48 IDA Help

[Fitzy1980]

Hey all,

Just after some info Re the current setup of my IDAs. Carbs were already configured this way so I'm curious as to whether it's close or needs some tweaking..

Have some driveability issues..

Ford 363
Dart Pro 1 CNC heads

Cam
Solid Roller
110 Lobe Centre
Lift 592/.592
Dur @.50 237/243

Carb Specs

42mm Venturi
120 Idle Jet Holder
70 F10 Idle Jet
F7 Emulsion Tube
200 Needle Valve
50 Pump Jet

Cheers

[Gaz64]

If not already done, adding a third progression hole can help.

I would also look at changing the idle jet holder to 100.

Also curious as the Pump Exhaust size, the calibrated orifice on the side of the inlet valve. Not to be confused with the Pump Jet size.

[byronpete21]

To help, would need some more specifics on your drivability issues. Low rpm stumble, rough idle etc. etc.

Best Regards,
Byron

[Fitzy1980]

Originally Posted by byronpete21

To help, would need some more specifics on your drivability issues. Low rpm stumble, rough idle etc. etc.

Best Regards,
Byron

Low rpm stumble under throttle, also pops, backfires etc through exhaust cruising also pretty strong fuel smell also.

Engine was originally setup for track use so I'm curious as to whether the weber setup is geared more towards that and not street use.

[byronpete21]

Sounds very similar to the problems I had been having, and have mostly solved. After finally breaking down, I purchased and installed an AFR meter to help. It turns out I was running very rich at idle, but then lean in the transition range around 2800-3000 rpm. After some trial and error, I ended up running a .65 idle jet with a .80 idle jet holder. This combo is still a bit rich at idle, but no stumble in the transition range (I figure this is a compromise I can/will live with). The other thing I spent a lot of trial and error time with is my timing. I finally settled on about 20 degrees of advance at idle, with another 18 in by 3500 rpm for 38 total. I run 91 octane and have not had any pinging or hard start problems. It even starts nicely when hot. Please feel free to PM me if you would like any assistance. Best of luck on your journey to Weber bliss. BTW I have a 347 stoker motor (302 block) running about 325 HP at the rear wheels.

Best Regards,
Byron

[Gaz64]

More details please.

What ignition system, advance curve would also be handy.
The pump inlet valve exhaust orifice size please, it is classed as a 00 if no orifice.
You might also be better with 40mm venturis if only street.

Yes, you need 3rd hole progression.

You probably need a whole setup change.

So a few more things needed here for info:

Carb Specs

42mm Venturi
120 Idle Jet Holder
70 F10 Idle Jet
Main Jet
F7 Emulsion Tube
Air Corrector
200 Needle Valve
50 Pump Jet
Pump exhaust

[moar_carbz]

Fitzy, I noticed you mentioning you had 42mm venturis. Without a lot of discussion back and forth and details we're just going to be giving you educated guesses, but one thing I'll tell you is that 42 is pretty big for the venturis and I believe that engine doesn't need them that big. One user had a 427 with 37mm venturis and they were ok up until 6000 rpm, then they ran out of air. HE is the user who needs to look at 40 and maybe 42 mm venturis, but on a 363 I'd suggest sticking with the original 37mm pieces, looking through the "Weber Jetting Survey" thread and see somebody who has a build that's close to yours and using their jetting, and their discussion of how it's working and how they arrived at that, as a starting point for yourself.

A lot of problems with Webers can be traced back to the user trying to use too large of a venturi.

[Andheeezonit]

Byron, I am seriously considering the purchase of a FAST AFR dual band meter to finish the tuning of my 48 IDA’s. The setup is pretty good now, but too rich at idle. Did you find that the AFR meter was a good tool and did the proper mixture coincide with the car running better? I have been told by a recognized expert that the Webers need to be rich at idle, but how rich. They are a commitment that I feel is worthwhile on a Cobra. Thanks.

[CompClassics]

I would deffinetly start off with 37mm chokes, specifically for low end operation and for the engine displacement. You need to provide the air corrector and main jet sizes. Have the carbs been balanced? Running fuel pressure? How soon (RPM) does your distributor mechanical advance come in? What is your total advance?

[Eljaro]

On mt 482 Sideoiler I ended installing 40mm chokes and it runs very well.
42mm is definitely too large for your engine. Go back to the 37 and start all over again with the jetting.