;peek;I wanted to move this out of my build thread since that's coming to a conclusion and post up this info here for some reading material...
I've run the AFRs on the stock engine and here's the main event in a quick rundown But first a lesson on what the AFR readings mean...
A “stoichiometric” AFR has the correct amount of air and fuel to produce a chemically complete combustion event. By definition, stoichiometric is the calculation of relative quantities of reactants and products in chemical reactions. Which is a fancy way of saying it’s a mathematically derived “ideal” ratio of air to fuel. For gasoline engines, the stoichiometric AFR is 14.7:1, which means 14.7 parts of air to one part of fuel.
The stoichiometric AFR depends on fuel type—for alcohol it is 6.4:1 and 14.5:1 for diesel. For the purposes of our conversation here, we’re just concerned with a gas-burning engine, so 14.7:1 is the ratio that lies in the middle of a “rich” or “lean” mixture. A lower AFR number contains less air than the 14.7:1 stoichiometric AFR, therefore it is a richer mixture. Conversely, a higher AFR number contains more air and therefore it is a leaner mixture.

For Example:

16.0:1 = Lean

14.7:1 = Stoichiometric

12.0:1 = Rich

.
Leaner AFR creates higher temperatures as the mixture burns. Generally, normally aspirated spark-ignition gasoline engines produce maximum power just slightly rich of stoichiometric. In practice it is usually kept between 12:1 and 13:1 in order to keep exhaust gas temperatures in check and to account for differences in fuel quality. A 12:1 AFR is generally considered to be about right on a gas engine under full load (wide open throttle, hooked up and haulin’ butt), though there are certainly exceptions depending on a million different things.

Now, in regards to my engine here's what I'm seeing...The "rule" is 475*F is the magic number on cylinder head temps...I'm getting more than that with even a brief time up above 2500RPMs...I'm talking 510 to 540 on the gauge and climbing...No I'm not staying on it for long after getting there but I've been asking myself how to cure this...
Obviously I need to confirm that's the actual head temp so I need a infra red temp pointer to see where I'm actually at ...I see no calibration screw for the gauge..
I could richen up the mix but it's already where it should be for the most part... Could it be because the engine is new with only 2 hours on the meter ??? Possibly because it's sitting on the trailer and the air isn't moving like it will be on the water ???:confused: These are some of the questions I'm asking myself..
the oil temps are steady at 175 for the most part and I can touch the oil cooler it's not really that warm as you'd expect but yet I see the CHT gauge and I get an uneasy feeling seeing the readout... Hmmmm....
Chuck had said to try and keep the CHTs around 450 or so...:shock:...I'm past that the first 5 minutes even at the lower Rpms below 2000...It's 72* here glad I didn't fire this up in the dog days of summer !!!:lol: If I didn't have this gauge I wouldn't even know there was an issue I can touch most of the engine and it's not smoking hot like you'd expect with those readings..
So, OK...I know it's a 50 buck uncertified CHT gauge but I can't stop watching this thing climb like I'm sitting in front of a timebomb...;rasta;

check with a lazer and see if it is that hot. there cheap on ebay. new paint and all i'm sure something would be smoking at that temp.

which cylinder is the CHT gauge hooked up to?
somewhere i remember reading that other have stated that the back 2 cylinders, # 3 & #4, would run a little leaner, due to more of the fuel dropping down into the #1 & #2 cylinder intakes,
i just can't remember which post i read that on, but when they went to the Empi carb. they didn't have that problem as much, with the fuel running through a down draft, and not the side draft carb.

Keep in mind that your reading will be higher running it on the trailer. Mine gets warmer much faster on the trailer vs running on the water. You'll know when it gets warm, you'll smell it and you'll hear the tink tink tink when you shut it down.

which cylinder is the CHT gauge hooked up to?
somewhere i remember reading that other have stated that the back 2 cylinders, # 3 & #4, would run a little leaner, due to more of the fuel dropping down into the #1 & #2 cylinder intakes,
i just can't remember which post i read that on, but when they went to the Empi carb. they didn't have that problem as much, with the fuel running through a down draft, and not the side draft carb.


Yes I've mentioned this a few times. Part may have been because of the slang left from casting but mostly the design.

I've got the thermocouple hooked up the the right rear cylinder {#3,second behind the oil filter} I figured this would be the hottest cylinder....On a side note on that plug,the sealing ring was oblong{that way when I took it off not from me overtightening} and not sealing too well so I took it off and just have the thermocouple ring as the washer.. It's sealed up but I guess I should have the compression washer there so I need some extra spark plugs..I did change the fuel back to regular instead of premium to help with the combustion and maybe help with the cooling.
The engine paint is discoloring close to the exhaust...Not burning off and flaking, just discoloring..This engine paint with ceramic in it is good to 500*{so they say} but no water cooled engine is getting that hot and living to tell the tale...And with 475-500 seemingly being the norm it's right there at the paint's limit..
I expected to see some lean readings from the stock carb then I could fatten up the mix to help with the cool down but as you see it's close I'd just be washing down the cylinders with extra fuel at the expense of the rings probably...
I did take the intake"joint" as they call it and debur/clean up all the casting flash so it's as good as it gets...

Well, I got my infrared thermometer now all I need is a nice day to continue the mission...I snagged it at lowes...I was going to get the harbor freight version but I was hoping this one might be a touch better quality...claims "accurate to + or - 2%" we'll see...It's got good reviews...
As I read more about the spark plug CHT gauge thermocouples in general...It's not the most accurate probe for it's intended use but if I can get a good reading using this gun I can possibly adjust the needle a touch and then know where it runs for a general quick check...
I have to wonder....Does anyone have an idea of just how the military read the CHTs and where they might have taken the readings at the head ????

So I had a chance to run this engine a little more today its 67* out...The engine is running fine....That number 2 cylinder is the cold one...20-30 degrees cooler than the rest...But still firing normally...It is the shortest/closest intake tube to the carb...As it turns out the number 3 cylinder{with the thermocouple} is in fact the hottest cylinder but not much more than the others...
After a brief warm-up I throttled it up to 3000 rpm...It runs fine, no miss and the hesitation from the carb really isn't that bad I could live with it to get on the water for now...But a few {2-4}minutes at 3000 rpm raises the temps to where its 500 plus degrees on the gauge...
And now I'm back to the same question I had before...Where do you take the reading for the head ??? If I shoot into the thermocouple/spark plug seat area I'm getting 40 degrees cooler than the CHT gauge reads...If I shoot the hottest head near the exhaust pipe I'm getting 500* and if I shoot the exhaust pipe an inch below the head it's over 600..This is with the oil temp gauge way below 175 and I'm not getting the hot engine noise papee is describing...The paint is discoloring a bunch now but if it's truly near the paints limit it will do what it's doing...
Do I have a hot running engine here?
Am I taking the readings incorrectly ?
Do I even have a problem and am driving myself nuts over nothing ???:lol:

i would say where ever on the head surface that is the highest would be correct reading. when they say head temperature i think any where the hotest reading is taken. just me but i would run it just below 450 and let run there and maybe loosen up and fix the problem. unless you have way out of time. if you had to put a fan blowing on it to keep it cool at least run it and give it a chance to seat in and if it don't you have an internal engine problem. no telling what. broke ring to tight of piston. no telling what you will find. but most engines i rebuilt or even new short blocks i installed run hotter for a bit before they seated rings. if timing is set right and fuel ratio is close than friction is causing over heating.

Thanks Bobby...I've got a little over 3 hours on this engine just probing all running data of this new engine...Mabe I'm expecting too much too soon...I've never read what others have done with an NOS engine as far as a break-in time or routine...Here's some pics of the number 3{hottest probably the leanest} and the number 2 the coolest and the one that had trouble in the beginning..Also I moved the thermocouple thinking the exhaust was somehow throwing the reading off...But no change after the move...Note the discolored engine paint is this normal ??

i would also do the mod to the carburetor an see if that helped no 3 is too lean.

I read through the o84 engine manuals (pdf) that are listed....
no where, that I read, does it state the gasoline spec or a minimum octane level...
anybody know?
higher octane burns slower and cooler.... Corky, do you want to try some of my 100LL av gas?
kent

Kent, the 084 has a low compression 6.9 to 1...I originally had some high octane in it then switched back to regular thinking the fuel was burning too slow and might have been going out the pipe more so than completely burning..So we were both thinking the same on that one as far as some type of fuel issue...But here's what I've been waiting for Bobby and others to call...
I too thought the number 3 is too lean by reading the plug...The strap is completely white and there's absolutely no color on the plug almost like it's too hot...And here's something else I've noticed...
As we've brought up earlier, the front two cylinders are the ones getting most of the fuel...You can see number two and on the other side number one is "wet" around the thread ring every time I pull it...But the back two cylinders plugs read both lean when I pull them...
So even though my AFR reads close to perfect I'll bet those back cylinders aren't getting enough fuel and the front ones are getting much more of the share...I was thinking today everything points to the engine running lean regardless of the AFR on the meter... But I didn't want to mention this and influence other's findings...

I've got another NOS carb coming so I'll go ahead and drill out the jets a few thousands and then see what I've got...I'll tune it by the plugs then see where the AFR readings are in the end...As long as those front two cylinders don't end up too rich I should be fine..I'm betting as the RPMs go up the distribution gets better with velocity but at this point I can't run it up and keep it there long enough to get a good plug reading....There's really no way out of this except just dumping the original carb and intake joint but I'm not ready for that quite yet...

I'm still going to get the compression for each cylinder just to be sure and in the process check for any intake runner leaks using a spray test...

i would run it just below 450 and let run there and maybe loosen up and fix the problem. unless you have way out of time. if you had to put a fan blowing on it to keep it cool at least run it and give it a chance to seat in and if it don't you have an internal engine problem. no telling what. broke ring to tight of piston. no telling what you will find. but most engines i rebuilt or even new short blocks i installed run hotter for a bit before they seated rings. if timing is set right and fuel ratio is close than friction is causing over heating.
Yes I know what you're saying about the first few hours on a new engine..This is the crucial time for break-in with the friction...I've added an oil additive with ZDDP to help the lifters and cam, etc... The oil cooler is doing it's job it's a good 20-30 degrees cooler than the oil temps at any given time..
Yes, I can run the engine and get some hours on it...It runs fine and there's really no cooling problem to speak of I was just wondering why it heats up so quickly... It cools down fast into the 400-425 range as soon as you drop the RPMs...
I realize in summary the engine is new, running a touch lean, and it's on the trailer while I'm tuning it..Now it's time for the next stage from the stock configuration and that's the factory carb mods...

do you know what your max rpm's are?

Yes, the prop is limiting RPMs to 3000 at the pitch it is set at... I've read where the IVO prop on some of the airboat pros builds were spinning to 3700 :shock:..

I've read so many different descriptions of the carb parts on this site I want to post a breakdown of the parts so everyone can identify them as originally named...I'm guilty of this also so now we can all be on the same page...Literally...:lol:...
Okay,the parts that get modified are highlighted in red...Anyone care to explain how to go about modifying these two components to richen up the mix ??? Papee ??? Bobby ???

if you have the rpm's maxed out to 3000 then when your anything over 2000 rpm's your engine is working full power set by prop pitch. with the belt drive that should be 3600. on a direct drive it should be at 3000. so what i'm trying to say is your loading the engine down before it makes its power and overheating. probably nothing wrong with the engine if the prop was set to 3600 and it would be working a lot less and not lugging down. if you had the power to plane out at 3000 rpm then you would be putting the prop under the rpm's it should be set for' my razor works best at 3600 to 3800 but i don't run it long at 3800. if i run it hard its just for short burst to get on plane faster. drill out the tip of the fuel metering tube also the side holes can be drilled out to but not a lot.the bottom jet that holds the float bowl on is the high speed jet the holes you drill out are above the gasket. you can drill out only one or both holes next to gasket. the 4a042 carb has a larger fuel tube and i think the venturi is a bit larger. i would start by drilling out the bottom holes on the high speed jet a couple thousandths.

Now that's what I was looking for thank you very much !! ;thumb; And it makes perfect sense...I'll check the pitch{I have a digital angle finder for the job} and keep bumping the degrees until I'm there at 3600..I would assume this is the first step before any mods are done...I have a diagram I'm working on I want to show you give me a minute...

for an reference, on an other post i put down an comparison of the 2 carbs the 084, and the 042. i used some small drill bits to try to get close to the size of the holes in the venturies and the fuel tubes. and put some pictures for the part together so some might see the comparison. i remember reading, on this forum about one, that purchased an new carb, and it would idle, but anything over 1500 rpm it would flood out. he came to find out he had purchased the carb for an 042 motor.
but at least with your O2 monitor you will be able to see when you drill it passed the point of no return.


http://miniairboatassoc.com/forum/attachment.php?attachmentid=2937&stc=1&d=1481481734

http://miniairboatassoc.com/forum/attachment.php?attachmentid=2934&stc=1&d=1481481549

OK here's what I've been working on...I know it's not exact but is this the basic theory for the fuel metering tube carb ?? The lower hole in the tube is submerged in fuel and the upper hole is at the carb venturi so the incoming air charge pulls the fuel from that upper hole ?? And in turn the carb "screw" as they call it has the holes around it's tube that let's a certain amount of fuel through into that well for the metering tube lower hole ??

i think the fuel metering tube controlls the amount of fuel for the idle circuit and the jet that holds the float bowl controls the amount of fuel at high rpm

for an reference, on an other post i put down an comparison of the 2 carbs the 084, and the 042. i used some small drill bits to try to get close to the size of the holes in the venturies and the fuel tubes. and put some pictures for the part together so some might see the comparison. i remember reading, on this forum about one, that purchased an new carb, and it would idle, but anything over 1500 rpm it would flood out. he came to find out he had purchased the carb for an 042 motor.
but at least with your O2 monitor you will be able to see when you drill it passed the point of no return.


http://miniairboatassoc.com/forum/attachment.php?attachmentid=2937&stc=1&d=1481481734

http://miniairboatassoc.com/forum/attachment.php?attachmentid=2934&stc=1&d=1481481549Bart, thanks for the quick link to those findings I was going to try and find those for reference as to the hole sizes....The old threads have Chuck stating he drilled the "main jet" to .040 and the tube to .038 or something close to that and I couldn't figure out what he was refering to for those mods...Man, I got holleys and edelbrock/carter carbs down pretty good but this simple carb is new to me I just want to make sure of the correct mods before I need some new parts because I didn't ask the right questions...

i put the metering tube from an 042 in an 084 carb an it ran like crap. couldn't get it to idle smooth. and hesitation was worse.

i think the fuel metering tube controls the amount of fuel for the idle circuit and the jet that holds the float bowl controls the amount of fuel at high rpm


Ok, so now I'm completely confused...:lol:...Not by what you're saying...But how these circuits interact with each other and their carb routing in the body itself...I guess I need to disassemble it and educate myself instead of asking what might be obvious answers after disassembly...
EDIT: I may have it figured out before the teardown...judging by those pics provided by Bart...Seeing that O ring on the "screw" I'm assuming it's a sealed unit and that WHOLE WELL is exposed to the air charge...So at idle, only the metering tube has the ability to distribute the fuel at low vacuum...But when the RPMs go up{and more vacuum is created} that whole well will have the fuel pulled up into the venturi from below...Did I get it right ???

the fuel metering tube meters the fuel for the idle circuit and part throttle. larger the tube the more fuel is sucked to the idle circuit but air gets mixed in that fuel. easy to get over loaded. the lower jet is enlarged to enrichen the high speed circuit. i had to almost close the mxture screw to make it idle when i used the large tube from the 042.

The drilling of the metering tube is to improve the stumble coming off the idle circuit but it does seem to improve overall performance a bit too..

The drilling of the metering tube is to improve the stumble coming off the idle circuit but it does seem to improve overall performance a bit too..
That makes sense because more initial fuel will help mask the transition between the two circuits...

the fuel metering tube meters the fuel for the idle circuit and part throttle. larger the tube the more fuel is sucked to the idle circuit but air gets mixed in that fuel. easy to get over loaded. the lower jet is enlarged to enrichen the high speed circuit. i had to almost close the mxture screw to make it idle when i used the large tube from the 042.
OK here's a question regarding the mixture screw...Is that adjusting just an air bleed or is it adjusting a mix of air and fuel like a holley idle screw ??? I know the target is 1 1/2 turns out from bottomed out judging by my AFR meter the idle circuit is very rich without any mods.. EDIT: yeah, I know it doesn't really matter just do it...:lol:..But you guys know how I like to be thorough in the knowledge...

it adjusts a mixture of air and fuel open it up and it gets richer. no need to make idle circuit any richer. just drill out the bottom jet. make sure not to go too large and enrichen the high speed circuit too much and start fouling all plugs. you can tell by wide band if you have gone too far. the idle circuit being too rich can foul plugs also. just by turning the idle mixture screw will show on the wide band. the idle mixture controls just so much fuel and air. the fuel metering tube controls how much the mixture screw can control.

Well I guess I'll be busy tomorrow...And so will you Bobby...Are you going to be safe where you're at down there ???

yea i live in an older house and my son lives in a mobile home. he will be staying with me through the storm with his 4 kids.

OK good, they keep changing the track of the storm and it's making me nuts...And I don't even live down there...:roll:..

Here's the progress report...
The prop pitch was 13* and limiting the RPMs to 3000...
I changed it to 11*...Now I'm in the target range of 3600-3700...
The engine likes this much better...It runs cooler across the board...I can hold it steady at 2000 and the temps are steady {475}...Sounds much better too it revs quicker and I'm not instantly in the danger zone running it up to 3600rpms....
;thumb; So it was on to the carb...I pulled it off and out of curiosity carefully checked the idle air mixture screw setting to get it back to where it was originally if I moved it.....:-?...:shock:...It was 4 turns out !!! Yep, there's the reason for the super rich idle AFR numbers I seen on the gauge...Way off from the 1.5 turns speced out....What the heck...Don't ask me why but that's where it was set I never touched it...No wonder I didn't think the transition between circuits was too bad it was dumping the mix in there at low rpms...I'll bet the number 2 plug will clean up after the adjustment...So no mods will be done to the metering tube only one mod at a time so I can see what is happening.. .Anyhow...

I want to be clear on what hole{s} I'm modifying on this "main jet"...Here's a pic with the holes numbered and for everyone looking there's another mirror image set on the other side of this tube...Judging by what's been discussed I think I only want to drill out hole{s} number 1 is this correct ??

that's the one.

OK great, I'm all set to open those up..Bart had measured these holes at .038...I've got a 1mm{.0393} drill ready for the task ...Then it's run time with the AFR meter...I'm going to sneak up on it...:lol:

So I opened up holes in the number one position in the above nut/main jet pic with a 1mm bit...That's what I had.. my numbered {60/.040} was broke/missing from my old index set..:roll: That's how it goes isn't it...It's tough "drilling".001 from a hole matter how big or small you don't think you did anything..So I "drilled" it and worked it in and out a few times to make it loose but not go overboard...I'm guessing it's at .040 for arguments sake...
The engine liked it...Felt crisp and snappy...So I left the engine warm up a bit then added the AFR meter..
Knowing how the engine was feeling in general I went ahead and turned the idle air screw down to get the idle charge around 13.5-14 instead of the super rich 10s it was at...Here's the rundown of the numbers from that setting.. I give up it wont let me load them in sequence so you'll have to jump around to see the results..
To give the quick affects: Turning the idle air screw did in fact get the engine in range for the idle AFR but in return made a lean spike at the transition around 1500...After that the main jet mods kicked in and added more fuel at the top end...As a comparison 3000rpm went from 13.1 to 11.3... which sounds too rich but the engine seems to like it and I'm sure it will run cooler at the upper rpms...The plugs will tell the tale...

So as everyone has been stating...The idle air screw has a huge affect on most of the lower end response and transition{and even some of the top end} AFR...Mabe the tech at the factory knew this and intentionally set it up like that??? At 4 turns out it barely had a stumble and the AFR didn't spike that lean...
So I ended up turning the screw back out to add more fuel and the lean spike went down..Now I'm at 2 1/2 turns out...
The idle afr is now 12.1 the transition spike is only 14.5 and the top end is 10.7 !!! The afr went rich across the board by simply turning the idle air screw...So you can see how much affect that small screw has on the whole tune...Now it's time to read the plugs and see what is happening in there but the "seat of the pants" and CHT meter says it's good...Again, the pics won't sequence the way I load them so you have to jump around..:-?

I put some of the measurements on one of the drawings. i can see where enlarging the bottom holes on screw, so the fuel is more accessible to be drawn up the fuel metering tube.
with the stock holes combined being only .076", in many other carbs i am used to seeing an unlimited area for the fuel meter tube to draw fuel from. not just these 2 holes. ( i can see where Papee would get frustrated in the past with these ports plugging up on him.)
until all this conversation started, i was assuming that it was the fuel meter tube that was drill out.
i never really thought about enlarging the feed ports in the bottom of the screw.
until i put these measurements down on paper,
so from what i gather, Corky has for this latest round of testing has enlarged the base holes on screw to .040, for a total area of .080.
(also the inside base of the screw is necked down, so that it is a snug fit where the fuel metering tube slides into the bottom part of the screw. but i do not know how snug the fitting is, as to where it might allow fuel to weep past it. which would allow more than the measured amount of fuel coming in through the .0550 ID of the tube.)

Now I feel I'm ready for the water !! The engine runs much cooler...I can hold it at 2000 rpm indefinitely and the temps hold steady at 450*...2500 gets me 475* holding steady...This is on the trailer and not moving so I should be fine...I ran it for about 1/2 an hour and varied the rpms here and there...
The oil temp gauge did go up until 200* and leveled off there...I'm not sure if that's good or bad?...I checked the oil cooler the oil is 30 degrees cooler as it comes out so it's working nicely...
Here's the plugs...Keep in mind this new engine only has 4 hours on it now it looks to me the rings aren't fully seated yet and hopefully the plugs will clean up even better with time...As before the front two plugs are running more rich than the back two...And the back,right{number3} is the leanest of them all..And the exhaust temps reflect this...
Edit :I wanted to add my unexpected moment of the day...:razz:...After posting about the mods and how nice it runs I went back out and started the next phase which was just a monitoring session to put some time on the engine and check the operating temps etc...And I couldn't get it started !!!;rasta;...So I messed around with the throttle,choke etc.., fired it and it proceeded to run rough as heck !!! The AFR was super rich in the 9s at 2000rpm?:shock:....So i shut it down wondering what was going on that's when I saw the gas running out the carb...My first carb malfunction !!! Yep, the curse of the opened carb...:lol: I was just in there so now it's going to break ME in...Rather than tap on the bowl hoping it was just the float I pulled the carb again and thoroughly cleaned the carb...There was some corrosion on the carb body{inside the bowl} from sitting since 1990 empty...And some other dislodged "dust" in there...So it had a date with the brush,carb cleaner and blow gun... Put it back together,installed it in record time{I can see where I could get fast at doing that} and it was back to normal and running as good as ever...;thumb;

So in conclusion of this thread I've got the engine tuned for this application using the stock carb...All in all it was a pretty simple having the right guys for oversight and tools to do the job..This should help others having trouble with a lean condition which probably happens a lot in our application if you miss it you want to go rich not lean it'll run too hot...Best advice I can give at this point is tune the engine between the leanest and most rich plug and find a good compromise between the two...The stock carb leaves quite a bit to be desired as everyone has warned me before I went into this thread but I wanted to show what can be done with it...You don't need an AFR meter you can simply read the plugs but the meter sure does help and speeds up the process...

Thanks to everyone involved in this thread...Bobby{Bgmcl60},Bart, Papee and Kent thanks a bunch for the great input and info I think we have some good thoughts and reference material for others...Good luck with those stock carbs everyone !!:lol:...;thumb;