The Money Pit

I have a Holley 3310 that I recently updated the main body to a Proform body in an effort to help tune out a idle issue. The 406 runs like a top otherwise,but I can't get the idle to come down under 1200 or so in gear,without stalling. I have a 3000 stall converter,and am happy with the overall performance,with the exception of the idle.In neutral I can adjust the idle lower,but in gear it'll stall,so at this point I just keep my big toe on the gas at stop lights,tach to 11-1200 and it'll idle all day like that.

I have read that annular discharge boosters would greatly improve this,but at this time,I'm not prepared to drop the buck on a new carb.The thought occured to me I could just change the primary boosters to annular and run with that.

Can it be done?

cardo0

I've only read that its not for the hobbyist as it take special tools to pull the old boosters out.

Good luck,
cardo0

Matt Gruber

the fix is to drill out the IFR jet .002-.008".
it is too lean.
say x idles at 1200 w/ 18" vac, a/f of 12 .
say at 800 it has only 9". it gets 1/2 the fuel per cyl firing! a/f 24! instant stall
see carb book

The Money Pit

I already went from the stock IFR size (.031) to .036,but I guess I could try to go bigger yet. Originally I had the mix screws out over four turns,now it's just over two.Worst case senereo I over drill,and have to get a new metering block.

The booster idea may be wrong to fix the idle,but after reading a magazine write up,they claimed some 95 ft lb gain on the low end,which would be nice.

Matt Gruber

u went +35%, but then u turned in @2 turns and leaned it out go back to 4 turns and try that. try to get it to idle 600 in N 3-4 turns.
then turn the idle speed screw up to ~1000. put in D. still stall?

do u know why 4 corner idle works well?
it's +100%
have u opened the rear same as the front? tiny stop screw. brings in rich transition from rear.
.
oh, boosters have nothing to do with idle

The Money Pit

I did try opening up the rear plates before I drilled the 3/32 holes. No luck,so I drilled the holes. This is like chasing your tail. I ended up on a distributer recurve expedition for a while,only to come back full circle to the carb,where I started in the first place.(But with a totally different distributer curve)

I am considering a set of Quick Fuel metering blocks to allow for easier,more precise IFR changes,but have yet to nail down the correct part numbers for my 3310.

I see the direction I need to go in with the IFR size,and was looking at BG's site at the Mighty Demon carb specs. Looks like they're running a .038 IFR,and rate the carb for up to 260 degree cams. I'm at .036 now,and getting closer to the idle I'd like.

Matt Gruber

ez way to see if it likes more gas:
idle in N real slow where it shakes.
then drip in gas w/ glass eyedropper(walgreens)
if it smooths out, drill IFR with confidence

Matt Gruber

next the transition needs to be leaned out(if u dont it will suck too much gas)
try .058"-.062"
how is the mpg?

The Money Pit

Last tank I checked the mpg was 13.6.The best mpg I have gotten with the 406 was 17,and that was with the 700r4 running mostly highway.The 3000 stall and th400 is costing me mpg's for sure,but I'll keep tuning the carb for the best overall performance reguardless of the mileage.
I played with wire in the idle air bleeds for a few weeks trying to fix my low speed idle,and discovered with only .021 diameter wire in the idle air bleeds,my range went down to only 180 miles a tank,where it usually runs 250 or so.Right now the idle air bleeds are the stock Proform set.I think they're 70's.

Matt Gruber

so u know when u richen the idle it sucks gas
there is a way to run around it.
what is the lash? vacuum at idle?
how much does isky say u can loosen it safely?
a c1 guy loosened his lash and idle vac went from 11 to 16, then 18 with vac advance.
then u don't need to richen the idle and mpg is good.
how much vac advance do u get at slow idle?

The Money Pit

I am not a fan of lashing loops,as you mentioned. In an experiment to see what cam the engine likes,yes,but not as a fix. I wonder if once I get the idle circuit happy,if I could then lean out the primary main jets and get some of the lost mileage back.

Originally the plugs were bone white with the 70 mains,and I swapped to 74's. Plugs are now light tan,which I think is what I want.
The wire in the idle bleed experiment showed just how much effect the airbleeds have on the cruise mixture,so I assume I could lean the mains once I get the idle straightened out.

As an absolute last resort,I still have the RPM intake that I could toss back on till the next rebuild,then cam "slightly" smaller when it needs freshing up.

Matt Gruber

ez test
turn dist. LOTS CCW(tune by max rpm, reset idle and mixture) and see where the vac. ends up and see if it will idle in gear. if that works u have hope