attacking a monojet

[Barry Donovan]

bimetal relief - fill in

I filled in the bimetal relief airea.. seems it is more rare to have a monojet with that in use than not.

I even found a 292 with monojet part # that did not use it.

anyway..cooled the area down..this means it played with something warm. pcv perhaps. Quite noticable difference. this means there was vac leak during warm up. At 20 inches of vacuum, not even the 108ci noticed much..except the random hesitation on take off.

Added pennzoil (loves it), 91 octane..and throttle springs brought back to the 1978 setup.

the load of resistance let go of throttle cable and springs don't feel so tough anymore. The bimetal stuff was doing something strange after all.

a good choice to fill the bimetal area in, leaving it all there for an archeologist 4500 years from now to dig at...
the copper high temp exhaust silicone from permatex. I wanted a conductive element as continuity from the barrel is not far away through the wall of carb behind the bimetal.

so if to ever use again, pluck the silicone right back out. I filled it to the rim. put cover right back on.

[Barry Donovan]

mpg: high twenties

verified what I thought I built. good news. first 50 miles on the highway. I also found one strut was sitting too long. the local putting around gets awakend on the highway. I only brought it to 80..in the cold. Never could do that before.
the bimetal stuff was a problem. Alot more power to be had and casually.

the needle needs to be upped about 1/8th, away it goes. This is all custom, so reading a manual is only for the six cyls it came from. I did alright, I must boast. The sound at full warm it finally achieved (this is a cold engine all winter), a full hummingbird type sound. the slight hesitation ruins a formula 1 snap..but the idle is fun enough to giggle at.

I verified previous carb was literally outrun with my simple build. the monojet fills it.

away it goes...

if the cryogenic act on the head that survived a disaster hangs in to a needed warm swell (there is signs already).. I'll be happier. the monojet helped bring that powerful move around to positive as well...

spring and summer is going to youthfully fun for this old sube.

a bit redundant to what I just typed, but this is in the cars diary:

Fuel is in the high twenties, maybe further. I tried out flooring the throttle at the wrong rpm to gain a lot of air. The right head got so cold the rockers sounded like piano keys. The monjet won't feed if it can't. that is genius I remember from my I-6.The needle is off by less than an eighth, this will fill in the air gap and not even use more fuel. Goal met…adjusted by eyeball first try. I cannot complain. from jet size to my own unique needle setting. For the first time.. the car idled like a humming bird, full equal headers. very civilized. I had hints of it with the oem smaller carb..but the litle bugger could not fill my simple build. The warmest reading I have gotten since the carb change, it needs to at least get to thermostat open once and awhile..the cabin heat steals the coolings full capable in the winter. the carb is a winner. the needle change will stop a small realm of thin stoich, away it goes. for now, another storm coming. I pick the darndest things to do to get over cabin fever. carb changes and tuning under hood is a spring time fun..not really for a maines february.

[Barry Donovan]

frosty throttle base

I teed off a fuel tank vent line to the float bowl vent line, then the biggest line at the end goes to the vent can...finished with modern setup. I have another post previous explaing some of it. This gets important real fast. I chose a cool rain today, foggy snow to open the lines get some connectors in.

The cough now could be my shaved rotor (I decreased dwell, as the hitachi carb sucked for dear life), now it needs it all back in the distributor. I forgot I did that. the carb runs too good to even doubt it. ignition focus is next. Before last nights highway I added 4 gallons, got my mark on the gauge (proper vent sets that fast, no yo yo reading - a tip to know vent is good)

put 4 more gallons today and went well beyond the starting mark. So beyond odometer, and end result, the fill back up shows well beyond mid 20s.. must be near the 30 nominal. An awesome trait about this carb with the needle..when you work up to 80..you can back off, do the same at 50s and 60s nd 70s... Tippy toe it any speed when reaching a nominal.
This means cfm is correct, no starving.

a start above freezing, in the rain.. I am looking over the carb and noticed the base at throttle shafts, the different looking lighter colored aluminum realm.. it started looking like the inside of a freezer. frosty hairs crystallizing in high idle as I am watching it. there is a compression after all.

This is with choke working, and my hot resistor on the fuel line, grounded to the carb giving it two different volts play with.

I really wonder how a hard working 250 cubic inches ran this thing...
that is where the bimetal relief kept it from implode/explode I presume. They really pushed some boundaries.

[Barry Donovan]

the cold coast

this is a ride that even rumbles a new jeep. no car is nice. no truck is nice . If the heat is working...that is good. makes a good ride.

temperature meets the northern atlantic..fog ensues to the storm that is warm everywhere but here. the snow on the frozen ground adds to the fog the ocean is already feeding...

lights aren't good enough in this fog even if you have 25 gigawatts and HID glowing phosphorous in innocent victims.

my humble goal was to see if the heavy cold ate the idle. Nope. sat there better than the I-6. nice robust..the ice on the throttle part of carb gets conquered in a few minutes...stays like an a/c unit dripping condensation. this disappears onto the intake with a coolant passage running through it. Self cleaner. nice.

it is a good thing I have the spec clutch in.. the needle plucked back up a bit is going to be quite a leap.

climbed all hills to the maine coast in lower rpms, not enough fuel..exactly the same outcome as my old chevelle, same goof up with the needle. this is tall geared enough, it probably sounded like a diesel doing the speed limit.

the 5/64 they have listed to the height of needle arm is way wrong. trial and error it is.

the biggest test I know of passed today.I know now it can do anything, anywhere. hot weather is easy.

the lean check for an old sube? if the heater is working..you got enough fuel.

[Barry Donovan]

main jet, and no meter needle at all?

the metering needle is a shy over 1mm. The main jet is 2.0066. I want to know how big a main jet would be if there was no needle in the middle of it.
Area of a circle figures out what the hole would be if the jet had no meter in it. Subtract the area of needle from area of main jet hole.
answer: 1.6782263137014626133167863761527 millimeter or 0.0660719021 inches.
a number 67 jet if to try no meter is a good place to start. I am not going to..but it can be done of course. Tri carb setups take the power valve and needle out entirely... for all but one carb.
if you saw the main jet in the hitachi, this number seems to be holding true, and slightly large by my good eye, and one big barrel. the jets in the hitachi are not even half a mm, 3/4 mm maybe for the second barrel.

Take the needle away and add just a jet..this is the size it would need to be to resemble the current needle and jet setup. I will not be giving up the benefit of the meter needle..just can’t use the taper like I wanted. if to go bigger jet and use the taper..it may be too rich somewhere through the rpm range. The monojet does most of its work with vacuum accurately. the four cyl is giving it an easy life. I want the needle to stop fuel quick every let off throttle..and will be pushing boundaries. this does not coincide with the instructions for monojet and the needle.. I have got away with it in the past, and will simply do it again.


********
in short, subtract 12 or 13 and get the jet that coincides for any setup.
I put in a 79 with the needle...67 is a minus 12.

[Barry Donovan]

first good tune

I am happy as a monojet saved from a 250ci pile of hot poop. Looking at the needle, it did cave in. Even without the spring pressed down, the needle was nearly filling the hole. This is designed, like all monojets, to barely use the taper. So, I bent gently up on the arm until the taper was barely in use with spring loaded. I was off by at least a quarter inch. Back together, cold start with less quarter century petrified rods and heads smacking around, and a very lovely sound. Did not have to adjust anything else..this means the idle circuit really is a separate realm. Set it once, tune from the there the upper stuff. I also gained a little more on the float bowl.
Will make a sunny day video

Very enthused. The let off of the throttle.. this is the stuff that makes me idolize the monojet.. it is like a switch. No need to druel a backfiring japanese fart can pop every let down..and that saves fuel where it matters. Why keep dumping after off throttle? This tease also gains the super lights flying through vent lines and the top of the bowl..sucks it into the cylinders...and this means engine cleaners. Every engine braking is an engine clean. Nice clean burst for the next throttle stomping.

without full warm, the engine got nice and quiet. Nice response on the throttle. still not full throttle yet on the misadjusted cable, but now can tinker with that having fuel to fill it.

just what the doctor ordered. I am actually not on my own for the fuel air ratio stuff, I got a bad lesson in it years ago, specifically the monojet...and some education. 20 years later, finally using some of it.

[Barry Donovan]

its a shrinker

looking over other measurements, other monojets...

this one did have a tragedy. Worst case scenarios.

the bimetal relief worked even in the cold. this means it was near on fire to anneal it to useless where it came from. the bimetal carbs and extra stainless linkage, covers, choke, thorttle plate, and even the barrel (high grade lively version of the monojet carb) are for trucks...perfect car candidates. I went some extra efforts.

After on the car about a week, I found the back bolts of float bowl loosened on their own. the backbone in the middle of carb changed shape. I began to put the pieces together.

the soap I thought was in it was actually ethylene glycol remnants and the cleaners that go with it. This not only had a gasket fail sucking on an improper fuel bowl vent hookup (they had open bottomed vent cans flowed two directions).. it had cow farm, bird poop, pebbles of hard grey steel (an engine valve), some brass speckles from the ever failing dighram fuel pump thumping on the engine cam timer...


and it still cryogenically healed and runs.

I have the less heavy duty version delievering today, and I am not swapping what this one did metallurgically after fixing it. Without the electromagnet spark plug wire sucker (idle shutoff solenoid) attached, this allowed for further toughening via cryogenics. It is up to the needle, pun intended. I do like to push boundaries there. Realizing a correct size jet can put the needle right back into its non-tapered use, but rochesters original intention was my learning curve...and this also makes idle solenoid not useful. the jet is so small it hangs on a sticky charge after shutdown, ready to sprak up quick to the engine on cold starts.

even after all this, it was many times easier than alot of setups..and it has some benefits not even todays fuel delivery gets.

big sun activity today. geomagnetic zappers on the way..maine locale responds to those.

I owned a 250. 1974...
the same tragedy on the fuel air. Outrageous heat riser, and a coolant channel all attacking the carb. a pulsed fuel pump that could have been a steady 8psi to feed the oversized monster engine sucking throguh the straw sized monojet in relation... attacked from every direction, vacuum near useless. Almost as crazy as a 70s fuel crunch pushes carbs too small on engines that could use 3 of the 210 cfm monojets (I found one, that is an impressive straight six).

there is manufactured problems, 70s stuff beware. (I did follow along to the monte carlo blog here at bangshift - that is only one of many sad engine outcomes and suffered near identical)

on the sube, cfm is not only correct, the paranoia about feedback of several different kinds by the engineers is turning out to be a cool peltier throttle base genius. I found the hookups at carb, the only one that gets a straight 12v, is the choke, subaru had two other hookups..and they are reistored before they get to the carb, less amp. That is their strange smarts. as if to use time and distance well thought out. anyway, this is knowledge I take with me... Off to normal runtime..

[Barry Donovan]

the top bolt

Like a dummy, I forgot the last trick to pull up at emulsifier..
the plenum bolt spanning the bar across the top of barrel. Using a CAI boot, I did not install it.

after installing, instant cure. The hitachi was the same, and actually needed a huge choker. the monojet is lively with just a little one. This makes the monojet one that does want to work in comparison.
I found the needle was adjusted too far up this time, and put it back down.
the cave in was lack of the magic plenum bolt. I used a cam casing bolt from an ea82. fat shank, one piece bolt that looks like it has a washer, but it is all one piece. Fancy machining, did the trick. Of course it all fits under the boot. being separated from the outside world like a plenum would not give it, makes it very stable all year round.

to get needle correct, I am on my own.. I simply went full throttle, spring tension on needle loose, and being sure it did not come out of the jet. That is as close as I am going to get. it does use the taper after all. I am enthused. the dynamics of this is better than injection.... my foot is the linkage.

The rest is crud quickly leaving..oxides, being aired with no fuel for some time takes aluminum awhile. I added fuel injection cleaner a few days ago, I may go for the enzyme version next (it does work).

[dieselgeek]

This is a lot more complicated than EFI. Just letting you know.

[Barry Donovan]

This is a lot more complicated than EFI. Just letting you know.

you don't need to let me know anything.


it is alot simpler than fuel injection, just letting you know. try putting even my bad foot in a silicon grid, I'll let you know some more...

3 psi going by my leg .. I feel safe with just that one of the hundred and 50 things I could jot down...

but no. onto mankinds retarded evolution with a fake smile on my face.

I kept a singular point injection, same engine, same intake, could swap it over right now.

keep the 8 points of throttling map and the injector that skips over some of it when the tropical weather that invented it is not just right.

for the machine I am running, electro mechanical (fuel injection of another kind) is the answer for me.

I still worship injection in a 550 cat diesel.

only two complications for the monojets 34 year old carbs design:

the jet height left me with my own needle adjustment...
and I did not utilize the original steel plenum setup (needs that to pull at emulsifier with static).

both cured with simple ingenuity...
and my version is a what goes up can stay up. the only error known locally to the monojet (and some others - not many attempted the needle)

[Barry Donovan]

baby monojet


little tiny barrel. this is for a chevette, 1.6 liter. can’t use it. Boxer would starve to death.

I can use idle mix screw..fat end like I guessed the big carb needed. I also noted the air bleeds are tiny. I will stay with the big ones, as well as the big throttle. I will be using this number 80 jet, needle, and power piston..as well as float, the pin, clip and needle seat for float. looks brand new. the culprit for this unhappy carb is the starving air bleeds, short venturi, too small at throttle, and accelerator pump is also a tiny version. The needle and seat must be some very stable… looking forward to trying it.

I can use everything but float bowl and throttle base.

this was yet another carb too small to stay real.

choke also works..that is 22 dollars I spent for the whole carb.
this carb has no odors, stains.. and did not lose any stickers. chevettes are little hotties.Original owner must not have liked it.

I may try float bowl cover as well. reduction in air bleed at the top.

[dieselgeek]

[QUOTE=boxer3main;617002]

it is alot simpler than fuel injection, just letting you know. try putting even my bad foot in a silicon grid, I'll let you know some more...

3 psi going by my leg .. I feel safe with just that one of the hundred and 50 things I could jot down...

If you're saying that a high pressure EFI fuel supply is less safe than a carburetor, well - that's inaccurate. NHTSA stats prove this. Carburetors expose raw fuel to atmosphere. Turn a sharp enough corner and your engine compartment is now a fireball.
Meanwhile, you seem to think I don't like reading your thread. You're wrong about that too, I like the pics and text. Carburetors are interesting to me, so is MFI. Carry on!

[Barry Donovan]

[QUOTE=dieselgeek;617081]

If you're saying that a high pressure EFI fuel supply is less safe than a carburetor, well - that's inaccurate. NHTSA stats prove this. Carburetors expose raw fuel to atmosphere. Turn a sharp enough corner and your engine compartment is now a fireball.
Meanwhile, you seem to think I don't like reading your thread. You're wrong about that too, I like the pics and text. Carburetors are interesting to me, so is MFI. Carry on!

raw fuel to atmosphere. that is only if you let it.
not all carbs are holowed out logs with a manual choke.

carbs are giant fuel injectors after the 70s.

arguing with salespeople relating to their own selfish careers is useless.

moving on...

to 35 years the same carb in the 30s mpg and 30s below if need be...

the baby monojet, is almost useless for internal parts.

I tried float bowl seat and needle, refused to stop overfilling it. a measurement shows it is taller than the 250ci version. it is frigid right now..did not want to tinker further. I need to use the fat float to guide the type of needle that is in it. maybe swap some things further see what happens. at 3psi fuel still has compressability, that means safe and darn cold on the fingers.


the .10 fuel bowl fill opening really stabilized a startup. Will wait for warmer weather and figure it out.

seems a coincidence the .080 jet and the .079 as a guess for the big monojet, right on the money first try. GM built their little one with a .080 and a fatter needle. If my hack is not exact, close enough.

[Barry Donovan]

tiny barrel



this is my thumb next to the baby monojets throttle bore.

...and I thought the hitachi was crazy.

I did get a good choke, and mount, various screws, linkages.

the float bowl cover, I had forgotten, does not have the progressive spot like the big carb. Another perfectly clean young looking piece to waste.

I also found the hesitation came back for a bit after putting the green old copper float bowl filler tube and needle..
infection I presume. I wonder if I can find a stainless one to resemble it.

the attempt at the shiny new looking stainless baby version was very nice. it did more than the startup, fixed something about the hesitation. Everything is clean, but that stubborn float bowl fill and needle.

time does win..but am impatient.

[Barry Donovan]

fuel bowl needle and seat

I was wanting to use something from monojet just purchased as it stayed very clean. I did identify the fuel bowl feed with a much smaller opening sitting there shining, odorless.Trying it out in the big monojet, it started up much more civilized, and even throttled dead cold..something I cannot do now with the quadrajet sized cold shock dumper that is in it. The problem with the little seat from the baby jet was flooding the floats ability to shut the little needle off. This is my answer to that. The old original giant opening and needle, and even seat, is infected with something strange enough to change the way it runs…and wow is it a stinker.

1/8th drill bit easily went through this. there is another hole on the other side, I simply went through the whole thing. I stayed just above the seat, so the float has an easier life. This is closed position on the .10 stamped needle.

Here is open. the protective chromate looking coating did wonders for this, it is 34 years old. In a frigid spell right now, a warm day is coming soon…will get this right in. The math I have correct already is simply getting slapped at by a carb trying to be a quadrajet sized dumper with a 1 and 1/16ths venturi. The baby monojet taught me a few things. Overlapping the two in the correct places will be a very nice runtime.


here is old seat and needle. quite a monster. the smell of tar. the gasket perhaps.. maybe this came off of a 305 racing category.
very poisoned..just taking it out of the bag filled the room in seconds and gave me a sick stomach. I wish I had a geiger counter..
dipped in toluene like every part. I only forgot this one. I will not be throwing this away.

edit: 12 hours in toluene, a few seconds it was bone dry..using a drmel tool and 50 different bits to choose from, scrubbed it right off. the end of the needle was the infection..may have reacted to another rubber in the built in fuel filter (which I do not use). Not sure how it got that powerful..still quite a stinker sitting there now shining.