Does the Dipstick hold oil pressure in the motor?

[Holzy22]

Does the dipstick have to be in to have oil pressure and compression?

I was flying down the highway and lost compression, smoke coming from the oil on the exhaust from it being sprayed all over. I shut it down and waited for things to cool off. I assumed I blew the motor, so I towed it back home. I pulled out the motor and on inspection I found that the replacement dipstick I used, the one with the combination oil pressure and temp was very loose and most likely blown open and looks all the oil was coming from there.

Is that where I could have lost all compression? Does it have to be in and fitting tight? Or am I wishful thinking and need to tear this engine apart?

[Angus II]

Hello,
What?. And, no.
Very wishful thinking... Time to get your hands dirty.
Oh, and could you show us this dip stick you speak of. It sounds really interesting.

[Wildthings]

If you have something wrong with your crankcase ventilation oil will blow out any and everywhere on an otherwise good engine. Did you do a compression test before pulling your engine. That would have told you if there was a gross difference from one cylinder to another. If one cylinder had really low compression that would have indicated that you might have a holed piston.

You can do a pseudo compression test by just turning the engine over two complete turns using your hands. All four cylinders should offer the same amount of resistance to your efforts.

The dipstick should seal to the tube, or even moderately high crankcase pressure can cause it to leak. Crankcase ventilation is extremely important, but must people do not understand it much at all or even know a system for venting crankcase gases exists in the first place.

[Holzy22]

no, did not do a compression test prior to pulling the motor. After turning it over a few times by hand, all seems pretty normal. Going to pull off the heads this morning and dive in.

So, I did put new larger pistons and jugs in this winter, went with thick wall 88's and had the heads machined. I had about 250 miles on before this happened. Engine was running really smooth and with much improved power. Then this happened, anywhere I should look first? I don't see oil coming from really anywhere else except the dipstick tube area.

All of my venting tubes are clear and hooked up as should be.

Here is that dipstick at CIP
https://www.cip1.ca/c31-919-081-111-1/

[PatJr]

when I had a similar experience it was a sunk valve
_________________
#############################################
1970 Transporter a orange one
#############################################

[Holzy22]

Going to slide the motor in tonight and test compression.

[timvw7476]

[Holzy22]

Well, when I drained the oil I found a pretty good amount of metal flakes, oh oh.

Compression test showed 0 on cylinder 3. In fact when I put the tester on, it made the engine sound weird when I cranked it, I did not get that hump of sort of heart beat with each stroke like i did on the others. So I think my hopes of this being a bad valve are gone. Now I am hoping for worn or broken piston ring.

Will pull the heads off tonight and have a look.

[mikedjames]

I used to get oil spitting out the dipstick hole.
It was the combination of worn piston rings causing blow-by and the use of an EMPI oil filler neck with a pathetic 1/4" inside diameter breather spigot.

And it did it again last year when I had melted a hole down the side of No.2 piston which increased the blow-by by a certain percentage.
_________________
Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[Holzy22]

Funny you should say that mikedjames, look what I found when I removed the 3/4 head. How does this happen?

[Wildthings]

Looks like hot running and preignition to me.

What was your timing set at?

[Holzy22]

I found it odd that with that hole in the piston, I found no oil residue that would have blown through there, would it have burned off in the heat and combustion? Could it have run hot from a lack of oil, hence no evidence of oil blowing through?

My pully doesn't have degree marks but I have the same advance that was on previous to the new jugs and pistons. Wouldn't all 3 run hot as well and show signs? #4 looks very healthy.

[Abscate]

GEX will call you to buy that piston for a rebuild …
_________________
.ssS!

[Wildthings]

[mikedjames]

Yes, my No2 piston looked exactly like that !

I think mine was a combination of things - slightly too much timing advance caused by using a pre-timed distributor dropped in when a condenser failed on the previous distributor in the bus.
But the timing light I had used turned out to have been defective...
And that was combined with a progressive carburettor with a sticking power valve.
Bought fuel from a different location to usual, different refinery.

Plus driving up hill overtaking trucks (over here they are limited to a sane 56 mph) with my super new powerful motor...
I had a temperature runaway on the cylinder head temperature gauges - a very rapid and unusual rise..


When it blew, oil came out of the crank pulley and the exhaust.
It also put quite a lot of oil into the oil bath filter through the breather ..

After about a mile, when I stopped basically there was just enough oil to provide oil pressure but not enough to show anything on the dipstick.

What is a bit scary is it tried to do the same thing again with a rapid temperature rise on the flat after I rebuilt it. But recognising the symptoms on the CHT, I backed off to 40mph and it eventually recovered.

Then I deleted the power valve on the progressive and dumped the coil and distributor - went crank fire instead , now I get the power without the heat as the AFR and timing is under closer control.
_________________
Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[SGKent]

Likely your timing was too advanced, and the mixture a tad lean. You have a really light color on the pistons so even though that might be a good mixture to make power, too much power in an air cooled bus can be a bad thing if the cylinders get too hot. That said, it is a common failure when these engines are pushed hard on cold dry days with advanced timing and lean mixtures. Or maybe the cylinder tin that goes under the cylinders is missing on that side.

The pressure in the cylinder was bypassing the piston and blowing oil out. Been there once a very long time ago.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Holzy22]

I just found out the new spark plugs I put in were the 1/2" shank and not the 3/4" so the plug sat up deeper in the plug well. Would this have cause and irregular burn and possibly a build of fuel/gases/carbon that would built up on the piston?

Pic 3 is the head with plugs in.
Pics 1/2 are my damaged piston. Did I have foreign object in there?

[SGKent]

I explained how it happened. When the mixture is about where yours is the engine makes a lot of power. That is done with the generation of heat. When the tiiming is a little advanced that makes more heat. When the air is dry it is more dense (H20 vapor is lighter than other molecules in air), when the air is cold it is more dense. That is like adding a small amount of turbo boost. If you were near sea level that is even worse. Buses by their nature make a lot of heat once they get up to cruising speed - they push a lot of air in front of them, and that makes a lot of resistance. They are also heavier than the cars the engine was originally designed for. You added additional cylinder area, which makes even more heat. The pistons got hot and melted. That is all that happened. If the cooling tin under the cylinders was missing, which it may or may not have been, that would make things worse. When you rebuild it, make sure all the tin is there, jet it a little rich, make sure there are no vacuum leaks, and keep the total mechanical advance at 28 or 29 degrees BTDC. Stay around 60 - 65 mph on the freeway and it shouldn't happen again.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[timvw7476]

as Mister Spock would say: 'fascinating'
As far as those sparkplugs & their sad reach, that may play a part. I recall Honda used a shrouded rich chamber to ignite the lean mixture in the main combustion chamber back in the 70's-80s' CVCC carb years....
Probably has to cut down on flame propagation throughout the combustion chamber.

The one thing that has to be respected when running a VW air cooled was well covered by John Muir in the Idiot book decades ago. Never time these anywhere near the 36 degrees Before Top Dead Center that water cooled engines operate at. They can't shed the heat fast enough to run there, so 29-31 degrees BTDC, vacuum advance plugged, is the ragged edge. You get any closer to 36 than that, you take operational hours out of the engine very quickly.
Some of those piston images look REAL close to 'Four Corners' two-stroke piston seizure images, those caused by lean mixture/high heat. Timing! Always triple-check that timing. Dynamic, with a timing light. Saves (engine) lives!

[Holzy22]

Thanks @sgkent and all.

Just seems wild that these engines are so temperamental. I redid my 350 SBC in my 69 GMC truck a few years, and its still running fantastic.

So how is timing checked with no degree marks on the pully. I guess I could grid one out on paper and transfer it to the pully, but how accurate would that really be. I have the 3 notches on the pully with the center one being TDC, I thought the factory wanted timing set at the notch to the right, static at 7.5?

All the tins are in place, I will run it a bit richer, but it blew on a beautiful warm Alberta day cruising down the highway at 110kmh (65 ish mph).