Oil burping out of one barrel of a new Dellorto build.

[nilloc]

New pistons and cylinders for a 1640 build, bottom end never got split (we were in a hurry to get it on the road and the rods, crank endplay, and cams looked good). EDIT TO ADD: Also new mid performance heads fully loaded from CB Performance, it was a while ago and I forgot!

It's got dual 40 Dellortos and no oil vapor capture, just a remote separator/breather off the oil cap. It's also got the Bergman fan kit, and remote oil filter, cooler, electric fan, thermostat and thermo switch. It also has empi stainless dual exhaust headers, so both banks are completely separate.

I think the carbs were a little rich, the plugs were black half way around, on the first check, but the owner messed with the timing on his first trip home with it. And it was probably a little hot based on the color of the exhaust.

We were getting random little pops and chirps (misfires) and assumed it was over fueled, but it could have been valve adjustment. Could have been that side of the engine but hard to hear where from.

Adjusted the valves at 180 miles and the #3 were tightest (valve stretch?). All were over tight so I re-adjusted to .006

Still chirped a few times I think, but not sure after valve adjustment.


200ish miles into the break in. And pretty sure we're a little bit rich, I decided to try and test out an AFR gauge I had for another project to get a reading and installed an old, version of the header with an O2 bung in it on the 3/4 side of the motor.
30 seconds after first start, puff of smoke out that side.

Cylinder #3 is spitting oil out and fouling the plug after 5-10 minutes of running. Blowing out smoke too, and the only pipe with oil in it is #3 It's possible the oil was there before the exhaust swap but we don't know for sure. The exhaust pipes were slightly smaller diameter than the empi ones, otherwise identical.

Endoscoping into the cylinder showed a little oil coming past the ring, but not really much worse than the other cylinders, maybe worse, but the camera isn't great.

All cylinders have essentially 0 leak down, and all the same on retest. The oil in the cylinder could be over-sealing the cylinder.

Questions are:

1. Oil level too high with cooler and filter above the sump height (dipstick reads about an inch from bottom, valve covers had normal amount of oil drip out when adjusting valves
2. Carb somehow sucking air up during intake stroke (doesn't seem like a valve problem after the leakdown results).
3. Failed oil control ring
4. bad valve seal

Gonna pull the intake and see if there is a failed valve seal with the camera.

Any ideas?

[mikedjames]

No3 inlet valve guide worn, so when it rattles around sometimes the vave does not seal properly and also you get a constant feed of oil into the cylinder at high speed when it fills up the rocker covers..
Has to be inlet side or rings to foul the spark plug.

Of course the exhaust valve guide on No3 could also be worn..


If the head under the rocker cover is golden or dark brown it has been getting hot.
Black marks round the exhaust valve spring would point to guide wear.

Take it apart..
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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

[oprn]

Chirps and pops are usually indication of a lean condition. Discolored exhaust would be from the same thing. You didn't tell us what the AFR meter read.

I'm with mikedjames on valve guide wear. Did you rebuild the heads properly when you had it apart? Also 87mm P/Cs have thin cylinder walls and warp more easily when overheated. Are all the engine tins and compartment seals are in place.

What car is this in? Hopefully not a Bus!
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Our cars get old, we get old but driving an old VW never gets old!

[APPLEGREENVW]

I believe 40mm dual Dellorto carbs are to big for 1641cc engine. Just my opinion.
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02/76 Beetle sedan

[nilloc]

[nilloc]

[nilloc]

Might have found the smoking gun (bad pun, sorry).

Both compression rings gaps are sitting at the bottom/right side of piston #3

And some pics of the heads and cylinder just in case.