Thanks for your observations and comments. It keeps ones head thinking, adjusting and confirming what is good and what is bad.
Yeah, that's popular in the racing world, where there's no heater core and the engine is run at heavy throttle/high rpm for long periods.
Pointless on the street.
There's no need to plug the hole in the block if the Vortec heads haven't been drilled to provide bypass flow--the heads themselves block the passage.
If there's no other bypass, that's a reasonable solution. If the engine has a heater core with no shutoff valve, you're just screwing-up a thermostat. The vehicle takes longer to warm-up, and may not achieve proper operating temperature in cold weather. NOT recommended on any vehicle that has some other bypass system--the OEM drillings, a non-regulated heater core, etc.
In our stock car engines we did not use thermostats. Usually a restrictor in place of the t-stat with a certain size hole in it to control the flow of cooling fluid. Wide open is never good. I think ours were usually about a 1/2"! Once of the mathematical whiz kids that use to hang out at the shop did some measuring and calculations with a t-stat and came up with that diameter as equal to flow.
I use to agree with you on the functionality of need of extra bypass/steam vents' until I spent allot of time at a very respected engine shop a couple of decades back. The reduction head temperatures at the rear cylinders where very evident on a dyno and being able to observe with sensors. Most recently my employers '63 Corvette proved the point again. Has a 383 (400 block) in it and local driving just could not keep the temperatures down and bleeding the cooling system was a pain in the tail. We had the intake off to fix a oil leak and change lifters out and I talked him into drilling the steam vents at the rear and we routed them to the front of the intake and drilled two 3/32 holes in the t-stat (note, this car does have a functional heater). This was 3 years ago and the car has not overheated, even on 110 degree Texas days during regular driving and parades.
Was interesting the first time I pulled a LM7 and found they have steam bypasses from the factory even with the reverse flow cooling.
I'm surprised you needed all that custom tuning. I'd have expected that engine to be close enough to stock that the OEM chip would have worked reasonably well in terms of driveability.
Perhaps not for performance, though.
I thought they same thing, that the stock tune would be fine, but it had very little power and would spit, sputter, cough and at times knock. This 5300 pound best just would not go down the road.
Checked everything several times as far as distributor settings, modules, wiring, for vacuum leaks etc. Was not until I changed the timing tables from the stock TBI to the iron head LT1 did it become drive-able, but ran very rich. As of last evening the VE tables are close and at highway cruise reading 17 - 18 mpg according to calculations. On ramp acceleration is near perfect and I don't have to worry about getting run over by special people.
The stock timing tables had 17 - 22 degrees of timing at my highway speeds, the current table is 24 - 30 in the same rpm range. I think there is still work to be done in the mid-range area but that will have to wait until we get back from Nationals the end of the month.
This engine has much better flowing iron heads, longer intake runners, headers (short tube), and a Taylor Helix spacer under the TBI (The Taylor spacer was on the original engine as well). All the sensors in the swap where new GM sensors.
Even changing from the '8625 pcm to the new '7427 using the same chip with the new tuning made a difference in the drivability. Not sure why, as the '8625/'7427 are suppose to be compatible swaps.
Is there ANY actual evidence that the "Ultimate TBI mods" make any improvement? I haven't seen any. I'm VERY skeptical. I think the "Ultimate TBI mods" are a heaping-helping of crap promoted by someone with too much time on their hands, and access to a Dremel. Looks pretty, makes a guy feel like he's "done something", but in the end, it's all cosmetic, not functional. What's being worked on and "smoothed" isn't the restriction.
Recent dyno test on a acquaintances truck without and with the modifications showed a +6 hp and 22ft/lbs torque difference just bolting it on and no other adjustments. After tuning and road test his highway mpg went up 1.5
Changing the fuel pressures and adjusting the tune accordingly also helps, although I have not got there yet. Another project that will be on hold until after Nationals.
EVERY functional OEM application of "hood scoop air" or "Cowl induction" has the throttle-body (carb or FI) sealed to the cold-air intake, with rubber or foam seals. You DO NOT want hood-scoop air flowing into the engine compartment, because it interferes with engine cooling.
Most "hot rodders" get this wrong. They have "cold" air bleeding all over the engine, reducing air flow through the radiator. Sounds like you're the exception--connecting (sealing) the airbox to the "scoop".
Yes, this air box and scoop will be sealed so any air coming through the scoop will be going to the engine. I have built functional scoop cold air boxes for about 35 years years in street, drag and circle track applications. And the difference between IAT's and underhood temps in on average 30 degrees.
I always have a good chuckle with the lid flip trick or the open element air filters. Lot's of extra suction noise, but more hot air being sucked into the engine.
This air box will also have ducting the the factory location in the fender so if I need to drive the truck on really crappy weather days I can plug the scoops intake to keep the engine from drowning.
Have a great weekend.
Louis
