TR4/4A TR4A Pinging Under Load

[KVH]

I've got it timed well, and it runs great, but my engine has lately been pinging whenever under load. The plugs look really dry. Could it be that my mixture is too lean? I already tried retarding the timing a bit, and that doesn't seem to resolve the situation, though it did help.

 

[Geo Hahn]

What gas are you using (grade & brand)?

I don't think it is my imagination that not all brands are created equal. My preference is Shell where, with my tune, I can get by with regular. Some stuff (Costco) I have to use the premium to eliminate knock.

I would expect the plugs to look dry but is the color toasty brown or more whitish?

 

[TR3driver]

Unless you are having trouble with overheating as well, I doubt it is mixture. The plugs are supposed to look very dry; any sign of dampness indicates a problem.

Have you checked the vacuum advance recently? Where is the timing set, and how did you get there? My idea of "timed well" is no knock ...

 

[KVH]

I static timed it, but that ended up being about 10 BTDC by a timing light--with way too much pinging--so I retarded back down to about 4 BTDC. The gasoline is Circle K High Octane, and I suppose I need to stay at Chevron from now on. The plugs are dry and look like new. They're so darned clean is scares me. I've had black plugs for so many years in these cars. Shouldn't I at least open up a few flats? About the vacuum, I always assume that's inoperable anyway. It's such a primitive contraption with so many chances for air leaks. Do I really need to worry about the vacuum?

 

[Geo Hahn]

You might see what your total advance is at high rpm (say 3000) when everything is 'all in'.

Note that shows distributor advance & rpms which are half that of the engine.

Also -- have you checked what number distributor you are using? -- not uncommon for someone to put on a replacement that is close (but perhaps not all that close).

 

[KVH]

You might see what your total advance is at high rpm (say 3000) when everything is 'all in'.

I'm going to check that. I think when I accelerate to 2500 or so, my reading is about 10 degrees BTDC. I do know for certain that it tops out, so that graph looks very accurate to me. Do you know whether rotating the distributor body to achieve proper timing is a better method than using the adjusting dial?

 

[Geo Hahn]

...Do you know whether rotating the distributor body to achieve proper timing is a better method than using the adjusting dial?

There are several different schools of thought on that.

Some like to set the distributor with the big mark (on the vernier) coinciding with TDC -- then set advance with the dial. That way you can easily tell what advance you have it set for.

Other set the vernier big mark at the usual (by the book) advance then move one side or the other from that as you road test. That way you can easily tell how far you've tweaked it.

Both are good methods, I do neither.

I set the vernier at the big mark then set the timing by moving the distributor. That way the big mark is where my best timing is. If I get some bad or sub-grade or California gas then I can temporarily adjust timing yet easily get back to where I want to be once the episode has passed.