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High Performance F-head Musings

Discussion in 'Early CJ5 and CJ6 Tech' started by ITLKSEZ, Nov 29, 2017.

  1. Nov 29, 2017
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    I've been wanting to start a thread for a long time on any or all options out there for boosting power in the old 134 engines. Do you have any experience with a high performance setup? Do you have any plans or ideas to add a turbo? Supercharger? Nitrous? Lets hear them!

    I'll post up my past hits and misses as I get time, and I'd love to hear and see what else has been tried.

    Disclaimer: I'm not trying to go down the "Typhoon Build" rabbit hole; lets keep this as a friendly discussion about what has been done, and what could be possible with some imagination and know-how. (y):watch:
     
    william_cj3b likes this.
  2. Nov 29, 2017
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    [Moderator hat ON]

    Let's keep the comments on topic & helpful on this one folks.

    [Moderator hat OFF]
     
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  3. Nov 29, 2017
    Karl Childers

    Karl Childers Member

    Taos New Mexico
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    Is one of the rules reliable horsepower? If not I vote for nitrous!:D I'm thinking with a motor of that size you can move the power up or down the rev range with The usual mods, cam, compression, intake, exhaust, timing, etc but with out a big displacement increase any power gains will fall into a narrow rpm range. An expert I'm not when it comes to performance engine builds so I'll watch this thread with interest.
     
    Last edited: Nov 29, 2017
    ITLKSEZ likes this.
  4. Nov 29, 2017
    jeepstar

    jeepstar Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sheboygan
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    Clifford headers makes a header for the 134 F head motor. That'll give you a slight boost in horsepower.
     
  5. Nov 29, 2017
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    I'm by no means an engine builder either, but at the point when I was experimenting with these, these engines were a dime a dozen, and I had a pile of them to mess with. If one got messed up, try, try again.

    My first attempt at getting a little more power out of one of these was through stock moving components, but increased fuel and air flow and higher compression.

    I started by taking the head to a shop and having them shave a full .125" off of it. I took painstaking measurements to make sure the valves would clear with that much machining. If it came back to me without them hitting any water jackets, I knew I was good to go with porting. I can't remember the exact numbers, but this was increasing my compression ratio from the stock 6.9:1 to around 10:1. I found this pic of the head on the bench after the mill. Check out the (thin!) corner of the casting in the very bottom of the first pic, and compare it to the casting on my stock head.

    [​IMG]

    [​IMG]

    Next up was to drastically port the intake passages, and match them to an adapter I made for a rebuilt 2G carb I picked out of a $10 bin at the local FLAPS. I hollowed the 1bbl intake passage out an obscene amount, trying my hardest to limit the amount of neck-down affect in that area. I was totally expecting to hit a water jacket, but I didn't. I still have that adapter, if anyone is willing to try it, let me know. :sneak:

    [​IMG]

    Next, I made a jig to grind the valves on a 3-angle design, and I hollowed out the ports to get maximum flow. I made a cheap-and-easy flow bench with a shop vac to test my improvements on the fly. The improved amount of airflow was impressive. Sorry, no pics. Pre-digital camera, and every shot cost money.

    I port-matched the exhaust ports to my headers and increased the flow in the block the best I could.

    [​IMG]

    Here it is, all buttoned up.

    [​IMG]

    Sorry, not dyno results, but this engine RIPPED. It was a dog off the bottom, but from about 2500-5000 rpm, it built impressive power. It would fall flat on its face at 5k with the factory cam and valve springs, but it acted as a natural rev limiter and kept parts from flying.

    A downside was, I had to cut a hole in the pristine hood of my 3b to clear the air cleaner, and I made a cheesy hood scoop for it. :poo:

    It had a radiator hose mishap in its inaugural run, and I cooked the engine by the end of the race. :( I took it home and tore it down to find the deck warped - it had a massive hump in it, but the head was fine. I put it back together with a new head gasket and drove it to MA from PA the next weekend for an all-Willys trailride. It was a great power spread for the freeway, but for trail riding it was definitely not optimal. I ran it as a daily driver for another few months, but it eventually developed a crack in a cylinder wall and I swapped out the whole mess. I think it's still stashed at my dad's, much to his displeasure. :whistle:
     
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  6. Nov 29, 2017
    GeoffreyL

    GeoffreyL Well-Known Member

    moorestown, nj
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    If it ever needs a new place to stay let me know, I've got a seized block laying around I could free up and bring it back to life. I do have enough spare parts now to build a whole jeep...
     
    ITLKSEZ likes this.
  7. Nov 29, 2017
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
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    Killer!
     
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  8. Nov 29, 2017
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    What do you think killed off the bottom end?
     
  9. Nov 29, 2017
    Rich M.

    Rich M. Shoe salesman 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Maryland
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    Too free breathing is my guess. I've seen many an engine lose the bottom end with larger exhaust/ less back pressure. Also the valve timing the intake probably didn't open soon enough.
     
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  10. Nov 29, 2017
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    When you put too big of a carb on an engine and open the ports, there isn't enough air flowing through it at lower RPMs to create enough vacuum and/or atomize the fuel. Larger passage = slower air speed. Once the RPMs get up into the low-end demands of the bigger carb, the engine is already spinning at 2k+.

    This is exactly why a small turbo or supercharger might be optimal for these engines. Low RPM airflow and fuel demands could be left alone, and the compression is already low enough to conceivably handle the boost.
     
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  11. Nov 29, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I've never understood the back pressure discussion/theory, I'm not saying it isn't true just that I can't wrap my head around it. To me getting rid of the exhaust as best as possible is number 1 priority.
     
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  12. Nov 29, 2017
    termin8ed

    termin8ed I didn't do it Staff Member

    Mason, MI
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    Guy i work with has a turbo from a 1.4 sitting on the bench. May be worth a shot. What would be a good "formula" for turbo size? I know in generl the smaller the turbo the quicker it would spool up.
    If you want any dimentions from it let me know
     
  13. Nov 29, 2017
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    I am right there with you as well Glenn...
     
  14. Nov 29, 2017
    73 cj5

    73 cj5 Not ready for the junkyard yet

    Clinton, Mississippi
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    with 4 psi of boost you'd be running around 8.8 for the fcr
     
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  15. Nov 29, 2017
    Karl Childers

    Karl Childers Member

    Taos New Mexico
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    Too free an exhaust only flows well at very high rpm's Good in race motors not so good elsewhere. Some back pressure is good as it prevents reverse pressure pulses from traveling back up to the exhaust valves and interfering with the next exhaust pulse trying to make its way down the exhaust track.
    A little back pressure helps the exhaust scavenge better. Getting everything to work its best on a performance motor can mean compromises unless it has a very narrow focus.
     
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  16. Nov 29, 2017
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    Put your seatbelt on... Here's the point in my life where I was on some good drugs. :cool:
    My second attempt at destructing... I mean, developing more power was a little more unconventional.

    Redneck Nitrous!!!
    :lol:

    Contrary to what Hollywood would like you to believe, N2O (nitrous oxide) is not flammable. At around 550° it breaks down and separates into nitrogen and O2. Again, neither of which are directly flammable. N is an inert gas, and O2 (as O becomes in the process) is simply an oxidizer that promotes combustion. The nitrogen indirectly has a cooling effect on the engine, and the oxygen allows much more fuel to be injected and burned, simulating a much bigger engine in the same small package.

    Knowing how this all worked, and wanting to squeeze more power out of the F-head, I went about building a system that would mimic nitrous without spending any money. Here was my attempt.

    - Older 4cyl Volvos have a 5th "enricher" injector mounted in the air rail of fuel injection system for cold starts. I welded a mount for one of these injectors into the riser on the Solex carb. This would inject more fuel into the engine when a switch was triggered.

    [​IMG]

    -I mounted a limit switch under the gas pedal that would...
    A) at full throttle, open the fuel injector to inject a heavy stream of raw 94 octane fuel into the manifold, and
    B) open a 12v air solenoid that would dump pure oxygen into the air intake horn, from a tank of O2 that was onboard. (Are ya scared yet? :rofl:)


    12v air solenoids (one was for my air horn, the other is for the O2 injection):

    [​IMG]

    Here you can see the O2 injection tube welded into the top of the air intake:

    [​IMG]

    O2 tank under the Driver's seat:

    [​IMG]


    So in theory, I was giving the engine everything it would have with N2O aside from the nitrogen byproduct.

    I didn't know how to make a fuel pump run at 60-80lbs of pressure with 100% resistance (while not in demand) without burning up. So, I made a secondary 94 octane fuel tank out of an old soft drink CO2 canister, and I pressurized the fuel with an inert gas, CO2 (that I already had onboard for my air horn), as to not make the canister an oxidized bomb.


    Fuel cell:

    [​IMG]


    CO2 tank under the pass seat for air horn and fuel pressure:

    [​IMG]


    The race was a brutal 7 mile course that was 4 laps, over huge rocks, roots, etc... For the first lap of the race, the system worked well. It gave me an easily noticeable increase in power at full throttle as long as my RPMs were up high. If I triggered it at low RPMs, it would backfire through the carb.

    But from the second lap and on, when the switch was triggered, it shut the engine off like a light switch. Release the switch, and the engine would run fine.
    o_Oo_O <-- Me.


    I checked the system and everything was working as it should.
    80psi of pressure in the secondary fuel tank.
    40cfm of O2 injecting into the intake.
    All switches were operational.
    The whole system was separate from the ignition system, so it wasn't cutting power to that.

    I finally figured out what was happening. The co2 actually impregnated itself into the gas while pressurized and shaking, making it carbonated like a big bottle of gasoline soda pop. The bubbles were suspended until the pressure was released, and then the co2 put out the flame.
    I couldn't figure it out until I got home and released the pressure on the tank and the foamy head shot out like shaken bottle of gasoline champaign!!
    It took a bit of trial and error to get the gas vs. O2 rates correct without preignition (knocking), but it didn't melt anything. It's actually the same engine that's in there today. That might explain a few of the busted rings I just repaired. :whistle:
     
  17. Nov 29, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    With the cylinder lying down you got liquid CO2 coming out. If it had been mounted vertical you would have only gotten gas out and chances are it would have worked the whole race.
     
  18. Nov 29, 2017
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

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    Jeez, I love this on so many levels.
     
  19. Nov 30, 2017
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    I love your CIS cold start valve/injector to enrich full throttle, but an electric fuel pump from the same Volvo would have been perfect to supply it at the optimum pressure. Yes, it would require a return line to the tank.

    I'll be picking up an engine (maybe the whole race Jeep) in a few weeks that got rainwater in the air intake 2 months back in the hurricane. It was running/driving back in August. It should be built pretty similarly to an engine i picked up a while back that pulled the wrist pin out of the piston at about 6300 rpm. It took out the rod, block, and crank. It has a side-ported head, 4 bbl on a fabricated manifold, custom ground cam, roller rockers, milled block, head, and pistons. These are sometimes turned up to close to 7000 rpm, and that on a flooded track close to 2' deep. Check out the Naples, FL swamp buggy races.
    Ryan is correct (post #10) as to why these engines have no low-end power, even with stock cams. With big porting, there is no velocity to atomize/mix the fuel until the rpm's are cranked up! The 4 bbl carb on the race engine I have flows all 4 ventuies, but the jets on the secondaries are soldered shut.
    -Donny
     
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  20. Nov 30, 2017
    fhoehle

    fhoehle Sponsor

    Harford Township, PA
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    Well this thread certainly has my attention!
     
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