Hello,

A friend of mine inherited a 1978 Buick century 3.8 four door. What an ugly car! Anyway this car was always garage kept and supposedly well maintained. It has less than 100K. The car appears to be in very good condition. It was sitting is storage for about a year.

We picked up the car in Dayton OH and drove it back to Michigan The carburetor kept clogging up and the only way to get the car to run was to race the engine and full choke the carb for a moment. This would clear up the problem for a little while. Perhaps old or bad gas.

By the time we got back to Michigan the Buick was hitting on four cylinders and barely made it home. I replaced the plugs and wires and the car ran fine.

The car ran well for a few days and died on the side of the road. I went to rescue my buddy and I managed to get the car running again.

The engine now sounds like a diesel when it idles, however the knock will go away when you rev it up. Its also only hitting on about four cylinders again and I haven’t had a chance to pull the plugs yet.

The cooling system is holding normal pressure and the oil level appears to be normal. The oil color is dirty but no water present. The exhaust tends to be dark sometimes when the engine is revved. No white smoke. The oil pressure lamp works with key “on “

I pulled the carb and cracked it open , however it appeared nice and clean. I replaced the fuel filter for good measure. I also replace the cap and rotor. The car still knocks at idle. There is quite a bit of blow-by coming from the breather tube.

The knock is a high pitch sound similar to detonation or pinging. It doesn’t sound like a main or rod knock.

I work on old Japanese and English cars, I never really worked on many old American cars..

I’ll have a chance to look the car over again tomorrow is there any odd things I should be aware of with this 3.8 engine?

Thanks

Jim

the 3.8 is generally a very solid motor. however, since this motor sounds like it's never really been touched, I would look at a rebuild. If you're getting a lot of blow by in the PCV system then i would think that your rings are blown, or that you've got extremely bad valve seals.
I think that you need to take a closer look at what colour the smoke is coming out of the exhaust pipes, either blue or straight black.
blue being really bad, and black being fixable.

Before doing anything else, reset the timing to normal. If you can't pull a number off the car, then 6 degrees BTDC should do it. After that, check the choke rod adjustment, if the choke plate isn't closed after the engine is warm and shut off, it'll force too much air and gas into the motor and cause all sorts of ugly problems like dieseling, and backfiring. I would also perform a compression test, and a leakdown test to see what kind of shape the cylinders are in.

Hope this helps!
Ben

Hi again,

Thanks for the advice!

When I ran the car the other day, I had a screw driver jammed in the carb to hold the choke plate open. The car was warm enough to run without the choke.

Anyway here is an update to the grandpa car’s condition. The oil was changed to eliminate any possibility of fuel thinned oil causing the knock. The filter was also changed. I put in six new plugs and started the beast up.

It’s still hitting on about four cylinders. I did a compression check on Cyl #1 and found “0” Psi. # 3 had 90Psi. I pulled the rocker arm assembly off the left hand cyl head and pressurized Cyl #1 and discovered that most of the air was leaking out the exhaust valve.

So the head is most likely going to need a valve job. I still haven’t a clue as to why the car knocks, however it seems pointless to continue. Also it seems odd that a perfectly running engine would disintegrate so suddenly. It’s a curious puzzle.

Although the car is in good condition, it dose not seem worth the expense of repairing it. I’ll go ahead and list it on ebay.

Thanks for trying to help!

jim