Guest tedy010 Posted February 24, 2010 Share Posted February 24, 2010 I have a 1967 Riviera 430CI and not long after the motor has warmed up I sometimes hear a loud clacking noise under load, particularly if I am going up a hill. The sound varies with the speed of the car and sounds like the fan was hitting the radiator but it wasn't. Anyone experience anything like this or have any ideas? Link to comment Share on other sites More sharing options...
Guest wildcat465 Posted February 25, 2010 Share Posted February 25, 2010 I have experienced this twice.Once after accidently putting low octane gas in the 68 Cat. Detonation.Once after spinning a rod bearing in the GS455. Leaving tranmission selector in low and the transmission forcing an upshift at about 6000.I sincerely hope that it is the former in your case. Check your timing, make sure you are using 92 octane or better, make sure your advance weights are not stuck, breaker plate moves freely, and vacuum advance moves back and forth when vacuum is applied and released. Fix ASAP as detonation can cause even more internal damage than a spun bearing if it continues.Good luck. Link to comment Share on other sites More sharing options...
George Buick Riviera Posted February 25, 2010 Share Posted February 25, 2010 Detonation - like wildcat465 wrote - from low octane, OR ignition is not correctly adjusted (ignition too soon) Link to comment Share on other sites More sharing options...
Guest tedy010 Posted February 25, 2010 Share Posted February 25, 2010 Thanks guys I have only used 98 Octane fuel in the tank and will check the timing advance weights, breaker plate and vacuum advance on the weekend, Cheers. Link to comment Share on other sites More sharing options...
Guest kaycee Posted February 26, 2010 Share Posted February 26, 2010 If, after you check the weights for sticking and also the springs, you still have the problem, try retarding the spark a couple of degrees. Hopefully the noise you're hearing is 'ping' or predetonation under load which can be corrected before damage is done. You might also check your plugs for carbon buildup on the electrodes. Good luck! kaycee Link to comment Share on other sites More sharing options...
George Buick Riviera Posted February 26, 2010 Share Posted February 26, 2010 Tedy010, an please let us know what was the reason ;-) Link to comment Share on other sites More sharing options...
Guest tedy010 Posted February 26, 2010 Share Posted February 26, 2010 I will certainly let you know as soon as I know the reason, (car is at a storage facility so don't see it every day), thanks again for the prompt suggestions Link to comment Share on other sites More sharing options...
Guest kaycee Posted February 27, 2010 Share Posted February 27, 2010 Tedy010, If after checking the above suggestions, you still have a problem, try pulling one plug wire at a time while driving the car to see if the noise lessens or disappears. If it does on one cylinder it'll narrow it down to one cylinder at least. I had a knock under load on a '65 Riviera 425 that turned out to be a crack in a piston skirt and did'nt show up on a compression check. Hopefully that's not your problem. It'll probably be just 'pinging'. Good luck! kaycee Link to comment Share on other sites More sharing options...
65VerdeGS Posted February 28, 2010 Share Posted February 28, 2010 If the noise varies with the road speed of the car (not engine RPM) then it might be a loose flex plate bolt. I think there are 3 bolts holding the flex plate to the torque convertor. I had this on happen to my '65 Riv. The clacking got progressively louder until the bolt sheared off. It got REALLY loud as I was gunning it up a hill, and I thought the engine was about to self destruct! I was able to replace the sheared-off bolt without removing the transmission, but was a bit of a tight and tricky job. Link to comment Share on other sites More sharing options...
Guest tedy010 Posted February 28, 2010 Share Posted February 28, 2010 Thanks Alex I will get my mechanic to check all af the suggested possibilities this week.Cheers Wayne ROA #12581 Link to comment Share on other sites More sharing options...
65VerdeGS Posted March 1, 2010 Share Posted March 1, 2010 Let us know Wayne what you find out from your mechanic.We'd be curious to know what the cause of your clacking noise turns out to be... Link to comment Share on other sites More sharing options...
JohnD1956 Posted March 2, 2010 Share Posted March 2, 2010 One more possibility, broken motor mount. Check the inside edge of the fan shroud and see if the blade of the fan is scraping the shrooud. Link to comment Share on other sites More sharing options...
RivNut Posted March 2, 2010 Share Posted March 2, 2010 You can check for broken or weak motor mounts by starting the car and putting it in gear. Hold the brake down firmly an increase the rpm's with the transmission in drive. If the left motor mount is broken, the engine will lift on that side. Do the same thing in reverse to see if the right side mount is broken or weak. I don't know of anyway to check to see if the transmission mount is broken except the way I did it in my '63 Dodge. Drive over some washboards on a dirt road at a pretty good speed and see if the top of the fan doesn't go through the back of the radiator as the engine tips forward. :eek: Needless to say, if you were on a dirt road, you were a long way from a phone before the days of cell phones. Ed Link to comment Share on other sites More sharing options...
Guest tedy010 Posted March 3, 2010 Share Posted March 3, 2010 The mechanic looked at the Riviera today and as usual we couldn't replicate the clacking noise. We tried everything hard acceleration, up hills etc. and no noise!Took the car back to the workshop and checked the timing and transmission, also did the checks on the engine mounts as suggested by Ed 'RivNut' and everything checked out ok.Drove the car all day today and she was fine so will just have to wait and see if it happens again.Thanks guys for all of your advice and suggestions, if anything turns up in the future I will be sure to let you knowCheers, Wayne Link to comment Share on other sites More sharing options...
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