1941 Flathead blowby

[41Joe]

Hello,
This is my first post to this Forum. I just recently aquired a 1941 Ford Tudor. Pretty straight. Frame is really nice and clean. I do have a problem with really bad blowby. It billows smoke out the breather cap like no tomorrow. I just checked the compression and I can't get more than 60 PSI on all cylinders. And that is with letting it crank until it builds up pressure. It's more like 30 PSI. It runs, but has a really rough idle.
This is where I need the experts help.
I was thinking of replacing the valves with the later model 1 piece valve guides and adjustable lifters. I did some searching here and it sounds like I can just replace the valve assemblies and lifters without doing any machine work besides lapping the valves. Is there anything else that needs to be done besides adjusting the lifters?
I probably need to replace the rings also. Here is my big problem. I don't really have the place to remove the engine. Is it possible to drop the pan so I can remove the pistons? I know these have the one piece pan that attaches to the tranny.
Second, what is involved in replacing the rings? I know some auto parts stores have the tools to remove the ridge at the top.
Sorry this post is so long, but thanks for any advice that can be offered.

[Bluebell]

Hi Joe, Is it firing on all cylinders?
Has this engine not run for a long time?
Some rings may be stuck. They may free up with use.
Answering the above questions might help with the answers from other people.
Good luck!

[trainguy]

Sounds like you may need a total overhaul.If your engine is original is has the infamous "tin cans sleaves"which was not one of Fords better ideas when worn they must be removed and the engine bored.Most often they are bored to 3 3/16 dis which is std. For a 239 ci engine.Sorry to be the messenger of bad news.Phil

[chap52]

Been there, done that.
Yes the pistons can be removed with the engine in the car. Remove pan, borrow a ridge reamer from Autozone, remove rod caps (make each so they can go back on the right piston in the same direction)
You may have to drop a tie rod to get the pan off. Also, I don't remember clearly as it has been 50 years since I was under a '41 but as you get into it you will see how to access those rear bolts. May have to remove the starter plate (You have to remove the starter anyway).
I have used this approach before, even going as far as loosening main bearing caps and slipping out old main bearings and sliding new ones in. A bit Neanderthal, but...
Then three years later I pulled the engine and did a much more complete job. Sure a lot easier with the engine on a stand.
You can rent a hoist, buy a $50 engine stand from Harbor Freight and go through the process of removing the radiator, then the engine, or...
BUT FIRST, if this engine has been sitting for a long while I would remove the plugs and squirt a little oil into each cylinder then re-check that compression. Beware, uncovered spark plug holes with oil in the cylinders will blow out oi all over the place. Cover those holes with a rag. You may get enough compression to drive this baby for awhile before you tear into it. It's all part of the "bonding process".
Also Joe, add your location to your profile, there may be a "flathead" guy in your neighborhood who could take a look at your project. OOPS, can I refer to someone a "flathead" without being sued?
Most importantly, ENJOY THE ADVENTURE, and don't be afraid to ask the knowledgable folks on this forum when you get perplexed. Welcome aboard

[MGG]

I started my 1934 flathead about a year ago after about 20 years of sitting. It had substantial blow-by for a while afterwards. The blow-by stopped after several months of intermittent running. As stated by Bluebell some of the rings must have been stuck and they eventually freed up with some running. Maybe you will be so lucky.
Recently I started up another old truck (not Ford) which had not been run for a long time. It had very little compression. I put Marvel Mystery Oil in the cylinders and let it soak for about a week. That did the trick. Now it starts and runs well. It must have also had stuck rings or valves.

[41Joe]

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Thanks for all the replies and advice.
I guess you never know what your going to get in a flathead. I had a 50 Lincoln that had been running but sat more than 10 years before I bought it. Tune up, oil change, and a little rewiring and the engine fired right up.
As for this engine, it does feel like it is missing, I am not really sure though. The plugs where really fouled. When I pulled them they were all covered in a somewhat thick black oily soot.
Maybe I can get a consensus here. If I replace the rings, do I have to hone the cylinders? If I do, how do I do that?

[41Joe]

I'll try the Marvel Mystery oil. I heard good things about that product. How much do I put in each cylinder?
New plugs, oil change... you never know.
Would using non-detergent oil cause any problems?

[41Joe]

So the first time I did the compression test I didn't know what I was doing. I didn't have the throttle fully opened. So I tested it again last night with WOT.
#1 65 psi
#2 63 psi
#3 70 psi
#4 72 psi
#5 45 psi
#6 60 psi
#7 58 psi
#8 60 psi

I didn't do a wet test yet, except on #5. The psi went up to 50. I know the rings on all cylinders are pretty worn.
Is 60 psi too low, or is it okay to run a little longer?
On #5 from what I have read here, the valves must be sticking. How do you go about fixing that? I was thinking of taking the intake off and cleaning out any sludge build.

[Bassman/NZ]

Those figures indicate worn rings. If you pull the engine, hone the cylinders, install new rings, you should see the figures jump to 95-105 at a guess. I did this same thing, plus installed new valve guides and lifters, and lapped the valves. While it was in pieces I also replaced the main and rod bearings. With milled heads I now get 125psi on the left bank and 135psi on the right bank, plus 60psi oil pressure. BTW: pulling the engine is so much easier than trying to do it in place, IMO.

[41Joe]

Nice.
That was going to be my plan in a few months. Right now I just don't have a spot that I can work on it.
Bassman, off the subject, how do you like it down in New Zealand? My parents moved there 15 years ago to Mangonui.

[WestCoast]

for an in frame engine over haul (rebuild in the car) I would strongly advise you to use Hasting Steel Vent pistons rings, they are cast iron and conform to badly tapered cylinder walls, they really help to hold compression and control oil burning, but pulling the engine is really the easiest way to work on the engine, I bet there is some one in your area that will let you use his engine puller and help you get it on a engine stand, if I lived closer to you ( I live in no calif) I would loan you mine till your done with it

[41Joe]

My plan is to get it in running condition and find another flathead to rebuild very slowly. The first flathead I had about 15 years ago had $7000 in machine work and all new parts. I regret selling it.
It's nice to know that there are still helpful people out there willing to lend a hand.

[Bluebell]

Bassman, The oil only raised comp by 5 lb. I would agree the rings were the problem in an engine recently in use, but no change essentially to compression. pressure indicates valves, because the oil should act as a temp. seal and raise the comp. I'd suspect rust or carbon around the seats and stems. To me, you either do you best to make it run reasonably or pull the motor and do it properly.
Id be checking all levels, making sure there is spark at all cylinders, and taking her for a run putting it under load to try and make those rings move in their grooves. If she turns out to be stuffed (why was she parked up in the first place?) then spend the $$ and do it properly.
Just my opinion.

[cmbrucew]

If you suspect carbon fouled valves, an old trick was to hold a fast idle, and squirt water into the carb with a pump oil can. Don't get carried away.
Bruce

[dono50]

Are you getting blow by from the oil filler pipe? If so, check for a blocked oil breather pipe.
I agree,cyl 5 most likely valves