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Technical High ratio rocker arms

Discussion in 'The Hokey Ass Message Board' started by Buffalobillmaggot, Apr 17, 2021.

  1. I've got a motorhome 440 with next to no miles on it, with the way down in the hole cast pistons. I'm putting an aluminum Edelbrock intake and 1 3/4 headers on it.

    Instead of changing the cam, would it be worth installing 1.6 rockers to bump up the lift of the stock cam? I'm imagining that the increased lift would help with the breathing, but no extra duration might keep the dynamic compression ratio from dropping too much?

    Am I off my rocker?
  2. AHotRod
    Joined: Jul 27, 2001
    Posts: 11,425


    I wouldn't waste the money and time.

    Just pick up the phone and call Bullet Cams and have them make a custom cam that will make the engine produce what you want.
    Max Gearhead, Deuces, egads and 2 others like this.
  3. foolthrottle
    Joined: Oct 14, 2005
    Posts: 1,146


    I always liked the simplicity of the stock mopar rockers, change the cam
    Deuces likes this.
  4. Agree, just put a normal performance cam vs the extra small duration rv cam. You'll gain more in power than you lose in the cylinder pressure.
    Engine will always be a bit sluggish without additional compression, crutch that by advancing the cam and running more than normal timing advance.

    Sent from my SM-A102U using The H.A.M.B. mobile app

  5. Joe Travers
    Joined: Mar 21, 2021
    Posts: 374

    Joe Travers
    from Louisiana

    Always check piston-valve clearance before making any changes in valve lift. Rocker change will provide good bit of additional lift. Better safe than sorry.

    Deuces and ekimneirbo like this.
  6. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,977

    from Oregon

    When you change rocker arm ratios, you usually need to also change pushrods. Changing the ratio results in the pushrod not running centered on the valve with the existing pushrods. So it's not as cheap or easy as just swapping in a new set of rockers.
  7. oldiron 440
    Joined: Dec 12, 2018
    Posts: 2,302

    oldiron 440

    While this is normally a good idea the pistons are so far down the hole in a motorhome 440 it's not necessarily in this case.
    VANDENPLAS likes this.
  8. A buddy of mine said red springs and a roadrunner cam would be great, is that sound thinking?

    On moho 440 heads, are the exhaust and intake springs the same height?
  9. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    Member Emeritus

    Sounds like the quench on a motor-home 440 MOPAR is really messed up; lots of detonation? Worked with a guy when I was in high school (66-69), at a Standard Chevron Dealer, who bought a new Dodge Charger RT with the 440. First thing he did during the first few weeks of owning the car, was to get a bushing kit, and advance the camshaft three degrees. He claimed it really woke up the motor, but he was also a sycophant in all his dealings, so I really have no idea what it did, if anything. Report back after you've done the work. I am Butch/56sedandelivery.
    Max Gearhead likes this.
  10. TRENDZ
    Joined: Oct 16, 2018
    Posts: 310


    If you have gear to gear timing, you will need to change more than just the cam.
    Some parts are different because of the reverse cam rotation. You will need a timing chain set, a new intermediate drive & bushing, and in some cases a distributor.
  11. GearheadsQCE
    Joined: Mar 23, 2011
    Posts: 2,783

    Alliance Vendor

    My new word for the day, "sycophant".

    I've known a lot of them but never knew they had a name! :D
    LWEL9226 and Max Gearhead like this.
  12. jimmy six
    Joined: Mar 21, 2006
    Posts: 9,737

    jimmy six

    Advancing the cam wakes up a lot of engines with added low end torque. I’ve done it to and the vehicle felt totally different and was ez to do. Not sure on a 440.
  13. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,051

    from Brooks Ky

    If you have Amazon Prime you can go to the Motortrend Network and watch Season 4 Episode 53 "The 440 You Can Afford" where they do upgrades to a motorhome 440. There are other sources than this, but I know its available there. Here is a "trailer"
    Buffalobillmaggot likes this.
  14. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,051

    from Brooks Ky

    I wondered about that a while back when thinking about using lower compression for engines that are going to be supercharged or have a turbo installed. The simple answer turned out to be that they still have a normal (?) quench area to start the burn and then drop off to a larger lower squish for the rest of the chamber. I'm not an expert on this, but the guy who explained it to me is, so I believed him.;)

    Additionally, I'm currently aquiring parts for a Cad engine which is also big cube low compression from the factory. One of the first things I learned was that the dishes used to drop the pistons compression are NOT the same as valve reliefs. So don't assume low compression means valve clearance.
    Last edited: Apr 18, 2021
  15. One thing surprisingly not mentioned yet is the possibility of valve spring coil bind. The springs have to be rated for the lift. I've seen spring failures (and subsequent catastrophic engine damage) when this wasn't checked...
    Tickety Boo likes this.
  16. lostone
    Joined: Oct 13, 2013
    Posts: 1,748

    from kansas

    Hughes engines makes a cam specifically for the motor home 440 called the whiplash cam.

    I just ordered the cam kit for my 440. You can use the original springs etc. Just change cam and lifters.

    According to their website it makes around 400 horse and it sounds really responsive too.

    Thru the yrs I've talked to 2 guys who used them and said on the street they were awesome and both would use the cam over again.
    Deuces and Budget36 like this.
  17. Have you found the valves chases the piston down the hole and that the valves are closed before the pistons come back.
  18. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    Member Emeritus

    Of course. Most of the "more modern" SBC 350's, have pistons that are not only dished, they also have four valve reliefs. And, we all know of the "rebuilder" style of piston that has .020 off the tops, or a relocated wrist pin hole. But, when I hear the piston is "way down in the hole", I have this "visual" in my mind,it's like 1/8-1/4 inch or more; and there's essentially, no quench at all. Like using a 350 piston in a 302 or 327 SBC; really big quench killers. Second time in a week or so we've heard about MOPARS, and pistons being down in the whole (this thread and the 426 Wedge piston thread). I am Butch/56sedandelivery.
    ekimneirbo likes this.
  19. AHotRod
    Joined: Jul 27, 2001
    Posts: 11,425


  20. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,076

    seb fontana
    from ct

    Additional lift would only be .035 or so. I was thinking of a 8-71; prob a little over kill..:rolleyes:
    Buffalobillmaggot likes this.
  21. low down A
    Joined: Feb 6, 2009
    Posts: 365

    low down A

    after reading all this bullshit it makes one wonder how them motor homes even ran, probably had to have them towed home from the dealership
    31Vicky with a hemi likes this.
  22. foolthrottle
    Joined: Oct 14, 2005
    Posts: 1,146


    I think the last 440's were trucks and motor homes around 1979, I liked them for the rear sump oil pans,and the motor mounts. the other issue was the 727 trans rear parking brake drum and getting the throttle pressure right. Theres a company that makes some stuff for these motors, Bourchillon performance, their throttle pressure cable set up was of interest to me
  23. No idea on springs and cam details, go with cam mfr recommendation. I believe the bigger problem on your MH 440 heads are they are basically small valve, small port style. As in intended for lower rpm torque and not for high end hp. So just be aware that your engine will not react the same as a normal car or performance oriented 440. The MH heads will just not flow and breathe well. I am not a mopar expert though and there are many more qualified people than me to give advice on heads.

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