Tune-up query

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KKV270
Senior Member
Posts: 347
Joined: Wed Jan 16, 2013 1:11 pm
Location: Nairobi- Kenya

Tune-up query

Post by KKV270 »

A happy New year to all.
I would wish to understand something that goes on in the engine while tuning up in a rush or emergency situation!
I noticed, with the engine running, if I kept advancing the distributor, the engine revs would first heighten but a clanking sound get louder.
What I'd want to understand is, what is that clanking sound that gets louder and louder? Tappets? Valves? What exactly is going on at this point??
I personally wait to hear that sound then go back to the point I hear it quiet...
hercdriver
Senior Member
Posts: 154
Joined: Sun Sep 30, 2012 7:55 am
Location: Beaver, PA

Post by hercdriver »

It could be any number of things.

Start with the basics. I'd check the valve clearances on a cold engine. Make sure it's actually cold. Dealers used to drive the car around the dealership and into the garage. That little bit of driving would add enough heat to the engine and throw off valve measurements.

http://www.vw-resource.com/valveadj.html

I use .006 inches for clearance on all but the #3 exhaust valve. For that one I give it a little more room at .007 inches.
KKV270
Senior Member
Posts: 347
Joined: Wed Jan 16, 2013 1:11 pm
Location: Nairobi- Kenya

Post by KKV270 »

Hi Hercdriver.
Thanks for the response. In this case, everything is well tuned including the valve clearance- I'm just curious at what goes on while either a heavy advance or retard on the engine, it starts running rough and a clanking sound follows...
thanks.
Blue Baron
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Joined: Sun Jan 18, 2009 8:34 pm
Location: Tampa, Florida

Post by Blue Baron »

Advancing the distributor too far is causing preignition. (It's sparking before the optimal closing of the valves.)

Basically, you're asking why does my car sound screwed up when I screw it up.
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