mineral co wrote:I spent part of the evening going through all my tools just to see if any particular ones have gone AWOL, and made a list of stuff to pickup once I get up to Denver. I think one of those "bit" sets is a darn good idea.
Since I'm still in the anticipation stage, let me pose what might seem to be another silly question. I'm at 9000' in elevation, and would like to use the GW as high as 13,000'+. May there be something to be gained by getting the throttle body and injectors from a 454 (7.whatever liter) since this would have the larger, 2" bores? (I would get the entire setup since it also uses the 7427 ECM).
I haven't thought this all the way through yet and if we were dealing with a carbureted system, then doing this would certainly have negative consequences but I'm wondering if this might provide a small advantage by getting as much thin air into the system as possible. We generally think that manifold vacuum goes to zero at WOT but in reality this isn't 100% true, especially at higher rpm. But the closer I can keep it to zero, the better, I think. I believe I would still run the injectors from a 5.7 if they would fit. Possibly even smaller (lower lbs/hr) as this would mean they had to be "on" longer to pass the same amount of fuel and that would help to minimize the effects of injector latency errors.
With EFI, the manifold vacuum is only used as a signal to the computer. This is quite different from carburetors, where the vacuum actually does work to meter the fuel in the carburetor. Then, too low a vacuum and you have no fuel control.
If you look at the CFM ratings of popular throttle bodies, they will be huge compared to comparable carburetors for that displacement engine. So you already have a big hole in a TB, compared to a carburetor.
Per Jaber's comment, it sounds like vacuum is just getting too low to reliably measure, with a 454 TB on a smaller displacement engine.
A significant down side with the 454 TBI will be cost of the pieces. I would think if you are running a 360, that's close enough to the 350's displacement that you should not see any advantage from the larger TB.
You can calculate all this... figure the volume of air needed to maintain your ideal mixture with the volume of fuel the injectors will deliver. There's a good introduction to the math on the Megasquirt site. I'm guessing it's not an issue.