Glasshole

I have about 1500 miles on my rebuilt, solid lifter 327. I noticed that the valves were getting noisier, the car seemed sluggish and I was getting some pinging on hard acceleration. I pulled the valve covers and sure enough the adjustment was way out. After setting them to proper spec. the car feels crisper and the pinging is gone. I do notice though that the idle is all messed up now. It wants to stall. It idled fine prior to the adjustment.

Does adjusting the valves alter the timing and/or fuel air mixture?

Should I get a better locking nut for the rockers so they don't loosen off?

MikeM

Your valves shouldn't get noisy in just 1500 miles. The rocker nuts should be tight on the studs. Hard to turn. Maybe 15 ft lbs torque to turn. I don't know, never really measured it. Never seen a spec either.

If the nuts are holding, look for the thread length sticking through the nut. They should be the same, all the way through with the valves adjusted correctly. If not, you may have a stud(s) pulling, cracked rocker ball seat(s), lobe(s) going flat and/or bent pushrods among other things. If there's any doubt in your mind about the nuts, get new ones.

I don't understand the relationship between "pinging" and valve adjustment. I do understand that if you get the valves too tight, you can create a huge vacuum leak through the valves and that can/will cause stalling. To answer your question, adjusting valves doesn't alter fuel mixture or timing.

Can you adjust the idle a little faster and get the engine to idle like it's supposed to?

What engine/cam are you talking about here?

Glasshole

It is my 63'. The engine is the original 327 built to the exact 360HP FI specs (duntov cam, 11-1 pistons, etc.). It currently has the 340hp manifold and AFB carb on it. I just went out and tweaked the fuel mixture screws 1/4 turn leaner and now it is idling like a champ. Go figure. All of the nuts had the same amount of thread showing however many them seemed way too easy to turn. I will replace these.

Glasshole

My thinking on the fuel mixture was that if the valve adjustment increased or decreased the vacuum it may need a slightly richer or leaner mixture as the engine would be sucking more or less air at idle. No?

MikeM

As the engine draws in more/less air, it also draws in a corresponding equal amount of fuel for a given carburetor setting. Without splitting hairs.

Glasshole

That blows my theory. Anyhow with that small adjustment it is idling fine now. I will replace those rocker nuts though......

Are the stock nuts best or is there an aftermarket nut that is better?

MikeM

I'd use stock type for stock applications. They should last you for the service life of that engine as long as you don't take the nuts all the way off/on several times. That ruins them.

JohnZ

Are you using a vacuum gauge to set the idle mixture screws, or just by "turns"?

63 340HP

No, the fuel mix ratio remains the same.

A really loose intake valve lash will shorten the intake valve timing and raise the dynamic compression (allow the intake to close earlier on the compression stroke). I would expect the valves would need to be considerably loose for this, and the actual static compression would need to be closer to the advertised ratio (as opposed to the point or more deduction in CR that most engines from the era actually had after the first rebuild with a composite head gasket).

Good to hear it worked out.

Glasshole

I had originally set it with a vacuum guage however this time I just turned them both in 1/4 turn and the idle came up and the stumble went away.

midyearvette

when using the vac gauge and by setting the mixture screws to achieve highest reading, most times this will give a too lean condition at idle and tip in and off idle and light cruise...best to richen 1/8-1/4 turn......

MikeM

Yep!