Some of the other experiments I tried:
1. Fuel line heavily insulated and run along the brake booster support to in front of the radiator wall, then to the carb via the cold air intake openings in the radiator wall. No noticable effect.
2. Trimming away the webbing on the cast iron exhaust manifold. No noticable effect.
3. 1/2"-5/8" thick phenolic spacer. Some improvement.
4. Vent the living crapp out of the hood. No rubber seals, holes and vents everywhere. Some improvement.
5. Electric fuel pumps. They help you "recover" from the problem of the gas boiling away in the carb much better, but don't stop the actual problem of the carb getting so hot that it boils the gas. I think every Opeler should use an electric fuel pump. Turn the key to Run, count to 5, your empty fuel bowl is now refilled, 3 pedal pumps, you can now engage the starter. Works marvelously.
6. Cold air intakes taken to the extreme. I've had the filter all the way up front pressing against the grill, followed by 5'-6' of duct work to the carb. Some improvement.
7. Keeping the engine fan. It is my opinion that keeping the engine fan is essential to helping cool off our hot GT engine compartments. They keep constant air circulation happening. I think it's utter madness to just use an electric fan, especially one on a thermostat that only comes on when your water temp spikes. I use both the engine and an electric fan. The electric one only comes on when the temp goes above 180*. I like the idea of electric fans that run for a while after shut down. Modern cars do this, so there must be a very effective reason to have this feature.
8. Headers and coatings. I've only actually used a Pacesetter header, but I used it for 25 years. This was the time period when I put 200K+ miles on my GT as a daily driver and the car that gave me the the most trouble with heat soak. It was a new big valve 2.0 with a Combo cam and a 32/36, plus an auto tranny. I got stuck countless times after short stops in the parking lots of convenience stores and at gas stations waiting for the carb to cool off and stop boiling my gas as I would try to restart. I think I used a mechanical pump back in those days. In recent years I've used the Sprint style cast iron manifold without the chimney. I trimmed the webbing away on one of them. That seemed to help a little, probably solely because air could flow through that area better. My present set up is a cast iron 2.4 manifold that has been jet coated. I don't think the coating does much of anything. I will soon be running Opel FI with it's freakin' huge manifold and runners. The runners are 3-4 times longer than the runners on a stock intake and the main plenum cylinder is over a foot long and 3" in diameter. It's also elevated almost 12" away from the exhaust and sits almost higher than the valve cover. The ones made for 2.4's are made almost an inch or two taller than the 2.0/2.2 ones that most of us use. Why did Opel opt to make such a huge manifold when they could have very easily made it much more compact and much lower in the engine compartment? I think they were worried about heat soak due to the inherent design deficiency of having the intake and exhaust on the same side of the engine right next to each other. And think about this: The entire FI manifold experiences almost zero fuel passing through it. The injectors are placed just 1" away from the ports in the head. That's the only area that has fuel passing through it. The entire rest of the manifold assembly has nothing but air flowing through it. Why the heck did they make it so BIG? Plenty of guys have installed individual throttle bodies on CIH's with almost no runners and no plenum. I don't recall hearing anyone with FI complaining about heat/fuel issues. Additionally, as related in previous discussions on this subject, you don't hear guys with Mantas and Kadetts complaining about carb boiling. Why? Much bigger radiators and much more spacious engine compartments.
I don't think the Shorty Headers will do a dang thing to reduce heat soak. That's not what they're for. They're so that you can use the stock headpipe and fit more compactly in a GT engine compartment. The previous types of headers had that crappy fitting 4-into-1 union at a custom headpipe union. The Shorties are 4-into-2(I think) at the standard Opel headpipe flange and location, the headpipe then merges the 2 into 1. That said, I think those Shorties are great and I would buy one in 2 seconds(gotta put down my beer first) if I didn't have the set up I currently have.
So, if you read my previous post and what I have said here, you will see why I don't think shields, wraps and coatings, fuel line rerouting, and fancy exhausts have any meaningful effect on carb boiling. What does seem to have the greatest effect is more engine compartment room(ie. engine compartment ventilation), good radiator cooling, and moving the carb as far away as possible from the exhaust.
Keep in mind that almost no one complains about heat soak, vapor lock, and carb boiling while they're driving. The problem occurs after you do a brief shut down after being at full operating temp or when stuck crawling in traffic. What's the difference? Airflow. And that air flow includes the air flowing through the carb. Air through the carb and intake naturally cools the surrounding metal.
Here's another thought: Our water pumps turn very slowly at idle, as do our engine fans. I get to experience getting stuck in traffic on a hot Summer day quite frequently. My bigger(ie. hotter) engine is encased with heat retaining chrome and has a heat retaining cast iron manifold, plus my engine compartment is congested with lots of extra junk. Parked in traffic, I get to watch my temperature gauge needle creep up into the danger zone quite often. Then I start to experience the precursors to vapor lock start to happen. The solution? Put the car in Neutral and keep the engine rev'd at 1500, instead of the 800 that the auto tranny forces it to stay at. Zooom! You can watch the temperature drop almost immediately. Need more cooling? Turn on the heater. Another 10-15% of cooling(and sweating your azz off in your car). My auto tranny is on a separate too large tranny cooler, so my auto tranny probably isn't the cause of water temp spikes. I also have a 3-core radaitor. Just reving the engine to 1500 dramatically reduces my car's engine temp. Why? I attribute it to my engine fan swirling the air, more cooling air flowing through the carb, and the water pump circulating the water through the system faster.
The above is what has worked for me while stuck in traffic. As far as boil off after shut down, yes, it still happens. But since I switched to side drafts there for a while, that problem diminished, probably due to the fuel bowls in the carbs being twice as big. I've been using electric pumps for 10 years now, so I can easily refill the fuel bowl before restarting. Just wait 5 seconds.
I'm quite intrigued about the concept of adding a fan to blow on the carb after shut down. Previous discussions have revealed that some cars with intakes/exhausts on the same side of the engine came from the factory with engine off carb cooling fans. So why can't we have carb cooling fans? Space is the big problem. Where ya gonna put it? There's not much room in that area. I've never heard of anyone doing a carb fan mod, but I'd love to hear the results from someone who has actually done it.
:veryhappy