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Thread: Where to start? Jeep CJ7 with AMC 360

  1. #11
    Thank you from BT Grease Monkey
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    Quote Originally Posted by JEEPCJ360 View Post

    I think the next upgrade is going to be exhaust. I know you are running stock manifolds, but what are your opinion on headers? Also, what are your thoughts on single versus dual exhaust? Thanks for your time.
    My opinion? Headers are for race cars.

    After listening to the wise sages of this board, there are only two choices for headers. Edelbrock shorties and full custom.

    The Headmans are really light construction and hang too low for a Jeep. (had a set and they rotted out) The fenderwell exits may work for a pavement pounder but I would not use them if they salt your roads in winter.

    Single exhaust is more suited for low end torque, where duals are more for high rpm. Some of the low torque can can be gained back by putting a balance pipe between the banks behind the engine. This can introduce ground clearence issues if you go off road.

    The only reason I'd go duals is racing or if you just have to have the tone (which I did) they are a PITA to route in a CJ frame. My exhaust guy almost fired me! (figure that one out)

    On exhaust I'd wait for some of the more knowledgeable ones to comment.

    If I were to do it again, I'd go single exhaust and try to find a home for a late GM pickup muffler under my Jeep. I'm just sick of listening to it and I'm running 2 chambered mufflers.

    Oh, and stay away from glasspacks, they are proven to reduce power.
    Its a Jeep Thing --- No one understands!

    "America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves."
    -Abraham Lincoln

  2. #12
    Thank you from BT Grease Monkey
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    Quote Originally Posted by JEEPCJ360 View Post
    I was going to go with the MSD or Summit CDI unit and stick with the Motorcraft dizzy but I have read so many threads on the jeepforum.com site of people having noticeable performance gains with the HEI. I will keep my duraspark/coil/dizzy in case the HEI fails, but I like the simplicity of the HEI. I have not read anything about clearance issues, but I would hope that Bulltear wouldn't sell HEI units that have this issue.
    The issue is not a Bulltear HEI one. It is a physical space limitation on the engine itself. Have you ever seen a GM HEI unit? They are huge and a PITA to work on. They also seem to be hydrophobic. A condition I can't explain.

    As to the Motorcraft dizzy issue; if the shaft bushing is wore out it will not hold a stable timing. This is true for all dizzys. The other issue is they tend not to be stable over ~6000 RPM. They are also much easier to tune than a HEI. IIRC, the HEI does not have a mechanical advance limiter, which is only a concern for high RPM usage. The only other downside is the external ignition module. I always carried a spare.

    The best part of a Motorcraft Dizzy is they were engineered to fit. The timing curve is also set close to what the engine needs. (70's dizzys)

    The only reason to use a MSD billit is for the predictable adjustability. I've worked on these and they are by far the easiset to adjust (versus factory units) thus easy to setup a custom curve. But you pay $$$ for it.

    Most likely the power increase you are hearing about is from guys with heavily emmisioned 6 cyl jeeps from the 80's. This was a transitional period where they started to integrate the carb with the ignition. You change the carb and the ignition is thrown off. So, drop in a HEI and OMFG, I got huge HP gains, when all that happened was the timing curve was corrected.

    In this society of advertising mania, the OEM gets lost in the shuffle. These engineers, or rather teams of them, spent uncountable hours designing and balancing performance to reliability. Race car stuff does not lean much to the reliable side. It just has to last for a race.

    Quote Originally Posted by JEEPCJ360 View Post
    I am running 410 gears so that shouldn't be a problem, right? I will check my timing and see where I am. IIRC i am around 10 BTC right now without vac advanced hooked up. I was a bit more advanced but was getting slight kickback when starting so I retarded it a few degrees.
    You did not mention tire size. 4.10's should be good for 35" tires on a D/D. I prefer 4.56 w/ 35" but that leans more to off-road use as the MPG would suck.

    Book says 8* @ 800 RPM for timing. I mispoke before as that was 258 w/ auto.
    Don't forget to check compression. This can tell you is you have a dead hole or burnt valve. Conditions that cause all sorts of gremlins. If you don't have one, most auto parts stores will loan you one and some for free! :)

    My jeep is an stubborn SOB on a cold start (after sitting for many weeks) but pops off in one or two revs warm. This may be cam related.
    Its a Jeep Thing --- No one understands!

    "America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves."
    -Abraham Lincoln

  3. #13
    Bulltear forum member New to the forum
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    Quote Originally Posted by msalaba View Post
    You did not mention tire size. 4.10's should be good for 35" tires on a D/D. I prefer 4.56 w/ 35" but that leans more to off-road use as the MPG would suck.
    Thank you so much for your well thought out comments. I truly appreciate your time. I am running the 4.10 gears with 33x12.50R15 BFG ATKO's. So that puts me at about 3000 rpm to do 70 mph.

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