@C Carl

Flatbread V8 blows.......

C Carl · 2021-04-20T02:57:09.000Z

.............. a cloud of blue smoke on startup after sitting for a month or two. But does not smoke thereafter. This is a 1925 Cadillac that a member is considering. The usual claims : Something like engine “rebuilt”, or maybe “gone through” or “overhauled”, or whatever. But you know, the guy died, someone else says, but can’t remember, just thinks it was re-Babbitted, etc . No receipts for alleged work done. In any case, it runs strong with good oil pressure. Typical timing chain stretch for maybe more or less 60,000 miles. No need to worry, but the engine could not have been just rebuilt without putting a new timing chain in it. I am helping over the phone. On my end , my 1924 Cadillac has in the 60s of thousands of miles. About the same play in timing chain, runs strong with good oil pressure. Although the engine is a rather tired old thing, the bearings are in VGC, totally in spec. So I will let it burn oil, and just let the blowby remind me of many old cars I have had. This one will survive longer than I will, so it is not likely to be opened up for anything. But it does not blow a cloud of smoke on startup no matter how long it has been sitting. Does leave a little smoke in its wake as it goes down the line. Which brings up the question. We are wondering what the reason is for the cloud of blue smoke ? I have way more overhead experience than flathead, and smoky startups usually means oil getting through the valve guides. But that does not compute to me for a flathead. Obviously I am missing something here. I can’t see what could make any difference whether a flathead sits for a few days, or the 6 months my ‘24 often sits during the Winter. I don’t think it would be asking too much for a compression test ? Some sellers are extremely cooperative, some even willing to let a qualified mechanic probe around at the buyers expense. At the end of the day, engine condition really is unknown. Biggest concern , of course , is bearings. But I hope one of you flathead experts can clear out some of these clouds of doubt we are having. This is now in the hands of you, the jurors. Thank you muchly on behalf of Kurt and me. - Carl

Apr 20, 2021 (edited)461 views

Replies (2)

· Apr 20, 2021

Still could have too much clearance in the valve guides. Stopping the engine allows oil to be sucked into the cylinders but not burned since the ignition is off.

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· Apr 20, 2021

Oops ! I had thought I was posting this up in General, but then did not appear. I thought it had been zapped into another dimensionso tried again with success. And now I see this crop up here. I think I might delete this to avoid redundancy, but that spellcheck on my ill-tempered mini iPad made flatbread out of the flathead, so maybe I will leave it up for fun ! Even though I had a delicious Italian flatbread and ham sandwich for lunch - seriously ! - I swear I typed flathead.

These engines are the last Cadillacs to require manual lubrication of the valves. Oil can not get up the valve stems into the combustion chambers. That is what is so weird about this strange blue cloud. I am quite far from where the ‘25 is , but will try to post a picture of the valve layout on my car soon.

Good news is that I have an appointment at the Apple store this weekend. Intention is to tame or replace this cantankerous upstart of a device. It really does have a mind of its own. Kind of a bully.

Thank you, JFranklin for taking the time to try to help us. If I was the guy seriously looking at the car, I would be very happy to pay a qualified mechanic which the selling agent trusts to dig deeper into the car than just a compression test. If not, I would come in light on the purchase offer. - Carl

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