383 tuning help

[daveosx]

A pair of 61 lb/hr TBI injectors are good for 205-210 hp @ 85% duty cycle at the stock 13 psi and if they were static, meaning on all the time, good for about 250 hp at most. Most engines run around 1/2 lb/per hr/per hp. 61 lb/hr x 2 injectors /.5 bsfc = 244 hp. Even if you were running a Vortec head and had a very good BSFC around .45 that is still only fuel for 270 hp.

450 HP Hour requires 9.16 Gallons per hour of Gasohol.
Mechanical efficiency of stock motor is 49% with new pistons rings increased compression and roller cam 76-80%

At 6lbs per gallon thats 54.96 PPH

The injectors will provide at stock fuel pressure 336HP no problem.
At 18psi like I recommend they will flow reliably at 74-75PPH

Simply advancing the base timing will also not work very well.

I agree base timing is really not that important but the 0degrees as stated would cause the exhaust vales and pipes to over heat at idle.
At 3000 RPM GM HEI will reach no knock retard maximum advance after 30 seconds.
That has been the normal for all SBC since the beginning.
Setting the timing to 38 degrees at this point sets the distributor phasing and the maximum no knock advance possible.
At 4200 and up knock will retard the timing 4-5 degrees no problem.

At 4200 shift point the roller rockers will make noise this is not knock but will retard the timing an additional 2-3 degrees.

The TPI heads you are running like about 34* of timing at WOT not the 38* mentioned above. 38* is for the older slow burning smog heads. With 20* of idle timing when you advance the timing to 12-16 as mentioned above you end up with 32-36* of idle timing which is too much for the mild cam you have. The advance curve is also slower in the ECM than what the TPI heads need. The TPI heads like about 16-20* of timing from 1,000 rpm through about 2,400, then up to about 30* from 3,000-4,600 and finally on to 34* above 4,600. The TBI heads have a substantially different timing advance requirement.

On this one I can authoritatively say that since I wrote the GM service bulletins on Corvette and Camero TPI ignition timing with aluminum heads.
That the timing retard for these heads was solved in 1991 with the new knock sensors and EST modules.
Yes there is a different module for the corvette and the sensors are different.
This was not for the cast iron vortex heads only the aluminum.
Same device was mirrored in 1996 with the different EST and Knock sensors on the LT-4 engines because of the roller rockers.

As for the power available and RPM capabilities of the GEN1 and GEN1.5 TBI engines with stock injectors and HEI
Here is a snap shot of a 1984 Corvette I am tuning tuning at @7400 RPM with no Knock and only a 4ms Pulse width on the Crossfire TBI injectors.
There is no load attached to the motor so no HP rating.
IMG_1401.JPG