My bird still has the stocker style dual action fuel pump - vacuum on the top end / fuel below. It delivers fuel OK - with no back pressure - but acts like it "gets behind" the engine and starves it when you hit it hard. The pump fittings have tiny little inlet and outlet holes in them - and I put a serious pressurized fuel filter on there in consideration of the crud in the ancient tank. I believe the more modern carbs have a bit more inlet pressure required than the old t-pot too. Does anyone have good performance data about one of these originals?
This week I splurged and replaced the Holley 600cfm outfit I had on there with a new 525cfm Road Demon Jr. To try and get a handle on the fuel supply thing, I borrowed Al Frakes dyno sheet and had a look at the BSFC (brake specific fuel consumption) numbers. It shows the kind of "pounds per horsepower hour" fuel demand present when you are making 300+ horses. The peak was .544 (#/hp hr) which is about 30 gallons per hour at the carb (at whatever pressure it demands - no big deal on the dyno, that one is a good sized electric that won't starve an engine under test). This number was produced at a rate of acceleration of 300 rpm/sec - not exactly drag race stuff.
I found this page out of the Holley catalog that shows "real" loaded performance data for their 80 and 110 gph pumps and gives some idea of what they do when the load is 4.5 psi. The 80 gph model looks like it could deal with the 300 hp situation - stays over 30 gph - but thats without a fuel filter or any loss due to sucking through a little 15 foot tube.
http://www.holley.com/BrowseCatalogs.asp?Catalog=Holley&Page=196
I am sorely tempted to try one of these FE pumps on my bird - but will it fit in the space by the frame rail? Has someone tried this particular brand of pump on a t-bird? I believe it will need a new (larger, cleaner) feed tube from the tank to work right. I promise not to cry over the loss of the "original vacuum wiper" system.
Al was thinking he would try to retain his original pump and then feed it with an electric "supercharger" pump. Is there someone using that arrangement with success?
Steve Metzger Tucson, Arizona