General Category > Quadrajet Carb Talk and Tips

cam selection

<< < (13/18) > >>

tayto:
Found a set of springs out of one of my parts distributors. Curve starts at 1050-1100 rpm. Timing mark doesn't move at idle now. Seems to have solved my light throttle tip-in detonation problem (REALLY noticable in 4th locked up at lower speeds), but still have a surge @ idle,it is slight but you can see it in the vac gauge and hear it. makes setting idle mixture a chore. I tried moving the chole closed still does it. Tried changing my initial from 0 all the way up to 15,still does it. It seems LESS with lower idle rpm, but that may be my imagination.

I notice when i swapped the springs and fired up the vac gauge was rock solid but as the engine warmed up it began moving as described above. truck has been sitting just over a hour before firing it up so it wasnt stone cold.

Cliff Ruggles:
Did you ever measure the idle airbleeds in that carb?

Some of the later carbs will have pretty large idle bleeds.  I've seen a few applications where I was able to clean up idle surging, running a little rough, etc by going a little smaller with the IAB's even when I had some control with the idle A/F ratio with the mixture screws.....

tayto:
Cliff,had a busy weekend and didn't get around measuring orifices in the carb.hopefully will have time tonight after work. should I pull the idle tubes and measure them as well? thanks.

BTW, the heavier springs seem to have done the trick on my tip-in detonation problem and same with lugging in 4th. not like i like to do this but it happens from time to time until i re-gear. havent had a chance to recheck the heavy load heavy throttle detonation i experience but

tayto:
Idle Discharge Holes: .089" (I assume this is a another term for "idle mixture holes" ?)
Idle Bypass Air: .046"
Lower Idle Air Bleeds: .075"
Upper Idle Air Bleeds: .067"
Idle Channel Restrictions: .046"
Idle Tubes: .033"
Main Air Bleeds: .086"
Main Jets: 73
Primary Metering Rods: 50C
Accelerating Well (main casting): ??
Accelerating Well (air horn): .051"
Secondary Air Bleed Tubes: .070" (??)
Secondary Metering Rods: DR
Hanger: I
Fuel Inlet Seat: .135"
Float Level: 13/32”
Air Flap Open Distance: 1.400"
Secondary Flap Spring: 3/4 turn
Choke Pull-off Release Time: stock

Cliff Ruggles:
For sure that carb needs opened up some for what you are doing.

Did you happen to check the vacuum at idle speed, down around 700-750rpm's?

At a minimum I'd open up the idle tubes and DCR's and see how it responds.  A little goes a long ways but .035-.036" on the idle tubes and .052" on the DCR's should really help things out......

Navigation

[0] Message Index

[#] Next page

[*] Previous page