The tuning discussions all seems ironic to me. I set up my first set of Webers on a Boss 351 in 1980 with the help of Jim Inglese. He was a "head hunter" back then as a profession and an amateur tuner and had bought boxes of jets and was willing to help out.
He literally lent me every combination between 1.10 and 2.00 fuel and air correctors. Only a few immulsion tubes, F7 (which I already had), F5, F11, F15.
Chokes 37 (which I already had) 40, 42 AND 44!
The idles were limited then because there was only one jet holder, a 1.20.
Pump jet bypass valves, blank .40, .70, .80, .90, and 1.00.
It took me about 4 weeks working every day, weather permitting.
Who was I to argue or refuse such a deal?
I am going through the jetting on this setup again now simply for one reason.
So many people have gone to tuners who have put them on dynos and come up with set ups that are different enough from mine, share the tune specs, that I need to try those tunes.
How can I argue with a dyno tune right?
I can say one thing with reasonable certainty. The wheel is round. The sun still comes up in the morning and water is wet.
My setup is right, or that's as right as you can get them. IF the tunes given to me are for real, than SOME of these dyno geniuses are just plain full of s h i t.
The only thing I can not speak for is how the larger bore IDA's work. I'd like to try the 51mm EMPI but the Hall manifold needs to be ported for them and if it sucks, there is no going back. Manifolds have become very pricey lately.
Bosswrench is referring to remarks that have been made by the Shelby race team that 48ida's were showing that they were a little small for the 289's. Restrictive is the term they used.
THEORETICALLY the bore of the carb should match the size of the intake valve. With a 351 that's something like 53 mm. 48's are way too small for a 427. The 58IDA's were made for the 427 Fords. It is said only four sets were made.
There is no way you can run the idles as lean as some say they are. The exhausts will pop. Pop is an understatement. You will blow the baffles completely out of the mufflers.
I have some old Walker Turbo mufflers that got blown out that way.
You can't run as heavy on the street with main jets as some say. The ratio is correct but the volume of fuel is for running flat out at LeMans FOR 24 HOURS!
With the IDA's the third transition hole helps, but sometimes it is still there. Depends on the weather?
I think that most of the problem with IDA's in the past, now, and in the future is a very simple one. New Weber owners have no idea what this setup entails, and they just presume that it is going to make THEIR 289 (or substitute your CID here) like a full race boogie 427.
Know what? Bunk! It ain't going to happen.
You are going to have a heavy idle (like a 750dp Holley), you are going to have fuel reversion (even with a special cam), some days the transistion flat spot will still be there and they are going to change with the weather. One day nice, next day miserable.
8 stacks are racing setups, pure and simple, with all the rights and privledges. PERIOD. Guys like Inglese have made them streetable...sometimes only marginally.
I don't think it really matters much if they are IDF's or IDA's?
Simplify your life, buy the tune from Inglese. He knows what he's doing. If "you" don't like the Webers after that, simply put, they aren't for you, because that's how they are.
Incidentally 72Pantera, very nice set up. Setting them up from scratch for me is great fun. Hope you enjoy it too?
Best of luck and enjoyment with them.