66-327/350 L79 Cooling

[Rich G.]

I had some work done to rebuild the distributor and replaced the cam and lifters with a stock cam. I did not do the work, so I can't tell you part numbers. The car runs better than it ever did and is perfect except that it gets hotter than it used to when it idles, so I know this has something to do with timing and perhaps the vacuum can which I will have the mechanic check.

But here's the real question for now. While checking temps with the IR gun I get the following readings when the temp gauge reads 210

Top hose is 178

Bottom hose is 181

Bypass hose is 206

Thermostat housing is 192

This is after driving for a while and stopping with the engine idling. The temp was slowly climbing but I think I got the readings fast enough. It will climb to 230 on the gauge if left to idle. Once moving it drops to 210 on the gauge.

Before this work it used to run at 180 and maybe get to 210 after a long idle.

So the question is, do those numbers look reasonable in relation to each other or is there something else up with the bypass being hotter than everything else?

It is a DeWitts radiator that's a few years old.

Thanks

Rich

[Jim R.]

Re: 66-327/350 L79 Cooling

Is your fan clutch working properly?

[Duke W.]

Re: 66-327/350 L79 Cooling

Rebuilt distributor? Was the VAC replaced? What's stamped on the mounting bracket. You may have to remove the cap to see it.

Duke

[Rich G.]

Re: 66-327/350 L79 Cooling

Jim, I think the fan clutch is ok, but I'm not sure how to tell. It does get harder to turn when hot, but I have nothing to compare it to.

Duke, B1 is on the can. I think this was on there before the rebuild. The springs and weights were replaced and it was supposedly curved for this engine. Before, the car would surge at constant rpm. Now it is very smooth and responsive.

Thanks for your responses.

Rich

[John H.]

Re: 66-327/350 L79 Cooling

While checking temps with the IR gun I get the following readings when the temp gauge reads 210

Top hose is 178

Bottom hose is 181

Bypass hose is 206

Thermostat housing is 192

Rich -

The top hose, just above the thermostat housing, is the most reliable source for an I.R. gun "shot" due to the matte surface, and that looks fine; it's not unusual to see the temp gauge read 30* hotter than the actual temperature (typical sending unit calibration error).

The bottom hose reading (181*) looks funky - it should be about 30* lower than the top hose reading; either the I.R. gun isn't close enough to the hose, or it's reading something else in the immediate area.

What's your base timing (vacuum advance disconnected and plugged), and your idle timing (vacuum advance connected)?

[Rich G.]

Re: 66-327/350 L79 Cooling

John

As far as timing goes, I'll have to wait until tomorrow. My timing light is dead and the car was set up by the shop I use. I'll also check that bottom hose temp again. I thought there should be a bigger difference, too.

Another dumb question. The vacuum line is connected to a port at the base of the carb. There is another port higher up on the carb that is capped off. Is the vac line connected in the right place? I know there is ported and non ported but I don't know which is which and which is correct.

Rich

[Duke W.]

Re: 66-327/350 L79 Cooling

Jim, I think the fan clutch is ok, but I'm not sure how to tell. It does get harder to turn when hot, but I have nothing to compare it to.

Duke, B1 is on the can. I think this was on there before the rebuild. The springs and weights were replaced and it was supposedly curved for this engine. Before, the car would surge at constant rpm. Now it is very smooth and responsive.

Thanks for your responses.

Rich

This is likely part of the problem. B1 is a boat anchor. It won't provide full vacuum advance at idle, which is necessary to prevent a hot and unstable idle. You need a B20 or B26. It should be connected to full manifold vacuum. You can determine which port on the carb to use with a vacuum gage.

With 6-12 degrees of initial advance, total idle advance should be in the range of 22-28 degrees, and should pull 14-15" Hg. at about 750.

Duke

[Rich G.]

Re: 66-327/350 L79 Cooling

Duke

Thanks. I will get that done. I was reading the shop manual about moving the base plate by hand to insure it springs back but I couldn't get it to move. The rotor does spring back. In any case, when we change the can we will look at that.

Thanks very much for your help.

Rich

[Rich G.]

Re: 66-327/350 L79 Cooling

Duke

Just checked the vacuum at 750 and it is 14.5 inches. That is the port that the vacuum advance is using. The other port that is capped off had lower vacuum.

When I remove the vacuum line and plug it there seems to be no difference I can perceive in idle. I don't have a timing light, so I can't see if it's doing anything, but perhaps the problem is, it is not working at all. We will dive into this tomorrow.

Also, very odd, but I checked a double checked the temp on the top an bottom hoses and the bottom is only a few degrees cooler, indicating to me the radiator is not radiating so maybe I have a bad fan clutch after all.

Rich

[John H.]

Re: 66-327/350 L79 Cooling

John
The vacuum line is connected to a port at the base of the carb. There is another port higher up on the carb that is capped off. Is the vac line connected in the right place? I know there is ported and non ported but I don't know which is which and which is correct.

Rich

Rich -

What carburetor do you have? You should have a Holley 3367 (unless you have K-19, in which case it should be a 3605), but they only have one distributor vacuum port, in the side of the baseplate, which should be full manifold vacuum. 3367's don't have another port higher up on the carb that can be capped off. Got a photo?

[Rich G.]

Re: 66-327/350 L79 Cooling

John, it is an aftermarket holly with an electric choke. I believe it is 600cfm which I think is smaller than stock 650?

I think I have at least two issues here. One is the vac can and the other is the lack of significant difference between the inlet and out let of the radiator when the car is not moving. Just for grins I did the same test on my 98 Volvo with 130K miles on it and there was at least a 50 degree difference.

More to come tomorrow

Rich

[Timothy B.]

Re: 66-327/350 L79 Cooling

Rich,

You need a vacuum can that's full in at 12" vacuum so the engines 14" vacuum pulls it full at idle. I am not sure about the part #'s Duke quoted, I thought B-22 is a 15" control but I may be wrong.

If you check the archives I am sure the #'s with specs are there.

[Duke W.]

Re: 66-327/350 L79 Cooling

My mistake! I meant a B20 or B26, and I corrected the previous post. The 15" B22 is for base cam engines with manual transmissions.

TWO-INCH RULE: The VAC must deliver full advance at not less than 2" less than typical idle vacuum. If it idles at 14.5" it needs a 12.5" VAC. The B20 and B26 are 12".

The installed B1 is probably frozen and is not advancing with manifold vacuum, and it needs about 18" to fully deploy, anyway, so it's not suited to the idle vacuum of the L-79.

That's why it's overheating at idle!

Duke

[Stuart F.]

Re: 66-327/350 L79 Cooling

Granted, your I.R. numbers don't bear this out, but I recently failed a new thermostat and nearly lost my engine. It was one of those "Mr. Gasket" specials from China that I'd picked up from a local auto parts store. I had heated the engine up past 200* idling in a car show entry line, and after it cooled off the thermostat apparently would not reopen. My bypass got me down the road until I jumped on it and it proceeded to puke out all the coolant through my surge tank (the cap worked as it was supposed to).

I only mention this as a precaution to NOT overlook that little bugger. It can be the source of a lot of cooling system problems. AND, to warn others to stay away from that junk in the fancy packages.

Stu Fox

[Rich G.]

Re: 66-327/350 L79 Cooling

Just an update. Looks like the fan clutch is NG and a new one is coming Friday. I have purchased a B26 vac advance can and that will be done at the same time.

I'll report on the results. Thanks for all the input.

Rich