New 'whack' sound on accelerate.

belston · Post by **belston** » Mon Aug 04, 2014 4:18 pm

Nice 66 with a 1600 engine bored out to 1720, just purchased. Huge trip home (2500 miles) not a note out of the engine. Now there's a 'whack' sound on accelerate under load. Re-did valve clearance .006 cold - both. They were a tight .004. Any ideas what else to look at? Thanks folks.

darzoom · Post by **darzoom** » Thu Aug 07, 2014 11:46 am

Whack? When depressing clutch in or out moving or not engine running or not? When moving, braking or coasting in gear or out of gear? When in gear moving or not? When out of gear moving or not? When shifting?

Need a bit more details on what is going on when the "Whack" happens.

It is kind of like "Patient says....Dr. it hurts when I do this!...Doctor replies...Stop doing that!"

belston · Post by **belston** » Thu Aug 07, 2014 11:57 am

It's been a noise in the engine without clutching involved when under load, such as loading up the low end of a gear and full torque pulls you up to speed. The 'whack' sound seems to be only under load, and disappears when you reach normal travel speed for the gear. And nothing at high revs. I've checked for end-play in the rear bearing - none noticeable by giving the main pulley a lift/pull with the generator belt off - again nothing. Thanks for the reply - "Doc", maybe if I just stop doing that

Appreciate the help.

h~moto · Post by **h~moto** » Thu Aug 07, 2014 2:18 pm

Whack noise? . . . that's weird.
Would it make the noise if you tried driving off in second gear? If so, try it with someone at the rear of the car with the engine cover up.

darzoom · Post by **darzoom** » Fri Aug 08, 2014 8:34 am

Check the generator bolt holding the fan on on the fron of the engine. If the keyway has sheared of the center of the fane that mounts on genrator shaft is worn or broken, it may be making the sound you said.

It could also be the keyway on the fan belt pully or the center of the pully may have worn ears (on 6 volt) or the oval (on 12volt) and the outer pully moves on the inner part of the pully. It is a long shot but easy to check.

Check those and give a shout.

darzoom · Post by **darzoom** » Fri Aug 08, 2014 8:55 am

Forgot to say to also check the crank pulley for wear. Take off the rear tin in the engine compartment remove the pulley. Check the groove/slot on the pulley and crank and determine if the keyway is tight in both.

One more thing. Check the motor/trans mounts by having someone stand in the back of the car, someone start it, put in first, put on the e brake, slowly release the clutch (not all the way) and the person in back watches the pipes and determines the amount of movement between the tail pipes and the rear apron. If more than 3/4 inch movement at the skirt, the mounts may be bad. The movement could be the pipes whacking the apron and would not be noticed any other time than when you take off in first. That is because the load up (vertical movement of the engine) on the clutch and mounts would not be noticeable and would actually stop after taking off in first gear

Again, I am giving things to check without any "major" work and possible engine removal.

Keep us posted!

darzoom · Post by **darzoom** » Mon Aug 11, 2014 11:48 am

any progress?

belston · Post by **belston** » Mon Aug 11, 2014 2:46 pm

I *think* I've found the source of the sound. There's an air re-direct flap on the air intake that had a cable stub attached. The cable had been snipped and the flap held in place by the bend in the stub. It had worked loose and was flapping around on heavy load. The suggestion to have someone listen with the engine lid open as I accelerated helped a lot.

Just re-anchoring the flap on the intake seems to have stopped that sound. Whew! I *love* simple (cheap) solutions. Thanks everyone for your suggestions for detective work on this. It's appreciated.