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Fri Nov 06, 2020 9:49 am

Thanks Orwell. I try to list specific details so folks can know the conditions under which things operate. When it was 100+ degrees a few weeks back I did some tests and noticed that CHTs we're about 330-340* which is about 10 degrees higher than what they normally are on the highway and around town low 300s.. but I didn't push it too hard cuz of the hot weather... Makes sense.

THall - CHT sender is the standard Dakota Digital sender ring and is installed under the #3 plug but sandwiched between the plug base and sealing ring/gasket. After reading Clatter's Cheap, junk, engine build thread I followed his advice and ground out a slot in the head so the sender unit could sit mostly flat. From there, the wires exit out the little temp sender hole in the cooling tin where I just cut a small slot in a new rubber flat grommet/plug and it seals well. If you don't have a hole, you can drill one about 1/2 - 3/4", clean up the burrs and Amazon has a kit of various size grommets, flat rubber plugs, and such that will fit about every unused hole in the tins you can find.

Mikey

Fri Nov 06, 2020 10:41 am

Mikey, sounds like it’s ready for shakedown testing in the Sierra’s. Great job!

Fri Nov 06, 2020 5:45 pm

I'll be in the back yard doing more Black Ops this weekend, but it's supposed to rain.. :(
Let me know if you want to put on a wideband..

Those CHTs seem really low.
370 is normal highway temps in my world; cool air, mild hills, by the ocean.
When I'm a bit too lean/clean, some 400+ temps will be seen.
Also like that pulling deep into the sierras in summer..
425 is the 'too hot' number for heads. Maybe 435.

Once you get to pulling loaded clear up 80 to Truckee, you'll see what the numbers are. :wink:

On huge pulls like that, don't be shy about gearing down.
Leaning hard into 4th gear with a heavy foot pulling speed kills these motors.
Gear down, spin the shit out of it - more fan air, more oil flow.
Your foot will go from 3/4 throttle to around a third..
Spin it, spin it.. Let the racing truck douchebags go around.
The dipshit derby will always be there, nice tight valve seats, not so much..
Fuckers got brakes!
:D

Fri Nov 06, 2020 6:40 pm

Thanks all.

The only thing that keeps me somewhat skeptical is that damn, occasional, very faint "knock" sound. It seriously sounds like if you take a piston pin in one hand and just tap it against the top of a piston in the other hand.

It's not constant, it's very faint, but it's the thing that's playing with my head saying "dude.. something ain't right". And it's been there since the beginning but has gotten no better or worse. I'm hoping I didn't jack something up in the build or overlook a tolerance or something. The only thing I can think of is it sounds like a piston rocking in the bore? Occasionally? Don't know if I need thicker oil, a Shaman... no idea. But it runs great, and that sound is not always there. I have enough confidence in it (thus far) to drive it long distances - like to Clatter's pad so he can tell me what the hell I fu&!ed up. Just can't figure out what that damn sound is.

The carbs are adjusted to 1/8ish turn past lean, best idle, it's not a timing knock, the cam gear and bolts are from the Type 4 store so no oil pump clearance issues - all red locktited' in, I have the spacer/pully behind the fan, and it sounds too deep to be a valve train thing but who knows. Again, it happens every now and then.

Anyway.. all that said.. back to happiness... I think I'm going to dump this 10W30 oil at 1600 miles and put in 10W40 high zinc just to see if it makes a difference.

Mikey

Sat Nov 07, 2020 6:35 am

Clatter wrote: Those CHTs seem really low.
370 is normal highway temps in my world

Yeah, that's why I asked how he has the CHT sensor mounted. I also see between 360-380 typically on the highway.

He has the CHT ring terminal between the crush washer and the plug base. I delete the plug washer. That may be the reason?

Sat Nov 07, 2020 9:05 am

In my experience.....425°F to 435°F.....is NOT.....the START of the "too hot" for heads range.....with anything below it being fine.

Right at 400° is already too hot.....but not critical.....DEPENDING .....on how often it goes there and more importantly..... how long it stays there. Having SHORT excursions of higher than steady running state temperature.....say to 400 and maybe up to 435...... when climbing a hill or accelerating up to highway speed in a ramp.....is normal.

Meaning high peak temps for a minute or two....cycling up....and then back to the normal steady state range.

But having constant steady state head temps of right at 400.....is not normal and not good.

Notice I said "not normal"......I said nothing about "common".

It is dead on true.....that the stock variants of the type 4 engines used in BUSES.....run a little hotter than those used in type 4 cars. But about 385°F should be best running range with quick peaks to 400-410-ish.

But....I fully agree. Your CHT readings.....are too low....even for a type 4 "car"....much less a bus.....especially as you note....staying steady like they were.

With a TC.....just reminding everyone.....the temperature "read point" is right at the welded bead of the two wires.....crimped into the barrel of the copper ring.

One of the common problems with this type of thermocouple sensor rings.....that can cause "unnaturally" low or uniform readings......is that the little weld bead can be crimped either too far from the inner end of the barrel crimp.....meaning too far from the hottest point.

Or.....as I think clatter mentioned.....if the barrel crimp is standing up at an angle and not FIRMLY in contact with the metal of the head.....it can read unnaturally low and stable.

Or.....and this is TOO common......the little weld bead/junction can be crimped into the barrel area.....with too low of crimping force.....so its not in hard contact with the copper.

I see the last one too often because those who are making these are afraid of "over crimping" the bead and cracking it.....which is also a not uncommon issue.

So what happens is that the crimping "SEEMS" very firm because its holding the WIRES very tightly toward the outside end of the crimp.....but in actuallity the hot junction bead itself is kind of floating inside of the crimp barrel. This gjves unnaturally low and stable temps.

Conversely....over crimping ....and you really have to get brutal for this ti happen.....cracks but does not fully seperate the weld bead. This causes intermittent operation at ceryain temp ranges due to expansion and eventually will cause a total failure.

When re-crimping with a GOOD adjustable crimper....first check the temp reading on a stable temp source....double checked with another TC of the same type.....then set the crimper force to basically 0.....crimp....release....check. adjust to somewhere between 0 and 1 (remove the lock screw to do in between settings)....crimp again.....check and repeat.

You can see and measure with a caliper if you are actually further compacting the crimp barrel of the ring. If you can compact it about 20% max and see no reading change.....you are good and that was not the issue.

Ray

Sat Nov 07, 2020 9:27 am

Mikey, my dumb ass was thinking exactly what clatter, Ray, and THall are thinking. I’m just not experienced enough to offer up that kind of information. I do believe you need to pack it up and take a real life road trip for more testing.

Sat Nov 07, 2020 11:54 am

a typical T4 bus engine reading #3 will be around 350F at idle or coast coming off the freeway, or 400F - 420F most of the time. It will rise if the bus is pushed over 70 mph. Someone who monitors temps in a 411/412 / 914 /912e will have a completely different experience. Bus engines cook compared to those.

I don't use the crush washer either because I found it pushes the CHT sender ring outwards and can cause it to leak. Over several plug changes the sender will get oval.

Sat Nov 07, 2020 12:01 pm

Hmmmm... very interesting. Thanks for the input. I have the old thermocouple ring that is a bit ovaled which did give higher readings but I figured it may have been because of the mouse nest between cyl 3&4. But I think I can straighten it out enough to where I would be able to install it for comparison sake.

Sat Nov 07, 2020 12:23 pm

MikeyM73 wrote: Hmmmm... very interesting. Thanks for the input. I have the old thermocouple ring that is a bit ovaled which did give higher readings but I figured it may have been because of the mouse nest between cyl 3&4. But I think I can straighten it out enough to where I would be able to install it for comparison sake.

when they oval they leak a little, and the exhaust leakage makes the reading higher.

Sat Nov 07, 2020 2:02 pm

Well shoot, now you guys have me all concerned and stuff. I guess I’ll install the old temperature sender just for giggles Temporarily to see if there’s any difference. Although… Could it not be possible that those temperatures are accurate? I remember Zed999, way back in the day, when he built his Frankenstein 103 mm piston/stock 2 L stroke engine with a stock cam and stock heads, his temperature never touched 300. But I think he is overseas, if I’m not mistaken, where it never really gets hot anyway. Just wondering

Sun Nov 08, 2020 8:25 am

MikeyM73 wrote: Well shoot, now you guys have me all concerned and stuff. I guess I’ll install the old temperature sender just for giggles Temporarily to see if there’s any difference. Although… Could it not be possible that those temperatures are accurate? I remember Zed999, way back in the day, when he built his Frankenstein 103 mm piston/stock 2 L stroke engine with a stock cam and stock heads, his temperature never touched 300. But I think he is overseas, if I’m not mistaken, where it never really gets hot anyway. Just wondering

They "might" be accurate.....but doubtful. Also.....do NOT go swapping parts around lookimg for a different answer. First.....do a little testing of the sensor you have and the quality of its mounting. You can do that on the workbench.

Prove that the CHT thermocouple you have in there now works right.

If your CHT is using a "thermocouple"....and not a "thermistor".....and they are the same type and have the same type of ring terminal crimped on......then both your old and new sensor should be reading within 1% of each other.

And......when testing your TC's......leave the gauge out of this for the moment. This is about testing the thermocouples FIRST. Use a VOLTMETER.....since virtually all voltmeters that read temperature with a TC...are cold junction compensated on the circuitboard.

So depending on what the plug or connector type is on the gauge end of the TC....get the proper adapter to plug it into a decent quality voltmeter. Then put BOTH TC's into your heated test liquid.
Plug one TC into the temperature point of the TC. Read the temp. Write it down. Immediately unplug that TC and plug in the other one. Write it down.

As the liquid cools or heats.....keep swapping TC plugs and writing down the readings.

Very shortly you will have a comparative list of how accurate the TC's are to each other or at all. These should be very close.

NOW......this is only a gross BASIC comparison of the THERMOCOUPLE function of each one. It does not tell you how good the crimping on the ring terminal is or what level of change you might get from mounting under the sparkplug.

See......the liquid is a full all around temperature immersion. It takes issues with the ring terminal crimping, proximity to the spark plug or airflow around sparkplug and ring terminal......out of the picture.
I suggest doing this test anyway.......because its dead simple and takes minutes.....and proves that the TC itself.....is functioning, is not shorted upstream and does not have a cracked weld bead.

For a more accurate test.....take a piece of steel or aluminum....drill two holes the size of your spark plugs.....tap them for bolts (or sparkplugs if you want).....and bolt both TC's to it. Place the metal piece in the liquid bath.....but not submerged. Make sure the top with the ring terminals and bolts....is dry. Bring it up to a high temp......oil works better here than water.....and repeat the test above.

This generally reveals any crimping issues. Ray

Sun Nov 08, 2020 5:38 pm

Just wait til you put an oil pressure gauge in there. That is also it’s very own field of study.

Sun Nov 08, 2020 9:40 pm

Pull the terminal ring out from under the plug.
Get a pot of boiling water and run it underneath your bus.
Dunk the sender in the boiling water plugged in to your gauge and see what you got.

This is the best way to test the actual wiring, gauge, sender, everything.

Water boils at 212F near seal level no matter what brand of gauge you are using. :wink:

While it might be accurate at 212 and wrong at 400, it will tell you something.

FWIW, i have seen a better cam make a decent difference in CHTs.
A dual-pattern cam and header can make it so 400 is pretty rare in normal highway driving.

Hard to give an exact number,
but i can run 65-70 or so on most normal hills around here on the highway around 370.
Bigger local hills pulling hard go up almost to 400.
Fully loaded with the whole fam damily in July over Donner pass,
it's either 425-435, gearing way down, leaving at dawn, or taking breaks to let things cool..
I'm convinced that if anyone tried to just pull Donner pass WFO on a hot day, (like so many have done, no doubt) they would be doing 25MPH in 2nd gear because their heads were at 260+ and the thing was just sick and frying itself.

My point is that it depends upon your driving conditions..

And you never really know what your numbers really are just using a gauge.
:?

Sun Nov 08, 2020 9:58 pm

Clatter wrote: Pull the terminal ring out from under the plug.
Get a pot of boiling water and run it underneath your bus.
Dunk the sender in the boiling water plugged in to your gauge and see what you got.

This is the best way to test the actual wiring, gauge, sender, everything.

Water boils at 212F near seal level no matter what brand of gauge you are using. :wink:

While it might be accurate at 212 and wrong at 400, it will tell you something.

FWIW, i have seen a better cam make a decent difference in CHTs.
A dual-pattern cam and header can make it so 400 is pretty rare in normal highway driving.

Hard to give an exact number,
but i can run 65-70 or so on most normal hills around here on the highway around 370.
Bigger local hills pulling hard go up almost to 400.
Fully loaded with the whole fam damily in July over Donner pass,
it's either 425-435, gearing way down, leaving at dawn, or taking breaks to let things cool..
I'm convinced that if anyone tried to just pull Donner pass WFO on a hot day, (like so many have done, no doubt) they would be doing 25MPH in 2nd gear because their heads were at 260+ and the thing was just sick and frying itself.

My point is that it depends upon your driving conditions..

And you never really know what your numbers really are just using a gauge.
:? we are somewhere around 415F heads and 250F oil in sump pulling any of the Sierra grades in hot weather. We have a 7 passenger so it is a lighter than a camper although we are always loaded. Winter runs are considerably cooler on the heads and oil. It has gotten up to 105F -108F ambient when we are on the highway but we try to travel in the morning on those days.

I would not stress too much over temps. The gauges mostly are for trending.

Mon Nov 23, 2020 7:57 pm

Good Lord. 415 is smokin. Ok so I've managed to run a series of tests that I think are valid but need input/reviewing/verification/and or constructive criticism but here goes:

Boiling water test.. measured with brewing thermometer to verify and CHT sender/ring submerged in a small pot of boiling water with ignition key on (like... live, on a camp stove under the bus, boiling, with the ring/crimp guy immersed through the foam engine bay seal, straight down into the pot of lightly boiling water). When the pot boiled, the gauge read between 211-213*. The only thing I can think of is that the thermocouple is in the airflow. BUT, installed, the crimp point it is touching the head and from the looks of it, it seems to be in the perfect location.

Again, I did make damn sure that every orifice was sealed... even overly sealed, I polished both the inside of the fan shroud and every fan blade baby butt smooth and did spend a lot of time ensuring that there was minimal, if any, light between the cooling system and the outside engine bay. My temps seem to be 275-295ish at idle, now that we're in cool temps, but I can get them to 340-350 if I push it on the freeway. I guess I need to find a LOOOOOOOOONG grade to really put it to the acid test.

Guys, All I want is for the temps to be accurate. And come to think of it, I have not yet pulled a 5+ mile grade at speed.

Advice?

Thanks,
Mikey.

Tue Nov 24, 2020 12:29 am

depends on outside air temps, depends on mixture, depends on when the burn completes. With an 1800 the head temps should be lower than with a 2L. You are combining 10% less fuel and air.

Tue Nov 24, 2020 5:02 am

http://thesensorconnection.com/cht-sensors/all-cht...d-14-mm-id
These are well built, they have type K also.

Tue Dec 01, 2020 4:35 pm

orwell84 wrote: Just wait til you put an oil pressure gauge in there. That is also it’s very own field of study.

Lovely. What have your experiences been in that respect? I ask because I have a VDO pressure gauge, just need to buy a sender and I'd like to get a temp gauge, as well and will do the brake hose / grease gun line setup for the pressure gauge. The temp gauge I think I might just install in the pressure relief locations since I don't really want to spend 50 bucks on a custom, hi-performance, billet aluminum, supercharged, taco plate from the UK. But I will if'n I really have to :).

Thanks,
Mikey

Tue Dec 01, 2020 4:43 pm

MikeyM73 wrote: orwell84 wrote: Just wait til you put an oil pressure gauge in there. That is also it’s very own field of study.

Lovely. What have your experiences been in that respect? I ask because I have a VDO pressure gauge, just need to buy a sender and I'd like to get a temp gauge, as well and will do the brake hose / grease gun line setup for the pressure gauge. The temp gauge I think I might just install in the pressure relief locations since I don't really want to spend 50 bucks on a custom, hi-performance, billet aluminum, supercharged, taco plate from the UK. But I will if'n I really have to :).

Thanks,
Mikey

You can drill a hole in the taco plate in the correct spot and weld a nut on the back to hold the sender. The main difference is that you get a little more sump oil temp at the taco plate than the pressure area. But in either case the temps are really for trending more than an actual oil temp.