Classic/Antique Car Repair: Problem 1948 Packard Deluxe Club Sedan, exhaust valve seat, head gasket leak

Question
I see that I have a head gasket leak between 4&5 cylinders on the side where the exaust and intake headers are located. Also upon heavy excelleration it shouds from the inside metal on metal but when in the engine compartment it sounds as if it is backfiring through the carb. I don't see any flames or smoke through the carb. I have 53,000 miles on the car and have driven it about 2500 miles in the past 2 years without any problem. The first indication was the loss of water. The oil looks clean with no filings & changed each spring and fall.

Thanks,

Terry Benson  

Answer
This is the usual place for this problem to crop up, because it is the hottest place on the engine (between the #4 and #5 exhaust valves).   

There is only one thing to do, and that is to remove the head and inspect the block surface very carefully, looking for any erosion on the surface or a crack from the exhaust valve seat extending to the water jacket inside the block.

If you can't see anything wrong on the block, then look carefully at the old gasket to see if you can find a passage between the two cylinders.  

If you're really lucky, all you'll need to do is to clean everything carefully and install a new head gasket.  

If you're not so lucky, you may have to have a new valve seat inserted into the block, or possibly even worse.  If you have a mechanic you trust, just let him diagnose it for you - he may want to send the block out for a magnaflux inspection - which if it fails you will have to have the crack welded up, or even replace the block.  This is really the worst case I am talking about, so please don't assume you are that unlucky.  But you have to pull the head and look to find out.

Sorry about that, that is one of the few weak spots of these engines, especially as they get old and crud builds up in the water distribution tube and in the block, and perhaps someone has set the valve clearance a little too tight (causing the valve seat to burn).

Good Luck to you, and let me know what you find out.

Dick Benjamin (still driving my 47 and 48 Packards after all these years!)