that had the sec throttle plates (lower) that only cracked half open.  They may have been on Pontiac 301's cant remember.  Thats probably a good choice, or it may be a flow killer...just trying not to go the full 750 cfm here.  It begs the question...did the Pontiac sprint six 250 I6 ohc , which runs a qjet, have full opening secondaries? Knowing how weak some of the smogger 305's were from the day, i think a hot 258 could handle a full opening qjet. If it wont fit on the clifford intake, i guess its a no go.  I think itd take a carter AFB (same as the "new" edelbrock carb) to qjet adaptor.  Your right, the qjet is amazing.  On my gto after changing to the holley, I had to give gas to back out of same exact driveway that the qjet would idle out of.  Thats the miracle of signal...which is the fast rush of air thru carb into intake ports.  I went to holley for its fast transition ability needed for that stick car.  Im very sure itd get alot better mpg on our 6's.  
75 gremlin x, jeep 4.0 headed 258,
264H Cliff cam, intake,header. 390 holley. I want a 282 VAM motor!

AC/PS/PDB.

72 AMX , 304 2bbl, 3speed, now disks...probably will sell, want an automatic /AC.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Class Guy Quote  Post ReplyReply Direct Link To This Post Posted: Feb/29/2012 at 7:38am
The Qjet is broadly adjustable and that is what makes it a very adaptable unit.  You need to know what you are doing, however, and have patience.  Get Doug Roe's classic book, or Cliff Riggle's book.  The secondary airflow is adjustable by the air valve spring tension more than the total opening of the throttle valves.  Also, know that 65% of the airflow is through the primaries where the metering is much better due to the triple venturi and airflow regulated fuel mixture.  An Edelbrock (Carter) AVS may also be a good choice to "dial in" to different applications.  From my experience with Qjets in varied applications, I caution you to look at the intake manifold as another source of performance tuning.  I have seen 30 hp difference using the same Qjet carb in a different intake configuration on the same engine.  GM configured Qjets on engines from 215 to 500 cubic inches. Maximum tuning of a carburetor is a quest, not a bolt-on.
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