attacking a monojet

[Barry Donovan]

Not full throttle

I thought I was full throttle...

making final cable connection at carb, making it neat, I realized I am about .5 inch too short. It is a bellcrank type ratio, the fianl for throttle. at idle up to about 90%..then the pedal is on the floor. all is right, except the pedal end (could do either way to fix it, but no)
could be as simple as the carpet at the pedal end. That is the end I attack from next.

To find a hard mount for cable, looking like it was meant to be, not buy any extras at the carb, using oem of both carb and car..I choose the pedal end for the last half inch.

A loooong pull for the monojet.

I was chugging along, to get to my place is as weirdly geographic as san francisco. A choice of three greater than ten percent hills to climb. A cough of something new, otherwise dialing in nice... I let it go down to 1500rpm in second. for 108ci and 2300 pounds, it climbed like a little cat diesel.
the one big throttle has some things to learn..

wide open on the monojet has an extra push, I found that in the manual. Looking forward to what this does next.

At <40mm throttle (oem subaru spfi) it peaked at 115mph and the 1990s ecu stopped it. I'll know the gain in the curve by guessing, just romping to a legal 75-80 local highway with the 43mm.

[Barry Donovan]

carb video

I thought this was cool.

in this vid, they did not mention the static gains by resistor choke, lively barrels made of exotic materials etc. It makes me wonder if the worlds greatest were done in more by a scandal jumping the gun, rather than evolution.

on the monojet, the lively barrel responds to the resistor for the choke (creates a safe world beyond venturi- shreds fuel), and the tapered needle to go with a main jet feed that responds to vacuum only, is the means to stop fuel when throttle is let off (I did not have to get that precise, but chose to).

That is how a 1 barrel can go all the way to a v8 today. The video shows the many more years carbs were not perfect, than the ones that can run forever.

[Barry Donovan]

update

6th day installed, less than 100 miles...it did get the 10 gallons for burn in, used about 7 of it.

runtime in to where it will stay, check valve at canister is real noticable on cold start..and as well as about 20 minutes after shutdown (car outside window) the very powerful soap this carb showed up with is clearing out at the invisible magic layer of things.

Getting more robust very slowly...
I was thinking to myself "this thing sounds like my old 305 when idling".
putting the facts together, they had the same size pistons. funny coincidence?

3 times smaller or not. there is overlapping math in many engines...revealed to those who know better.

seeking another monojet prefix part #
17058***

this means 1978, where the 8 is can be a 7 or a 9.

scouring ebay daily...

I think "chevaroo" has stuck for my nick for the orphaned ten geared suby.

[Barry Donovan]

hitachi carb


the tiny carb. the primary barrel is less than 3/4 inch at the venturi. the second barrel is about an inch. This did a lot of work for a long time. I found the smell of road tar, digging into things. I am glad to have the bigger rochester in. I also found, the venting at float bowl was even bigger for this hitachi than the rochester. The external one on the rochester has been reduced to resemble this hitachi. there is actually many exits on the hitachi. I am glad the rochester is simple. Given air can only break down so much...the math for venturi seems correct, and maybe even bigger for the hitachi..but in reality, I learned that air can only go so small. the gas is willing, air is not. Another reason for the one bigger barrel..


the reason for rochester...the hitachi is mathed correct for some beautiful air, but not in the north. At 15F and below, the 1 barrel side had nearly no function. must have been whistling into a 100 below zero...how do you break that air? I don't want to know the overthunk answer.
Rochester seems full power all year, and then those magical times when racing is favorable, the rochester rises ever so subtle (rich oxygen fall and spring and summer)

I mentioned smell of road tar, and even bird poop. Fat molecules could not even shred with this the little hitachi. Todays fuel has cleaners that rid of that stuff in realtime..but the venturi must be big enough to have air to go with it. The rochester can, and is still willing to keep up.

hypermiling was nerdy fun.. I drew the line at 30mpg and no higher..ever again. I learned there is danger building, and it does explode into a finale. The little subaru taught me that. Reality for this needs a tropical self cleaning island. Big fat air molecules 99% of the year. Maine needs the northern stuff... of course it is stereotypically "paul bunyan".

[Barry Donovan]

monojet + zalman fan resistor


the zalman 56ohm green resistor you see is my spare for reference to what is in the inside of the aluminum tube (seems to be aluminum, act as cooler). The reddish silicone is some silly stuff that claims to hold 750 million degrees with copper in it for exhaust gasket making. (since when does permatex and silicone do what they say?).. anyway, a good spot for it is this tiny resistor and a humble 150 degrees, I hope it can handle it. The zalman resistors can be other colors, some shipped as red. they use this from a 12vdc in a computer to reduce fan speed and chatters, drops it to approx 5 volt, and stable(quiet). I am using it to ground to the carb, and zip tying some heat to the metal part of the fuel line before it enters carb. Double purpose. it does get warm, but gentle. The barrels of late model carbs (1978 is a last generation carb believe it or not) are lively tough materials, could be as simple as t304. More than old fashioned draft, a prime and a choke shutting (1960s was the last of those)..these carbs are lively enough to use the old choke simply to protect the barrel after shut down, and run the electricity of whatever gadgets (choke, resistor, I use both) across it to liven up the air before venturi. In many ways its the reverse of an injector.. injectors use electric and ignore air at throttle, the last of carbs use real throttle and air, and keep the electric in one spot.( it all variates either version for efficiency.)

installed, cold start was 3000 rpm instead of 2500. It is 22F and howling the north death wind. This kind of cold contrasts a fuel line in the span of six inches about 150 degrees. The stainless off to the right, to my amazement, was also acting as a heater/bridge as intake warms up, transfers to the fuel line. Still a blip in throttle, I noticed a dimple at the accelerator pump linkage seal on the outside of carb..this means a pause if the slot inside the bowl is too open. When this is dimpled, the plunger sits up farther to the feed slot, a source of pause. this sloppiness is something I did from the inside with a stainless washer way back when. This one looked aligned nicely, dimpled or not. given the smell of truck grease is in the black puff of pause.. it may simply just be at battle with a flow getting tighter, and air it never had enough of. My I-6 did that for quite some time after a rebuild with monojet. Too cold to judge any further. I am keeping the little resistor heater there all year round, and the preoccupy trick, primitive electro-mechanical worked from the split second the key started it. Good spot for the ground, (blue connector). The nominal throttle at full warm gained 100rpm.

[Barry Donovan]

needle cave in

upon the resistor grounding on top of float bowl.. I revealed the I-6 mishap it came from (they push up on everything with heat). I shrunk the whole thing. Good strong carb now..

it is not as silly as it seems ..if you have encountered it. Cryogenics is every alloy. The hitachi with EGR (oem subaru)... my god man, makes an I-6 blowing its butt up a monojet look like no errors at all.

so, needle not out of the seat enough, and it was 10 degrees. I will be "limiting the ceiling", rather than bend the arm inside the bowl.

"limit the ceiling" simply means, pull the meter out of the hole with the outside linkage..as full throttle curve rolls around, the power piston it is attached to, cannot have anymore needle. this is a delicate game, and worth many dollars as of today.

to determine if you need a limited ceiling...
once you get by the cough of needle too tight, judge the speed and feel on the highway. Still spongy, bend the arm in the bowl. if throttle feels good, engine happy, you can limit the ceiling by using outside linkage to gain more jet at slow speed..and leave partial and top speed alone.

the little sube not only took a tiny 2mm jet, I may be placing the ceiling limit beyond half and still acheive 100 or so mph.

4pm. got a tiny amount from external linkage.Gaining the little bit I did verifies I need to pull needle back up. Drivable. I have to take float bowl cover off again. I did not know the resistor was going to gain the carb this fast. kinda glad it did. retarded timing and got a big pop through the top. this is definitely fuel starvation. the measurement is so close.. I may give it extra as that is the way the 250 ran anyway. it could care less about a taper. in fact needle did not do much except slap around in a big hole.I could also solid the needle..but cryogenics really does happen. direct affect first thing is the damn needle. That is probably why they have it on a spring. shrinking and growing, hot and cold..I thought it was simply there for genius about weight gains in fuel, and that probably is a factor.

drivable is keyword. There is optmism to taking real settings. the carb as I mentioned is in a spot that does not get physics much better. even the vacuum suck in the center of the intake is exactly the same both sides. dual back to back fires.

anyway, moving on. this weather and my only fun being outside.. adjusting the needle in the snow falling is a bit impatient. will wait to take carb apart.

A more important note is that this one will be using a return fuel line. I could have guessed it. having a small jet and taper functioning..pressure is going to snap right back at the outside world. Remember the 250 dumped it like a garden hose..never used a taper to slow fuel, no brain no pain. The inlet let out a drop, caught it in action. rather than a fuel regulator, I am going to spend a whopping 5 bucks for a t- fitting and a valve..not even use a pressure gauge. just leave a barely open valve of relief on the tiny japanese fuel return line (bizarre size.. it may not even be 3/16ths I.D.)

[Barry Donovan]

home made regulator


There I fixed it. Something I noticed at all times on the original carb..pump never shuts off. little seeper, super slow mode. The return was at carb, and after all filters..and a small return line it is.. I am simply doing the same. the easiness of the monojet setup is that the electric pump is low pressure to begin with, and the monojet wants a bit more in the bigger bowl. Same purpose. the check valve being added seems to be at least 1 psi, came with the subaru. this will be in the direction where carb can have nothing back from return of course. I suppose I built a real regulator.

this ought to do it. the pump is 3psi, and there is a crazy high mode, very rarely heard (there would have to be a leak)

this is something I wanted to do for the chevelle. I ended up getting so mad, I bought a 350 unkown condition and swapped the 250 ci monojet engine during a 4 hour limited span. It was not the best monojet.. a few years ahead of sharing the main well with accelerator pump (another gas dumper), the pump had an exit of its own, with a giant 3/16ths passage...but hey, it could have been smarter in another place. being the venturi is less than an 1 and half by far..why why why did they make the crazy dumpers? anyway, they did get smart. if the monojet has an electric choke by oem (mid 70s), it is one to go slow with long term clean. it can do anything.

one thing I never get mad at is good stuff in the wrong places. They need justice. the monojet is just one. I mention subaru here, it is simply a destination. feel free to apply this to any monojet machine. Another note for anyone, is the return for the single barrels do have a means to get busy. they are very precise in pressures because of a singular on and off. Some claimed this was another factor in crazy low gas mileage: no return to take a squirt off.

edit:
I have since installed this and it works. I heard a perfect low whistle..could not place it. I thought it may have been the squeeze of the little T I used to build the return, as it is a real venturi. less than an inch long, the width of two clamps to have just enough room. on the pressure side I did use a fuel injection clamp (those are solid, no ribs) to overcome the pressure of downsizing a short distance. Nope the whistle was not there.. it was the carb. It loved it. As large as a monojet can go, this one is at a tiny 2mm jet with a meter in the middle. The summer time the little return will get busy. I found late summer is outrageous. car does not even have to be on..in fact, idle and off is when it is used the most.

this means fuel savings, and even power. As fuel warms it expands, it needs to move. this will move it. keeping cool density equals power.

Upon reading on the net, nerds have a number of .00528 expansion for every so many degrees. wherever they committed to testing worships bad math. I clearly remember doing our own math here at the guard base with planes holding 115000 pounds. I have concluded 6 cubic inches from my 10 degree tank to the 150 degree jet. That means my pump could should off, and I could drive ten miles before it ran out. I did have a dangerous condition to get over the cold here.

you know it is fixed if you here the infamous low whistle sound from the monojet. the other carbs get a higher pitch to more barrels, and everything is smaller. No whistle? it is cramming. keep an eye on stuff.

[Barry Donovan]

the fuel system

I wanted to sum up what this is made of entirely.

the tank freakishly has four lines. one must be a spare in a big hurry.
3 are in use. the subaru did have a early multi point in the 80s, and for turbos. playing with egr and turbos..they had some serious sideways boxer heat going. the gas tank even has a surge tank hidden in the right rear quarter (I had to poke a secret vent in the well thinking of safety if it failed)

• fuel line goes to normal spot, 5/16ths, whatever is normal.
• the return is the smallest one of all. I did learn you give an inch it can take a mile. I leave this check valved to never come back at carb.
• the biggest line of all is the gas tank vent. this goes to the bowl vent line with a T and I choose check valved at the canister (that is not a nerdy emission item, it is keeping you from getting killed) to enter, and out of tank vent to leave only.
• constant run pump can keep going.

25 years errorless. this same setup will work on anything known to man.

[A/Fuel]

It looks like your oil pressure is a little low in the video you posted.

[Barry Donovan]

It looks like your oil pressure is a little low in the video you posted.

it is a ground error.
the static pressures of a one wire gauge system uses the engine and system to find its own back side.

in short:

I have got this little dog lit right up. most likely using the stainless headers and air to not even see itself back at the dash. A two wire setup on the gauge may be next, as that fixs it. I was going to use something from a ford. standard stuff.


the only one that stays happy is the coolant gauge..of course. it is dipped in its own means to ground, and on top of the engine before it gets thieved..

here is the dainty oil pump (find one bigger, I'd like to see it).

I have had these on direct line hitting 106 psi.

[Barry Donovan]

fuel inlet

I took advantage of warm engine, took the fuel inlet out due to a drop that just wants to hang out there and added the pro seal silicone only to the head of inlet.. i do not want to bother threads. Perfect past, no burrs on anything. The silicone loves gas and aluminum. in fact some of it disappears at a moleclar level, changes the surface of aluminum.

the fuel inlet must be original. Not sure of history, but I was told if it "still has the heavy stainless inlet it is oem". I guess they are not easy to find? I find new inlets, lo and behold, they don't appear like what is in it. I also noticed the hole opening for inlet is the same size as the bypass gadget I made. Here I was thinking I might be restricting something..and I am not at all.

quick ride, the fuel relief was a huge improvement. I know the needle is where I want it. when I backed into my spot, a unique oxide of aluminum in the exhaust came by window..that must be the carb finally moving its bottom.

no adjustments yet. waiting for fuel inlet to dry / calm..try later. oxides and static blippers...how the heck can I judge a needle I know is correct yet?

a few throttles was a surprise, then the blippy hesitation. not impossible, can drive around. Another dumb thing I have done in lack of self confidence...no long highway run yet. Adjustments are good, and am going with it. give it a couple hundred on the highway and go from there. Yet another dumb fact I forgot.. the spec stage 1 clutch does not even have 200 miles on it. speaking of new statics bothering things...

[Barry Donovan]

20 inches Hg

Checked vacuum. the monojet reads 20 inches on throttle. It was cold so reading 18 at idle. the hitachi read 22+ inches at idle, dropped to 20 during throttle…sometimes. Other times, it stayed right at 22.
the monojet did gain some much needed relief. To theorize the pressure of 22 inches Hg..it equals ten psi. I could not wait to gain some, especially down low..partial to half throttle. This is interesting. The little 108ci can take a 300 cfm, and read about 16 to 18. The vac gauge is a tell all. This current reading does indicate the lower throttle is much larger than a 2 barrel..up top is unknown as of right now. The 210-250 cfm I saw written for this monojet does seem to match.
This does really misplace this on a 250 cubic inch engine. Still reading high on less than half its size.
fuel inlet sealed…and I have choke set too hard. Getting there slowly..lucky it has been easy.

this carb is just right.
I wonder if a 300-350 cfm exists.

the choke set hard means too tight, gains real high throttle, 3000 rpm. This carb is set up to purge with air bleeders and a bimetal valve built in. From dead cold, demanding crazy high idle is not a good idea. I do reel in yet another setting from the 250ci. Could use half choke..this gains purge through bleeder/vent (those are shits every car has at cold start- not even blow by most of the time, it is fuel itself.) This is yet another relief gaining sanity. subaru not only knew the carburator they used was tiny, they used external purge control valves with yet more wires and hoses..proper cfm in cold start does not need extras. The monojet doesn’t. proper carbs don’t.
Getting to another mystery. To gain oil gauge reading..which supposedly acts as a pressure switch simultaneous. The car having no computer, yet knowing when to open purge valve. It can’t be all that complicated.. under the dash is a baron as an old dodge pickup. I did have to remove a thermal vacuum switch that did not work when I took it out..could be that simple. I want no extras..let mechanicals and real pressures and reliefs take over. The monojet is a great start.

so.. future is simply backing choke off, funny enough, to a similar setting as the 250. they did not like the high idle lever kicking in all the way either. startup around 1800 is the friendliest...right into below zero F. Right now it is roaring to a fight to 3000.

[Barry Donovan]

upper throttle

finally got some tougher upper throttle adjusted in. stretched the cable. no worries as the tiny feet and little legs standard spring of the original has never seated an american tug its whole life. probably wound the cable tighter.

I got mad and literally grabbed the entire pedal assembely and bent an I-beam the long way with one hand...upper throttle is amust have. I could not gain enough at the pedal end. Now that is maxxed out, and need to move the other end again because of the stretch. it stayed elusive because it is indeed tougher to pull at.

I need to move the throttle again to peg the stopper..but am within the .25 needed to get that nice bellow of extra boost ricocheting through the CAI. Tried it out getting on the dreaded short onramp..best it has been in 25 years. forgetting the tread is 3 inches taller and 55 is 65 in the climb. shot right out on the highway with a little 108ci.

the noise is something I will be recording. A rochester sound I do miss.

EDIT:

if anyone reading this understands static from a spec clutch in an all aluminum drivetrain..
I have a mystery. I do have four of my own grounds, nice thick.

I am finding the monojet also has the same blip hesitation as the hitachi. I know it is the clutch if I let it out too fast. A peculiar note is instant tall gear after first. This means gear calc numbers have no games, it is right on the money. Speedometer has been useless for a long time anyway.

my complicated question is... how do I stop that blip. If I take off fast, it is like I need to stage, upper rpms, let it burn rubber to maintain higher throttle or stall. I am greatful for a natural feedback setup. I don't even want to know what would cook in the electron world with that clutch and my current setup..

..or do I just need to learn. I have found a sweet spot to drive in civilization with. the "daily driver" part of the clutches description holds true... a little blippy, but do take off.

[Barry Donovan]

progressive vacuum

The cold start problem that recently arose… I found the choke pull is not on a progressive pull like it ought to be. if to open jet more and lose 10mpg..that is ok to be full open right away. To stay where I am at with fuel (it is doing awesome), I need to find a progressive spot or not use it at all.
The next carb is this monojets clone..will be drilling a true progresive. this needs to T off to choke pull and the second half of my vacuum advance.

ran into an impossible problem without removing carb..no progressive vacuum spots anywhere.
this must have run like ass on the 250 worse than it ran like ass already on the 250.

bizarre. not one progressive vacuum. spots are there untapped. I try for a second carb later, same year..will do the extras to that one.

I noticed the second half of vacuum advance is no function..The top port on the carb is some tester for the bimetal valve. quick pulse then nothing. nice to know the valve is tensioned..moving on. I need the progressive for the second half of advance as well as choke pull.

lots of spots, can even make it look oem..just never tapped to be one functioning.

edit:
unplugging choke pull did not help any. Cold start on its own is one quick attempt with itself, then out comes starting fluid. I do remember this from the 250 after rebuilding..in fact alot of this routine is the same..invisibles, time gets it. I did add a relief for fuel, as tank gets lower, weight changes, and the tank is now accepting whatever new thing I did in the return line from carb..crap is no doubt in there now. So lots of fuel diluting mysteries is next (I have low light on playing around where it sits). The jet is so small and in tune, it responds precisely to choke..which is just right as of now. Am loving the largeness of every piece of this..the idle is that of a hard thumping diesel.

in embarassment to admit...I literally used to wait for the cold smoke and something to come alive in the matter of five to ten minutes in this cold. the oem hitachi jet is less than 1mm (how did it run?).
this is where the "large stoich" and "little stoich" separate the same smooth 700 rpm from another. A good ear identifies it.
the rochester is quite freaking powerful.
next is 92 octane, some gumout, maybe even some octane boost (the engine is over tens to 1 of the 1960s kind in compression)..and dilute with a highway run as I have not had more than 16 miles highway.

[Barry Donovan]

1 monojet 17058035 --124 8 BCJ

found my carbs clone. this one uses a high idle screw, must becloser to 1979..the hint of green on choke linkage and no bimetal relief is an indication this was not on the truck straight six.


$22.84 delivered. I hope the guts are there..

I can use either version..but this one is a better candidate. Simply swap throttle over. I found one recently that measured 1 and 3/4. That means not only did they make a giant venturi with giant throttle, they also had a smaller venturi with a giant throttle. the one I have is the small venturi with big throttle. oddly enough this better candidate is to be the spare. Will share how I get a progressive vacuum spot and maybe some nice bushings. This one obviously has nothing to win in the alloy, stickers did not even come off...maybe a cool small straight six. the 194 perhaps.

I will be going surgeon on the choke. the little sube fights like a devil with the -12v. the rochester choke has strong guts for the big juice forward.. with one dainty error , the sube kills it.I'll photo what it is this time.


searching around for where the monojet without the lively parts would have been bolted to, and found a 1978 chevette witha 98cubic inch fitting the bill. Painted linkage, high idle screw, no bimetal relief.

swapping parts around...and will use the best of both. the float bowl area interests me for the chevette. did they reduce air bleeds too? wherever the new crb went, it better fits a smaller engine, just by the bimetal valve not in use. the stainless choke, etc, of the truck carb is stuff I want to use. Mix the two of them up.

funny to think they used the same carb for 98ci all the way to a 305ci.