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66 cuda' with 318/340 HiPo cam and heads,won't run right,HELP!!

Discussion in 'Performance' started by john slawsky, Nov 7, 2015.

  1. dartndodge

    dartndodge Member

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    Oh I forgot to mention....even better heads are the Swirl port 80s/90s heads, Magnum heads are also good, but need oil mod (pushrods). 340 heads are overkill.
     
  2. dana44

    dana44 Well-Known Member Ad-Free Member

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    Using Magnum heads requires heads, valve covers, intake manifold, exhaust manifolds are recommended (they breathe better and the ports match better), AMC V8 lifters and I think the Magnum pushrods (they have oiling holes in them), then the pushrod holes need to be drilled out larger to accept the offset of the lifter spacing compared to the LA blocks, but they do work, there is a slight boost in compression, have 1.92 intakes which is needed and good for breathing. There are plenty of articles on this swap.

    On the 318 heads, the exhaust valves are OK, it is the intakes that need increase. Stock 1.88 340/360 intake valves (to keep the cost down) can have the seats ground and the port then blended like a tulip or inverted bell shaped to really breathe well. And for the record, 2.02 intakes fit the 318 bore, but a little overkill.
     
  3. Volunteer

    Volunteer Active Member

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    Maybe I'm wrong but I thought the Magnum engines were 'rollerized' - like the last five or so years of the 'LA' - meaning long (tall) lifters and short push-rods.
    Also, if the ignition conversion is from MP (including that nasty looking orange ECM) then the internal curve specs are good as-is. Not sure if you mean that the full centrifugal is all in by 1800 engine RPM's OR distributor (cam) RPM's. Big difference. Full advance by 1800 engine revs will not only produce significant 'rattle' at part throttle but the springs would be too 'soft' to return the counter-weights to '0' position - especially once the moving parts get sticky.
    I haven't read all the posts so won't comment on other suggestions. Is there an Update on results? Or, is this on another thread?
     
  4. TM1963

    TM1963 Member

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    How does it start? Right up or need to crank crank crank?

    I have a similar setup in my 69 Charger - 71 318 block (bored .10 over) , 340 heads (older 2.02 intake), 340 cam (not sure which one, it was free - from a 68 Dart?), 340 intake (Carter AVS carb), double roller timing set. I had a hard time starting it, had to crank the distributor (stock 318 single point) way over - and then couldn't adjust the idle down. I had the distributor in 180 degrees out. Shot fire out of the carb doing that. Put the distributor in right - bingo! (I am a bit fuzzy as I did this 30+ years ago)

    hope it's that easy!
     
  5. Bearhawke

    Bearhawke Things happen for a reason

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    The timing jumping all over the place bothers me as well, that and a possibly sketchy carb.

    Many years ago; I had a 1970's 318 on which I threw on a set of small valve 360 heads, stock Mopar cast iron spreadbore intake and a ca. 1972 Chevy Q-jet carb that I overhauled. Vehicle (1974 B200 van weighing 5,000 lbs) was soft running from the line with its 3:21 gears but; that combo pushed me past 100 MPH. I did that once between inviting a felony speeding ticket if I got stopped and, more importantly, my van was was quite unstable at much over 65 MPH.
     
  6. valiant67

    valiant67 Rich Corinthian Leather Level III Supporter

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    We may never know - he hasn't been back since the first day he posted.
     
    DC-93 likes this.
  7. dana44

    dana44 Well-Known Member Ad-Free Member

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    Yeah, never like to hear that your compression is down to around 7.3:1 and a big cam in there, yeah, it will do fine until you get her under power and sound pretty good, and talk about doing fine on the top end, similar to having too big a cam, wind her up and she purges fine, just have to get there first. Total timing in by 1800 is a problem, should be around 2800 for small blocks, 3200 for big blocks, and can't adjust the carb is running too rich, period. Pretty simple.
     
  8. Volunteer

    Volunteer Active Member

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    Agree totally. I cannot imagine driving anything these days with lumpy camshaft. Best to have throttle response from off-idle to 5000 as opposed to (between) 2500 and 6500. Much more fun. If not mentioned already, my standard procedure is to have engine idling at 8 or 900, timing at +8 or 10 and then read off on vacuum gauge. If under 10 inches, it simply won't be fun to drive in stop and go traffic. The low-speed circuit gets all messed-up and it can no longer be tuned simply with a screwdriver.
    Hopefully 'O.P.' will post an update (eventually).
    The rest of you have a great New Years! - and all the best in '16.
     
  9. jerseyjoe

    jerseyjoe Plymouth Makes It

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    Compression is too low for that big a bump stick. If its automatic you need a high stall torque converter and at least 3.90 diff no matter what trans you have. Clutch flite or a 4 speed GM trans built to neutral start, tires need to spin or you will crunch drive train. Will be tough on rear springs and mounting points. idle set to a point above stalling in gear. Small 4bbl should be good for a good launch and that's it. Thermo quad or quadrojet carb with drag kits would be better. You need to go to someone who can set that system up. Try talking to guys at drag strip. That setup is not a cruiser unless you like lumpy idle. Need hot ignition with long duration, mopar set might not be best, stock distributor cap no good. If it has points you are asking for drivability issues. Good luck have fun. I love the smell of unburned gas in the morning.
     
  10. con383

    con383 Active Member

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    If I May..... Check your timing case cover and make sure the timing marks arn't in the opposite side to the model of the engine.
    earlier LA have the timing marks on the right hand side of the engine and later ones have the marks on the left side,,,,,, Just sayin
     
  11. DC-93

    DC-93 Member

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    Yet another "one post ghost"... lol....

    I have found its best to not reply if you expect an answer from these guys. Life is too short to waste time. Ok, off my soap box and back to work! :cool: