Still vapor locking

[crvc]

1 or 2 years ago I rebuilt the bug engine. It was a mild winter day when I drove the bug an hour south to Manilla, a small town in Utah. When I got to the only gas station in the town I recall checking the oil level. When I lifted the engine lid the heat wave nearly knocked me over. Eventually got home and the bug died a few miles from home. After a year of emails and suggestions and trying different things I eventually welded vents into the engine lid.

I decided to try the trip to Manilla again today. Back at the station I wasn't slapped by a heat wave when I checked the oil. I brought my laser thermometer. Pointing it to the Zundfolge mark it read 250 degrees (F). Then laying on the ground and pointing it to the cylinder fins it read 300 degrees. The dipstick was too hot to hold without a rag. Anyone know whether 250/300 is too hot for bug engines?

I drove it home and it died 10 miles from the house. Luckily I was on a hill and was able to coast the ten miles to the bottom, half a mile from home. I remembered someone suggesting I spray cold water over the engine. I had brought a liter with me so I used it. Within minutes the engine started and I was able to drive it home.

So I still have the vapor lock problem. For the drive to Manilla the car had power to spare. No problems staying in 4th gear when climbing hills. On the flats the car averaged 70MPH and I could have gone faster. A mechanic in Colorado had suggested I remove the thermostat for now. He also sold me an electric fuel pump that doesn't need a pressure regulator. I never got around to installing it.

I have two short blocks, both with new bearings. And both have the vapor lock problem. I have one set of tins, thermo, shroud and fan from a '74 engine. So I switched everything from one block to the other. I can put the electric pump in but that won't help the engine if 250 degrees is too much. Any other tricks to cool the motor?

TIA,

kevin

[Ol'fogasaurus]

Kevin, do you have an oil pressure gauge? I think I would be watching that pretty closely.

There is supposed to be a small air deflector on the undersides of the engine between the cylinders, it is there?

I don't think I would shock the engine with the cold water trick again.

What kind of oil cooler setup are you using?

Just some thoughts.

Lee

[crvc]

I don't have an oil pressure gauge, just the red and green idiot lights. I've got those deflectors that go between the cylinders on the underside. In fact I have several from various engines. I could see one as I was pointing the laser up at the cylinders. It wasn't exactly ice-cold water, merely tepid. And it worked. I put an oil pump in that came with a screw-in filter. I have the stock doghouse oil cooler. If I have to remove the engine again I'll probably buy a new cooler just in case the old one is plugged up. But I used pressurized air to test the old cooler and it seemed okay.

kevin

[FJCamper]

Hi Kevin,

At 280º to 300º F. vapor lock is the least of your problems.

Let's presume your oil cooler is clean, your oil pressure relief valves are working to divert oil to the cooler, and your pump-filter unit is working to specs.

It seems like the overheating happens under max load in the mountains.

It is possible your fan housing thermostat air flaps are partially closed and the run through the mountains is too much for what air that gets through.

Your timing can be just enough over advanced for mountain roads.

Your fan belt might be just snug enough to spin the fan at up to 3000 RPM, but slips above that, say if you're hillclimbing at 4500 RPM in 3nd.

Check these little things out first and let us know.

[crvc]

Thanks for the replies. I use a stock oil bath air filter and stock exhaust. Plus a vacuum dizzy with an electronic module. I set timing at 5 degrees BTDC with the vacuum line removed. I don't know how to check for the fan belt slipping but it defects less than an inch when pushing on it with my thumb. I removed the thermostat. The flaps were wide open as I unscrewed the thermo. There's a spring on the front of the shroud that holds the flaps open fully. If I pull the thermo rod down then let go the flaps snap open loudly. Sometime closer to winter I may try widening the slot on the bracket that mounts the thermo to the block. When I put this block together I used new bearings for the camshaft. Also putting the cylinders in I wasn't too careful about the ring gaps being 60 degrees apart. So maybe there's some friction as the rings and bearings are wearing in.

kevin

[FJCamper]

Hi Kevin,

There is a small halfmoon key that holds the generator/alternator pulley hub (back half) in place on the pulley shaft.

If this key is not in place, the pulley will spin at medium to high RPM's. No cooling.

Usually, the friction of a good tight belt will spin the pulley at low to medium RPM's and for short trips, no problem. Of course, eventually the pulley will wear so much it will friction weld itself to the shaft. Then break loose again.

Remove your fan belt and see if your pully will rock or rotate ... and the fan does not move.

There is a near identical and more common circumstance with a pulley broken off its hub.

FJC

[Piledriver]

As Marc has previously noted, if you have a doghouse cooler/fan setup, it takes a wider (11mm?) belt.
The older 9mm belt can slip silently and cause overheating.
(the 11mm belt also is deeper, more area on the pulleys)

Also any "used" cooling air that can get back to the fan, will.
The seals must be ~perfect.

Also, from what I have seen the easiest way to make an ACVW run hot is INsufficient timing at light to medium loads.

I'm hesitant to post my current timing map, but I cruise at ~55 BTDC at ~3300 RPM, heads are 15 degrees cooler than with 45-50, even though it is 10 degrees hotter outside. 3 degrees more run even cooler but feels bad/uses more fuel and takes more throttle. I cruise at 19:1 and ~ 65 KPA/96.5 kpa typical ambient at my altitude on a level stretch.
(I have programmable EFI/ignition, so it is far too easy to play with this)

My motor is much different than yours, but do not be afraid of vacuum advance, and what it does at idle matters little as long as it is ~ 10 BTDC, the stock 5 ATDC is for emissions and is guaranteed to cook heads at idle by design. It can make a >50 degree difference at idle.

Below ~83 KPA you can ~get away with murder timing wise, the engine will tell you what it likes.

Reducing the total mechanical advance range probably kills baby seals, but it will help drivability and CHT at idle tremendously.

[Marc]

As Marc has previously noted, if you have a doghouse cooler/fan setup, it takes a wider (11mm?) belt.
The older 9mm belt can slip silently and cause overheating...

Actually the wider fan in the "doghouse" setup is a consideration, but the gen/alt selection seems to be the more determinative factor. I've found the 9.5x905La belt to be adequate with a 30A generator, borderline with a 38A (Bus/Thing) generator, and hopeless with a 50A or larger alternator - for those you should only use the 11.3x912La belt.
1" belt deflection is a bit on the loose side (½" is more like it) but you don't want to go excessively tight either since that'll shorten the bearing life. Avoid chrome pulleys. Personally, my go/no-go test is whether I'm able to just make the crank rotate 360° by rotating the generator pulley... obviously a high-compression engine is going to be a little harder to get past TDC in a hurry, but for a typical stock/mild engine, anyway, that seems to usually result in perfect belt tension.
If the belt's slipping it'll typically take on a "glazed" shiny look on the sides - once that's happened it'll be more prone to slippage at the same tension, so it's time to relegate it to "spare" status.

[crvc]

I have several of the half-moon keys. I lost the last one--then ordered a bunch--and remember tapping the key in. Also remember there's a much larger half-moon in the fan. That one is in also.

We talked about this before; How much does a deep sump help with overheating? I have a sump and the Berg bolts for mounting it but never used it. I thought it created more opportunities for oil leakage but at this point I'd trade a drip for less heat.

A metal ruler shows the belt to be roughly 12mm wide. No 'glazing' either. So I should rotate the dizzy to 10BTDC? I'm using a stock pulley but I could guesstimate 10 degrees.

kevin

[Marc]

...I'm using a stock pulley but I could guesstimate 10 degrees...

...I set timing at 5 degrees BTDC with the vacuum line removed...

Hmmmm. Can't think of a stock pulley with a 5°BTDC mark, so you must already be doing some "guesstimation". Look at the back rim of the pulley (closest to the bumper)...there should be a shallow dimple at TDC. Is the mark you're using to set the timing to the right or to the left of that dimple?

I use a.. vacuum dizzy with an electronic module...

Doesn't tell us much - there are many "vacuum" distributors.
You may have posted this before but could you save me the time of searching for it and give us the distributor model number? Preferably the 10-digit Bosch number, stamped into the housing.

[crvc]

https://www2.cip1.com/ProductDetails.as ... %2DD186504

It's a petronix svda with ignitor module.

There's a factory notch on the pulley to the left of the TDC mark. I assumed that's 5BTDC. There's also two notches to the right of TDC. I think I timed it using the notch on the left.

kevin

[Max Welton]

Also, from what I have seen the easiest way to make an ACVW run hot is INsufficient timing at light to medium loads.

Agreed.

And the need to coordinate more timing with lean AFRs is very true as well (I see the same things) but not what Kevin is dealing with.

Kevin, timing that is not advanced enough will show very clearly as increased EGTs and also as increased CHTs. But I don't suppose you have that sort of instrumentation.

Max

[Marc]

https://www2.cip1.com/ProductDetails.as ... %2DD186504

It's a petronix svda with ignitor module.

There's a factory notch on the pulley to the left of the TDC mark. I assumed that's 5BTDC. There's also two notches to the right of TDC. I think I timed it using the notch on the left.

kevin

That one is 5° AFTER TDC, or about 12½° retarded from where it should be for an SVDA (that's the mark for use with a DVDA). You should be using the first mark to the right of the dimple, which is 7.5°BTDC....is that what you meant by "notch on the left"? - the leftmost of the two to the right? If so, initial timing's not the problem.

What vacuum source are you using for the vacuum-advance canister? (Where does it come off the carb?)

[crvc]

http://i1325.photobucket.com/albums/u63 ... 4a6bf0.jpg

Blurry photo but it shows a notch left of the TDC mark and two notches to the right of the TDC mark. Now I'm confused but think I timed it to the solitary notch on the left of TDC. The vacuum hose attaches to the carb on the left side, the only spot for a dizzy to connect.

Tonight when it's dark enough I'll check timing.

kevin

[Piledriver]

Where are you?

Around here,~any chain parts store will merrily loan you an advance timing light to use in the parking lot and even show you how to use it.
(if you want to take it home that have loaners you can KEEP, but you get to make a full price (but refundable) deposit)
The good ones have a tach built in, so you can actually test what the advance curve really is.

Once you have actually determined the TDC mark...
...Set 32 BTDC w/o vac can connected (and line plugged) @max advance and let idle fall where it may.
With the distributors all over the place it is the only safe method.

If you are at high altitude it may want more... much more.

Then we can make sure your vac advance is hooked up/working properly.