PWB Posted July 11, 2019 Share Posted July 11, 2019 Happy Summer all! Maybe I'm paranoid but to me it seems my motor is rocking a bit much? I do keep my idle RPM a bit high due to garbage gasoline. I'm running 93 Octane and all is tuned to my best ability. Please view the video and let me know? Thank you https://youtu.be/S29IETJTDLc Link to comment Share on other sites More sharing options...
60FlatTop Posted July 11, 2019 Share Posted July 11, 2019 A compression test is the starting point to diagnose that. Have you taken readings? 1 Link to comment Share on other sites More sharing options...
PWB Posted July 11, 2019 Author Share Posted July 11, 2019 No sir. Never have. I'll put it on my to-do list though and get the equipment. Ugh Thank you Mr. Bernie Link to comment Share on other sites More sharing options...
JZRIV Posted July 11, 2019 Share Posted July 11, 2019 Slightly higher RPM should make it smoother if anything. Looks like it might be shaking a little more than normal 1 Link to comment Share on other sites More sharing options...
johnrex Posted July 11, 2019 Share Posted July 11, 2019 Check the timing! 1 Link to comment Share on other sites More sharing options...
psychostang Posted July 11, 2019 Share Posted July 11, 2019 Vacuum leak or misfire. 1 Link to comment Share on other sites More sharing options...
60FlatTop Posted July 11, 2019 Share Posted July 11, 2019 (edited) If you don't have a compression tester get one that uses a nominal 10": hose with a quick disconnect for the gauge. The old tapered rubber plug ones work but space can be tight on newer stuff. It is an easy test and, from reading internet posts, an uncommon approach to tuning issues. I am leaning back in my big computer chair and on the shelf above my PC are the four volumes of mechanic books my mother helped me buy in 1959. They state the compression test is Step 1 in any tuning issue. All X number of cylinders need to be close. One wobbly valve guide will show up dramatically. I have seen that the most over the years, one valve seat beaten to a rounded edge. Oh, the reason I bought the books was because I was suspicious about the tales those old guys were telling me. Turned out learning where to buy books was the best thing and, anal as it sounds, repeating the same procedures for everything I do helped a lot. Some things just become natural. A while back my wife saw me putting new laces in a pair of shoes. I got this rhetorical question from her "What are you doing?" "Well, the laces from the outboard eyelets have to cross over the one from the inboard eyelets. They can't be all mixed up!" She shook her head and left, but she doesn't understand following procedure. Edited July 11, 2019 by 60FlatTop (see edit history) 1 Link to comment Share on other sites More sharing options...
telriv Posted July 11, 2019 Share Posted July 11, 2019 Number one it's idling MUCH TOO FAST to really tell ANYTHING!!!!! Next, onto the compression test. Dis-connect & ground the coil wire. Next, have someone hold the gas pedal to the floor to allow all the oxygen available to flow into the cylinders. DON'T let up on the pedal UNTIL ALL 8 CYLINDERS ARE DONE. OR, put the pedal to the floor & insert a screwdriver into the secondary side of the carb. to hold the secondary's open. DON'T FORGET TO REMOVE THE SCREWDRIVER WHEN DONE!!!!! Record the readings. The lowest reading cylinder should be within 20% of the highest reading cylinder. IF the engine is in good, healthy condition should be around 170-190lbs. YOUR NEXT BEST FRIEND, besides the chassis manual, IS A VACUUM GAUGE. A relatively in-expensive tool NO TOOL BOX SHOULD BE WITHOUT ONE!!! Do yourself a favor & learn HOW TO USE IT!!!! Link to comment Share on other sites More sharing options...
telriv Posted July 11, 2019 Share Posted July 11, 2019 Forgot to mention. ALL THE SPARK PLUGS SHOULD BE REMOVED!!!! 1 Link to comment Share on other sites More sharing options...
68RIVGS Posted July 13, 2019 Share Posted July 13, 2019 . . . good advice so far Mr. Paul ! Link to comment Share on other sites More sharing options...
EmTee Posted July 13, 2019 Share Posted July 13, 2019 Have you tried adjusting the idle mixture screws? Maybe before the compression test I'd reset the idle and check timing. Once that's done, try adjusting the mixture screws. If they have little or no effect I'd begin to think carb kit (after the compression test). Another quick check would be to pull one spark plug wire at a time and note the RPM change. If I recall, something like -200 RPM is typical. If one doesn't seem to be pulling its weight, then I'd pay close attention there with the compression gauge. 1 Link to comment Share on other sites More sharing options...
KongaMan Posted July 13, 2019 Share Posted July 13, 2019 You might also check the motor mounts. 1 1 Link to comment Share on other sites More sharing options...
RivNut Posted July 14, 2019 Share Posted July 14, 2019 Open the hood. Sit behind the wheel and start the engine. Put the trans in Drive, set the brakes good and hard with your left foot. With your right foot give the car some gas, as much as it will take to tell you the left side motor mount is holding firm. When you're finished doing that, put the trans in Reverse. Repeat the process but watch the right side. If either side of the engine "lifts," the motor mount on that side is shot. 1 1 Link to comment Share on other sites More sharing options...
jsgun Posted July 14, 2019 Share Posted July 14, 2019 On 7/11/2019 at 1:15 PM, psychostang said: Vacuum leak or misfire. I agree. On my ponycar, when the engine started shaking it was a vacuum leak. It would also explain why it runs like bad gas. Higher idle mask it some. Link to comment Share on other sites More sharing options...
60FlatTop Posted July 14, 2019 Share Posted July 14, 2019 (edited) I have tested motor mounts by placing a short bar between the frame rail and exhaust manifold. You can tell by the lift or look for daylight at the mount. If both mounts are bad sometimes there is a round imprint of the fan in the radiator, but that usually comes after a panic stop. Edited July 16, 2019 by 60FlatTop (see edit history) Link to comment Share on other sites More sharing options...
RivNut Posted July 14, 2019 Share Posted July 14, 2019 2 hours ago, 60FlatTop said: If both mounts are bad sometimes there is a round imprint of the fan in the radiator, but that usually comes after a panic stop. I've found the imprint of the fan on the radiator to be the sign of a bad transmission mount. Link to comment Share on other sites More sharing options...
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