Installing 48 IDAs

Pmccooey · #1 (**permalink**) 01-31-2026, 10:58 AM

I’m planning on installing a set of Weber 48 IDAs that I picked up from an estate. The carbs were done by Jim Inglese but I have no idea what type of engine they were jetted for. I plan on stripping g them down, cleaning them up and setting them up for my car just to get it started and tune from there. So I’m looking for a little help as I’ve never ear done Webers before but have been reading and going through as many tips as I can find.

Currently have a Contemporary Cobra with a 427FE, mild cam, 750 double pumper, mechanical fuel pump on the block, toploader, Jag IRS at 2.88 (but looking to swap those gears out this winter also for 3.54 or 3.73). I’m in lower NY so about 300’ above sea level. Car just sees local driving with an occasional spirited blast to open her up.

I’ve been looking around for same base setups for jetting and pumps on the Weber to get rough start. I’ve found two for a 427FE but they seem to be quite different.

Can I run my mechanical fuel pump to a pressure regulator dead headed to the Webers? Otherwise I’d need to pull the fuel tank and start a whole new fuel system.

Any other tips or tricks from some Weber people would be greatly appreciated.

KarlzEE Bebout · #2 (**permalink**) 02-01-2026, 07:20 AM

I've always had a mechanical fuel pump for my 44 IDFs with no problem. It's very important to restrict the fuel pressure to about 3#s. It's also very important to have the correct cam because too much overlap will let fuel blow back up through the stacks. My 2¢

bobcowan · #3 (**permalink**) 02-01-2026, 10:26 AM

For any ITB system, getting the linkage exactly right is critical. And I mean exactly. You need to use something like a synchrometer, or vacuum balancing kit. If it's not perfect, no amount of tuning will get it to run well.

https://duckduckgo.com/?q=carb+balan...pic_-_Copy.jpg

bobcowan · #4 (**permalink**) 02-01-2026, 10:33 AM

For any ITB system, getting the linkage exactly right is critical. And I mean exactly. You need to use something like a synchrometer, or vacuum balancing kit. If it's not perfect, no amount of tuning will get it to run well.

https://duckduckgo.com/?q=carb+balan...pic_-_Copy.jpg

PDUB · #5 (**permalink**) 02-03-2026, 10:49 PM

Quote:

Originally Posted by Pmccooey

I’m planning on installing a set of Weber 48 IDAs that I picked up from an estate. The carbs were done by Jim Inglese but I have no idea what type of engine they were jetted for. I plan on stripping g them down...

Why do you need to strip them down?

Pmccooey · #6 (**permalink**) 02-04-2026, 03:18 PM

Quote:

Originally Posted by PDUB

Why do you need to strip them down?

Because I have no idea what engine they were set up for so I need to go through it and inspect/change the jets, pump valve, etc to set it up for my 427.

PDUB · #7 (**permalink**) 02-05-2026, 10:23 PM

...by your post it sounded like they were coated with something icky

!

Veg · #8 (**permalink**) 02-09-2026, 03:33 AM

I stripped mine and found one of the jets wasn't the same as the others plus a few bits were missing. Nothing Weber is cheap but they are very simple carbs so easy to work on.
I purchased a copy of the Weber Tuning Manual (can't remember where from) which is very simple to follow.
My 289 engine is in set-up so no idea whether they need another idle jet drilling or if I can live with the hesitation at 2,500rpn....time will tell