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Technical 354 Hemi Manual

Discussion in 'Traditional Hot Rods' started by spillaneswillys, Dec 20, 2021.

  1. I am going to test out the 354 Hemi in the 39 Plymouth project I bought and have no idea of how to install the plugs and tubes. Would also like all the other specs for tuning. Who makes a good manual for what I want to do?
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 51,242


    ski, ekimneirbo, Tdesoto276 and 3 others like this.
  3. What do you need to know specifically? Basics include, do you have the correct length tubes (should be 3/8" or so higher than the top of the valve cover), do you have the tube seals (big rubber donuts that slip to the top of the tubes)? Do you have long reach insulators for the spark plug wires? And of course the spark plugs themselves have extra long threads.

    Assuming you have all the widgets, slip the rubber seals on the tubes, drop the tubes in the holes thru the valve covers. Get a spark plug socket with a rubber insert so you can lower the plug thru the tube without dropping it. Install the plugs WITHOUT the washers they come with. The tube acts as the washer. Then just snug the plugs as you would any engine.

    I set the timing on my 354 with a vacuum gauge. Unhook the vacuum line from the distributor and hook it to the vacuum gauge. Need a tach too to be totally correct but I do the rpm by ear. Then start the engine and adjust the carb idle screws to proper idle speed, and twist the distributor for maximum idle manifold vacuum. Will need to go back and forth between the distributor and idle screws a couple times to get it perfect. Back off distributor a touch and you have the perfect timing for your engine.

    Here is a modification I did on my engine to get a good seal on the top of the tubes.

    The factory used these big washers on top of the rubber donuts, squished down with the plug wire pans that most hot rodders toss. Thus the rubber donuts just sit there not sealing very well.

    I fixed this by making a wood jig that I could clamp the tube with 3/8" or so sticking up.
    IMG_1537.JPG IMG_1538.JPG

    Then I gently bent the rim over with a ball peen hammer.


    Here is the stock hemi ceramic insulator next to an ACCEL silicone boot. The modern unit is the way to go.
    plug insulators.jpg

    All ready to plug up.

    I used these Toyota hole covers from the junk yard. Get the ones with the "R" on it. Have to trim off the large seal ring with a razor.
    Rubber shields.jpg
    Last edited: Dec 21, 2021
    Fordors, Hnstray, bobkatrods and 9 others like this.
  4. oj
    Joined: Jul 27, 2008
    Posts: 6,313


    Try the original Chrysler manual, they have very detailed photos and dwgs.
    Just Gary likes this.

  5. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,845

    Atwater Mike

    Nice tutorial, @willys36... I did that spark plug 'bell job' on my old Reath hemi, back in '62...
    Desoto291Hemi likes this.
  6. Great minds think alike!!!!
  7. George
    Joined: Jan 1, 2005
    Posts: 7,524


    I use straight boot generic Accel wires.....Wheel cyl boots work good for keeping water out of the tubes but can be too good a seal & the air expanding from engine heat can cause them to pop off.
  8. How do I measure to find the correct tube length. Please keep in mind I am a woodworker that can do mechanical things but really no
  9. Nemosgarage
    Joined: Sep 21, 2009
    Posts: 140


    Very impressed with willys36 ideas and workman ship!
  10. I think there are three lengths:
    6 13/32" - '51 - '53 331cuin
    6 1/8" - '56 - '58 all Chrysler, and all DeSoto
    5 29/32" - all Dodges.

    If you have tubes that came with your engine you should be ok. Just avoid Dodge Red Ram tubes. Contact Hot Heads for the facts on any Hemi issue.
    Last edited: Dec 21, 2021
  11. Marty Strode
    Joined: Apr 28, 2011
    Posts: 6,831

    Marty Strode

    Buy a magnetic plug socket, a quality one like Snap On.
    RDR likes this.
  12. Kan Kustom
    Joined: Jul 20, 2009
    Posts: 2,703

    Kan Kustom

  13. deucemac
    Joined: Aug 31, 2008
    Posts: 1,235


    Ron Ceridono wrote an excellent book several years ago on early hemis and discusses this along with lots of other hemi specific topics. It comes up on Ebay fairly often. Good to have.
    Just Gary and Tdesoto276 like this.
  14. I sold a spare copy on ebaY a couple months ago.
  15. lostviking
    Joined: Dec 23, 2019
    Posts: 54


    Rockauto has both the repair and parts manuals.
  16. Here is a picture of what I have. I also have a set of rubber seals so I am assuming they will finish these tubes off. They look high to me but I'll find out. Can't do anything until I get it moved into my heated garage over the next few days. I am old and cold! Thanks for all the info. Joe

    Attached Files:

  17. Those are too long to get the seals to work but plenty long to do the fold-over mod I show above. If you don't use thewire pans, that should be done on any hemi for a good seal.
  18. I agree with the good magnetic spark plug socket. Should be mandatory for hemi owners.
  19. Would these valve covers be aftermarket? I would assume the factory ones would have said firepower or chrysler firepower?
  20. Are you sure that is a 354 Chrysler? It appears to have a thermostat housing on the manifold. If so it is a 331 if a Chrysler but my guess it is a Dodge or Desoto which have the shorter valve covers. Some Dodges had no name covers. All Desotos had no name covers, their logo was stamped on the plug wire pans. Finally Dodges have the water crossover thermostst housings whereas Desotos have the thermostat on the manifold which is what you have. That would mean you have Chrysler tubes in Desoto valve covews which explains the tall tubes.

    Need to get the serial number off the front top edge of the block and check with Hot Heads web site ID page to nail down what you have.

    Here are some Desoto engine photos.
    Last edited: Dec 22, 2021
    squirrel likes this.
  21. lippy
    Joined: Sep 27, 2006
    Posts: 6,164

    from Ks

    And if you are running an injected nitro engine with titan rockers, and have inch spacers under the covers you can run 426 tubes. :D
  22. The end of the cylinder heads look like the truck heads. The truck vale covers are plain with no lettering. Did you put the tubes on over the spark plugs?
  23. Good point. I didn't notice the truck head bosses. And I just finished installing truck heads on my '52 331, bored to 354!! Regardless, cross reference the engine number on the identifier chart.
  24. I did nothing to the engine yet. This is my starting point. I will get the numbers as soon as I move it into my garage. thanks again
  25. I bought the car with the understanding it is a 354. If it is a Desoto I guess I will have to live with it.
  26. The block numbers are L8-D7-1673. It appears to be a 1958 Dodge truck 354 engine. Hot Heads does not list the trucks so I went to the web.
  27. I just spoke with Debra at Hot Heads and she is a plethora of information. She says my block is probably a 56 354 block.
  28. gimpyshotrods
    Joined: May 20, 2009
    Posts: 20,264


    I wonder if those are 331 tubes, in 354 valve covers.

    Those do look like 354 truck heads.
  29. saltflats
    Joined: Aug 14, 2007
    Posts: 11,308

    from Missouri

    This is my 1958 Dodge truck head a valve cover.
  30. Guy Patterson
    Joined: Nov 27, 2020
    Posts: 370

    Guy Patterson

    Truck heads breath nice but intakes are a bitch to find

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