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Blue smoke on cold start even with new valve stem seals

 
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Old 07-10-2019, 05:37 PM
Johnkimble
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Blue smoke on cold start even with new valve stem seals

Hello,

I recently assembled and installed a 428 fe into my f250. The short block was already assembled and just needed the heads/manifold and accessories installed. The heads it came with were already assembled and ready to go too. The one drawback was the engine sat for about 10 years, covered in a dry shop.

I assembled it, broke in the cam, no issues. Runs fine, except the blue smoke on a cold start, and the oil it burns when doing so.

I figured the valve stem seals dried out from sitting for so long. Took it to a local hot rod shop to replace them as I'm tired of working on this thing nonstop. They replaced them and reported it is still smoking on a cold start. Any ideas?

By the way I have approximately 75-100 miles on this engine. I changed the oil right after break in with no glitter or shavings. Cut open the oil filter and that was clean too.

I don't get any smoke on acceleration, warm starts, or any other time, only when I leave it overnight.
 
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Old 07-10-2019, 08:18 PM
f5fordgirl
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If you're running an auto trans, that smoke might be coming from a bad modulator on the trans, after it sits for a few hours, pull the hose off the modulator, if oil runs out, that's the problem.
 
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Old 07-10-2019, 09:25 PM
Johnkimble
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Thanks for the reply. I forgot to add it's a 4 speed NP435. I also replaced the PCV valve as a precaution, but that was not the issue.
 
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Old 07-11-2019, 12:35 PM
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Are these positive valve seals, or the old umbrella type? Were the heads redone with new guides?

Was the oil feed restricted in the heads? New rockers/shafts? You could have oil pooling in the heads, when you shut it off, some of it runs down the guides and you get that blue puff on startup.

Another thing to consider: Intake vacuum leak between the intake and the heads. Take it out, rev it up in 3rd gear to like 3500+, let off, let it coast down to 1500 or so (high vacuum), and then hit the gas. Do you get another blue puff?
 
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Old 07-11-2019, 12:43 PM
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I will check on what type valve seals were used.

I did restrict the oil flow to the heads with a carb jet (forgot what size). I'll try the high vacuum test, but from the miles I've put on it and frequently checking the rear view, I've only ever seen blue smoke on a real cold start.
 
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Old 07-11-2019, 01:01 PM
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And check the plugs after that high vacuum test. Keep track of which plugs come from where, and post pictures of them if you can.
 
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Old 07-11-2019, 01:13 PM
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Is it possible fried rings could cause blue smoke only on a cold start? I'd imagine if my rings were fried, it would smoke all of the time.
 
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Old 07-11-2019, 01:40 PM
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Originally Posted by Johnkimble View Post
Is it possible fried rings could cause blue smoke only on a cold start? I'd imagine if my rings were fried, it would smoke all of the time.
Generally, you are right - cylinder/piston/ring issues would smoke all the time. If there's too much clearance at cold start, and then as things heat up the clearance goes down, that could explain it. But let's not go there yet
 
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Old 07-11-2019, 01:59 PM
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I replaced the pcv valve as a precaution, no changes. I believe my pcv is setup correctly. Passenger side pcv vents to the carb, and the driver side valve cover is just a breather.
 
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Old 07-11-2019, 02:04 PM
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Sounds right. Same as the stock 360 in my highboy.
 
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Old 07-11-2019, 07:09 PM
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The valve stem seals the mechanic used were Fel Pro SS13401. He said the originals all looked fine with no signs of cracking or damage. I tried the high vacuum test and did not notice any smoke out of the rear. The mechanic said since we don't know what type of rings were used, he recommends waiting until I have around 500 miles on the new engine and see where it's at then. He said it's possibly either bad rings or a leak at the intake manifold causing oil to get sucked into the cylinder. He said the #8 cylinder had oil in it and on the spark plug, all the rest looked fine.

He said a leak down test with smoke after 500 miles will narrow it down. Aside from that, it runs like a top.
 
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Old 07-11-2019, 07:19 PM
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Cool, let us know how it turns out.
 

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