Scary knock over 4k rpm then gone

[Headrage]

I decided to drive my car to the office today since it really hasn't been out of the garage since the WCC and decided that since I've got over 500 miles on it I should be able to take it a little higher in the rpm range. As I'm leaving my daughters school on a long stretch of road I shift into 3rd and step on the gas pretty good. Car pulls really strong up through 4k then I get this rapid knocking sound. Got nervous, backed off and sounds gone.

I drove this thing all the way to Camarillo and back over the grapevine with absolutely zero issues and even took it over 4k during the failed poker run attempt.

Any thoughts???

[914GT]

This is really hard to diagnose without hearing it and trying to figure out where it's coming from. If it's strictly rpm over 4000 when it does it, and not speed, then at least you can narrow it down to the engine. Assuming nothing seriously wrong inside the engine, things to check might be an unbalanced fan, worn distributor shaft bushings or worn out alternator. Also check the motor and transaxle mounts to make sure the engine is not moving around.

[Tidybuoy]

I didn't see your engine size posted...

My "914 Tech Tips" states:

If upon acceleration, your engine makes a noise like a wet flag flapping in a violent storm, your head gaskets have blown out and the engine is leaking compression. This is a common problem with 1.8 engines. Remove the heads, weld and resurface them, and install new head gaskets.

I'm not sure if this is your sound but this book has helped me cure every problem I've ever had (914 related).

Vern

p.s. what is WCC?

[Dave at Pelican Parts]

WCC == West Coast Classic; it was a massive 914 event in the High Desert around the Camarillo area.

--DD

[Headrage]

Thanks for the replies. I'm sure it isn't a head leak as I have heard them before. Not sure about the unbalanced fan either. This is a brand new motor with only about 500 miles on it and the fan was balanced before it was installed. I haven't had a chance to dig into it yet but I'm hoping that it may be a timing issue. Worst case would be a rod (doubtful) or piston to valve contact.

[SGB]

maybe get under it or reach under with a stethescope or rubbber hose maybe to listen fer an exhaust leak....

[AL MEREDITH]

I once had a loud knocking, seems a pushrod slipped out of the center of the follower. We relocated the pushrod and everything was fine .

[Jared at Pelican Parts]

Originally posted by Dave at Pelican Parts
WCC == West Coast Classic; it was a massive 914 event in the High Desert around the Camarillo area.

--DD

Uh, Dave?

Since when is there a desert near Camarillo?

[Dave at Pelican Parts]

Sorry, I meant the High Desert and Camarillo.

--DD