: Tapiti tapiti tap - help!



Sponson
09-21-10, 10:45 PM
Hi, I have a 69 DeVille and the prior owner had the engine rebuilt 700 miles ago due to the engine overheating - new pistons/rings, bearings, cam, lifters, bored out, hardened valve seats, new oil pump, new water pump - I have the receipts and talked to the guy who did the job and believe that all of this was done. Sounds good...... but, I have two problems: 1) about half the time I start the engine, I have a very distinct, loud, single tap tap tap tap. After anywhere from 15 seconds to a couple of minutes, it goes away - althought it faintly comes and goes sometimes. 2) under more than light acceleration I get what seems to be a moderate multiple tap or valve noise. The engine starts (and stops) great, acceleration is good, it idles steady (with point/condensor), timing is 5btdc, mechanical and vacuum advance are working properly, engine oil is 10-30 and is less than 200 miles old with a new filter, and the car was not driven hard the first 500 miles after engine rebuild. I put a container of CD3 (extra engine oil detergent) in the oil to help clean out any potential gunk that may have somehow gotten into a lifter and cause the tap tap tap. I've also been using 93 octane and recently put some octane boost in to see if the acceleration noise was engine knock, but I did not notice any difference after adding it (it didn't sound much like engine knock anyway). Hmmm. Suggestions on what's going on? Thanks!

jayoldschool
09-21-10, 11:02 PM
Pull both valve covers and check the rockers, to start.

Sponson
09-21-10, 11:24 PM
I was thinking of opening them to take a look - perhaps a broken rocker, spring, or loose rocker mount shaft? If I had any of these I would think I would hear something more ominous at idle, and it does idle smooth without bad noises except when I get the single tap tap tap. I could also pull the push rods to see if they are still straight. Any other suggestions? Thanks.

csbuckn
09-22-10, 02:42 AM
The valvetrain noise under acceleration is probably too much timing. I had this same problem and called MTS and he told me to back off the timing, I did and no more noise under load. How big of a cam? You can also put an oil pressure gauge on it to see what its reading when its ticking.

caddeville89
09-22-10, 07:37 AM
Could be piston slap. Had my motor rebuilt and have had piston slap ever since. Sounds like valvetrain noise upon acceleration. Means they didn't machine the cylinders correctly.

carnut
09-23-10, 08:22 PM
An exhaust leak at a flange or where the manifolds bolt up to the heads can sound just like valve train tick, tick. Once they warm up, they seal up.

Garys
09-23-10, 10:12 PM
I would change to 10-40. Also, check the oil pressure. If low, the spring that regulates the oil pressure (part of the oil pump) could be defective, or not properly installed.

Thats where I would start.