1970 Coupe Deville engine miss? Please Help!! - Page 2
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500, 472, 425, 368 Discussion, 1970 Coupe Deville engine miss? Please Help!! in Cadillac Engine Technical Discussion; When you start hearing loud ticking in the exhaust it is either a burnt valve or a sticking valve. Since ...
  1. #16
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    When you start hearing loud ticking in the exhaust it is either a burnt valve or a sticking valve. Since the new points didn't make any difference it is sounding that way to me. It is nice to adjust the points with a dwell meter so you can hear how the engine responds. You said the top end was rebuilt and the compression was decent in all cylinders, That kind of kills my burnt valve theory. I guess I'd have to hear it. A burnt or stuck valve will make a loud ticking echo all the way down the exhaust. I have removed some very loose timing chains over the years out of engines that were running fine. I don't think they cause driveability problems until they jump a tooth and quit altogether. It's a stumper.

  2. #17
    Hooligan63 is offline Cadillac Owners Member
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Man,I'm still thinking problems at the crank,which might also have to do with the timing gears/chain

  3. #18
    steelybill is offline Cadillac Owners Enthusiast
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    I would agree with the abrupt failure of a timing plastic gear. They almost always fail when the engine is turned off for some reason, at least in my experience.
    This problem is really getting interesting.

    I still think an inspection of the valve springs and rockers is a good idea. Pulling the coil wire and rolling the engine over without starting will be a way to look-see how the rockers and springs are working, and if there is ample lift etc.

  4. #19
    PsychoBillyCadillac is offline Cadillac Owners Member
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Didn't get a chance to play with the caddy much today but for what it's worth I took a look at the distributor rotor with the cap off while I turned the crank pulley with a wrench. There doesn't seem to be any noticible play between the two, a tiny hesitation, if anything. I suppose it's still possible it jumped a tooth or something if the gears are plastic as you say, but there doesn't appear to be any play in the chain. I also thought it important that I mention that I didn't do a COMPLETE top end re-build. The engine had blown the head gaskets and was taken down to repair that. The heads were shaved 30 thousanths to straighten them but I did not do a valve job. The valves, valve springs, rockers, and pushrods are all original to the car with 115,000 miles on them and it is making a noise just as Al mentioned, a loud ticking, not from under the hood but "echoing down the length of the exhaust." What would be the remedy for a sticking or burnt valve? Pull the heads and do a complete valve job?

  5. #20
    Hooligan63 is offline Cadillac Owners Member
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Quote Originally Posted by PsychoBillyCadillac View Post
    Didn't get a chance to play with the caddy much today but for what it's worth I took a look at the distributor rotor with the cap off while I turned the crank pulley with a wrench. There doesn't seem to be any noticible play between the two, a tiny hesitation, if anything. I suppose it's still possible it jumped a tooth or something if the gears are plastic as you say, but there doesn't appear to be any play in the chain. I also thought it important that I mention that I didn't do a COMPLETE top end re-build. The engine had blown the head gaskets and was taken down to repair that. The heads were shaved 30 thousanths to straighten them but I did not do a valve job. The valves, valve springs, rockers, and pushrods are all original to the car with 115,000 miles on them and it is making a noise just as Al mentioned, a loud ticking, not from under the hood but "echoing down the length of the exhaust." What would be the remedy for a sticking or burnt valve? Pull the heads and do a complete valve job?
    Yeah,a complete valve job is usually the solution.Now,if there's vibration,take it to a shop and have them inspect your u-joints,because a lifter or valve isn't going to make your motor shake.

  6. #21
    steelybill is offline Cadillac Owners Enthusiast
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Sounds like a compression test is what's needed if you think a valve is burned or sticking. Too bad you didn't do the valves when you had it down for the head repair.

  7. #22
    PsychoBillyCadillac is offline Cadillac Owners Member
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Well just wanted to say that I really appreciate all the help and suggestions that you all put forward on this, it is most appreciated. Unfortunately, I think this is where I have to draw the line. With all the money that I have invested into the caddy, I am really loath to think about selling her but at this point I am so frustrated by the prospect of possibly having to pull the motor back apart that is likely whats going to happen. I think I just have too many irons in the fire right now, as I also have a 1969 Ford F-100 Ranger I am restoring as well. Thanks again for all your efforts and expertise fellas. If anyone out there might be interested, please feel free to contact me at: theadirondackhermit@hotmail.com

  8. #23
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Since these engines weren't meant for unleaded fuel, the heads and valves supposedly erode and don't last very long. I personally haven't driven any old engines that far for that to happen. It sounds like that's what may have happened to your engine though If that is the case it really should have at least one cylinder with low compression. I'm surprised the machine shop that worked on your heads didn't try to sell you on a good valve job with hardened valve seats to make it unleaded compatible. He missed a marketing opportunity there. The car would probably sell for a better price if it had a valve job with hardened seats. I think I would have a hard time pulling the heads off unless I definitely had a dead cylinder but it is just a matter of time anyway.

  9. #24
    PsychoBillyCadillac is offline Cadillac Owners Member
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Funny, thats the same thing my Dad said when I put the question to him. He is an old gearhead from way back and told me that the gas today is basically "piss" compared to the higher octane leaded fuels which these older high compression engines were originally designed for. Just as you mentioned, over time the newer unleaded fuels supposedly can deteriorate the valve seats as well as other components. Anybody else ever have this happen to an engine or hear of it?

  10. #25
    steelybill is offline Cadillac Owners Enthusiast
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    The lead in fuel builds a coating on the valve faces and seats, which helps them last. Without lead for a break-in, the valve may get a bit of a groove or seats may get hammered a bit. I get by fine on Chevy small blocks that are old engines, without hardened seats. Don't know how a Caddy holds up.

  11. #26
    PsychoBillyCadillac is offline Cadillac Owners Member
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Just wanted to give all the guys who helped me out here a little update on this car. Sold the '70 Coupe DeVille, hopefully to someone who is going to give her the teardown she needs. I have been missing her though, I mean what is a man without a Caddy? So lucky for me this past week I happened upon the BARN FIND of the century!! A 1968 Calais with 53,000 original miles! The car had been sitting in a garage about 10 miles away from me since 1975!!!! Still has the original bias ply tires even and not a speck of rust anywhere!! Even the interior is immaculate. She has one brake line that needs replacing and has a slight lifter tick, but runs like a champ! Anyone have any tips for getting out a lifter tick? I'm guessing it's because the engine wasn't run in so long that one probably lost it's prime. Anyway, I'm beyond happy with her and everything has worked out great so far. Thanks again for all the help.

  12. #27
    PsychoBillyCadillac is offline Cadillac Owners Member
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    Also forgot to add that the red engine temp light stays on all the time for some reason. Even when the car is cold and not running. The gauge says the temp is fine so why would the idiot light stay on like that? Any ideas?

  13. #28
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    After reading this thread over again, I think the '70 might have had a bad coil too like Bill suggested. A compression test would have ruled out the stuck/burnt valve. I did have a brand new chrome coil fail on me once and the car ran so terrible I thought it was dead and parked it. A couple years later I went to put that new chrome coil on another car and it ran terrible too. I put a new coil on the old car that I parked and it ran like a champ. I always thought a coil either worked or didn't work but I found out they can barely work and make an engine run very badly. Too bad we didn't try that before you sold it. I love a '70 Cad. The echo down the exhaust pipe did sound like a burnt valve to me though. Good luck with the '68.

  14. #29
    steelybill is offline Cadillac Owners Enthusiast
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    You will likely change the oil and filter on the '68, and when you do, add a 1/2 pint of Marvel Mystery Oil to the oil. It will likely un-stick the noisy lifter, and any sticky valves. I use it in airplane engines all the time, and nothing else seems as good.

  15. #30
    PsychoBillyCadillac is offline Cadillac Owners Member
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    Re: 1970 Coupe Deville engine miss? Please Help!!

    I will definately do that, sounds like it would probably do the trick. I know that marvel mystery oil has a reputation of doing amazing things. I tried unplugging the coolant temp sensor in the intake and that stupid light still stays on, even with the keys not even in the ignition. The only time it goes out is when you unhook the battery. Weird. Could it possibly be a fuse or something? The accompanying gauge seems to work fine.

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