original Weber jetting

[John Fitzpatrick]

I got this response to a inquiry I sent Carroll Shelby some years ago. I thought I'd post it FWIW for anyone running 48IDAs on a 289/302.



John,

Carroll Shelby sent your question to the Shelby American Automobile Club
and I contacted THE expert in the Webers for Fords field; this is his
answer:

Howard C. Pardee
************************************************************************

The 289's run best with 37mm chokes in the 48 IDA's, but if it's strictly a track car, put the 42mm chokes in. Run a 155 main jet, and a 215 air corrector. If running open headers, however, drop the air corrector back to about a 170. The idle jet is going to be a 60 f10, and the idle jet holder should have a 1.10 mm air bleed. If it won't run well on that, go up to a 65 f10 idle jet and a 1.20 air bleed in the idle jet holder. Set the idle mixture screws by seating them, and then open each one exactly 3/4 of a turn. Do not exceed a full turn open, and if you have to, then go to the bigger idle jet, then turn the screws back down. The correct setting on the mixture screws should not vary more than 1/8 of a turn from the 3/4 open position. The emulsion tube is usually an F5, and try a #50 bypass valve in the bottom of the fuel bowls. Set the floats exactly to factory specifications, and install a Grose Jet in place of the Weber needle and seat. The stock needle and seat is not at all tolerant of pressure rises, and will leak easily. The D&G valve will handle up to about 6 lbs....cheap insurance. They'll cost about $30. These are sold by D & G Valve Co. in Massachussettes; they advertise in Hemmings (no, I'm sorry I do not have their phone number). Fuel pressure is very critical, and should be strictly regulated not to exceed 3 lbs. Fuel lines must be a minimum I.D. of 3/8". A mechanical, block-mounted pump should be used in conjunction with a Holley low-pressure regulator...the red one...not the high pressure blue one. I've set up a couple of these; this info should get you out of the woods.

Good luck.

 

[John B]

Please post that what heads and cam size you are using. If someone uses this configuration, they may run into a lean/ rich problems. Though this is a good base setup, you will still need to watch your spark plugs for correct ajustments. Caution! posting tunning specs may be good for run engine but me a disaster for the next. I have been running Webbers on my SHELBY 350 for 10 yrs and my setup is far off your setup. /ubbthreads/images/graemlins/fyi.gif

regards
Oliver

 

[John Fitzpatrick]

The set-up is, as the respondent stated, only a starting point. My own setup is: 289 HP, 351W heads, 180 degree headers, Le Mans cam. What I found most helpful were the recommendations to drop the air corrector jet with open exhausts and substitute the D&G valves.
YMMV.

 

[Ron Earp]

Chokes seem small for an engine that runs high RPM. What do you run yours to? I like that block mounted fuel pump suggestion - exactly what I wished to do as well to keep it really simple.

R

 

[John B]

Ron,

There is no simple set-up to webbers. But once you have them set, webbers are the easy to maintain. and of course the power curve is neck snapping power. Once you use webbers, it's hard to go back to carbs. Also the most people don't know that the "W" in webbers means WHAT! HOOOOW MUCH! AND "WHAT THE F%$#@.. BUT YOU GOT TO LOVE THE CHALLENGE. Every time I pop the hood and show my webbers, the first question everybody ask is "How hard is it to tune the webbers?Well! I thought it was easy!
I got the book on webbers and read all about them. Once you know the theory the rest is common sense. The book on Webbers explains in detail all what you need to know.

Jeff! If you are running 351 heads with a 37 choke, For sure you are running lean and Kiss the motor good buy if you put it on the track. I'm running 42 chokes on my 289 with stock heads and I
had to use a bigger main jet and idle jets than what you are using. At High RPM, your going to lean out that engine and blow a piston.Please check you spark plugs and for color..Black=rich light brown=good mixture.. white=lean. If you find that it is a little black it's OK..I would rather be a little rich than too lean. You also may be ok with the 37 chokes but you are going to have to put bigger mains in. what you have may be Ok for running to the store and quick cruise...On the track? maybe not. In order to set up webbers perfectly you need a dino..Most people set them up in the garage. It is criticle you check the plugs! I don't claim to be an expert, but I can trouble shoot just about any webber problem.. I have been tunning them and rebuilding them for over 10 years. That is what is so great about webbers..You can tune them for the type of driving you do. But most people won't take the time to understand the theory and give up. But that is the glory to owning a car with webbers. It steals the show every time and knowing that you did it yourself.

Regard

Oliver

Regards oliver

 

[John Fitzpatrick]

My problems went back to the original owner. In tuning his setup on the cheap, he drilled out several of the jets and didn't bother to re-stamp them. Saved him a couple of bucks, but drove me nuts! I discovered what was amiss when I went to open up a jet and the drill just fell through. Meanwhile, the Shelby America Club came through (I had written them in the middle of the mess, thinking the Weber book must be wrong) with the recommendations above.
I don't remember what my final setup was, but I did end up going to #300 needle valves (that was somebody at Moon's suggestion)!

 

[Ian Clark]

Thanks for the info John, I'll add it to my bag of tricks. All knowledge has value.

We're seriously considering a chassis dyno for the shop. It seems like our customers are evenly split between Webers and 8 Stack EFI. Niether is simple to do and both are engine specific.

It's easy to romance yourself into believing anybody can do it, however we know better

 

[Ron Earp]

Ian,
How many of the new CAV cars have you received and are under "construction" there in Canada? You're near Toronto right, I might be up there soon on business and could visit maybe.
Ron

 

[Ian Clark]

Hi Ron,

It would be great to see you when in the area. There are normally a couple of cars in the shop so there's always something to see. We're not big or flashy but there's neat stuff going on.

I have new product coming from SA and all of CAV Canadas rolling chassis delivered are completed running automobiles, now if I could just find time to work on my own car!

Looking forward to meeting you.

Cheers

 

[Chris Martino]

Ian you've first got to stop stuffing your mush with Tim's finest, just put down the donuts - nice and easy and slowly back away...

There ya go, now get to work on your chassis. /ubbthreads/images/graemlins/beat.gif

Chris

 

[Ron Earp]

Excellent - I was to be up there this weekend but managed to send someone else on that trip due to a death in the family. However, I imagine that I'll be up that way around March or so. Best,
Ron

 

[Ian Clark]

Hi Ron,

My sympathies to your family. Looking forward to seeing you in March.

 

[Rick]

I realize this is an old thread but it is timely for me as I am in the midst of attempting to get my IDA's on my 289 dialed in. I have yet to drive the car but with 60 F10's and 120 holders, it seems like it may be lean as it wants to spit back as RPMS are slowly raised. Mixture screws are open 1 full turn. 200 airs with 155 mains, f7 emulsions, 50 accelerator squirters and 55 exhaust in the float bowl. I am thinking of changing to 100 Idle holders.
Ideas??

 

[Rick]

Followup...........I changed the Idle air holder to a 100, (1.00 mm). It instantly changed how the engine ran (much better overall). The drivablity is quite good, transition seems to be seamless. Yesterday on one of the first opportunities to drive it any distance I noticed while cruising at about 2800 RPM I could hear a slight "flutter" in the exhaust note. If I raised the RPMs it seemed to go away, this would seem to be indicative of a lean condition? Suggestions???

 

[Ian Clark]

Hi Rick,

The transition from idle to main circuits happens in the 3000rpm area so that's probably what you're hearing. It's a good idea on these short hops to dial in the carbs that you keep an eye on the plugs. Drive it a bit, then read the plugs. Adjust idle screws and do it again. If your plugs are a bit sooty your fat (the mixture of course) and that won't melt anything. While you're turning in the idle screws, really keep an eye on the plugs.You may find one cylinder showing the right colour well before the others, At least this shows you're on the right track. 1 turnout on the idle screws is way too much, could you turn then in after reducing the idle jets?

Cheers

 

[Rick]

Yes currently screws are open about 3/4 turn. Still have the slight miss. But it is only apparent at cruise speed (60 mph) not while accelerating with light throttle through the gears. Main jet ?? Air Corrector?? If I increase the throttle the least little (Very little) bit the miss goes away as it accelerates.