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Mon Oct 26, 2009 3:17 pm

I solved my jumping timing mark by getting an original distributor that works really well. I have my dwell at 45 deg, timing at 7.5 btdc and my bus still runs between 390-435 deg on the DD and it's only 70+ outside. What gives? I have everything, and I mean everything blocked off and sealed up tight. All engine tin, foam seal, even my heater works great cause i made sure things were tight. I'm running a stock muffler set up for the '77 also. Which I heard can increase temps, but come on 435?! This is driving me mad...

Mon Oct 26, 2009 3:51 pm

Where does the timing mark move to when you disconnect both hoses and rev the engine until the mark advances no more? (usually around 3000 rpm).
You did have the tin off and cleaned out the cylinder and oil cooler fins didn't you?

Mon Oct 26, 2009 4:19 pm

Quote: 390-435 deg on the DD and it's only 70+ outside

at what speed and road condition? If you are at 40 straight and level that is too hot. If you are at 70 and flying down the freeway that might be normal (although it is still hot and will shorten the life of the engine).

Mon Oct 26, 2009 5:04 pm

How does you dipstick feel right after a drive? It should be cool or warm to the touch. If it is hot, then your engine is indeed overheating and your DD is working correctly.

My bus was running warm/hot until I replaced the AFM quite by accident. I thought that it was ok (from opening the cover and looking at the tracks) until I swapped it out with a friend who had a new one laying around (he originally bought it thinking that it was the problem with his bus...which it wasn't). Lucky for me, he forgot to return it in time for a refund and sold it to me for a good price. My bus temps went down.

Thare are a variety of things that can cause an engine to get hot...this is just an example how I "fixed" mine.

Mon Oct 26, 2009 5:13 pm

i dont know if it helps, but my CHT gauge was reading way hot. i found out that the sender was VDO and the gauge was a DD. The resistance of the thermocouple is specific for the gauge and sender. in my case i replaced the sender with a DD and reads accurately now. also, how do you have the sender mounted. if any gasses are blowing by the plug you will get faulty readings.

Mon Oct 26, 2009 6:14 pm

New engine, cleaned all tins, painted and all that jazz.

I have no exhaust leaks in the og system, which is a shocker.

Speeds at 55-60mph mainly, and on occasion I'll hit around 63mph but thats when the temps go 430+.

DD CHT with correct sender wiring from DD.

Dip stick is cool to touch, and I can grab it and hold on while removed.

I replaced all vacuum lines with the kit from German Supply.

Got the Dwell/tach everyone was giving me hell for not having.

Timed it all nice and within specs, and its still running hot.

Mon Oct 26, 2009 6:30 pm

make sure the door flaps are opening all the way when it is warm. Also check the air to fuel mixture to be sure it is around 14:1. This is a type 4 motor right?

Mon Oct 26, 2009 7:51 pm

As noted above confirm that it is truly that hot first, then
Have you checked that your Thermostat is opening the air flaps? Or that there isn't like a rats nest at the flaps blocking airflow? I've seen pictures!@!

Mon Oct 26, 2009 8:06 pm

timo78 wrote: As noted above confirm that it is truly that hot first, then
Have you checked that your Thermostat is opening the air flaps? Or that there isn't like a rats nest at the flaps blocking airflow? I've seen pictures!@!

Brand new motor with absolutely NO rats nests. I've had walnuts on my old engine before...

Flaps open correctly with a NOS(not anymore) Thermostat.

Air/fuel mixture not too sure of. I don't own a fancy exhaust sniffer to test this out. Wish I had one, and someone to help me with it.

Mon Oct 26, 2009 8:19 pm

Smurf wrote: Timed it all nice and within specs, and its still running hot.

Whose specs??? 7.5 at idle could be anything at speed if your distributor is more than 6 months old.
You may consider $50 on one of these IR thermometers, what's your new engine worth and can you trust your temp gauge 100%?

Mon Oct 26, 2009 8:25 pm

Loose spark plug at the sender? Maybe an alternative thermometer down there and see if there's a huge difference between it and your installed unit when hot. Is the compartment, Tin, distributor base, etc !HOT! when your gauge is berzerking?

Mon Oct 26, 2009 8:27 pm

busdaddy wrote: Smurf wrote: Timed it all nice and within specs, and its still running hot.

Whose specs??? 7.5 at idle could be anything at speed if your distributor is more than 6 months old.
You may consider $50 on one of these IR thermometers, what's your new engine worth and can you trust your temp gauge 100%?

Within your specs! haha You guys busted my balls for a long time about getting a dwell tach and gave me advice... remember?

What's that thermometer gonna do? I'm guessing you point it at the CH and get the temps like an oven thermometer?

Mon Oct 26, 2009 8:47 pm

timo78 wrote: Loose spark plug at the sender? Maybe an alternative thermometer down there and see if there's a huge difference between it and your installed unit when hot. Is the compartment, Tin, distributor base, etc !HOT! when your gauge is berzerking?

The tin gets pretty hot, but not to the point where I can't touch it. I never tried grabbing the distributor base yet...

Tue Oct 27, 2009 12:20 am

Smurf wrote: Dip stick is cool to touch, and I can grab it and hold on while removed.

Pretty sure it's safe to say it's not running hot if that's possible. I'd say your gauge is kooky.

Tue Oct 27, 2009 2:29 am

SGKent wrote: make sure the door flaps are opening all the way when it is warm. Also check the air to fuel mixture to be sure it is around 14:1. This is a type 4 motor right? 14:1 is a little lean if you ask me, rather go with 13-13.5:1

Are all injectors checked and okay? Are you running stock tires?

Tue Oct 27, 2009 12:08 pm

14:1 is fine under medium-light load and it will also pass smog. Under WOT it will drop to 12.5:1 if the AFM is working correctly. If instead you set it to 13:1 at med-light loads it will drop to 10.5:1 under WOT and that is way too rich. It will wash the oil off your cylinders and cause fouling. We are running 13.9:1/14:1 under medium-light continous loads and there is no O2 left after it goes through the cat so we have just barely used up all the available oxygen it can breathe. You can't get a more perfect burn than that. Any fuel left over unburned will cool the valves but it will cause slow wear on the cylinder walls and cause the cat to wear out sooner if you have one.

Tue Oct 27, 2009 12:11 pm

stock 6ply tires

rebuilt injectors from BD.

I have a lot of condensation coming from the tailpipe during warm-up though... No sure if this has anything to do with air/fuel mixture or not.

Tue Oct 27, 2009 12:17 pm

Did you install the DD using the ring under the spark plug trick? If so, did you cut/grind a little out of the case so that the DD ring would lay flush? If not, the ring would have ovalized when you torqued down your plug and may have caused a small leak around the plug that would jack up the temp readings.

Tue Oct 27, 2009 12:35 pm

That "grab a hold of the dipstick test to see if it is hot" really doesn't work well for a type 4 engine. That is a type 1 thing, so don't worry too much about it.

Make sure the DD sender is installed correctly as stated above.

You are probably running a bit lean. That "laser thermometer" is not going to do you much good when it comes to CHTs though. Those only get important when you are under a big load load and you can see the head at taht point. I have one, it just doesn't do much for CHTs.

Make sure that you are indeed getting full advance out of the distributor when the hoses are removed from the vacuum can and the engine is all wound up. With your timing light hooked up, you will see when the distributor runs out of any additonal mechanical advance it has to offer at about 3500 RPMs or so. The exact RPM really doesn't matter.

Make that point of no further advance to be 28º BTDC on the timing scale. Tighten clamp. Let it loaf back to idle and see where the initial timing falls and then set the idle speed using your dwell tach to ~ 850 RPMs. It should be roughly 7.5º BTDC but don't change it.

Take it for a test drive and see what happens.

Tue Oct 27, 2009 5:06 pm

When I unplug the vacuum on the distributor and rev it up it goes way past the 28deg mark on my timing scale, but then when it idles it goes to 7.5.

So you're telling me my timing is way off then, maybe too far advanced and could be the reason why its running hot?