New Engine Help

[Fast355]

I can post up the timing table from that 406 that I mentioned earlier. With the 170 etecs and 219/227 @ 0.050" 112 LSA hydraulic roller cam it should be pretty close. Set the Lb/hr to 90% of whatever the injectors flow at 25 psi. If you use their actual setting you'll end up with the high MAP areas of the VE table maxed at 100% and still won't have enough fuel.

What intake manifold are you planning to run?

I actually have Etec170s on the L31 shortblock in my Express with a 215/220 @ .050 cam in it. Not sure if my timing table will help though as the LS stuff does not use MAP for the load reference theu use GM/CYL air mass. The lowest point in my timing table is 12* with a very quick advance curve. I run within 4* of total advance by 2,600 rpm. I run 25* from 2,600-4,800 and climb to 29* by 5,600 and drop back to 26* @ 6,400. Cruise timing is pretty aggressive with 39* advance at the highest points.

[Roadknee]

I actually have Etec170s on the L31 shortblock in my Express with a 215/220 @ .050 cam in it. Not sure if my timing table will help though as the LS stuff does not use MAP for the load reference theu use GM/CYL air mass. The lowest point in my timing table is 12* with a very quick advance curve. I run within 4* of total advance by 2,600 rpm. I run 25* from 2,600-4,800 and climb to 29* by 5,600 and drop back to 26* @ 6,400. Cruise timing is pretty aggressive with 39* advance at the highest points.

That's similar to how we set up the 406 except it's running 31 total by about 3,500 rpm. A heavy truck might not get away with that much timing though. The 406 is in a 3,000 Lb. Nova and accelerates damn fast. It also likes 40° cruise timing by 2,000 rpm.

Fast - how did you determine the need to reduce timing past 5,600 rpm at WOT? Did it make better power or was that required to keep it off the knock sensor?

[Fast355]

That's similar to how we set up the 406 except it's running 31 total by about 3,500 rpm. A heavy truck might not get away with that much timing though. The 406 is in a 3,000 Lb. Nova and accelerates damn fast. It also likes 40° cruise timing by 2,000 rpm.

Fast - how did you determine the need to reduce timing past 5,600 rpm at WOT? Did it make better power or was that required to keep it off the knock sensor?

It was on the knock sensor pretty hard on 87 octane. I played with the timing on the dyno and even running 93 octane there was less than 2 HP difference running 26* vs 30* at those RPM levels. With the Etecs and somewhat decent quench it made peak power at only 29* total advance on 87. My combination is pretty timing sensitive. Mine really wants more cruise timing but to do that I would have to advance the physical distributor which would throw the cam sync off for the fuel injection. At about 42* it starts jumping to the previous cylinder and misfiring. It pulls the brick aero of a fullsize van down the highway at 70 mph at about 2,400 rpm pulling at around 50 kpa. My sister has a 5.3 Tahoe that I have datalogged into the 52*+ range at very light load cruise. One of the benefits I hope to soon have when I go with the EFI Connection 24x on the Express. My old 83 G20 with TPI ran up into the high 40s at cruise and was happy with that, but it was also under 9:1.

[Roadknee]

It was on the knock sensor pretty hard on 87 octane. I played with the timing on the dyno and even running 93 octane there was less than 2 HP difference running 26* vs 30* at those RPM levels. With the Etecs and somewhat decent quench it made peak power at only 29* total advance on 87. My combination is pretty timing sensitive. Mine really wants more cruise timing but to do that I would have to advance the physical distributor which would throw the cam sync off for the fuel injection. At about 42* it starts jumping to the previous cylinder and misfiring. It pulls the brick aero of a fullsize van down the highway at 70 mph at about 2,400 rpm pulling at around 50 kpa. My sister has a 5.3 Tahoe that I have datalogged into the 52*+ range at very light load cruise. One of the benefits I hope to soon have when I go with the EFI Connection 24x on the Express. My old 83 G20 with TPI ran up into the high 40s at cruise and was happy with that, but it was also under 9:1.

We were messing around with the 406 one night in search of better fuel economy. It runs 70 mph at 2,000 rpm around 50 kpa if I remember right. Its a Holley Commander 950 system. We set the cruise on a level highway and started messing with timing and watching injector duty cycle. 35 to 45 degrees timing made no difference so we left it at 40. It has the wideband upgrade so we also tried leaning it out. Duty cycle decreased each time we increased AFR, indicating economy was better. At 17:1 it started missing and throttle response suffered so we settled on 15:1 AFR cruise.

[Engine07]

On the heated plenum question again...I know the older heads had the exhaust crossover the vortec style heads do not have. How are you guys with vortec heads solving the cold weather issues? The heated passage is not needed for summer right? So in theory, if I take my heater hose and reroute it through the heated plenum passage on the vortec manifold, then it would provide enough heat through the plenum in cold weather while the heater is running? I wondered how it would be while the engine was warming up but most of the time in cold weather I start the truck about 15 min before I leave anyway so the truck has time to get warm because I don't like climbing in the truck and freezing on the way to work. Would this method provide the heat needed to the manifold?

[Roadknee]

Whether the heated plenum is needed is a matter of personal opinion and preference. It would not be near as important in a carbureted application because the emulsion circuits in the carb do a great job of proper fuel droplet formation. The TBI injectors meter liquid fuel on top of the throttle plates and rely on manifold heat and vacuum to properly vaporize the fuel. I would recommend you figure out how to heat the plenum year around like GM intended it. Yes, you'll give up a few top end HP, but the increase in economy and running consistency as the seasons change will be well worth it.

[Fast355]

Whether the heated plenum is needed is a matter of personal opinion and preference. It would not be near as important in a carbureted application because the emulsion circuits in the carb do a great job of proper fuel droplet formation. The TBI injectors meter liquid fuel on top of the throttle plates and rely on manifold heat and vacuum to properly vaporize the fuel. I would recommend you figure out how to heat the plenum year around like GM intended it. Yes, you'll give up a few top end HP, but the increase in economy and running consistency as the seasons change will be well worth it.

Its actually quite the opposite. The carb needs more manifold heat than the TBI does. At part-throttle the intake is under a vacuum which reduces the fuel boiling point and creates sheer off the throttle plates. I ran an edelbrock air gap victor jr 2bbl single plane in temperatures under 20*F without any issues. If you run into pre-heating issues I would suggest using an OEM style air cleaner and a preheat tube on the header/exhaust manifold. If you were to abuse an old carb V8 right after cold start and say floor it from idle there is a pretty good chance it will stall out on you or have a bad bog.