No Impala, I wish. Its a 1991 Caprice. Not an LT1 Either. Its the stock 305 bored .040 over, some work done to the heads, and some bolt ons. I will tell u this, its running with the LT1's and moving my 24in rims like they were stock. Its come a long way and i still got more to go.
First of all, sorry for the delay on getting back with you. I had a small matter of water in the basement.Unfortunately too, I have more questions. You said you are getting a slight ping early into the acceleration. Do you have an EGR valve, and is it working? I am surprised with that little based timing that it is pinging. Did you raise the compression ratio in the engine? Do you have a timing light that has a degree dial on it? And lastly, is the distributor new, remanufactured, or a used piece?
I wouldnt advance your base timing more since it is pinging. That is telling you it has reached it maximum limit. Now if you dont have a working EGR valve, that will change how much advance timing you can have. The EGR valve recirculates exhaust gases back into the combustion chamber, which actually has a "cooling" effect. Since HEI dist were introduced on emission vehicles, they are curved already for that extra advance to compensate for the EGR valve.
What you need to do is see how much advance you are getting at what RPM, and by waht part of the distributor is giving it. Good chance you will be "recurving" the distributor. The vacuum advance is not adjustable from the factory. You would have to put an aftermarket vacuuum advance diaphram on it if it is necessary to make it adjustable. But for now, I wouldnt worry about that. I would just see how much advance it does give you, and what kind of vacuum source you are running to it. GM set it up for manifold vacuum, not for "timed" or ported vacuum. Roughly speaking, the vacuum advance will give you around 10 degrees.
What you will be focusing on is the mechanical advance. If this is a used ditributor, you need to make sure it is working properly, not sticking in advance, or has broken pieces to it either, making it advance too soon. Take the dist cap and rotor off, and under the rotor you will see the advance weights and springs. Check and make sure the advance weights have not worn into the pivot pins, and both srings are there, and they dont show signs of being stretched. If it looks OK, put the rotor back on, and try to rotate the rotor counter-clockwise. You should be able to turn it a little, feel tension on it, and it also should snap back when you let go. If it does that, it is working OK, and now you need to check the curve. Put it back together, start the engine, and with your timing light, watch the timing marks at the crankshaft while slowly raising the RPM's. If you get a lot of advance early, with the vacuum advance unhooked. you will need to put a different set of springs on the dist weights. That will make the advance come in later, or higher RPM's. Re-curve kits are available at most auto parts stores, or any speed shop. Also pay attention to how much complete advance you get with everything hooked up. Basically speaking, most cams are set up to where you get best performance with 28 to 32 degrees full advance. If you are getting a lot more than that, leave the vacuum advance unhooked, and see how well it runs like that. I am sure it will effeact idle performance if you had it with manifold vacuum, but that is OK for now. If it runs good this way, you will change the advance weights also to give it less mechanical advance, then you can hook of the vacuum advance again.
I know this was a lengthy response, sorry. I hope I didnt make it too complicated to understand either. But if you are getting spark knock or pinging with only 4 degrees base timing, something isnt working right. Ihope this all helps you Octavio, good luck!
Thanks buddy and I know what you mean about making sure things go right and just when you think everything is good and dandy somthing happens its not fun but hey thats why we do what we not because its easy because its hard. But yea Id love to see your vehicle when its all said and dont man that would be great.
Yea man I get were your coming from. Id rather be pulling a motor or a tranns and working on it that being the gf haha. They take to much money and bitch to much. But if you had one that would love helping you work on that motor that might be a differenc story haha. But yes this is going to be one hell of a project and I cant wait to get started. Im doing my best to make my dakota one of a kind and i just love doing this stuff man.