Iron Duke engine

Discussion in 'Flat Fender Tech' started by autocartodd, Oct 1, 2009.

  1. Oct 1, 2009
    autocartodd

    autocartodd New Member

    Western Pa.
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    I've been talking to Larry at Clifford Performance. He recommends the Pontiac 151 "Iron Duke" engine over the 3.0 Mercury engine.

    I saw a CJ2 A at a truck show last weekend. it had a 231 V6 in it. It was a nice job, however it was a little too close under the hood and I think I'd prefer a 4 cylinder. Anyone have any experience with this engine in a flat fender? I know it was a standard engine for a while in the CJs.

    What kind of performance can I expect? Anyone done a performance build up on this engine? Thanks Todd
     
  2. Oct 1, 2009
    michigan_pinstripes

    michigan_pinstripes I'm not lost, I'm wandering Sponsor

    Clarkston MI...
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    Where is your flat head? That is more than enough engine and bolts up. If you need one, I have a complete unit in the garage, cheap -- ran but was pulled due to a rod knock :rofl:
     
  3. Oct 1, 2009
    Vhunter

    Vhunter Member

    Redding, California
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    I have the Chevy II 153 four, and it is a good engine that fits real well in a Flat Fender Jeep. So why does Clifford research like the 151 better?
     
  4. Oct 2, 2009
    autocartodd

    autocartodd New Member

    Western Pa.
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    Larry says it's a better design. he also says they can build more horse power and torque with it. I'm sure it's like the Ford/Chevrolet battles. I just wanted some opinions, not to start any battles..... Thanks Todd
     
  5. Oct 2, 2009
    superjeep

    superjeep New Member

    cincinnati,ohio
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    I would stat by saying this was put into jeeps around 1980. I am putting one in my cj2a but I am also using trans and transercase plus hanging pedals.I found a complete donor
    vehicle. My other jeep I have the same engine it has a big cam ,balanced, and running a 390 cfm holley 4barrel carb. I could run down the highway around 70mph with 33"s.

    If you want some pics send me an e-mail and I will send you some and give you more info on any part you need.

    <smaglecic@hotmail.com>

    Shawn
     
  6. Oct 2, 2009
    jpflat2a

    jpflat2a what's that noise?

    Riverside CA
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    not worth spit in my opinion..boat anchor.
    as mentioned, used starting in 1980 in CJ Jeeps.
    oil leaking, rod knocking, camshaft spitting, piece of junk.
    we called them: Pontiac Pukes
    a real headache for the dealer
    you couldn't give me one
    just my opinion
     
  7. Oct 2, 2009
    sparky

    sparky Hoon Staff Member Founder

    Toowoomba, QLD
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    I never had a problem with the two that I owned, one in my S10 the other in my Fiero, and a third that was in a friends Scrambler we did try to kill and couldn't.
     
  8. Oct 2, 2009
    duffer

    duffer Rodent Power Sponsor

    Bozeman, MT
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    My $.02 worth: The amount of work to transplant another 4 cylinder will not be any less than installion of a V6 or V8, both with grossly more bottom end torque available; and a transplanted 4 banger will not make it any more stock than the V's. The weight and space issues are always brought up. The weight is a non-issue. A sbc with aluminum heads and intake weighs less than 10 lbs more than a 134F head. Space wise, most of the V6's are as short as the 134's and fitting an eight is not that difficult. What you gain is a huge amount of drivability, especially off road. I am pretty partial to sbc's simply because they were well designed and offer unparalleled ability to build a bore/stroke combo taylored to a very specific application, for a very reasonable cost. The 381 I am running in the 3B will actually pull at less than 500 rpm and still develops what I am sure is over 450 ft lbs torque someplace between 3500 and 4500. My opinion is that if you want a 4 cylinder, keep it stock. If you really want torque and hp, put in an 8. The 6's are a bit of a compromise but in my experience, only come up short at higher highway speeds. Once you pilot a Willys with either, it is very difficult to go back to a 4 cylinder if you really use the vehicle.
     
  9. Oct 2, 2009
    Warloch

    Warloch Did you say Flattie??? Staff Member Sponsor

    Falcon, CO
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    I've been putting V6s in Flatties since the late 70's. For me, it's an easy swap. I also agree that any swap - V8, V6 or 4 cyl will require close to the same amount of work. Maybe not the same work, but the volume is going to be the same. I know alot of folks who replaced the 4 cyl for another thinking it would be easier, in the end, it worked out to be about the same as the others. They all require the same degree of planning to put them in and do it right, Motor Mounts, Tranny match, Tcase Match, height under the hood, Drive shafts, battery, cooling...

    Having done V8s, I would have to lean toward them being tougher due to the length more than anything.
     
  10. Oct 2, 2009
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Ok, the L134 makes 60 hp at 4000 rpm. The 151 "Iron Duke" in a Jeep makes 82 hp at 4000 rpm. The AMC 150 cid engine in a Jeep makes 123 hp at 5250 rpm in its final MPI version. The 225 V6 makes 160 hp at 4200 rpm - but this is the old 'bhp' (gross hp) rating, and should be derated maybe 30% to be comparable with modern net hp ratings - so roughly 115 hp. I expect the L134 is also bhp, so 42 net hp.

    I've always heard that the 153 cid 4-cyl was a terrific 4-cyl engine. It was very popular with midget racers, who modified the heck out of it. I also recall that the 151 does not provide much hop-up potential without significant outlay, ie aftermarket crankshaft, rods, etc. AFAIK the performance parts are out there, but you need to spend a lot of money to get significantly more power out of the 151. I know I read this in an article online, so look around the net for info about hopping up the 151.

    The 151 does have one thing in its favor - it's cheap and plentiful.

    Now, if you want a really high-performance 4-cyl, you could consider the Chevy Atlas engines, like the 2800 cc (169 cid) LK-5, which makes 175 hp at 5600 rpm. If I wanted a 4-cyl, I'd look at the LK-4, the AMC 150, and the Chevy stovebolt 4s (153 and 181/3.0L). The 153 and 181 are proven options; online sources list the 3.0L at 140 hp, so I'd guess you'll have about 3x the power of the L134 with the 3.0L.

    Note that, in general, the newer the engine design, the more hp it will produce in proportion to ist displacement. However, modern engines come with more complexity (ie MPI, multicoil, etc.) and won't provide their rated power without all this extra stuff. I'd probably choose the TBI era (ca 1980-90) as the best compromise between power and complexity, if I were concerned about excess complexity.

    BTW the Justice Brothers (Wynn's Friction Proofing) Racing Museum in Duarte CA, has one of the 153 midgets on the museum floor, if you are in the area and interested in seeing one. Free admission - call ahead.
     
    Last edited: Oct 2, 2009
  11. Oct 2, 2009
    autocartodd

    autocartodd New Member

    Western Pa.
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    Thanks for all the imput. Now I have more information to keep me up at night.... Todd
     
  12. Oct 2, 2009
    jpflat2a

    jpflat2a what's that noise?

    Riverside CA
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    just seems that every late model GM engine (2.5 4 cyl, 2.8 V6, etc) was just a big oil leaker; intake manifold, valve cover(s), fuel pumps, distributor o-rings, rear main seals, etc etc.
    I'd look out on the dealer lot, see a new CJ or XJ being delivered, only to know that in less than two weeks, those owners would be calling to bring it back in for oil leaks.

    It was rumored that when AMC/Jeep bought an engine from GM, there were 3 different grades or levels of engines to buy; the good ones, the okay ones, and the problem ones.
    I don't know how many Pontiac Puke short blocks or crankshafts we put in them for various rod knock/run-out problems; we were replacing crankshafts because we couldn't stop a rear main seal leak; they use a full lip seal at the back of the block.
    The 2.5 when it ran was just a noisy engine, compared to AMC engines.

    AMC/Jeep tech support/field rep would come out to inspect a 2.5 oil leaker; he would tell us to remove the spring from a new rear main seal, cut 4-5 spirals out of the spring, re-install the spring on the seal, and back fill the empty cavity of the seal with RTV to try and make the seal fit tighter/snugger against the crankshaft (if you can believe that).
    anyway, hope your engine works for you and gives no trouble.
     
  13. Oct 2, 2009
    autocartodd

    autocartodd New Member

    Western Pa.
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    Maybe the V6 oddfire I got on the engine stand would be a better choice after all. Thanks again for all the input Todd
     
  14. Oct 2, 2009
    Bob Greenslade

    Bob Greenslade Member

    Roseville CA
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    Wasn't it the Iron Duke that had the distributor down real low on the side of the engine and every time you did a water crossing you had to dry it out if wasn't sealed properly?
     
  15. Oct 2, 2009
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Like this?

    [​IMG]
     
  16. Oct 2, 2009
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    The "better design" of the 151 may be the flow-through design of the engine, where the intake is on the opposite side of the engine from the exhaust. The 153/181 have the conventional design for OHV inline engines, with the intake and exhaust on the same side, and the distributor on the opposite side.

    If you want a flow-through engine, you could consider the Ford 2000/2300 OHC inline 4. This engine seems to be universally praised, and is a proven conversion in a CJ. It also has a lot of hop-up potential. Novak makes an adapter to the T-90, and it's a less expensive adapter than for the GM engines. It might take a while to find the bellhousing you need to use with this adapter, but lots of them were made, so you should be able to find one if you're persistent.
     
  17. Oct 2, 2009
    Mike C

    Mike C Member

    Austin, TX
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    Cross flow head has intake on one side, exhaust on the other.

    One of the things I find appealing about the Chevy 4 is the bellhousing. It will use a cast iron large bore bellhousing from a truck which are available large bore for an SM465 or small bore for an SM420. Then just adapt to T-case. Either one of the GM motors has quite a few parts available in the aftermarket, and I personally like the idea of the 4 cylinder packaging. More than anything for myself, I just want to do the Mercruiser swap.
     
  18. Oct 2, 2009
    47willys

    47willys Member

    Austin, Texas
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    It never ceases to amaze me the knowledge you guys have on what parts will mate up with what else. I'm not worthy. Now, if only someone wanted to know something about aviation history or Radio Control I could help.
     
  19. Oct 21, 2009
    woodsy

    woodsy New Member

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    Hello, Newbe here. Sorry to rehash an old thread, but this one is of great interest to me. I have an '80 cj5 with an Iron Duke. I bought it 8 years ago with a knock in the motor. It had been in storage for 10 years without any prep. I tore it down and found a broken ring and cracked skirt on #4. Apparently the ring cracked when they tried to fire it up, then the resulting piston wobble cracked the skirt. I then did a complete rebuild. I bored 30 over. I replaced the head with swirl port head off an '85 Camaro, which also boosted compresion from 8/1, to 9/1. I removed and capped off the EGR, drilled out the main jet one size larger, cranked the base timing from 6 degrees to 12 degrees, and run 91 octane. I then replaced the SR4 four speed with a T5 five speed. I'm running 31s with the original 4.10 gears. The one thing I havn't done, is install an electric fan. 8 years later, I have had none of the issues listed in this thread. My Duke runs like a top, has been very dependable, and gets over 20 MPG on the road. It's the perfect trail rig for our Northern Wisconsin logging roads. I've run it on the Colorado Alpine trails and was very pleased with how it performed. I have a CJ2a project that I am planning on installing a later model Iron Duke out of an S10 with TBI, so I am very interested in your project Superjeep. If I was running primarily sand or mud I would be considering a V8 swap. The actual cost of installing V8 may not be much different than swapping in a 4 banger until you have to start replacing the rest the drivetrain to handle the extra power, and all that beef also adds weight which then requires more horsepower and kills gas mileage. It's a visious cycle.
     
  20. Oct 22, 2009
    lynn

    lynn Time machine / Early CJ5 HR Rep Staff Member Sponsor

    Huntingdon PA
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    My son had a 151 in his '81 Scrambler. Had about 80K on it. He over-revved it on a snow run 3 hours from home, got a rod knock. Drove it home... it lasted for two hours of the 3-hour drive... then blew a hole in the block the size of a softball, scattered parts and oil all over the road... :shock:

    I've seen plenty of 225 V6s in flatties. Nice fit, great power-to-weight. No question which way I'd go. :v6:
     

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