kwilliamson

Need help!

Here’s the deal

1. I have a 1970 L46 convertible with 90,000 miles that I purchased four months ago.

2. The car is all original and stock except for an Edelbrock aluminum intake and a new Holley “Street Avenger” carb.

3. The heads were reworked about 1 year ago according to receipts I got with the car. The previous owner did not rework the lower end of the engine at that time and I don’t think it has ever been done. (This should have been done when it was apart because the engine is burning a little oil.)

4. When I drive the car I noticed what I call “valve chatter” upon acceleration at mid-range RPMs.

5. I checked carb adjustments and timing. Timing didn’t seem to hold and I had a professional mechanic check out the original mechanical distributor. He said it was shot and I just replaced the original distributor with a new HEI unit.

6. After I installed the new distributor I attempted to set everything up – carb floats, fuel mixture, idle and timing. Carb floats are good, fuel mixture screws had no effect until they were nearly all the way in. The idle set screw is all out and the RPMs won’t go below about 7500. Oh – the “valve chatter” is still there.

My opinion at this point is that there is trash in the carb.

Any ideas or advice?

Thanks in advance

Durango_Boy

Have you considered maybe replacing the timing set? If there is slob your timing could be erratic.

Merlinhaggard

The idle set screw is all out and the RPMs won’t go below about 7500.

Your saying when you start it up it goes straight to 7500 RPM's??. Then you have to kill it?.

FeedVaal

I'm assuming you meant 750 rpm.

brookman

If you dont get a change until the mixture screws are almost all the way in - you have a vacuum leak somewhere.

Now - that being said. Make sure that the primary throttle plates are closing completely when the choke is disabled.

I had a car that the throttle cable was too tight and actually held the plates open when they should have been closed.

TimAT

I'll bet the "valve chatter" is pinging/detonation.

Durango_Boy

That would sure be bad...lets hope it's not.

kwilliamson

Yes, I meant 750 RPMS.

calwldlife

I see alot of potential issues.
Your def of valve clatter? Check the rockers for adjust and travel
cam flat? Carbon? poor intial adjust after heads worked?
Burning oil...........fouled plugs chatter.
New carb? vacuum leak...............
You need to look at things.
Have you pulled any plugs?
Check your valve train..........