MTFCA Forum

Hello, I'm looking at a 1925 Roadster. It has smoke coming from a hole down inbetween the cylinders, to the left of the manifold, which the owner says is normal and is a crankcase breather hole. Is this normal?

In a 27 block If you have a different carburetor than the Vaporizer, you must drill a hole in the block between 2 and 3. Also cut a hole in the one piece valve cover. That hole is where the blow by comes out. If it is really Steam you might have a crack in the block. I am not sure about a 25 block.
Norm

Yes it can be normal. Except for the gasket between the cover and perimeter of the block where the cover fits, it is pretty open so any crankcase vapers can escape through the drain holes valve chamber and the breather/filler cap.
For lefthand drive cars, the space between #2 and 3 cylinders is open to allow the throttle rod to pass through, along with an opening in the valve cover.
For righthand cars, not sure if that space is open or not or if they would have used the cover without the hole.
For 1926/27 US cars fitted with a vaporizer, the web was not open between the cylinders and the cover did not have a hole for the throttle rod.
What color is the smoke?

Sort of. There are two holes in the valve chamber open to the crankcase, oil vapor is expected to lubricate the valve stems. The 1925 one-piece valve cover leaves the gap between cyls. 2&3 open to the left side of the motor as well as through the opening that admits the throttle pull rod.

An excess of vapor indicates either far too much oil in the crankcase, or a really loose, worn-out motor, or both. But . . . Smoke ??? Real smoke ??? Exhaust smoke ??? Worrisome.

How does it run ? Is it “smoke” or oil vapor ? How much ?

There is a name for that. Blow by.
If you ever owned a pre 1963 car you would know that it is crankcase blow by. The more you have the more worn the rings are.
Or the amount of smoke is directly proportional to the amount of wear in the rings.

It's old enough to smoke.
Seriously, it's probably ok. It's what they do occasionally. As was said, It may or may not be the sign of a tired engine. Question the seller what they know about if/when/who it was rebuilt. If they have documents, that is best. Make sure it's not running too rich and keep an eye on the oil level.

Dan Hatch wrote: ↑

Thu Aug 29, 2024 11:50 am

There is a name for that. Blow by.
If you ever owned a pre 1963 car you would know that it is crankcase blow by. The more you have the more worn the rings are.
Or the amount of smoke is directly proportional to the amount of wear in the rings.

Expect to speed a bunch of money on motor work.
But isnt that expected with any T purchase unless you know/trust the engine builder?
& a stack of receipts dosent necessarily mean your engine was built correctly.

You should do a compression check before opening your wallet.
There are 3 ways to ascertain a T's compression.
1) A bonified compression test with a gauge. All cylinders should read consistent @ 55-60# on a really good stock engine.
2) Electric start turning the motor over with the ignition off listening/feeling for a consistent rythem.
3) Hand crank. Feel for consistent resistance/friction @ each cylinder as it comes up on compression. Helps if you have ever tried to hand crank a good motor.

If you have a steep hill nearby, try going down the hill on compression, in low gear or Ruckstell with the throttle closed. Then when you get to the bottom, open the throttle. If you get a lot of blue smoke out of the exhaust, it is oil burning. That is an indication of worn piston rings. Or sometimes the gap at the end of the rings is not staggered so the blow by can come right up into the cylinders to burn and when you pull the head you will have oily carbon deposits in the head and top of pistons. So, anyways what I am trying to explain is the blow by goes both ways through the rings. Into the crankcase when accelerating, and into the cylinders when slowing down
Norm