Dakota Digital CHT gauge installed.

[MikeyM73]

Hi all, happy ho hos, Merry Kwanza, happy Kahuna, etc. So I got my DD CHT guage installed and it went pretty smoothly but I'd appreciate some input / feedback on my temp readings under various conditions. I used the ring thermocouple under plug #3. After all is warmed up it seems that my operating CHT temp at idle is about 315-325*. All cylinder tins are in place but there are 1-2 unplugged holes and I'm missing the alternator "seal" - the ring looking one that goes under the alternator tin. If I let it sit and idle for 5-10 mins, it creeps up very slowly to 330-335. I tested it under various loads, hills, full throttle, light throttle, etc. and my readings are as follows:

Idle:
Above

Around town:
Normal driving between 0 and 40 mph, moderate and heavy acceleration, temps stay right about 330-350*. Cruising at 3000 rpm in 3rd - about the same. At times if I hang in 3rd at around 3500 rpm for a while temps go up but not over 350*... in town. Then back down to 330-340. Hills in 3rd seem to make the temp creep up to around 360 but then they quickly come down upon deceleration.

Freeway:
This is what I really wanted to see.
60 mph @ 3500 rpm is about 350-360ish. It will usually stay around that range.
65-70 mph @ 3750-4000 rpm for a sustained run of about 7 miles, relatively flat ground, showed 360-375* but would start creeping up to about 380/390* which caused me to let off a bit and then temps went back down to about 370/375. At NO time did it ever get above 400 (which is where I set the flashing to start) but it was close. I was hoping that a sustained 375* at 3600-4000 would be acceptable.

Full throttle acceleration on the freeway from 60-80/85 showed a very slow temp increase from about 350 to 380* but once I leveled off around 70/75 mph, temps started to creep up past 390*. I then let off to 65 and temps went back down.

So.. there you go.. my newbie report. I'm wondering if my primary main is a bit too lean. My timing is about 45* total advance with the dizzy VA hose on - Pertonix dizzy. If I increase the primary main jet, I would suspect temps to go down a bit but I think I'll do some more testing and see if I can get multiple baselines.

Anyone have any input or feedback? I think I know the general consensus would be the numbers look ok around town but highway driving, to me, seems to be a little to hot. What is the general consensus of a sustained CHT on the highway? How much is too much to sustain?

PS - I have read many CHT threads and they have good, helpful info so just trying to see where I fit in in all that fun.

Thanks for your time,
Mikey
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'73 Pop-top Westy, found sitting in a field for 10+ years, cleaned up, rebuilt furniture, reloved. Original 1.7 block/fully polished crank, 93mm 1.8L balanced AA pistons & cylinders, new 1.8L balanced rods, HAM 42/36 heads, Scat C25 cam & lubalobe lifters, Dual HPMX40s, R2C filters w/ Outerwears pre-filters, functioning thermostat & flaps, Pertronix Flamethrower III, 4-1 exhaust w/ Cherry Bomb 2" turbo muffler & OEM heater boxes, averages about 19-22ish on the highway.

[orwell84]

That’s roughly what I get except my CHT’s tend to stay around 375 and not usually creep up, though I suppose they might at sustained speeds of 70-75. I keep it around 60-65 which keeps CHT’s, oil temp, oil pressure and me...all in comfortable ranges.

I have been running a single progressive out of the box, so I don’t know how it compares with your jetting. I think mine is running rich. I also run a Webcam 73 grind which is supposed to help with CHT’s at higher speed.

I also ran a shitty GEX engine for many years with only an oil temp and often flogged it at 70 plus with no ill effects on the heads.

[Gregg in the 603]

Your highway CHT's are normal. I run 390 at 65mph all day long. If I break 410-ish, I'll dial in some OHMs but that's increasingly rare now that my motor is fully broke in. I don't touch that dial much at all these days.
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1979 Mexico Beige Westy auto
Dirty Dover, NH

[MikeyM73]

Thanks guys, really appreciate the replies. Greg… What are you referring to when you say “dial in ohms“?

I think over the next few days I will finally get off my ass and fab up a alternator “seal“ in the hopes that I might be able to drop CHT‘s another 5 to 8°, at higher speeds. Also, after a couple more high speed extended freeway runs, I might increase my primary main jet one size and see how that compares.

Thanks again,
Mikey
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'73 Pop-top Westy, found sitting in a field for 10+ years, cleaned up, rebuilt furniture, reloved. Original 1.7 block/fully polished crank, 93mm 1.8L balanced AA pistons & cylinders, new 1.8L balanced rods, HAM 42/36 heads, Scat C25 cam & lubalobe lifters, Dual HPMX40s, R2C filters w/ Outerwears pre-filters, functioning thermostat & flaps, Pertronix Flamethrower III, 4-1 exhaust w/ Cherry Bomb 2" turbo muffler & OEM heater boxes, averages about 19-22ish on the highway.

[MikeyM73]

Well, after a bunch of high speed tests I went up from a 145 primary main to a 150 and didn't notice much change in CHT temps @ 65-70. In fact, I hit 400* once and had to back off a bit. Air temps are bit warmer today by about 6 degrees so not sure if that made a difference. I would have thought that going up one jet size might have helped... oh well. My timing is set to 45* total advance but settles back down to about 4* at idle. I don't think I want to advance the timing any more than it already is for obvious reasons.

So other than maybe installing that alternator "seal", anyone have any input on how to bring highway temps down some? For the most part, all is well. Around town in 3rd gear and in 4th, under 45 mph, temps stay under 330. It's only on the highway above 65 that temps start to creep up. at 63 mph, level, for about 4 miles, the temp sits right at 367*.

Thanks,
Mikey
_________________
'73 Pop-top Westy, found sitting in a field for 10+ years, cleaned up, rebuilt furniture, reloved. Original 1.7 block/fully polished crank, 93mm 1.8L balanced AA pistons & cylinders, new 1.8L balanced rods, HAM 42/36 heads, Scat C25 cam & lubalobe lifters, Dual HPMX40s, R2C filters w/ Outerwears pre-filters, functioning thermostat & flaps, Pertronix Flamethrower III, 4-1 exhaust w/ Cherry Bomb 2" turbo muffler & OEM heater boxes, averages about 19-22ish on the highway.

[airkooledchris]

when someone says “dial in ohms“ - they are referring to a trick you can do with Fuel Injected systems to dial in a richer mixture from the drivers seat. It's a really great mod for those who want to be able to control your mixture while driving. If your carbed, just ignore that.

Honestly your numbers sound fantastic. I wouldn't go messing with it at all. From the factory it ran hotter than what you have now.

[MikeyM73]

Ahh.. thanks Chris. So I do have a parts bus that's a '78 FI with all the components there... they're just old, crusty, and in need of full refurbishment. But that's for another discussion, I guess. So maybe I'm over-reaching but ultimately, I'd like to just get this thing to sit at 375-380 * sustained on level ground @ 65 mph. IF I can achieve that, I'd be completely happy. I'd be giddy as a clam (some clams are giddy) if I can hold 70 mph and stay at or under 390.

Granted, the RPMs at 70 are 4k but the balance is good and it still has plenty of throttle left. I wouldn't want to sustain that rpm for long and I do realize that these buses aren't speed demons but it would be nice to continue doing subtle mods that make them as driveable for today's real world as possible while keeping the reliability solid.. aka, good oil temps and CHTs.

By the way.. does any know... or is there an accepted "up to" safe, sustained, operating CHT for the type 4 engines? I've read many a post only to find suggested ranges, etc. If that's it so be it. Just curious.

Thanks,
Mikey
_________________
'73 Pop-top Westy, found sitting in a field for 10+ years, cleaned up, rebuilt furniture, reloved. Original 1.7 block/fully polished crank, 93mm 1.8L balanced AA pistons & cylinders, new 1.8L balanced rods, HAM 42/36 heads, Scat C25 cam & lubalobe lifters, Dual HPMX40s, R2C filters w/ Outerwears pre-filters, functioning thermostat & flaps, Pertronix Flamethrower III, 4-1 exhaust w/ Cherry Bomb 2" turbo muffler & OEM heater boxes, averages about 19-22ish on the highway.

[orwell84]

How are you timing your engine? Maximum timing should be set at 28-30* @ 3500 rpm with vacuum hoses off. 45* is way advanced. If you are checking your timing with vacuum hoses on, I think it’s normal for it to advance that much but check with hoses off.

[my59]

Ambient temperature makes a huge difference. When it's in the 90's, 60 on the highway results in 390 or so.
When it's in the 30's, I can run 80 on the highway at 390.
Timing also makes a difference; instead of 32 degrees I tried 28 and it dropped the running temp 5 to 10 degrees.
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my59: Well son, my grandfather died before I got to drive it, so does that answer your question?
our79: sunroof bus w/camper interior and 2.0 FI
Other:'12 Jetta, '77 Benz 300D, and a 74 MG Midget.

[Amskeptic]

[orwell84]

I think the best thing you can do is make sure every little piece of tin, seal, weirdo metric grommet, whatever is in place. It all contributes something, but beyond something big obviously missing it's hard to tell how much. It's usually kind of a cumulative effect and there never seems to be one particular thing that suddenly makes all the gauges behave as you think they should. Proper timing, valve adjustments, a well sealed intake and exhaust...you get the idea.

Gauge readings can be an endless source of worry because they are all over the place depending on air temp, driving conditions, etc and because that's how aircooled VW's run. Driving to work on an early summer morning gives me a totally different gauge reading experience from driving home again in the afternoon. By mid October, I can't get a good gauge swordfight going no matter how I drive.

If you have a well built, rock solid engine with a known history, I think you can feel more confident driving at higher speeds. Because I don't have such an engine, I prefer to drive slower...in the 60-65 range. From a functional perspective, I'm not really getting where I want to be all that much later and it is a more enjoyable drive. I don't like high speed highway driving anyway, especially when I'm on vacation in my bus.

[MikeyM73]

Good points and good info, thanks. So per your earlier question, the total, all in advanced timing is 45* with the VA hose connected. When I initially timed it, I did it per the standard - VA hose off, pluged, about 30* @ 3k RPM. Blipping the throttle lightly would make it advance as far as it would and that was right about 30*. That resulted in static timing landing right about 6* BTDC or so, then with the VA hose connected, about 45* tops.

Yea, I agree with you on a cumulative effort of all the parts, seals, etc. I think I'm happy with it as-is because it simply says that I'm seeing pretty much what you guys are. The engine, itself, is in fair shape. It''s old and tired but doesn't shake, it idles smooth, etc. I think I'm a little low on compression on one cylinder but for what it's worth I have plenty of freeway power so it's good.

Thanks all,
Mikey
_________________
'73 Pop-top Westy, found sitting in a field for 10+ years, cleaned up, rebuilt furniture, reloved. Original 1.7 block/fully polished crank, 93mm 1.8L balanced AA pistons & cylinders, new 1.8L balanced rods, HAM 42/36 heads, Scat C25 cam & lubalobe lifters, Dual HPMX40s, R2C filters w/ Outerwears pre-filters, functioning thermostat & flaps, Pertronix Flamethrower III, 4-1 exhaust w/ Cherry Bomb 2" turbo muffler & OEM heater boxes, averages about 19-22ish on the highway.

[FLUX]

Have to bring this post back from the dead. I recently installed a Dakota digital head temp gauge on my 71' bus and it reads horribly slow. My oil temp changes faster than the gauge does. Plus I haven't seen the gauge go above 90 degrees F. I doubled checked all my connections and all checked out fine. Checked my grounds and they are good. Double checked the gauge setting and it is set to Fahrenheit not Celsius. I am curious if I have the wrong sender setup. I bought the 14mm spark plug sender with 18 foot cable which I thought was supposed to be one piece, but the spark plug sender only has a six inch reach and then two eyelets to connect the rest of the harness to with little screws and nuts. Is this what you guys are using? Thank you, any help is appreciated!

[SGKent]

[FLUX]

Yes that cylinder is 100% firing.

[SGKent]

[FLUX]

Found the problem. Wires were reversed. News to me that you can hook up a thermocouple backwards! Working great now.

[ac78]

[Randy in Maine]

224º F sounds pretty low. Mine is set to about 400º F to flash.

[ac78]