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304 Camshaft: Help Me Spend My Money

Discussion in 'Intermediate CJ-5 and CJ-6 Tech' started by Chilly, Nov 24, 2018.

  1. Nov 24, 2018
    Chilly

    Chilly Active Member

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    Been searching for 304 rebuild advice on the world wide interweb. Lots of hot rod recipes for "making power", which translates to "runs poorly before 2.5K". Figured I'd ask this crew what has worked well for a Jeep engine recipe, which is considerably different from a Javelin engine build. My cam doesn't look so good on one lobe, and according to the TSM it was a paltry 0.266" lift anyhow, so it'll be changed. I'll try to detail my goals, what I'm willing to do, and what I'm not willing to do. Some of what I write is me just "talking out loud" to help me (and maybe you) arrive at some conclusions. I don't know a lot, but I know some stuff, but I do welcome any corrections to what I think I know. I spent MONTHS considering Harley cam grinds, then changed cams again after all of that. Nice thing about Harley builds is that there are so much dyno data available for a wide range of builds. Not so much with these old engines.

    GOAL: Build a reliable engine using well-matched and high quality components that complement one another. It's a CJ5, not a hot rod, so high RPM performance is not a priority. It's also a 304 so let's be realistic about the starting point and not try any David vs Goliath heroics.

    INDUCTION: Given my goals for the engine I see few reasons to modify the stock induction system. The MC2100 behaves very well, the intake manifold fits the carb, both probably breathe well enough for an engine that will rarely see 5K RPM. Smallish venturis give good throttle response through mid RPMs, and the conservative intake with relatively narrow runners keep the mixture velocity high. I'll perform some "free" upgrades, such as port-matching, maybe massage the intake ports a little where it counts. Will stick with stock valve sizes.

    EXHAUST: I have a very nicely built stainless 2-1 system with a Flowmaster 40-Series muffler fed from stock cast manifolds. I don't care much for headers and I want the stock appearance under the hood. Aside from smoothing the exhaust tracts in the cylinder heads I'm not inclined to make changes to the exhaust system.

    VALVE TRAIN: This engine was built in June 1973, just after the transition from stud rockers to bridged rockers. Cast aluminum fulcrum surfaces are badly worn, as are some of the opposing seats in the stamped rockers. I have another set of heads that are of identical construction but may be in better shape. I haven't disassembled to look yet. Since I'm likely buying all new rockers and bridges anyhow I'm not opposed to the idea of converting to the stud-type rockers. On its face it doesn't seem like a difficult job, unless I'm missing something. Machine off the pedestals, screw in studs. Am I missing something here?

    For reliability concerns I'm probably not looking for significantly higher spring seat tension. The cast iron seats don't look too bad yet and if I don't install hardened seats a cam requiring stiff springs may beat the valves into the head. This may be an important consideration for camshaft choices. Super-snappy lobes require stout springs, and they slam the valves shut rather than setting them down.

    COMPRESSION RATIO: Comes stock at 8.4:1 and no plans to do a lot about given the fuel quality today, and who knows what it will be in ten years. CR might go up a couple of points due to boring over and kissing heads or engine deck to flatten them as needed. This engine could use a cam with eary intake timing that builds higher pressure, probably a relatively tight lobe separation angle.

    GEARING: T15 3-sp so 1:1 top gear. 3.73 gear sets. 32" tires. Let's say I'm at 3K in 2nd gear, 42 mph, when I shift into 3rd. Revs drop to 1645, then up to 2350 when I'm at 60 mph. With a T15 3sp one can see why a cam needs to come on fairly early.

    IGNITION: Has the original points system. I'm sure there is room for some improvement here, even staying with a points system. My assumption is the centrifugal advance springs are heavier than optimal (lazy curve), and vacuum diaphragm spring lets the advance go retarded a bit premature. There are probably better coils than what I'm using, too.

    I suppose the heart of the build is the camshaft so given what I've typed I could use a hand figuring out what cam will "really tie the room together", to quote The Big L.

    Thanks,
    Chilly
     
  2. Nov 24, 2018
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
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    I like the idea of the 304. I had one in my 77 cj5 and it was always reliable. Really, it was a fine engine for daily driver reliability. It was lacking in power, but pushed my jeep along down the highway at 60 mph. Mild off road it was fine.

    I have also had an Fhead powered cj2a and now my present jeep is a lengthened cj2a with a 66 buick 225. Its basically a junk engine with HEI/offy intake and holly carb. Runs fine.

    Mild off road, they are all the same from my point of view. 4 low or high idling along is all the same unless you do the real stuff that breaks things.

    From my experience the best engine I have had is the buick 225 (375lbs/160HP). Lighter than the Fhead (470lbs 75 hp) and lots more power. The 304 (550LBS/ 150~210HP ) has more weight and possible less power. If I were to go with a V8, I would go chevy since parts are readily available and relatively cheap.

    I had to make decisions when I built this present jeep. I just went with what was cheapest and seemed to be an upgrade. To do it again I would go FI 4.3 only for the factory FI. I like the weirdness of my odd fire, but I am realistic too. Price is always a driving factor for me and its really the driving force behind the "upgrades".
     
  3. Nov 24, 2018
    Rich M.

    Rich M. Shoe pusher

    Maryland
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    Much like the 225/231 the 304 has the same onus which is small valves and was known for being hard on exhaust valves. Frankly I wouldn't get jiggy with it. A basic rebuild with quality parts ( as needed) spend the money on having it balanced ($2-300) clean up the heads ( wouldn't bother porting, you can polish them yourself in an afternoon)and a mild cam/ lifter set. Off the shelf should be fine, I've become a little partial to Lunati after spending time on the phone with my 231 rebuild ymmv. Choose a quality shop if your outsourcing. Rest of your mods look solid.

    I'm sure when outshopped you can find the next weak link if you have a heavy right foot.(y)
     
  4. Nov 24, 2018
    Chilly

    Chilly Active Member

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    Im compelled to keep the 304 because this is the SuperJeep. I'd risk being justifiably homicided if someone discovered a SBC in there.

    As luck would have it my diesel repair owner buddy (named Otto, if you can believe it), stopped by. He had some engines headed to his machinist so we loaded my block and stripped heads into truck of his volvo. It seems like Im actually going to have this thing rebuilt. I'll do the assembly. But I suppose now time is short for me to make a decision on pistons.
     
  5. Nov 24, 2018
    Keys5a

    Keys5a Sponsor Sponsor

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    The 304 wakes up with some modifications. I'll see if I still have any cam cards from grinds I've used years back. I used to always use Crane because they were semi-local (Daytona) and were super nice to work with, just calling them up for information. That gone now, but there are RV grinds that are similar.
    Do your heads have dogleg exhaust ports? If so, they flow pretty good, especially with some pocket porting and blending.
    An aftermarket alloy 4bbl intake like Edelbrock works well with a small, like 450 cfm carb. I've also had great results with a small GM Quadrajet.
    The AMC engines have oiling issues, so I usually drill the main galley up front and run a 1/2" line down to the rear of the lifter galley to get more oil for the crank.
    I also install roller rockers to bypass those stupid bridged rockers that are used stock and end up with a superior system.
    I'll be going through a 304 pretty soon for a project, and want to compare some 360 heads to the 304 heads to see if there is any significant difference.
    The AMC engines are kind of a forgotten engine, so parts are not as popular as a Chevy or Ford, and cost more when you do find them. Keep an eye out on eBay for a cheap intake manifold, or put a WTB add on the forum.
    -Donny
     
  6. Nov 24, 2018
    Chilly

    Chilly Active Member

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    Yes, dog leg ports. Probably stick with stock induction for now. I do like the MC2100 and alloy manifolds are all 4b. Maybe a different Jeep will someday get a few more mods but I'd start with a 360 when I do.
     
  7. Nov 24, 2018
    Daryl

    Daryl Sponsor Sponsor

    Bonney Lake, WA
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    Good reasons to end up sbc. Probably make it worth more to most people anyways. :D
     
    duffer likes this.
  8. Nov 24, 2018
    Chilly

    Chilly Active Member

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    You cant really believe a restored Daisy Yellow 1973 Super Jeep will increase in value with a SBC instead of the original 304? Not that its a convertible hemi cuda, but still...
     
  9. Nov 24, 2018
    Chilly

    Chilly Active Member

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    That said, next Jeep might have a SBC if the engine needs a rebuild.
     
  10. Nov 24, 2018
    Chilly

    Chilly Active Member

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    Except that I keep ending up with rare stuff. My "free" Jeep is a 1982 Superstar CJ7 that is pretty much a near-Laredo. Unremarkable except so few were made and my tub is so thoroughly decayed. Other than that its just a CJ7 with terrible carb, terribler computer, and more worser axle gearing.
     
  11. Nov 24, 2018
    Daryl

    Daryl Sponsor Sponsor

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    Actually, done right yes it probably would have more value to many over an AMC 304. It takes a pretty amazing Jeep to have any real collector value. Even then most are not even worth $10,000. Almost impossible to sell for what it takes to restore one. These are simply a labor of love so build what YOU want and don't worry about " correctness" or originality. A Yenko Camaro or Shelby Mustang they are not.
     
  12. Nov 24, 2018
    timgr

    timgr Jeepin' Nerd Sponsor

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    304/360/401s are all dogleg, pretty sure. The 290/343/390s were not.

    360/401 heads have bigger valves than the 304 heads, the same otherwise AFAIK. The bore diameter of the 304 is too small for the 360/401 heads - the valves will interfere with the cylinder walls. Some have experimented with relieving the 304 cylinder walls to clear the larger valves, but supposedly the resulting shrouding of the valves results in no net gain over 304 heads ... supposedly.

    A 360 is just a 304 with a bigger bore. Same crank, same rods, same stroke. Conventional wisdom says the most cost effective upgrade for a 304 is to replace it with a 360. Of course, you can't economically make a 360 from a 304 because the blocks were cast with different cores. I presume you could put a 401 crank in a 304 block and make a 60-over 336 stroker.
     
  13. Nov 24, 2018
    heavychevy

    heavychevy Sponsor Sponsor

    Danielsville georgia
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    Went with the rv cam in my 304. It made a big difference espcially below 2000 rpm
     
  14. Nov 24, 2018
    Chilly

    Chilly Active Member

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    What is the lift limit for stock springs? I am thinking any cam meeting my performance goals will be within stock valvetrain limits buy I will not assume anything.

    I have not read about valve-on-valve violence with these heads. I suppose the small 304 valves might make it a non-issue?

    About that Harley cam: picked a nice tall cam with 0.590 lift. Then discovered the crankcase needed cut to give clearance for the big bugger. And stout springs. And roller rockers were needed. And adjustable pushrods. It became a very expensive selection. So I am now being careful to understand implications of these choices.
     
  15. Nov 25, 2018
    Rich M.

    Rich M. Shoe pusher

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  16. Nov 25, 2018
    timgr

    timgr Jeepin' Nerd Sponsor

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    I believe valve-on-valve collision is not possible, since the valve bores are parallel. Never heard of valve-on-piston collision either.

    That Lunati looks like a good option. Comp Cams gets recommended pretty often - I'd think you could go with the XE256H, or either the 252H or the 260H. 10-214-5 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts
     
  17. Nov 25, 2018
    74CJ5 Renegade

    74CJ5 Renegade Member

    Houston, TX
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    Why not bump up the compression?

    I am running 9.5:1 and now that I have a MSD Ignition I wish I was running 10.25:1. I never had an issue with 9.5:1 on stock ignition. I have always run her on super.

    8.5 is just such a low ratio....
     
  18. Nov 25, 2018
    Chilly

    Chilly Active Member

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    I dont want to be forces to run high octane, and what really matters isnt static compression but dynamic compression. Running high static compression allows (requires) a cam with long duration, and thats a good cam for high RPM.

    My approach is to decide what RPM range I want to optimize, then build an engine around that. An engine like Im building doesnt need a high static CR, and the cam suited for my RPM range wont tolerate it.
     
  19. Nov 25, 2018
    Chilly

    Chilly Active Member

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    Checked data on quite a few options. Probably down to Comp 260H and Lunati 10100700. Both should build good cyl pressure with 8.5:1.

    The 260H will probably hit sweet spot just a bit higher RPM than the 10100700. Could flip a coin and be fine either way, I think.
     
  20. Nov 26, 2018
    Chilly

    Chilly Active Member

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    I'm curious how you arrived at 9.5:1. I can find no pistons except the slugs that are all dish and no quench. I'm not paying the asking price for custom pistons. I could get a 360 core for less than the difference between in-stock pistons and customs, and there are higher compression stocked pistons for the 360.
     

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