Rookie needs help with 50 flathead

[Pats1950]

Hi guys new to this bought a barn find 1950 a few months ago. Motor was frozen found another was able to rebuild with parts and pieces. New mains new connecting rod bearings one new piston New rings on all pistons.fired right up been trying solvecooling issues every since. Compression 95 pounds on all but number 3 which is 30 lbs not sure if this is causing overheating issues. Have double gauges heating issues appear to start in this bank. I have changed head gasket twice can see no cracks in block. I picked up a 42 flathead 6 cyl getting ready to pull v8 and put in 6 cyl unless anyone has any suggestions. I did put new valves in number 3. I had never done this before enjoying the work just getting a little frustrated. My son thinks the block has an issue I can not see. Have a good day and thanks.

[Barry-ct]

Sounds like you have a couple of issues there. Did you lap the new valves into the seat in the block? That would tell you if the valves were seating properly in the seat. If it is not, most likely the valve is not sealing, thereby the cyl can't build up proper compression because it's leaking by the valves. Or, the rings haven't seated to the cyl walls yet. Do you get any backfiring thru the carb or exhaust. That would tell which valve is not sealing properly also. You say you rebuilt the motor, did you have machine work done, new rod and main bearings, piston rings, cyls bored at all, etc.. or did you just "refresh" the motor without machine work. A magnaflux of the block would have been the first thing I would have done to make sure the block was good and not cracked. If it tested good, then a rebuild. Any water in the oil? Can you get a infrared temp sensor that you can point at the block and various spots to better tell how hot it's running?
You need to post exactly what you did during your rebuild so others can better help diag your problem. Don't give up on the V8 just yet.

[Ross F-1]

Sounds like a valve in #3 is sticking open. Even lousy rings will give more squeeze than 30 psi if the valves are halfway decent. Did you replace the guides?

Pull the plugs and rotate the engine while watching the valves on #3 thru the plug hole.

[George/Maine]

I would look at the valves and see if the other valve work like #3 check cam lift and valve clearance.
Check the bolt area head bolt and see if blowing into water jacket.
Move piston up and down its there right before your eyes.

[Pats1950]

Ok thanks guys no I did not have machine work done I have two kids in college so limited budget. Starting from the beginning this is what I have done. Pulled motor and stripped down by the way the no 3 cyl was the one piston I had to replace it was seized had to beat out cylinder walls after honing all looked good block was still stock bore.Cleaned up block and heads as I said before new main bearings rod bearings and rings. I replaced valves on number 3 and lapped them visually looked pretty good even better than the other cylinders carrying higher compression. I did a check for hydrocarbons in coolant it showed they were present this went away on 2nd head gasket change. I changed valve guides and put in new seals. No water in oil on oil in coolant. Can drive about 5 miles than it starts creeping up the pass side bank seems to be about 15 degree hotter from the get go. I have and infrared it it shows the same as my dual gauges. I shut her off when it gets 210 and continues to climb. Again thanks for any help. till having fun and learning what my dad did for a living.

[JSeery]

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This information is a little late for you, but you really need to have flathead blocks checked for cracks as they almost all have them and you need to know where they are and how bad they are. The second issue is cleaning the water passages, a lot of flatheads need extra cleaning in the water passages. Next would be good water pumps. This does not necessarily address the low pressure in #3 cylinder. As it was the one that needed work in the first place there may still be an issue with it. How did you hone it out, what type of hone? How much oversize was it when you finished honing it? How much taper? Could be separate issues or could be related. Flatheads are also very sensitive to ignition timing as far as overheating goes. Is it running lean? Lots of things could be going on.

[ford3]

it really doesn't matter which valve is sticking, either one will cause compression lose, first make sure your timing is not slow, if you have no water in oil and no water coming out the tail pipe you can just about eliminate a cracked block or blown head gasket, that leads us to the radiator, use your heat gun on it, both sides of the top and bottom, heat should be about 40 degrees cooler at the bottom than at the top, both sides of rad should read close to the same, if the radiator is hot at the top and cold at the bottom the rad is plugged, plugged rads usually show up as a slow temp increase the farther you drive the car, try 4 or 5 oz.'s of marvel mystery oil in 10 gallons of gas, and put a qt of mmo in the oil, if ts a sticking valve that should clear it up in a couple hundred miles, I all ways face all new valves, even new ones can be warped a .001 or so, and I polish the valve stems before I install them in the engine, I chuck them up in the drill press and use real fine emorey cloth, and I would be nice if you would go back and edit your profile , city and state, some one may live near you and can stop by and give you a hand

[Bassman/NZ]

Did you clean out the block? When I did mine, I found one side relatively clean, the other had quite a bit of gunk (rust scale, sand, bits of ?? ). I had the pumps off, and shoved a water blaster wand up as far as I could. Also a very long screwdriver. Amazing the crud that came out.

[Pats1950]

Thank you all edited profile live in Rome City, Indiana trying to answer all questions. First the cyl with issue is number 2 second one back pass side. Both motors I have appeared to have an issue with this cyl. I am getting no backfire from exhaust or carb. there is no water out the exhaust. Not loosing and coolant until it starts to get to hot and push out overflow. water pumps are new from speedway. Radiator is new alum from Champion old one was shot. I scraped dug and power washing and flushed inside of block and heads.Have tried two different heads on block with same results low on no. 2. I switched distributors last night same results. Timing light does not seem to show advance when vac line is hooked back up? I also rebuilt the Holley 94. New points cond, rotor and plugs. I have tryed with 6 volt and 12 volt. Still using stock fuel pump. Guess I will keep trying a little more before I pull and put in 6 cyl with everyone's help. I have one of the heads at machine shop being checked thought it may have been warped in the no 2 area. have a good day heading to work.

[JWL]

If there is no ignition advance the heating problem can result and the engine will be sluggish. Check the vacuum diaphragm on the distributor for rupture/deterioration.

[Walt Dupont--Me.]

Originally Posted by Pats1950

Hi guys new to this bought a barn find 1950 a few months ago. Motor was frozen found another was able to rebuild with parts and pieces. New mains new connecting rod bearings one new piston New rings on all pistons.fired right up been trying solvecooling issues every since. Compression 95 pounds on all but number 3 which is 30 lbs not sure if this is causing overheating issues. Have double gauges heating issues appear to start in this bank. I have changed head gasket twice can see no cracks in block. I picked up a 42 flathead 6 cyl getting ready to pull v8 and put in 6 cyl unless anyone has any suggestions. I did put new valves in number 3. I had never done this before enjoying the work just getting a little frustrated. My son thinks the block has an issue I can not see. Have a good day and thanks.

I've read all the replys but that 30# cyl bothers me. You said you replaced both the valves and lapped them in. How did you set the valve clearance? Did you butt grind the stems? What was the final clearance? Walt

[lesbliss]

I can't address the low cylinder but I do think that the secret to a cool running flathead is cleanliness. We run our '51 Mercury here in Las Vegas when the outsde temp. is in the triple digits and it runs 180-200. The most economical and effective cleaner I've found is white vinegar. Drain all the radiator and block and fill with 100% white vinegar. Less than 2 bucks a gallon at the discount places. Run it for several days then drain backflush and fill with a 50-50 mix of water and antifreeze. If this doesn't cool her down something is preventing water circulation.

Les Bliss

[D. Jones]

Like Walt I'm concerned about your valve job. If you replaced a valve or valves in #3 and lapped them in and didn't butt grind them for proper clearance one or both may not be closing completely.

[Pats1950]

HI guys again thanks for all your help. I plan on doing the following check vac advance for bad diaphragm. Set my valve clearance when I did initial refreshen at .017 exh and .013 on intake I ground the ends of valves, plan on pulling intake and check. I will get the vinegar and give this a try. My question at this point do you think the low compression and overheating are related or two seperate issues. Will keep trying all your suggestions and will post as I go.

[Bolts]

Pat, are you running thermostats? If so, try pulling them and see what the temp does.

[Walt Dupont--Me.]

You've got 2 different problems, overheating and low compression. What I'd do next is put air into the cyl with valves closed. I just made a couple of adapter to go in the plug hold for the air hose. Take an old sparkplug, grind off the lip where the porcelen goes into the plug and punch out the porcelen, brass a fitting on so the air hose will snap on. It only takes 20-30# of air, make sure valves are closed, if air is coming out of tail pipe, EXh valve not seating, if comes out of carb Int valve, If a lot of air is going Into the base, ring problem. If bubbles in radiator, head gasket. Walt

[Kahuna]

I had a new water pump (Drivers side), that had very little flow caused by casting flash inside the pump. I found this by trying to get thru the passage way with a piece of wire.
The pump was cast in India.

[George/Maine]

If your valves look good and cam has good lift, my only guess would be some thing in intake blocking air flow.

[BrianCT]

Originally Posted by JWL

If there is no ignition advance the heating problem can result and the engine will be sluggish. Check the vacuum diaphragm on the distributor for rupture/deterioration.

X2 !! Jwl has given you good advice.

[billwill]

Did you check valve seat and stem clearace when you installed new valves goodluck