I pulled the motor out of the 51 to check what the insides looked like.The motor did run prior to taking it out and it seemed to run pretty good. The compression was low 40 -45 lbs per hole. This motor has not run in about 20 years prior to me running it . When I got it started it had good oil pressure 50lb. I have taken the heads intake and pan off. The mains look good have not mic any thing yet no scoring on the journals just the center main bearing cap bearing look like not wear but maybe from sitting that long it was I would have to pic it to show what itlooked like. I wanted fresh up the motor and put new rod and main bearings in. Put new water pumps on. There is alot of rust in motor.The Thermostats were cloged with rust and heads had some of the holes plugged with rust.The valves have carbon on them which have alittle build up.Lifters rotate and move well when turning over by hand. The down fall these are not adjustible lifters,my under standing is that the stems have to be ground to make any adjusment.The motor had no water in the oil I have looked between the valves looks good no visable cracks.
I would like to get your input on what I am planning to do now first I was going to clean up and put back in.Now Check the crank and if possible new bearings new rods bearings. I would like to take the block have it cleaned and fluxed for cracks and new cam bearings.The valves is another problem
if I were to take out and put back in the same way I took apart after wire brushing What are the chances it would be right? There very little sludge on the valley and pan.This motor is a remanufactured motor from Rogers in Atlanta Georgia the tag on it said main were 0.10 over and rods 0.20 over
can not read the cyl spec. And yes new rings .
Or may just bite the bullet and do it all the way with new lifters and cam deck the block pistons balance the lower end. $$$$ Got to love our sport.

 

By all means get it thoroughly cleaned to get all the rust out of the water jackets, preferably dipped. Even after that it pays to take some metal rods and drop them thru the water passage holes in the deck and chip away at the crud in the lower, rear part of the block. The engines tilt to the rear and that stuff can't get out when you drain them. High pressure water spray thru the holes to wash the crud out the front of the block where the water pumps mount. This pays real dividends in a cool-running engine. Same treatment for the heads.

I did pretty much what you are asking; I took everything out, kept track of where it went, cleaned them, and put them back. I didn't fix the valves that had too much clearance and now I wish I could have, but I don't have a seat grinding machine (for valves with too much clearance). My engine has a few "tickers" but runs great for the most part. I am probably going to take it down and do it properly this winter, but I've gotten almost 5 years of driving out of it for the cost of my time and a gasket set.

If you put in new lifters, you'll have to worry about break-in with the new low-ZDDP oils, be cautious!

PS -- piston O/S should be stamped on the piston crowns.

 

I'm in the same boat with an old rebuilt, that was never quite finished. So I'm subscribing to this thread, and thanks. (I haven't done mine yet, due to space limitations in my garage, and not sure if I had to move this last year or not)

 

Take the heads and soak them in a solution of wood bleach (hardware store) and water. Make sure it says oxalic acid. Leave them in the solution for a few days. Check the progress. It will clean the rust out without eating the metal. I would go through and clean everything else, as has been suggested. Might even plastigauge the crank.

 

Thanks Fellas AlbuqF1 havi 1952 for your input. Also Dmtrkr for his valve tool, I did a version on it kindof. The only change the handles to long ones that you can put the attitude on.
I took out the valve and guides they came out pretty easy.The flat head gods must be looking down on me.I think after I get the block cleaned and flux Check the bore and if that is ok put in new mains and rods bearings
of course check the end play on the crank. I want to be sure the lower end is correct and strong. I did do the plastigauge on the mains which were
0.0015 Which I think are in line. i didnt have the yellow for the rods but i am hoping they are good after I check them. Now I am thinking of putting the johnson adjust lifter in and new valve guides and seats valves and springs because I would like to put one of those smile drive by cams in.
I probally do a new oil pump along with new timing gears . Now I have to think about carb and dizzy . i would like to do a couple of duces with a high rise,not sure on the fire of the dizzy.If ya"ll have any input please let me know.
Again I would like to thank all for the the great information and help.Oh yes the heads. What to do?