Oh, one other thing (minor though)....though the analogy to the BBC is somewhat useful, the physics of the BBC combustion chamber are slightly different than the SBC....the amount of turbulence created in the typical SBC chamber is greater proportionally than the BBC, thus leading to quicker combustion times.

The burn rate stays the same, but the flame propagates faster with more turbulence, thus burning more endgas at once, thus the fast burn time.

 

I think what were missing here is there are 2 different tuners. It is a long story, but one , the first tuner, hid some things in his chip, and gave me very little timing advance. A few heavy tuners were saying I needed much more timing. I went to another tuner, and after installing his chip, I had all kind of codes. So I asked What happened and he told me tuner A was hiding all these issues, and to prove it , he had me disconnect the battery, and install the factory chip. The codes were there, but with tuner A all were gone, in other words turned off. He had the mixture all wrong. SO tuner B set to tuning, and walla more HP and TQ. Now, think of a carburetor, if it is lean, richen it, and play with timing. I think tuner B went a step further and played with timing, pulse width etc etc to keep the pinging down to 0, as there was pinging on one of his chips. Its all in the tuning. I bet a Jim Formato chip will show some aggresive timing, and other things. His cars were tuned very well, and he told my friend whne he did his modified LT-4 GS, this car requires SUPER unleaded, as it will be on the edge.
Also, I justr checked my data from my factory original LT-1 Diacom data, 36 degrees with no retard. So it is only a few degrees more

 

I understand Tuner A hiding codes and half-butting the tuning...please share the name so people can avoid him!

By fixing Tuner A's screwups, you should most definitely gain power. However, even 5 degrees more advance than optimum should cause a net loss in power. FWIW, the pulse-width of the injectors shouldn't affect knock. As far as needing that much timing advance to make max power....it's possible that the port-job on the head reduced the turbulence in the chamber enough that it slowed the burn rate, but it would have to drop it almost 10 degrees in order for MBT to change by 5 degrees. This just doesn't make any sense to me....I still think there's something else going on here...

 

Tuner A= Ed Wright, Tuner B = PCM4LESS
Heads CNC heads from Florida. Extensive head work, and when you see them you go " nice work", at least the machine shop here did, and they prot and polish heads. Of course, FWIW, I have a slight dish on the psiton.

 

Hmm, what sort of codes and such did you have that the Ed Wright chip was hiding? I've got one of his chips now which I have further tweaked a little but I can't do anything until I get a new chip burner. Until then I want to really look over my program.

 

I too have a Ed Wright chip (cookie cutter) that needs some tweaking as well. My car runs very rich (I get about 10.5 mpg) and needs some changes regarding A/F and timing.

When the 3.73's are installed, I will be having a new chip burned from a local tuner, who does a number of the MORE Performance chips. We will also have the use of a local dyno to dial it in. All this for the same price that a typical Ed Wright chip costs (around $350)...

Mike

 

I had O2 and Knock sensor codes. I put the factory chip in, rran it with Diacom too, and it showed these codes. WHne his chip was in there, no codes. It was running rich, and he thought it was fine, even when I showed him the Diacom data. Well, 381 to 407 rwhp is enough proof for me. Tuner B whens, and it was only 150 bucks plus 6 months of free tuning afterwards, not 50 dollars a mod after you paid 350.