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Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

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old28racer
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Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #1 by old28racer » Sun Aug 09, 2020 3:11 pm

I have both Offy DP & Clifford 4V intake, the Clifford 4V also has a 4x2 adapter for Holley or Autolite 2bbl. Looking for the best mileage carb/intake combination at sea level. If using a 4V carb it should have small primary as I am not in the secondary much at all, this is just a cruiser around town truck. Would like to stay in the 350-450 cfm range on a 4V carb, I have a Autolite 2100 1.08 for my 4x2 adapter along with my current Holley 2300 350cfm 2bbl.

Truck/motor information, F250 300, C4, 3.73 rear gears, 9.50/16.5 31" tall tires, 300 motor has headers, dual exhaust, Pertronix Ignitor 1 in stock points dizzy, flame thrower coil. Don't load truck or make long trips, just an around town cruiser. Thanks for looking.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #2 by old28racer » Sun Aug 09, 2020 3:26 pm

Wanted to add current mileage with my Holley 2300 2bbl mounted on the stock log intake with a 2x1 carb adapter is 9-11 around town and 15-16 Highway. Around town 40-50 mph & 55-60 highway. My on board AFR reads around 14.5 in town or on highway. Need more information please ask.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #3 by sdiesel » Sun Aug 09, 2020 9:32 pm

For mileage / performance a q jet is hard to beat. Properly built its a real tiger.
a long love affair with the 300 six.
my lastest and final fling is a fresh 300 in an 88 ford f350 dually 4X flatbed

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #4 by pmuller9 » Sun Aug 09, 2020 11:29 pm

It would be interesting to use the Autolite 2100 on the DP using the back two holes so that only the upper section of the manifold delivers the air/fuel mixture. This would keep the velocity high.
The Autolite carb is annular discharge which does a better job of atomizing the fuel than the Holley 2300

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #5 by old28racer » Mon Aug 10, 2020 12:25 am

sdiesel -- Performance is low on the list as I just cruise the truck around town. At 73 I'm in no rush to get any ware.

pmuller9 -- So to do that I would build another aluminum adapter to mount the 2100 over the two holes for the upper runner & block off the lower runner two holes, correct?
If that is right it is no big deal making one as I will be 4 months testing the 2300 & 2100 on both intake setups and getting new base line AFR readings for town & highway along with seeing what each setup does for my gas mileage.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #6 by old28racer » Mon Aug 10, 2020 1:02 am

Has anyone ever run a Holley Economizer 4bbl list 7555 on a Offy DP intake for gas mileage like we ran in the 70's & 80's? I think they are mechanical secondary carbs.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #7 by xctasy » Mon Aug 10, 2020 2:09 am

old28racer wrote:Has anyone ever run a Holley Economizer 4bbl list 7555 on a Offy DP intake for gas mileage like we ran in the 70's & 80's? I think they are mechanical secondary carbs.


Yes, on a 308 Holden T bucket, and a propane 202 Holden in line six. . Great Q Jet replacement carb. David Vizard has used one on a Car Craft Z28 in 1979, the article is road load tested on a dyno and is excellent, and it works really well if the five following points are taken care of:-

The 4360 series 450 CFM Holley 4 barrel spread bore carbs.


1. The very sensitive boosters don't like radical cams.

2. Since its a light kind of zinc oxide and made by Weber under licence for Holley, you have to use WEBER 32/36 DGAS jets to be able to tune them.

3. Perennial problem is the flat spot opening the secondaries which is can be sorted by bending the accelerator pump rod give a bigger stroke.

Full list #'s for Economizers are. 7454, 7455, 7456, 7555, 7558, 7955, 7956, 7957, 7958, 8001, 8002, 8003, 8149, 8158, 8203, 8204, 8206, 8479, 8516, 8517, 8642, 8677, 8771, 8874, 8875, 8876, 8877, 8914, 8958, 9088, 9105, 9112, 9162, 9185, 9192, 9193, 9694, 9777, 9875, 9931, 9935, 9973 and 80086.

4. They are okay if the housing isn't warped, and the plastic plugs for the lean mixture adjustment are not broken. Its a bitchy carb with Weber close limit jets are very accurate and is kind of an squired taste.

5. Tuning is via manifold vacuum. If you get that right, it'll work okay. Manifold vacuum is the be-all and end-all

viewtopic.php?f=5&t=31388&p=550411&hilit=David+Vizard#p550411
xctasy wrote:I'll do an example of this, but first I'll state generally the procedure.

Example is the table from a Popular Hot Rodding article in January 1981. Table 5, at the end, has a road load calculated fuel consumption.


Image


xctasy wrote:
Meantime, best we can do is this 1979 Chevy Camaro 350 with 2.73 gears

Image
Image
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #8 by BigBlue94 » Mon Aug 10, 2020 11:50 am

Well, on a .040 reman 300 with clifford headers, a 390 holley mounted on a clifford got me an average of 12-14 mpg. 65% highway miles.

With my built 300, with same intake and headers, a 450 quickfuel (holley 4160) gets 12 mpg avg. 10 up hill and 14 down hill, er up from 1000 ft to 12k+, down to 9ish, back to 12k, and down to 4000.then wheeling in Moab. Then reverse for the trip back.

AbandonedBronco used all sorts of carbs on his 300... Holley, eddy, q-jet, qft, and finally a holley 2bbl sniper. The sniper gets the best milage, but the q-jet was a close second.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #9 by old28racer » Mon Aug 10, 2020 11:59 am

xctasy -- Couple of questions.
(1) Are all the Economizer carb numbers listed the same CFM?
(2) If not were do I find the cfm for each.
(3) Do all the numbers listed have the same base mounting bolt pattern?
(4) Is the mounting bolt pattern the same as Holley 2300 & Autolite 2100 2bbl?

My 300 motor in my F250 has a manifold vacuum of 19".
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #10 by xctasy » Mon Aug 10, 2020 3:35 pm

old28racer wrote:xctasy -- Couple of questions.
(1) Are all the Economizer carb numbers listed the same CFM?
(2) If not were do I find the cfm for each.
(3) Do all the numbers listed have the same base mounting bolt pattern?
(4) Is the mounting bolt pattern the same as Holley 2300 & Autolite 2100 2bbl?

My 300 motor in my F250 has a manifold vacuum of 19".




1 and 2 . yes, 450 cfm all
3. Yes, all Q JET Spreadbore 4bbl bolt spacing
4. No,Q JET Spreadbore 4bbl bolt spacing
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #11 by old28racer » Mon Aug 10, 2020 5:18 pm

Both my Offy DP & Clifford are square bore pattern mounting. If I want to try a Economizer carb I will have to run Squarebore/Spreadbore adapter, correct? 450 cfm sounds like a good cfm for a 300 cruiser rig. Can kits & parts still be had for rebuilding these carbs?
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #12 by BigBlue94 » Mon Aug 10, 2020 6:02 pm

old28racer wrote:xctasy -- Couple of questions.
(1) Are all the Economizer carb numbers listed the same CFM?
(2) If not were do I find the cfm for each.
(3) Do all the numbers listed have the same base mounting bolt pattern?
(4) Is the mounting bolt pattern the same as Holley 2300 & Autolite 2100 2bbl?

My 300 motor in my F250 has a manifold vacuum of 19".


At 1000' my manifold vacuum is 17" just for reference.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #13 by old28racer » Mon Aug 10, 2020 7:03 pm

BigBlue94 --- My 300 in the F250 is a basic stock rebuild with headers, dual exhaust, Holley 2300 2bbl, Pertronic and I am very pleased with 19" vacuum at sea level. I may be in much better shape when I install my modified 240/300 log intake that is setup for my 2300 & 2100 carbs. It will flow more air than the current 1x2 restrictive adapter and will help get my AFR closer to 15.5-16.0 range. This in it's self will improve my mileage. Same goes for the two carbs on my Clifford with a 4x2 adapter.

I think the Autolite 2100 with a pair of stock 57 jets will get the best mileage on the two intakes. My Holley 2300 runs 62 jets. I am going to play with the jets a bit on both carbs on both intake setups.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #14 by Firepower354 » Mon Aug 10, 2020 7:28 pm

Bad(?) part on the DP, the rear/upper/secondary runner is isolated from getting any heat. It does have, IMO, a much better runner route to 3/4 ports though. Welding the 6 lowers shut at the head end and plumbing water or exhaust through, would address that and flow plenty for a small non-stage 2bbl. I'd even thought of pouring aluminum "tongues" in the head, giving uniform runner and a nice tall short side to sculpt. Maybe even a bit of a swirl-inducing bias?

The lower dumps right at the ports. I sold mine this weekend, but had sketched up a "fix" to get better heat, more even runners, with a progressive 2bbl, that involved milling out the primary to an oval, and making a stuffer. The lower level extends way back under the top run, and forcing the flow there should give longer inlets for 3/4 and better vaporization for all.
It gets 10MPG, but goes up to 14 if I lie.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #15 by old28racer » Mon Aug 10, 2020 9:20 pm

As for intake manifold this is a subject I have never looked at. Living in southern Calif. where the average temp is 68-70 F I have never had any heat tubes or hot water lines to any intake manifolds. I don't even use a choke in middle of winter. Just thinking that I will end up with my autolite 2100 on my milled out 1bbl log manifold or on the Clifford with 4x2 adapter. We will see what the test cruise results have to say.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #16 by Firepower354 » Tue Aug 11, 2020 12:34 am

If the heat is not an issue, the upper runners of the DP should best either of the other options.
Clifford has a lot of plenum volume, stocker has it's distribution issues.

Image
It gets 10MPG, but goes up to 14 if I lie.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #17 by BigBlue94 » Tue Aug 11, 2020 10:47 am

old28racer wrote:BigBlue94 --- My 300 in the F250 is a basic stock rebuild with headers, dual exhaust, Holley 2300 2bbl, Pertronic and I am very pleased with 19" vacuum at sea level. I may be in much better shape when I install my modified 240/300 log intake that is setup for my 2300 & 2100 carbs. It will flow more air than the current 1x2 restrictive adapter and will help get my AFR closer to 15.5-16.0 range. This in it's self will improve my mileage. Same goes for the two carbs on my Clifford with a 4x2 adapter.

I think the Autolite 2100 with a pair of stock 57 jets will get the best mileage on the two intakes. My Holley 2300 runs 62 jets. I am going to play with the jets a bit on both carbs on both intake setups.


19" is great! Oddly (or maybe not, im a carb rookie) in my quickfuel 450 4bbl (holley 4160) im running i think 55 jets.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #18 by old28racer » Tue Aug 11, 2020 7:57 pm

Firepower354 -- Is the reason you would use the upper runner of the DP because it flows more volume even though it has less velocity than the lower runner?

I think I will be able to drop my Holley 2300 2bbl jets from factory performance 62 jetting down to better mileage 55-57 jetting. Along with that I will change accelerator pump from a 30 to a 50 unit. My AFR gauge will tell me if I am going in the right direction.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #19 by pmuller9 » Tue Aug 11, 2020 8:15 pm

Firepower354 wrote:It does have, IMO, a much better runner route to 3/4 ports though.
The lower dumps right at the ports.
.
This is one of the reasons I suggested using the upper section.
The 3 and 4 runners of the lower really create a problem with fuel distribution.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #20 by Firepower354 » Tue Aug 11, 2020 10:48 pm

old28racer wrote:Firepower354 -- Is the reason you would use the upper runner of the DP because it flows more volume even though it has less velocity than the lower runner?

I think I will be able to drop my Holley 2300 2bbl jets from factory performance 62 jetting down to better mileage 55-57 jetting. Along with that I will change accelerator pump from a 30 to a 50 unit. My AFR gauge will tell me if I am going in the right direction.


That, and using only the lower would really limit power. The upper isn't much over half the port size, so it's still going to have some good velocity. If using just one half, I doubt the lower would suffice.

A staged 2v would allow the primary insert, to guide the mix under the shelf of the upper plenum, mimicking the upper deck. Lots of material there to roll that edge, and other sharp spots, once cut in to two oval openings.
It gets 10MPG, but goes up to 14 if I lie.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #21 by old28racer » Tue Aug 11, 2020 10:59 pm

pmuller9 & Firepower354 -- Is this picture showing what might work?
Image
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #22 by Firepower354 » Tue Aug 11, 2020 11:19 pm

old28racer wrote:pmuller9 & Firepower354 -- Is this picture showing what might work?
Image



Yup. You could make it from 1/4 aluminum plate. and thread for the engine side, as the outer should match your carb.
It gets 10MPG, but goes up to 14 if I lie.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #23 by old28racer » Tue Aug 11, 2020 11:46 pm

Firepower354 -- Thanks for the mounting idea, I have some 3/8" aluminum plate that will work well for the adapter.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #24 by Soldmy66 » Wed Aug 12, 2020 12:51 pm

You might be able to find brass freeze plugs that would fit into the holes you intend to block.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #25 by old28racer » Thu Aug 13, 2020 11:31 am

That's true but I have to make an adapter plate anyway so I might as well use it to cover the lower holes.
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #26 by F-250 Restorer » Thu Aug 13, 2020 11:58 am

After reading an untold number of posts about mileage and carb choices, I began to see a common thread. The commonality I noticed was that mpg seemed to be dictated by the rear end gear ratio. Those with the high ratios (4.10, 3.74) were reporting unremarkable mpg findings. Those with gear ratios around 3.00 were reporting mpg around 20 mpg on the freeway/interstate.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #27 by BigBlue94 » Thu Aug 13, 2020 4:55 pm

F-250 Restorer wrote:After reading an untold number of posts about mileage and carb choices, I began to see a common thread. The commonality I noticed was that mpg seemed to be dictated by the rear end gear ratio. Those with the high ratios (4.10, 3.74) were reporting unremarkable mpg findings. Those with gear ratios around 3.00 were reporting mpg around 20 mpg on the freeway/interstate.


It certainly plays a part in it. But for multiple reasons I think. The fullsize trucks generally got 3.08, 3.55, or 4.10 gears. Some 2.73 and a few 3.31. You have three types of people driving these trucks; people working them hard, people who just need it to putt around town, and people who modify for performance or offroad.

A guy who just wants it to putt around town and get good milage will eventually end up with a 3.08 or 2.73 gear. They may get a 3.55 to begin with and not get as good of milage, and sell it off.

A guy who works it hard wont even consider a truck with numerically less than 3.55 gears. 4.10 is common for the heavier pickups. These guys are spending a lot of time with some sort of added load on the engine and aren't going to get good milage either way. The 4.10s may actually increase milage in their specific situation.

Guys like me who build for performance and offroad have thirsty engines and big, heavy tires. My tire and wheel combo, on an aluminum wheel, is right around 100 lbs. And much of that weight is 18" away from the rolling axis. The big tires need more gear to get the engine in the proper rpm range. 3.55s and 37" tires is an absolutely terrible combo. I actually got better milage after swapping from 3.55s to 4.88s in a 351 powered bronco on 37s. And on the trail, milage is inconsequential, as long as you have the proper amount for that trail. 33 gallons nets my bronco at least a 300 mile range; more than enough to get to the trail and home. I consider 12 mpg good enough for my needs, since its a brick shaped toy and not a DD.

So is it the gear ratio that determines the milage/usage, or does the desired milage/usage determine the gear ratio?
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #28 by guhfluh » Thu Aug 13, 2020 11:12 pm

Um, my highway mileage is around 20 and drops to 17-17.5 on the interstate at 75mph, yet my factory gears are none of those listed. ;)
1967 F-250 Crew Cab 2wd, 300 6cyl, T-170/RTS/TOD 4-speed overdrive
240 head, Offy C, EFI exhaust manifolds, Comp 268H, mandrel 2.5-3" exhaust, Edelbrock 500, Pertronix ignitor and coil, recurved dizzy. 200whp/300wtq

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #29 by BigBlue94 » Fri Aug 14, 2020 10:18 am

guhfluh wrote:Um, my highway mileage is around 20 and drops to 17-17.5 on the interstate at 75mph, yet my factory gears are none of those listed. ;)


Those numbers are for 8.8 and 10.25 ford and most dana axles. 9" are slightly different. What ratio do you have? Your 4sp OD helps a lot in the milage dept.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #30 by guhfluh » Fri Aug 14, 2020 10:58 am

BigBlue94 wrote:
guhfluh wrote:Um, my highway mileage is around 20 and drops to 17-17.5 on the interstate at 75mph, yet my factory gears are none of those listed. ;)


Those numbers are for 8.8 and 10.25 ford and most dana axles. 9" are slightly different. What ratio do you have? Your 4sp OD helps a lot in the milage dept.
3.73 Dana 60 :) Not sure on the tire height, but it's a hair taller than stock I think because the speedo is off a touch. The truck is lowered, which helps too. :)

I don't tow with the truck, only load the bed very rarely, and mostly cruise around. In town stop and go mileage is 14.5 at best and about the same when I try to stay 80-85 on the interstate. My Edelbrock is not the best for mileage either and I get better average with a tuned Holley 600, but the Holley doesn't drive near as good.
1967 F-250 Crew Cab 2wd, 300 6cyl, T-170/RTS/TOD 4-speed overdrive
240 head, Offy C, EFI exhaust manifolds, Comp 268H, mandrel 2.5-3" exhaust, Edelbrock 500, Pertronix ignitor and coil, recurved dizzy. 200whp/300wtq

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #31 by BigBlue94 » Sat Aug 15, 2020 10:08 am

guhfluh wrote:
BigBlue94 wrote:
guhfluh wrote:Um, my highway mileage is around 20 and drops to 17-17.5 on the interstate at 75mph, yet my factory gears are none of those listed. ;)


Those numbers are for 8.8 and 10.25 ford and most dana axles. 9" are slightly different. What ratio do you have? Your 4sp OD helps a lot in the milage dept.
3.73 Dana 60 :) Not sure on the tire height, but it's a hair taller than stock I think because the speedo is off a touch. The truck is lowered, which helps too. :)

I don't tow with the truck, only load the bed very rarely, and mostly cruise around. In town stop and go mileage is 14.5 at best and about the same when I try to stay 80-85 on the interstate. My Edelbrock is not the best for mileage either and I get better average with a tuned Holley 600, but the Holley doesn't drive near as good.


I skipped 3.73 due to it not being in 80-97 trucks. It is really a pretty good ratio. Not to high or too low.

My 99 econoline has 3.73 in a SF d60. 28.5" was stock and i got about 14mph mixed. 4.2L v6 for power. Im on 31.5" tires now and milage is oddly the same. Though with the wide 33s I was running for a while, I got about 12 mpg.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

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old28racer
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #32 by old28racer » Sat Aug 15, 2020 1:35 pm

I really like my 3.73 gears, like you said not to tall/not to short. I just installed a new set of 16.5 10 ply that are 31.5 to replace my 30". On the trip home on freeway at 60mph my 300 was sounding a bit less worked. new tires are taller & narrower than the old tires, same pressure at 70#.

Really would like to try my Autolite 2100 on the Clifford with 4x2 adapter. If I could improve my mileage to around 12-14 around town & 18-20 on the highway I would be a happy camper.
Bad Day Racing Is Better Than A Day In The Stands :mrgreen:

crgintx
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #33 by crgintx » Fri Aug 21, 2020 9:45 pm

I use a 500 cfm Summit with a Dual-port. I get 16+mpg with what I assume is a stock cam in an '86 F-150 single cab, with Hedman headers into a single exhaust, 235/75R15 stock steel wheels with a 4speed T-178(4th gear is OD) 3.08 stock gears, I have a camper shell as well. Cruise speeds on the long trips range from 65 mph-80mph. Driving at 65. I topped 18 mpg on one trip. The engine needs definitely a rebuild, it has over 200k miles on it. Thinking about adding a T-5 and a Schnieder 262-70H cam.

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old28racer
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #34 by old28racer » Sat Aug 22, 2020 12:06 pm

I get 15 on highway 60-65 mph & 9-10 around town 40-50 mph with the setup I have now. Freshish rebuilt motor, headers, Holley 2300 2bbl on a 1x2 adapter, dual exhaust, C4, 3.73 gears, 31" tires, no load.

Highway ain't all that bad for the carb/intake setup that is currently on it. If I can just get the town mileage up into the 12-14 range that would be fine. That is why I have looked at a Rochester Quadrajet 4V with it's small primarys to help with the town driving that I do 90% of the time on flat land at sea level.
Bad Day Racing Is Better Than A Day In The Stands :mrgreen:

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #35 by sdiesel » Mon Aug 24, 2020 12:41 pm

The q jet was designed for just that kind of driving, total compromise between this and that.
Perfect carb for the purpose.
I'd like to see more q jets in service, I believe they would be very effective alternative to the no hum .

Muller mentioned the q jet being of limited value in a high boost application, which of course is Holley territory anyway..
But for 7psi, everyday driving from point A, a q jet seems ideal....
a long love affair with the 300 six.
my lastest and final fling is a fresh 300 in an 88 ford f350 dually 4X flatbed

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #36 by pmuller9 » Mon Aug 24, 2020 4:00 pm

sdiesel wrote:Muller mentioned the q jet being of limited value in a high boost application, which of course is Holley territory anyway..
But for 7psi, everyday driving from point A, a q jet seems ideal....


You need to find a way to seal the throttle shafts and accelerator pump shaft from letting fuel pass when the carb has internal pressure.
The cups under the metering rods need to be sealed with epoxy to keep them from leaking fuel into the intake manifold.

The vacuum operated secondary air valve will no longer function and needs to be eliminated.
Unfortunately this feature was used to allow a 750 cfm carb to be used on smaller displacement engines so now the carburetor is too large at WOT for a mild 300 six with a turbocharger.

What I mean by too large is the lack of ability to control boost.
Without the secondary air valve the Q-jet transitions from 200 cfm to 750 cfm very quickly as the large secondary opens.
You go from no or very little boost to full boost in a very short throttle transition because it take far less than 750 cfm to get there on a 300 six.
Now imagine that on wet roads as you are turning from a stop sign trying to merge quickly into traffic.
A spread bore is not a good choice for a street driven turbo engine.

The Q-jet uses a metering rod to control fuel and doesn't have a power valve circuit that can be used to add fuel under boost.
At 7 lbs of boost the engine is requiring about 50% more fuel than normal.
You would have to figure out how to get the secondary metering rods and jets to deliver the extra fuel without disrupting the air/fuel ratio when not boosted.

I've heard of it being done but haven't seen a successful running engine.

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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #37 by THE FRENCHTOWN FLYER » Mon Aug 24, 2020 7:00 pm

pmuller9 wrote:
sdiesel wrote:..Now imagine that on wet roads as you are turning from a stop sign trying to merge quickly into traffic.

Reminds me of driving my hot rod to high school on a snowy winter morning. What FUN!!!
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

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Shorty
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Re: Good Mileage Carb/Intake Combination with Offy DP or Clifford 4V

Post #38 by Shorty » Mon Aug 24, 2020 9:25 pm

"steer it with the throttle and turn left to go right" doc hudson the fabulous hudson hornet (also six inline) teaching lightning mcqeen in "cars" animated movie. Reminds me of my chevette I shoehorned a v6 and 5 spd in with bald tires in the rain, or even dry pavement for that mater....
85 F150 on 78 bronco frame C6 np205 welded dana44 front, trussed posi nine inch rear. EFI exhaust manifolds into one 2 1/2" rolls on 35x12.5x15 Maxxis Trepador.

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