Register now to get rid of these ads!

Technical Cadillac 390 power loss when in gear

Discussion in 'The Hokey Ass Message Board' started by ElZilchoTX, Jun 23, 2018.

  1. rjones35
    Joined: May 12, 2008
    Posts: 865

    rjones35
    Member

    Ah, bummer. Second guess would be cam then....
     
  2. Truck64
    Joined: Oct 18, 2015
    Posts: 5,325

    Truck64
    Member
    from Ioway

    20" steady on the vacuum gauge is a good number, they don't replace a compression gauge but it's got reasonably good compression or it wouldn't pull 20". It won't hold a high number like that either if there is an exhaust restriction (rev high to be sure) or if the initial (or base) timing is late.

    No idea what the problem is but you're starting to know what it ain't.

    Make sure the mechanical (centrifugal) distributor timing is advancing fully.
     
  3. Definitely need to check timing chain, but quite certain it would give an erratic vacuum reading
    I think...Bad cam lobes can be checked with compression gauge hooked up, internal Schroeder valve removed and compare all cylinders
    One things for sure when you’re done with this you’re going to be a better mechanic.
    Torque converter has some possibilities too. Stall test is in most factory manuals
    Good luck.


    Sent from my iPhone using The H.A.M.B. mobile app
     
  4. Not sure of your question, but I think yes is the answer..It doesn't take much to pull the centrifugal advance back for starting. As I said, points will do it.
    Is the advancer free? Clean?

    So what did you find out with a single, light spring?
     
  5. After following along here for a while I'm beginning to question whether your expectations are realistic. A 390 Cadillac in a fair state of tune should have plenty of beans. But we're talking 1962 here.

    A '62 Caddy is a quite heavy car. A Hydramatic 315 is probably not a terribly efficient transmission. These cars weren't designed to be tire-smokers. They were boulevard cruisers that could also run 75 mph all day on the freeway. And run a power steering pump, a big generator and maybe an A/C compressor. And pull an Airstream trailer up a mountain grade.

    This same engine in a lighter vehicle with a more modern trans and torque converter should be a real handful. But does anyone remember from 50 years ago that these 4500+ pound cars were particularly well suited to smoking the rear tires?
     
  6. I had a slightly newer Caddy rag top with the 429 and TH400. It had over 200K miles and it would smoke the tires. It was a different car but probably heavier than a 62.
     
    ElZilchoTX likes this.
  7. Being a convertible, it probably was heavier. It also had almost 40 more cubic inches and I suspect you had something of an advantage with the TH400 trans. But mainly, I'm kind of just grabbing at straws here. :rolleyes:
     
    ElZilchoTX likes this.
  8. Ditto What Bleach said.
    Just spun both tires (not together but when it swayed side to side!), yesterday,
    on my wife's '67 429 with 118000 no problem at all!
    Could also get easy rubber on my '58 with 4 speed auto
    and 365.
    Caddy's rock!!
     
    ls1yj, clunker, Bleach and 1 other person like this.
  9. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    Well for the first time since owning her she smokes the tires.

    Exhaust is still dropped and I fiddled with timing and carb tuning a little and she behaves much much better.

    The tranny was a little low and she still doesn’t shift quite right, but progress has been made.

    Will still check my cam lobes for the general knowledge.

    Thanks to ‘49 Ford Coupe for coming out and taking a look and confirming my suspicions overall.
     
    jakespeed63, ls1yj and '49 Ford Coupe like this.
  10. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    Not looking to win any drag races, just looking to not get flipped off every time the light turns green...
     
    ClayMart likes this.

  11. Well more power to ya' them! :D Having a second pair of eyes and ears and hands is probably what made the biggest improvement. ;)

    Smoke 'em if you got 'em! :rolleyes:
     
  12. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    Best part is we really did next to nothing...I fired her up, let her warm up, tweaked the timing by ear/vac gauge. And futzed with the carb for like 3 min then took her out and romped in her...

    Shrug
     
  13. The old Hydramatics shifted different from later TH's. The one I had in a 51 Caddy shifted through the first three gears fairly quickly, 1st shift was almost instant.
     
  14. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    I’m only getting 1 shift. :( confirmed with tach.
     
    rjones35 likes this.
  15. Engine man
    Joined: Jan 30, 2011
    Posts: 3,480

    Engine man
    Member
    from Wisconsin

    Try some K&W Trans-X in the transmission. I've seen it cure many shift problems. I put it in my neighbors car when they were going to scrap the car because they were told it needed a transmission. They are still driving it 4 years later. If it doesn't cure it, it will be much cleaner inside if it has to be disassembled.
    [​IMG]
     
    Last edited: Jun 29, 2018
    rjones35 likes this.
  16. I have the same set up. Once you’re dialed in you will see that your car has the nuts. I live near one of those busy divided hiways with stores all over it. I don’t hesitate to rip that 5,000 tub right out of a parking lot right into the 75 mph fray of people texting in their black SUVs. No problems. I keep accelerating until I’m in the fast lane whipping by them all. The only reason I slow down is for gas mileage sake.

    You just have to sort out what’s going on. My guess is that it’s a combo of things, and you sound like you’re well on your way to figuring it out.




    Sent from my iPhone using The H.A.M.B. mobile app
     
  17. Atwater Mike
    Joined: May 31, 2002
    Posts: 11,625

    Atwater Mike
    Member

    Still like to know exactly WHAT that bug was...Love them 'Kitties'...
     
  18. You're only getting one shift on a four speed trans.? Suggest it's not starting in first gear then.
     
  19. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    It is definitely taking off in first...as I can smoke the tires, doubt it would do that in 2nd or higher from a dead stop.

    I’m going to go through he troubleshooting steps in the FSM for the hydramatic. Believe I’m missing 3&4 or 2&4 hard to tell on the short romp I took it on.
     
  20. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    I’m thinking trans still as the main culprit
     
  21. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    It is either condition 2-6302, 2-6602 or 2-7452.


    I’ll check the transition and coupling signal valves as well as the governor
     
  22. Okay, so jack up the rear wheels, put it in low and drag the brakes as you manually shift it. Still might be hard to feel the 1-2, but as you say, you know that's working. Watch the tach and speedo.
     
  23. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    Thanks, I’ll give this a shot.
     
  24. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    After going through the coupling valve body once more I now seem to have all 3 shifts. 1-2 and 3-4 are barely even noticeable, with the 2-3 being a little long but not horrendous but I will adjust the TV Rod to shorten it and not have as big of an rpm drop.

    With the ever so slight shifts I did some ratio math to ensure I was getting all four gears.

    Knowing the tranny gear ratios, rear end ratio, and tire size I simply monitored my rpms at various speeds on a healthy 30 min drive and did the math to ensure all was on the up and up.

    I can now easily smoke the tires from a stop. (Not that I plan on making a practice of this)

    The only remaining items are:
    1) reattach the exhaust, which is pending the arrival of the correct size flange gaskets (first two sets were the wrong size).
    2) reconnecting and testing vacuum powered devices (throttle dashpot, A/C throttle adjuster, auto park brake release, A/C dashpots)
    3) check cam lobes for giggles

    Like an idiot, today, after replacing the ignition switch, I fiddled a bit with the carb tuning and got it a little off tune so my vacuum isn’t holding rock steady like it used to, a minor vibration in the needle really. I’ll retune after the exhaust is hung.

    I’d like to thank everyone for their suggestions and ideas in trouble shooting this issue. Also thanks to ‘49 Ford Coupe for taking some time to take a look at it (and loaning me his pressure washer to remedy the ATF spill)

    Final assessment: transmission coupling valve issue and a severely overfilled transmission (unless everything goes back to shit when I reconnect the exhaust, then it was clogged exhaust). The missing advance spring was causing the mechanical advance to come in early and hat wasn’t helping matters but was not the overall cause of the lack of power.
     
    clunker, Bleach and '49 Ford Coupe like this.
  25. Still haven't told us how a missing advance spring can cause a lack of power and response.;)
     
  26. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    I never said that was the cause of the problem, just something I discovered during the triage. It was jacking with my overall timing curve as it was allowing the weights to shift outward with less resistance. Replacing the existing spring and the missing spring resolved that issue. But as I said I. The quoted post, this was not the cause of the issue.
     
  27. What issue?
     
  28. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    The timing curve issue was resolved by replacing the springs. The timing curve issue was a side issue and not the cause of the lack of power.
     
  29. ElZilchoTX
    Joined: Feb 26, 2016
    Posts: 93

    ElZilchoTX
    Member

    This is from post #5 on this thread, as you can see I didn’t believe a missing advance spring could cause the power loss issues.
     
  30. Okay, again, what I asked you is how a quicker centrifugal advance could cause a lack of , or slower response. You said
    it didn't , but it was jacking with the timing. I was curious how that was manifesting itself, and how you were monitoring it. Sorry if I wasn't clear on that.
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.