Old school engine work

I'm still working on getting my '51 Plymouth to actually fire on 6 cylinders. From driving it and adjusting valves I got compression from 60-30-0-0 -60-60 to 60-60-35-0-60-60. 60 PSI on all 6 is enough to make the engine run okay as it starts near instantly and generally runs great other than the skip

I actually did a leak down test and found the intake valve on #3 leaks pretty good ( 35 PSI ) and the intake valve on #4 leaks a lot. The rings seem to be okay but being I can't exactly hold pressure I'm not sure, but there isn't much air going out the tail pipe. I also found that the #4 intake valve seems to stick up just a little with a borescope.

I ordered intake and exhaust valves for both #3 and #4 cylinders, NOS valve stems, retainers and keepers to eliminate all possibilities that way. If the valve seats are in decent shape, can I just lap the new valves in? Normally I'd drop the cylinder head at a machine shop and have new guides and seats installed/ cut but being valve in block, I don't have it that easy. From reading the plymouth manual, I know doing some of this stuff in car was common/ expected back then. And how can I test the rings? Is the timed liquid test accurate? If the rings are bad or if there is light damage the manual says that I can hone out light imperfections and only to re bore if it's out of taper or out of round tolerances, which are quite generous it seems. Stuff I know wouldn't fly at a machine shop today. Hopefully tonight I'll have the head pulled for a second time

 

There is no reason you can’t fix/overhaul most everything in the car with the correct tools. If you’re removing the head and pan and your crank is fine. I would remove all of the pistons and rods, clean up all the bores with a glaze breaker and finish with a carbon ball. Tape or rubber hose the rod Journals and turn the crank in the hole your glaze breaking to have the most space for the glaze breaker home. Have a pan under the engine (I like 3’x3’ white plastic for washers and dryers) and I squirt with kerosene or diesel fuel when doing the work. Put in a new set of rings…cast iron rebuilders are best. You can have up to a .030” gap and be just fine. I can’t remember the flat head 6 valve guides but a good lapping will do wonders wwith ne seals. Don’t worry about the width on the valve seats it not a race engine. You can actually roll in new main bearing with the crank in place. Egge can supply you with all the parts if you can’t find them online. I knew guys in the 60’s who did jobs like this every weekend for extra money.

 

I pulled the head and really inspected the bores and they look good. Filled the suspect bores with wd 40 along with one known good cylinder and they all held the oil for hours. Intake valves on 3 and 4 are pretty bad. 4 doesn’t hold back liquid at all and 3 holds a little. If I get time tonight I’m going to pull the valves on those cylinders and see if the seats need cutting. I have the new valves coming.