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Header Or No Header?

Discussion in 'Intermediate CJ-5/6/7/8' started by shadetreetim, Dec 17, 2019.

  1. Dec 17, 2019
    shadetreetim

    shadetreetim Member 2020 Sponsor

    Riverside, Ca
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    Oct 2, 2019
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    80
    In my recent desert trip one thing stood out, I'm getting horrible gas mileage. I used 12 gallons over 2 days while my buddies 1.6 powered Samurai used 5 gallons. Not sure how many miles that was as my speedo isn't hooked up yet. I've been looking for a reason to get rid of that 1 barrel carb, I guess mileage will do.

    My 4.2 already had a Davis Unified HEI ignition on it when I bought it. I've read a swap to a 2 barrel like the Motorcraft 2100/2150 will improve mileage and performance. Today I picked up a later model 2 barrel manifold to get started.

    Now my decision is; do I buy a Header? Or buy a later model cast exhaust manifold? With the header I could go to a 2.5" muffler and piping.

    What say you? Any advise, concerns, ideas?

     
  2. Dec 18, 2019
    jpflat2a

    jpflat2a what's that noise?

    Riverside CA
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    Jul 30, 2003
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    7,884
    Don't think that's fair comparison between the two vehicles.
    Yes there are probably some mods that would help you in that area.
    But I doubt you would double your fuel mileage off road.
    As far as the header is concerned, seems like folks with those on straight sixes are always fighting exhaust leaks.
    Tell all about your desert trip in the trail ride section.
     
  3. Dec 18, 2019
    shadetreetim

    shadetreetim Member 2020 Sponsor

    Riverside, Ca
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    Oct 2, 2019
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    Yeah I doubt I’ll get to what the Samurai got, but that doesn’t mean it can’t be better than it is. The only purpose of the comparison is because I didn’t have mileage data to figure actual MPG. As another comparison, the same weekend of wheeling in my old 3.8L JK would have used about the same as the Samurai, and it only got 11 MPG. This is an area we wheel frequently. I was shocked how much fuel I used. Any improvement will be better.
     
  4. Dec 18, 2019
    bigbendhiker

    bigbendhiker Member 2020 Sponsor 2019 Sponsor

    North East Texas
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    May 26, 2019
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    Still not apples to apples, but my comparison is much closer than your buddies Samurai. I've got the Dauntless V6 in my Jeepster. I've got headers, dual exhaust that exit in front of each rear wheel. It also has a Holley 390 4 barrel carb. I checked my mileage after driving on Interstate 20 at 60 to 70 mph. I got almost 12 and a half mpg. While I haven't checked mileage off road, I suspect it's less than 10 mpg. Your buddies 1.6 liter might be getting 20 to 25 off road which probably puts you in the neighborhood of 8 to 11 mpg off road. You might get a little better with a 2 barrel, but I wouldn't expect much. If you go the fuel injection route you might improve it a little more, but not enough to pay for the conversion.
     
  5. Dec 18, 2019
    mrtii

    mrtii 1972 cj51986 cj7 2019 Sponsor

    gilroy, California
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    Oct 3, 2016
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    I would stay with cast iron exhaust manifold for reliability purposes
     
  6. Dec 18, 2019
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    Heat is my biggest gripe with headers. There’s a substantial increase in underhood/floor heat from headers.
     
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  7. Dec 18, 2019
    bigbendhiker

    bigbendhiker Member 2020 Sponsor 2019 Sponsor

    North East Texas
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    May 26, 2019
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    I'll vouch for that. Mine came with the long tube headers already on it. They also have a good bit of rust on them. Between the noise and heat I'm considering going to either shorty headers or back to the stock manifolds.
     
  8. Dec 18, 2019
    Alan28

    Alan28 Well-Known Member 2020 Sponsor 2019 Sponsor

    Châtillon en...
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    I complained to my specialist about gas comsumption, he told me that it was difficult to do better. Clean and check all, maybe some problem with an old carburetor but when all works well, I just pay for the gasoline.
     
  9. Dec 18, 2019
    Jw60

    Jw60 Recovering Jeepaholic

    Sedalia MO.
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    Oct 5, 2018
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    I would:
    1 check for leaks. Fuel and vac They can be sneaky and evaporate off of hot surfaces like blocks and intake.
    2 Double check tuning.
    3 tally up the costs for efi.
    4 look at a progressive 2 bore (a small primary will help with mpg and the 2nd will give hp and burn gas fast)
    5 rebuild a low vac engine with internal wear or issues.

    If a f134 can get 16mpg I beleave anything can get 16mpg
     
  10. Dec 18, 2019
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Headers: noisy, hot, fragile, leaky, expensive race car tech. Otherwise they are great.

    Jeeps are a tough environment for headers.

    IMO if you want the most efficient you can get at a reasonable cost, swap in a 4.0L HO with the excellent Mopar/Bosch MPI from the factory. AMC/Jeep thought long and hard about making their inline sixes more efficient, and that's what they came up with.
     
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  11. Dec 18, 2019
    shadetreetim

    shadetreetim Member 2020 Sponsor

    Riverside, Ca
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    Oct 2, 2019
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    Ultimately the 4.0 head and fuel injection would be a nice project I wouldn’t mind doing. But I don’t want the Jeep down for a long project. Need to do all the research and gather a few parts before I do that.

    The 2 barrel solution will be temporary more than likely, but it would be a quick, if slight, improvement. In that line of thinking, the later model stock manifold is quite a bit less expensive than a header for a temporary solution.

    Plus I hadn’t thought of the heat shedding off the header.

    I get that a Jeep that I’ll only drive less than 500 miles a year isn’t a concern on fuel mileage for cost savings, but at roughly 5 mpg I need to do something. I do need to double check the timing/plugs from PO.

    So my obvious symptoms are slight dieseling at shut off and poor fuel mileage. Bad carburetor or poor timing, or a combination of both, can contribute to both symptoms.
     
  12. Dec 18, 2019
    steve1973

    steve1973 Member

    Nolensville, TN
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    Jul 27, 2011
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    65
    Not sure what tires your running, but my 73 with 30” bfg km2’s gets 17 combined. With AT tires I’m sure it could get 1 - 2 mpg better. Tires play a big part. I have a Weber 38 with an adapter for the original 1 bbl carb and a Msd billet distributor, msd 6 digital box, wires coil and iridium spark plugs. Too many cons of headers in an old CJ, to make it worth it.
     
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  13. Dec 18, 2019
    Ol Fogie

    Ol Fogie 74 cj5 304

    Jasper
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    Nov 24, 2019
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    I have tried all kinds of engine mods/ improvements ect. including headers never did find one that I felt it saved enough gas to pay for its self. The best thing you can do is simply maintain the entire factory stock setup, keep every thing operating at its top efficiency and ride on. Just my experience as an ol fogie with four jeeps over the years with the f-134 and L-134 engines and two with I-6 engines and two with 304 v-8. Just my opinion. BTW the I-6 232 gave the best mileage of them all about 19 or 20 mpg while easy hwy cursing at about 50 or 60 mph. Never bothered to check while off-roading.
     
  14. Dec 19, 2019
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    The biggest fuel-waster off-road usually comes from fuel slosh (one of the biggest reasons fuel injection gets better mileage off-road), and from your foot bouncing on the pedal over bumps.

    Depending on your carb’s vent design, the smallest of bumps could pour raw gas in your intake. If your carb’s vent is open to the top of your carb, try soldering a copper tube into the vent to raise the opening a few inches, just so it clears the top of the air cleaner. Much less fuel will spill out, and it will run better on angles.

    If your gas pedal is too soft, you might consider adding a heavier/another spring.
     
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  15. Dec 19, 2019
    shadetreetim

    shadetreetim Member 2020 Sponsor

    Riverside, Ca
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    Interesting. I kept smelling raw fuel when we would stop. No obvious leaks though.
     
  16. Dec 22, 2019
    Raven74CJ5

    Raven74CJ5 New Member

    san diego,...
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    Jun 13, 2018
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    Funny I am having the same issue of smelling raw fuel after it has been sitting for a few minutes after running. The carb is dirty and has no leaks... which is leading me to think it is just in need of a serious rebuild. Found Mikes Carb Parts " Jeep/Willys " has not just the soft parts but a deluxe kit that has the replacement hard parts as well. I'll let you know if my rebuild corrects the fuel smell.
     
  17. Jan 11, 2020
    shadetreetim

    shadetreetim Member 2020 Sponsor

    Riverside, Ca
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    Oct 2, 2019
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    I appreciate all the thoughts and comments in regards to my post 3 weeks ago. I searched other sources for data on this topic as well. I like researching and planning projects, and hearing differing opinions. But at the end of the day, I have to make a decision and get started. With a Jeep trip long planned for MLK weekend, I was running out of time if I wanted to make any changes. This was my last weekend to wrench on the Jeep. Fortunately everything I ordered came in on time and I had time to mock it up last weekend on my workbench. That led to some last minute purchases, but last night I was ready to start.

    What did I decide to install? Well I couldn't resist a Hedman 6 into 1 header, Autolite 2100 carb, and 2-1/2" exhaust with a Turbo Muffler. I wanted to see for myself how well this combo worked. While I was at it I replaced my leaky valve cover gasket and finished up the wiring where I added a fuse/relay assembly under the hood for all the extras.

    After work yesterday everything came off quickly. The old block was wasn't that dirty. Wish the other side was stripped down this far.
    [​IMG]
    I found some engine paint that looks close enough for me. Had to disconnect the clutch assembly to get the header in place.
    [​IMG]
    I discarded the weird adapters Hedman ships with the header to compensate for the different heights of the header and intake. Instead I found a thick washer on the header side made the stock heavy washer sit flat, so I cut a thick washer in half and welded it to one side of the factory washers. They bolted down nicely with all new bolts. This was how I left it last night..
    [​IMG]
    This morning I addressed the accelerator cable bracket. The 2100 pulls from the side instead of the back so the stock bracket wouldn't work. The 2 barrel intake came with its old bracket, which gave me some different parts to work with. I cut and welded a few parts, added some metal from my scrap pile, and came up with a mount that puts the accelerator cable where it needs to be. Hard to see in pictures after painting it all black, but it mounts to the manifold in the stock location and is braced.
    [​IMG]
    Here you can see the new 6 fuse, 5 relay block next to the battery, and the wiring. I didn't have a horn so I added those as well. Also on display is the LED lighting I attached to the bottom side of the radiator support rods. They are switched under the hood, and give great light right where you need it.

    This new intake is supposed to have the heater hoses routed through it to heat the manifold. I still need to do that, but I was anxious to drive it around the block, or two.
    [​IMG]
    With the carb idle adjustment roughly set to 1-1/2 turns out it started right up. I let it warm up in the driveway until the electric choke opened, and all the paints were burning off... Drove around the block and pulled back in the driveway to fine tune the idle mixture. Took it for six blocks, then tweaked a little more. Then took it for a few miles.

    Pretty impressive compared to the old, stock, probably needs a rebuild, 1 barrel carb. Before while driving, it smelled like it's running rich. It ran smooth but sounded like it was laboring. Today it sounds like it's running freely, feels responsive. Pretty happy so far. Now to see how it runs out on the trails.
     
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  18. Jan 13, 2020
    Raven74CJ5

    Raven74CJ5 New Member

    san diego,...
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    Jun 13, 2018
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    16
    Who makes the 2bbl manifold you used... I have been considering switching over to a 2bbl carb but havent had any luck with finding one other that the one from Clifford performance.
     
  19. Jan 13, 2020
    shadetreetim

    shadetreetim Member 2020 Sponsor

    Riverside, Ca
    Joined:
    Oct 2, 2019
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    80
    It’s stock off a later model 4.2L. I think CJ7 and early YJ had them. There’s one on eBay right now for $150. When I found one on eBay cheaper than that I snatched it up. It still requires an adapter for the 2100 carb to bolt up.
     
  20. Jan 13, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Aug 10, 2003
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    20,422
    In 1981, Jeep introduced the lightened 4.2L that included new manifolds. The old bolt-together manifolds are gone, replaced by the new aluminum 2V manifold (seen above) and lighter, smoother iron exhaust manifold. I put a pair of these manifolds on my J10. Note there is an electric carburetor heater in the underside of the aluminum manifold that, along with the heater water, warm the intake and replace the exhaust passage and flap in the old iron manifolds. You could rig some kind of timer/sensor and relay to make it work, perhaps using some of the parts from the manifold donor.

    Looks good! Good work with the washers, and the color is good too. Quite close to the factory color.
     

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