[jls74formula455]

I have a L-75 455 with the factory ram air set up as ordered when new. The original intake is back on my car and a correct numbered & dated previously rebuilt carb gone through by Mr. C. Ruggles is about to follow. My very experienced classic car mechanic who makes house calls recommends that I re-install the EGR for proper idling. I got an EGR from an original '75 350 4bbl Firebird motor (see pic). My intake looks like the one on the SD motor pictured, lacking that black fitting by the thermostat housing as seen on the '75 motor (it looks as if the vacuum line from the EGR goes to the black fitting). Does anyone have a diagram that shows how the EGR is supposed to be set up for my '74 intake? My '74 shop manual diagram shows that black fitting by the thermostat housing (???).

Does anyone have any experience with blocking off the EGR on '74 Firebirds and its effect on idling?

Can anyone tell me how many vacuum lines should come off the back of the carb and where I can find the correct "branch" fitting that screws into the carb where all the vacuum lines are connected to?

[1qikta]

The 74' Pontiac service manuel will help a bunch. It has a section on the EGR system..even all the corect colorcoded vacuum lines and where they go.

The 3 split branch off the back of the carb goes to the Brake booster (center),AC system (left) Dist Vacuum advance(right). Cliff has a lot of Carb Vac fittings...Give him a call.

Good Luck...

[jls74formula455]

Thanks Jay. I'll double check my service manual for the EGR set-up.

[rwinkles]

EGR should not be on or active at idle and therefore should not affect it. If it is, it will cause significant idle problems. EGR is used to dilute the mixture and reduce pumping losses. It also reduces combustion temperature thereby reducing NOx formations. It also has a big effect on burn rates and delays. It will make your car feel a bit more sluggish but it will improve fuel economy if you are after that. If you remove or render the EGR inoperative (as I do) you will need to reduce the vacuum spark by about half or you will knock at part load (due to the burn delay and rate changes mentioned above). I usually replace the 25 degree can with a 12 degree can and all is well, overall drivability is improved.

[Brewster]

Wow, did you get that? he's back!

[superdutybob]

Brew:

It's been a while since he was here now that he is a Viper snob. At least he bought a Carousel Red one.

[jls74formula455]

Thanks Dick, very helpful. I think I'll go along with the changes you suggested and keep the EGR disconnected. The original 455 in my car is stock except for a mild 068 cam and roller rockers the previous owner installed. Will this affect the changes you described? Should I do something different?
- Joe.

[rwinkles]

Originally Posted by jls74formula455

Thanks Dick, very helpful. I think I'll go along with the changes you suggested and keep the EGR disconnected. The original 455 in my car is stock except for a mild 068 cam and roller rockers the previous owner installed. Will this affect the changes you described? Should I do something different?
- Joe.

Joe - Should work fine. It's always a good idea to get your distributors advance curve checked (on a machine or at least in the car with a adjustable light). I like to use something like 12 to 14 degrees basic with 20 to 22 mechanical advance all in by 3000 rpm (total of 34 for a typical Pontiac). Stay with about 12 degrees vacuum advance ported to a full time vacuum source and you should be good!

[jls74formula455]

Thanks Dick, I really do appreciate your help. I'll forward this info to my mechanic and let you know how things work out.