THermo-tec products as heat protection to avoid percolation under hood

[Mark Maras]

 I too, have pondered the why some do and some don't. The earlier the Z the less chance of heat soak, it would seem. Could it be that one of the larger puzzle pieces that is almost ignored is the fan. The heat soak problem happens in traffic (low to no speed), idling, and after shut-down, all in hot weather. It never happens at speed. At least if the engine is near stock. (the cooling system doesn't even need a fan at anything over about ten mph) So my line of thought is fan clutches. The resistance in them is all over the place, with varying ways of testing them. Personally, I've thought they sucked (definitely no pun intended) from the first time I owned one. I was never convinced that they were very efficient at pulling air, depending, of course, on how much resistance they had. A fan shroud would definitely help the alleviate the problem too, IMO.

 When the fan clutch froze up on my early 71 (metal fan), it sounded like a Cessna throttling up and it felt like the engine was down on power about 25%. Since I had a lousy opinion about the fan clutch to say nothing of the weight of that steel fan, I bought a flex fan with an extension. Previously I hadn't experienced drastic over heating. The temp would go up a bit in traffic. No heat soak problem. The flex fan did pull more air at idle. The temp didn't go up quite as high in traffic as before and it seemed like the engine revved faster. Probably because I dumped the boat anchor steel fan. The fan has to be a key element since it's job is not only to cool the internals of the engine but the externals too. BTW, If anyone with heat soak and is desperate enough, I have that flex fan set-up which could be borrowed to see what difference it makes, if any. 

[siteunseen]

I tried putting a 5 blade zx fan on my 240 but it's offset is too different. I have a 280z radiator and two piece full shroud of a zx.  Another thought is the splash pan. One of those and a good fan clutch pulls air like crazy sitting in my garage but once I get on the road I wouldn't expect it to help that much. 

Hang in there Mark and maybe you'll figure out his problem?

He bought a California Datsun motor if I remember right. That dude would sale me garbage and I would make the trip to settle any issues I couldn't get satisfied. Just think how he would treat someone from South America?

[siteunseen]

Mark do you not think if the floats are set and the valves working properly there would be a consistent flow of fuel circulating through the return line function of the fuel system?  No fuel staying still long enough to "percolate"?  That's my common sense thinking but that usually don't mean squat.

Once again I'm done but am trying to help you figure something out.  I've got a slab of beef ribs, a bone in ribeye plus two quarter dark meat chickens. 24 frosty bottles of beer and a booty call coming by later, after I do all the coking of course.  Girls without kids don't cook but they make up for it in other ways. 

Hope to post in the morning, if not I'm dead from exhaustion or in jail. I can see it going either way.

Edited July 2, 2017 by siteunseen

[Mark Maras]

2 hours ago, siteunseen said:

Mark do you not think if the floats are set and the valves working properly there would be a consistent flow of fuel circulating through the return line function of the fuel system?  No fuel staying still long enough to "percolate"?  That's my common sense thinking but that usually don't mean squat.

Once again I'm done but am trying to help you figure something out.  I've got a slab of beef ribs, a bone in ribeye plus two quarter dark meat chickens. 24 frosty bottles of beer and a booty call coming by later, after I do all the coking of course.  Girls without kids don't cook but they make up for it in other ways. 

Hope to post in the morning, if not I'm dead from exhaustion or in jail. I can see it going either way.

 I do think that's how it's supposed to work, in theory, but what if, when the engine isn't under a load and not using much fuel, the valve doesn't allow enough fuel to return. Now I wonder what, if any, change has anyone had when they removed the valve but kept the return line? Can anyone enlighten me on the purpose of the valve in the return line? Is it just a Miss Tilly's Orfice in the return line?

 I too am working on a slab of St Louis cut pork ribs. BTW, you left an o out of cooking, Freudian slip? Stay safe, in all ways.

[siteunseen]

Maybe that wasn't a mistake? Young girls like the coking. 

KIDDING EVERYBODY, THOSE DAYS ARE IN PAST!  Pablo is dead.

[Patcon]

23 hours ago, siteunseen said:

KIDDING EVERYBODY, THOSE DAYS ARE IN PAST!

Yes, yes. That is a dangerous place to live...

[siteunseen]

No regrets but my doctor doesn't agree with my youth. We have a new plan for aging Cliff and believe it or not he says beer is good for my health?  No driving though but I have a pretty neat house with plenty of company, no need to leave other than zcon. 

[Redwing]

On 7/2/2017 at 8:29 PM, Mark Maras said:

 BTW, If anyone with heat soak and is desperate enough, I have that flex fan set-up which could be borrowed to see what difference it makes, if any. 

Mark,

Is this the problem where one symptom is the large whooshing when the gas cap is opened?   Redbird has now resumed that problem since summer is here, along with slow response re-starting in the heat.   Are these involved with the heat soak?   If RB ramps up her past problems of stalling and not wanting to re-start, I might be interested in the fan set up you have.  So far it is not that bad.  Not sure what will show up when it gets horribly hot here.

Oh, BTW, the second trip to Pete for A/C work, he found something that was loose and fixed it, as well as adding freon with dye.  So far no leaking out, and a crisp coolness surrounds me as I drive.  Love it!

Jai

Edited July 4, 2017 by Redwing

[Mark Maras]

 @Redwing  I don't know much about the whooshing sound from the tank. When you loosen the cap, is the whooshing excess pressure (positive pressure) in the tank or does it seem like a vacuum (negative pressure)?

 Anyone, Was the 76 gas cap supposed to be vented? Is the whooshing sound normal?

 The hard start symptoms are typical of a minor? heat soak problem. Interesting that Redbird only has a small problem with it considering the 76 doesn't have hood vents.

 You could try cracking the hood when shutting the engine off to see if venting the heat will help it start faster. If you definitely want to try the flex fan let me know and I'll ship it to you. Relatively easy to install. Just four bolts.

 Congrats on getting the AC working. Z's can be brutal in hot weather.

[jalexquijano]

Even though i have already wrapped both of my heat shield extensions with thermotec adhesive i am still experimenting heat soak/ fuel percolation during long idles at traffic jams. Would wrapping the intake which faces the manifold help this problem in some better way? The fan blower does not blow enough air to flush that kind of heat that concentrates under the hood. I already ran out of the thermotec product as i already used it with bothe heat shield extensions and wanted your opinion before ordering more material.

[Patcon]

Did you ever try rubber fuel lines or running with the hood popped open? You need to identify a solution then make it pretty!

[siteunseen]

That would be less chaotic. No fun!

Liked I said three years ago, Camry or an Accord.