Overheating Help

[Snoopy1971]

Decided to remove my oil pressure relief valve to see if it was stuck. It was stuck all the way at the top of the bore.

But I do have a question about the spring, but I started a new thread on that here:

https://www.thesamba.com/vw/forum/viewtopic.php?p=10417044#10417044
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1968 Bug

[Eric&Barb]

Info on the grooved oil relief piston:

Later info on the piston:

IOHO run the grooved piston for now and once the engine stops being so hot due to wear in and any fix required, then switch to the non-grooved piston since you are definitely not in a tropical climate.

Info on the springs:

https://www.thesamba.com/vw/forum/viewtopic.php?p=8680566&highlight=#8680566
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In Stereo, Where Available!

[Floating VW]

Making an ACVW engine run cool is something I've taken a considerable interest in over the past decade or so. I won't claim to be an expert, but I've gotten pretty damn good at it (if I do say so myself!).

There has been a lot of good advice (and, sorry, but also some not-so-good advice, if I'm being honest) given out here, so I thought I'd add some of what I've learned over the years to the pile:

Concerning compression and compression ratios. . . There are a lot of misconceptions surrounding this topic. Yes, higher compression does generate slightly more heat on the compression stroke, but it does NOT create higher engine temps. Just the opposite, in fact. Higher compression creates a more efficient combustion cycle; more efficiency = more energy is used for work and less energy is wasted as heat. In other words, increasing the compression makes the engine run cooler, not hotter.

When people talk about compression ratios, 99.9% of the time they are talking about the "static" compression. There is a big difference between STATIC compression and DYNAMIC compression. I won't go into the difference here (but I would encourage everyone to research it), but I will say that the ideal DYNAMIC compression ratio for a street engine running pump gas is between 7.5 and 8.5 to 1. With a stock camshaft grind, stock 69mm stroke and stock 137mm rods, you will need somewhere between 8.0 and 9.0 to 1 "static" compression to achieve the ideal "dynamic" compression.

How this applies to you: If your "static" compression is 8.5 to 1, and your cam, crank and rods are all stock dimensions, then you are exactly where you want to be for an efficient and snappy engine. DO NOT reduce your compression by increasing the deck height! That is an excellent way to reduce power and efficiency and potentially cause detonation. (Side note: there are three ways to eliminate detonation. 1. Lower the compression. 2. Increase the octane of the fuel. 3. Improve the design of the combustion chamber. In my opinion, the first option is the last one to consider; do the second option only if you have to; spend most of your time and energy perfecting the third option. A tight deck = improved combustion chamber. )

Concerning air/fuel ratios. . . The hottest burning air/fuel ratio is 14.7 to 1 (look up "stoichiometry"). Yes, running your engine RICHER than 14.7 to 1 will burn cooler. However, running your engine LEANER than 14.7 to 1 will ALSO burn cooler! Both richer AND leaner than the stoichiometric ratio generate less heat, because the further from stoich you get, the more incomplete the combustion. Less combustion = less heat. (Side note: 14.7 to 1 is not only the hottest burn, but it is also the FASTEST. The further you get from stoich, in either direction, the LONGER it takes to complete the burn, and the more timing advance you will need.)

At light cruise (i.e. low engine load), the most fuel efficient ratio in an ACVW is around 16.0 to 1 (very lean of stoich). At wide-open throttle (i.e. maximum engine load), the best ratio for making power is around 12.75 to 1 (very rich of stoich). At idle, the most stable ratio is about 13.5 to 1. What actually destroys engines is when you have maximum engine load AND an air/fuel ratio around 14.7 to 1. Under these conditions, the inside of the combustion chamber is burning hotter than the devil's rectum! So when people say "running lean destroys engines", what they really mean is "getting close to 14.7 to 1 at wide-open throttle destroys engines".

Spark plugs and how to properly read them. . . Don't feel bad if you get this wrong, most people do (and they don't even know it!). Ironically, the part of the spark plug most people pay the most attention to, is the part that should be mostly ignored. . . I'm talking about the white ceramic insulation around the center electrode. Any discoloration (or lack thereof) on the ceramic insulator is merely the result of whatever additives were in the fuel when it was burned. The only thing you should be looking for here is tiny grey specks of metal, which means you have bits of piston being blasted off by detonation and melted onto the center electrode. Pray that you don't see any specks of metal on your nice, white (or tan, or grey) ceramic insulator!

The second thing everyone gets wrong when reading plugs is the correct procedure for shutting down the engine. It's actually very simple: the plugs will only show you what the engine was doing when it was shut down. For example, if the you shut the engine off while it was sitting in the driveway at idle, the plugs will only record what the engine is doing at idle. If you want to know what is happening inside the engine when you are cruising down the highway or when you are at WOT, then you need to shut off the engine while you are cruising down the highway or when you are at WOT.

The three main things you want to look at are: the ground strap, the center electrode (not the ceramic insulator!) and the base ring. The ground strap will tell you if your heat range is correct, the center electrode will tell you if your timing is too advanced (but not if it is too retarded), and the base ring will tell you if your air/fuel is rich or lean. I can explain that process better if you want, but I'll spare you a boring lecture if you'd rather do your own research.

How this applies to you: What I can tell from the pictures you posted of your plugs (and I am assuming you shut down your engine while it was idling in the driveway) is that your idle mixture is maybe a fuzz too rich, but not terrible, you haven't experienced any severe detonation, and the plugs have not been run long enough to see whether the heat range is correct or if the timing is too advanced.

Concerning timing and the 009 distributor. . . The problem with a mechanical-only distributor is that, at most, you can only get 32 degrees of advance out of it. At light cruise, when RPM is high, engine load is low, and the air/fuel is at a proper 16.0 to 1, 32 degrees of advance is not enough. It's not even close! Under those conditions, you need closer to 40 degrees of advance, maybe more. For that, you really need an SVDA or a DVDA distributor.

While too much advance can cause an engine to run a bit hotter, timing that is too retarded is what really makes it smoke! The reason for this is two-fold: 1. The farther the piston travels down the bore before the fuel has a chance to properly burn, the less pressure is generated in the combustion chamber. We already know that low compression = less efficiency and more waste heat, therefore, the more the timing is too retarded, the more waste heat is created. 2. The exhaust valve actually starts to open before the piston has reached bottom-dead-center on the power stroke (look up "exhaust blowdown"). If the timing is retarded enough, the cylinder gases might still be combusting while they are being ejected from the engine. Burning gases in the exhaust ports = melted exhaust valves and cylinder heads.

How this applies to you: Ditch that POS 009 distributor and get a proper SVDA in there! Then get your air/fuel at light cruise in the ballpark of 16.0 to 1 for maximum efficiency, and just watch the temperature of your engine drop!

In summary. . . I think your overheating issue is being caused by several different things, some more than others. This makes it frustrating to solve the problem, I know. If it were my engine, I would focus on:

1. Get an SVDA distributor, time it correctly (28 to 32 degrees advance at 3300 RPM with the vacuum line disconnected). Don't be afraid of 32 degrees advance! Most engines are jetted way too rich because every car guy has been conditioned from birth to be terrified of "running lean", and a little more advance can help the engine compensate for this overly rich mixture. It's not ideal, but that's the way it is.

2. Get your carburetor jetted correctly. This is hard to do, I know, especially if you lack the knowledge and equipment. So acquire the knowledge and purchase the equipment! Learning how to properly read a spark plug is a good start.

3. Definitely get some flaps and a thermostat back in your fan shroud! Proper and even cooling is absolutely CRITICAL for an air-cooled engine. Would you take the thermostat out of a water-cooled car? Especially if you are trying to get your new rings to seat; if your engine can't warm up the cylinders properly, those rings will NEVER seat in! Your engine will always run either too hot or too cold, and raw fuel and other blow-by gases will always be contaminating your oil.

4. A dog-house fan shroud is nice, but the dog-house/non dog-house debate is a bit of a red herring in my opinion. The dog-house shroud's main claim to glory isn't so much more cooling, as it is better cooling. As long as your fan shroud is original German, or at least a high quality reproduction, you should be fine. Definitely get the biggest fan you can stuff in there, and a make sure your fan belt isn't slipping.

5. 10W-30 synthetic motor oil. The only exception to that is 5W-30 synthetic (which is what I use). On a properly tuned, well-running engine, there is no reason in my opinion to use anything else. Thinner viscosities won't provide sufficient lubrication, thicker viscosities will bypass the oil cooler, generate more heat from friction, and not provide sufficient lubrication during cold start-up (which is when 90% of the wear and tear occurs). Oh, and if your oil bypass valve gets stuck in the closed position, that will cause your engine to run cold, not hot. A closed bypass valve sends the oil through the cooler; an open bypass valves allows oil to bypass the cooler. If the valve were stuck open, then that would definitely cause the engine to run hot.

6. There are several, more "esoteric" things that can be done to make your engine run cooler, such as thermal coatings, venturi rings, etc. I can give you some more ideas if you want.

Sorry for the book, I hope this helps!
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"It's time you started treating people as individuals, rather than mathematically predictable members of an aggregate set, regardless of how well that works."

[Snoopy1971]

[Eric&Barb]

[Snoopy1971]

[Eric&Barb]

[Eric&Barb]

[bsairhead]

If your tune is good stock cooling is enough. If you know how to drive it.

[Floating VW]