Smoking

[Dodgeb4ya]

Exhaust valve guides have the counter bore end always up.

[David Muma]

http://www.imperialclub.com/Repair/Lit/Master/027/Cover.htm

see page 19

[John-T-53]

After reassembly, the engine ran fine. Broke in the new rings and guides and changed the oil. After about 600 to 700 miles on the oil, the same type of smoking and strong blow-by smell started to occur again, getting progressively worse. MPG was in the 10-12 range.

After double checking the dwell, timing, carb, plugs, and PCV, and determining them working satisfactory, I did some more searching on here and a couple threads mentioned an internal leaking fuel pump - leaking into the crankcase.

I pulled the fuel pump and noticed it's indeed leaking out of the mount side, into the oil. Over time, the oil has been getting dilluted with fuel. The PCV sucks the fuel vapors in the crankcase into the combustion chambers, leading to a rich mixture and smoke/soot out the tail pipe. This might explain the excessive carbon in the combistion chambers after 3k miles (pictured below).

I was driving a lot at highway speeds before, for long periods, and dilluted oil with the RPM's encountered might have played a factor in the rod bearing failure that happened (also pictured below).

I never replaced the fuel pump when I redid the engine because it didn't leak and seemed to pump fine. Who knew that it was leaking unnoticed into the crankcase and leading to excessive damage?

That's my theory - what's y'all's take on it? Can we put this one to bed?

[Dave72dt]

Diluted oil can definitely take out brgs. Keep a close eye on the oil level. I've never known an engine yet that would make more oil than was put in it.

[JBNeal]

Yep, thinned oil won't provide enough protection...as I was taught by a few older mechanics, developing a feel for oils & greases is a skill that can be used in diagnosing problems. My Firestone co-workers wondered why I wiped the dipstick with my fingers instead of a rag when doing oil changes, and this is why. Oil may look okie dokie, but if it doesn't feel right, then there's a problem afoot that needs attention.

When I first got the '48 running back in '96, I had not rebuilt the fuel pump or distributor. This was my first engine rebuild, and being in college, I didn't have much $$$ for the peripheral stuff, so I focused on the engine internals, starter/generator, and carburetor. The truck had sat in the TX sun, heat & humidity for 20+ yrs, and I was about to learn alot about that. The engine ran fine for about a day, then the fuel pump diaphragm came apart. When I rebuilt that, I reckon that AC pump dated from the 60s. When I got it on the road after fixing the brakes, it ran like carp going up hills and couldn't go over 30mph. That's when I realized the distributor vacuum advance had come apart. So I parked it for another 2 yrs while I replaced every rubber component on that machine when I could scrape up the $$$ as I was now assuming they were all very close to being rotten.

With the advent of the E10 gasoline blends that are prevalent, this only magnifies the need for replacing all rubber fuel components on these old buggies. I've spied a few vintage NOS fuel pumps on eBay and I know they will need a rebuild kit to update the rubber parts, so I stay away from them. I found several Power Punch ring sets on eBay, and one set had little pock marks in the auction photos so I stayed away from those as I was certain that the seller had cleaned off some oxidation but didn't get all of it.

IMO I think your bearings were going to fail from the oxidation that had occurred before installation, but the oil dilution accelerated this failure.

[grey beard]

The air cleaner in the pictures on this thread - the one that fell off - is the heavy duty larger type, as compared to much smaller ones that were standard. The heavy duty air cleaner was optional. I have one on my truck, as well. Point is, these air cleaners all came with a brace that went across the cylinder head and up to mid-point on the air cleaner. Removing the thing involves both the bottom clamp and the side brace. Looiks like both were left off on the one pictured. JMHO

Sure wonder what ever happened to the engine in this original thred, after the autopsy. Haven;'t heard a word . . .

[Dave72dt]

He's had the engine refurbished. Smoking is believed to have come from a leaking fuel pump loading up the oil with gas. The pcv system pulled the vapors out and ran them back through the carb creating an overly rich, smokey exhaust. It also may have contributed to some failed rod brgs from the first rebuild. Found the pump problem after the smoking started again after the second rebuild. i don't know if he has the new pump on and is running again but he'llneed to put some miles onit to test the theory.

[John-T-53]

I got a call from Napppa yesterday and my new Airtex fuel pump has arrived, ahead of schedule. Unfortunately, I'm in LA area today for a wedding with the lady and we won't know anybody there but the bride, and it should be in interesting one....(the groom's name is Shahab Mahmood or something like that). Anyways, I'd rather be in my driveway right now with an ice chest of cold ones and working on the truck. Instead I'm sitting in a hotel room writing about it. That's my rant for today.

Anyways, looking forward to changing the oil and installing the new pump. I think the fuel in oil condition not only leads to smoking through the PCV system, but thinner oil probably slips past the rings and valve guides a lot easier, compounding the smoking symptoms that way too.

This time, since the second rebuild, I've kept the mileage and rpm's low, and the rod bearings are a lot better quality than the ones that were installed previousy. So, I'm hoping I haven't done any damage.

I will begin testing the theory next week when back on the road!