Tapping from engine when going from no throttle to throttle
 

When my engine is “coasting”, in gear or not, and I add throttle I get two or three sharp “clacks” from somewhere in the engine. I’m guessing slack in the valvetrain is causing the noise as the components go from dragging to being pushed? Any suggestions on where to start troubleshooting? The noise only exists in this transition period from closed throttle to open throttle.

Thank you!

Re: Tapping from engine when going from no throttle to throttle
 

Since the valves are pushed open by the cam lobes and closed by the springs, they don't know if they are "dragging or being pushed". On the other hand, the pistons, wrist pins, rods and mains are all affected by changes in combustion pressure caused by going from closed to open throttle. If you can duplicate the noise by opening the hood and moving the throttle by hand, try grounding out each spark plug one at a time and see if the noise lessens or goes away.

Re: Tapping from engine when going from no throttle to throttle
 

If you open the throttle a little then let off and repeat that several times and you hear the clacks rattle between on and off it is a pretty good sign of a bad rod bearing.

Re: Tapping from engine when going from no throttle to throttle
 

Aluminum timing gears can make some interesting noises.

Re: Tapping from engine when going from no throttle to throttle
 

With the hood open, work the throttle by hand and isolate the noise. We need to know where the noise seems to be coming from. Grounding/shorting each cylinder as 40 mentioned will help if the noise is from a certain cylinder.

Re: Tapping from engine when going from no throttle to throttle
 

I've just done a 1,000 mile run in my '30 CCPU, the longest in it so far. I heard a similar noise coming from up front somewhere and wondered about the aluminium timing gear. The noise seemed to be getting worse but we made it home OK. By now, the car was due for a grease and while I was checking things over, I found that one of the small bolts that holds the horn on was missing and the other very loose. There's the rattle! New bolt, a little Loctite 290 and the timing gear is not making any more noise. Remarkable!:rolleyes:

Re: Tapping from engine when going from no throttle to throttle
 

LOL. Its funny how those pesky little horn bolts can cause the timing gears to rattle around.