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Question for waynep71222

Posts: 648
Joined: 07/06
Posted: 12/04/12 03:15 PM

I am quite familiar with Holleys and carb theory, I have Holley Performance and Holley books nearly memorized. Something that concerns me now that I have a T5 OD, and changed to a 350 ratio, crusing at highway speeds (55-70), I'm barely off idle in 5th gear and think I may be actually cruising too near the idle curcuits and wasting fuel. Maybe a smaller cfm carb to get the butterflies further away from those transfer slots at 55-70? Oh, I'm running a Holley 650 now. The tach is not functioning at the moment or I could probably answer my own question. Duh?


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Posts: 455
Joined: 04/12
Posted: 12/04/12 11:14 PM

ok.. you want answers...  idle transition circuits can be TUNED...... and sometimes EASILY... sometimes not..

there are a few ways to get on the main circuits earlier..... demon jr carbs are available with primary bores the size of the 390 CFM holley and secondary bores the size of a 650 or 750.. this is still being a Square bore carb.  

you can use a 390 holley ... yes you will loose some top end RPMs... but the increase in fuel economy is tremendous..  just don't let anybody look down the venturi's .. so they don't see how small they are..

on HO 5.0s in the mid 80s with the strange holleys .. model 4180.  its idle circuits are different than the other model 4150/4160 versions..  they don't like being run without a proper air cleaner and an air cleaner mounting gasket...

i don't know much of the early history of the 4150/4160.. but i do know that a lot of reenginnering was done for the 4180... there are 2 good articles on them in the archives.. just type in 4180 in the search window ..   again.. if the various air bleeds are dirty.. you will hate the carb..  according to what i have read.. the 4150/4160 series was introduced in 1957.. i saw a friends 57 lincoln 430 sitting on a stand one day.. i looked at the carb number .. LIST 3310... wow... 1957...

idle transition circuits are tunable..

if coming off idle.. and you are monitoring the air fuel ratio with an air fuel ratio gauge..  if you go lean... increase the size .. ONE step at a time of the idle feed restriction...

if it goes rich as soon as you come off idle...    you will need to decrease it.. either with a piece of very small wire to reduce the opening size.. or by opening the idle air bleed size...

as you recall.. the size of the air bleed effects the amount of fuel pulled up and over...

summit overs their summit carbs.. that are actually holley model 2010 and 2011 models.. they are direct grandchildren of the autolite 4100 carbs... except that summit offers idle feed restrictions and air bleeds as replaceable ...

spend some time with a fully warmed engine and a vacuum gauge hooked to manifold vacuum...

the 4180 has idle mixture screws in the base plate..  with what seems to be a much finer thread pitch than the 4150/4160 models...

i was going to post some photobucket images that i had not posted on the other thread.. but my photobucket account is acting really strange. takes about 10 minutes to get it fully open..

i will come back later and add the photos here..

here is one that i cobbled together...  with a 4180 thats on my ford van..

4180 Motorcraft Holley Idle Air Bleeds Zps7c98df5f

showing somewhat how the idle air bleeds and circuits are routed... i have messed up when i labeled this.. as one marked idle air bleed is actually the IDLE TRANSITION AIR BLEED... i will have to grab the spare parts of the 4180 i have and dive deeper into the idle transition circuits..

Please... don't go mucking around with the idle air bleeds... or the idle feed restrictions.. until you have completely rebuilt the carb and verified the circuits are clean with a spray of carb cleaner or what i use.. cheep brake cleaner..

take a look at where the idle feed restriction is in the AFB/AVS...  the idle air bleed is on the work bench... the idle feed restriction is where the drill is sticking..
Afbidle Channel Restrictor

i think i am going to come back and edit this...  so do start from the beginning ...  

Post Reply
Posts: 455
Joined: 04/12
Posted: 12/04/12 11:37 PM

lets look at some of the options i have run across...  that might help in fuel economy..

and i am not saying that you can get improved fuel economy. it takes tuning to calibrate the fuel curve to your motor...   people get used to OEM spec carbs.. but the oems spend hundreds of hours on a fully instrumented dynos and on fully instrumented Mule cars testing them..
including cross country trips... cold weather trips.. hot weather trips..

Sum Rm08600vs W

you can get the idle feed restrictions for them also...

Sum M08041 W

These S brand idle feed restriction tuning kits are designed to fix low-end drivability issues, such as black smoke, poor fuel economy, and surging at idle. They include four each of 0.043 in., 0.046 in., 0.049 in., 0.052 in., 0.055 in., and 0.059 in. idle feed restrictions. These S brand idle feed restriction tuning kits also include two nozzle bar gaskets and a detailed instruction sheet for easy installation.

and accelerator pump discharge restrictions..

Sum M08040 W

These S brand accelerator pump discharge restriction tuning kits will cure those pesky hesitation and flat spot problems. They include four each of 0.031 in., 0.035 in., 0.037 in., 0.040 in., 0.042 in., and 0.045 in. discharge nozzle restrictions to help you dial-in your carburetor to your engine. Eliminate low-rpm hesitation and mid-rpm flat spots with one of these S brand accelerator pump discharge restriction tuning kits.  

Post Reply
Posts: 455
Joined: 04/12
Posted: 12/05/12 12:01 AM

lets see what CC said about the road demon JR..

seems they even offer these as twin 4 bbl carbs for supercharged applications...  

Post Reply
Posts: 648
Joined: 07/06
Posted: 12/05/12 08:52 AM

Thanks for the response, now I have more to think about. Although my 650 double pumper does well, there is an RPM range when going up through the gears 1,2,3 that feels like their is some surging going on then it runs on out of this feeling and smooths out. There is no flat spots and I am more pleased with the 650 than the 700 I ran previously. It was fouling spark plugs after a couple hundered miles.


Post Reply
Posts: 455
Joined: 04/12
Posted: 12/05/12 08:20 PM

stop by your local exhaust shop... ask how much they charge to install an oxygen sensor bung in the down pipes... or if you have headers... either in the collector or in the collector adaptor..

some will weld bungs in for 15 to 45 bucks..   plan ahead.. take the new sensor with you..  or have an OLD big ford spark plug.. RF 10 Y.. something with 18 MM threads works great .. just be sure to clean the threads before installation..   i wonder if one hooked up a high voltage coil to that. making it spark.. if it would.. perhaps.. ignite the exhaust..  becoming a weed burner if the fuel ratio is too rich..

if you have headers.. you will need to have a 3 or 4 wire oxygen sensor with a heated element to get an accurate..

did you see that air fuel ratio displays start at 30 bucks.. 50 bucks there are more.

oxygen sensors start about 16 bucks.. but one wire versions are less than 35 bucks ..
16 buck ones.. look up an 86 F250 4x4 5.0... i was amazed at the universal fit sensors.

install a vacuum gauge also...  so you will need a double gauge bracket...    an old cigar lighter power cord to hook the oxygen sensor up without chopping into the harness and make it easily removed..  so you would only need a single wire from the sensor or 2 wires if you run a 4 wire sensor.. to the gauge. and a vacuum hose for the vacuum gauge..

under the hood.. you can run a relay off the I  terminal to the 85 pin on the relay.. ground 86... 30 gets power from the battery side of the relay..   pin 87A goes to the oxygen sensor heater circuit .. and the oxygen sensor heater wire is grounded.. this allows you to operate the oxygen sensor.. as long as the relay has a low enough turn on voltage to operate on the reduced voltage at the I terminal on the solenoid...

depending on the price of the bung installation.. you might be able to get out the door for the whole package .. less the vacuum gauge. for just under 100 bucks..  

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