Questions on 1946 flathead engine readings
 

Hello, I've been driving my "new to me" 1946 coupe for he past couple months nearly everyday. It runs very good, but just seems to lack a lot of power. I bought the car with the understanding that the engine is tired and will need to be addressed. I also talked to two past owners (back to the 60's in the case) and both asked me if I've fixed the engine yet. So it seems that this car has notoriously had a sour engine.

It runs great, always starts, does not smoke. It is stock aside from headers and dual exhaust. It seems very faithful and reliable, so I've been driving it like crazy. Last night I decided to do a compression test, and the readings actually surprised me

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This is cranking with 6V as well. I expected them to be a lot lower. Also, all 8 plugs look great having a nice brown center. Now I'm starting to wonder why the engine runs so "tired". It has a slight miss at higher RPM's occasionally, otherwise it runs good but just does not have a lot of steam. Can anyone think of anything that may be holding it back?

It has all new tune up components, distributor by Bubba (fully advanced), rebuilt Holley carb. I have not peeked inside the engine. The guy who bought it in the 60's told me the engine was stuck when he got it. I assumed it broke the rings when he "drug it until it freed up" and it had low compression...but without burning oil and decent compression readings I'm now re-thing that. Odometer shows just over 50,000 miles. No idea if that is original or not, but the car is a nice old car.

Anyone have any ideas?



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Re: Questions on 1946 flathead engine readings
 

My idea is for you and your dog to enjoy the car. It doesn't sound like anything is too bad for an old Flat Head. Later on when you have the time and money, rebuild it.
It is a good looking car from the photo. Enjoy !

Re: Questions on 1946 flathead engine readings
 

Give it a test drive without that air cleaner...those little chrome ones are at best marginal and at worst absolute engine killers.

Re: Questions on 1946 flathead engine readings
 

I knew someone would bring that up. I have run it with no air cleaner at all, no noticeable difference.

The car runs OK down the road. Underpowered on the highway and I live up a long steep hill (mile long, 6% grade) and the car struggles reaching the top of the hill in high gear. All my other flathead cars have zero trouble making it to the top. This car just feels like it does not have a lot of power. Like it's not getting full throttle (hey...maybe I should look into that...)

Re: Questions on 1946 flathead engine readings
 

If it has a stock rear end it has 3.54 gears versus 3.78's that were used before and after 1946 which may be part of it. I would still check the carb.

Re: Questions on 1946 flathead engine readings
 

When I got my '51 almost 40 years ago, it had compression figures like that. Like yours, it ran great, didn't smoke, had good oil pressure, but was a little doggy. It soldiered on admirably until last year, when it started to make a funny noise and the starter Bendix went out. That was a year ago, and I'm still working on my replacement engine. As you can see from some of my threads, I succumbed to the "creeping elegance syndrome" and it's attendant problems, and it's still in pieces. Since you seem to have other cars, I wouldn't tear into this as long as it seems to run OK. On mine a complete ignition tuneup and a GOOD carburetor after I had it a couple of years helped performance quite a bit. Me? I'm satisfied to putt around in my "parts runner" (inside joke).

Re: Questions on 1946 flathead engine readings
 

True and I have a pretty tall tire on the back. I have not checked rear end gears. Car rolls very nice, I know it's not a brake sticking or anything.

However, with 3.54's this car should just sing down the highway...but this car only does about 60-65 and it's done. I wish you guys could drive it...it's definitely not "right"

Re: Questions on 1946 flathead engine readings
 

This car has low oil pressure. Both the stock gauge and known working mechanical gauge I installed read around 20lbs cold and nearly down to zero warm. I am not too concerned about it. And not too concerned about the engine either. But, it I could do something simple to improve it...that's why I asked for the brain storming session.

I bought this car as it has a back seat, and serves as a great family car. It's nice having a nice roomy car we can all take out and enjoy...tired engine or not!

http://i307.photobucket.com/albums/n...ps8ztlzeez.jpg

Re: Questions on 1946 flathead engine readings
 

The flatheads had a lot of rings for oil control both above and below the wrist pin. Gravity is a big help with oil going through worn valve guides so the old engines only start to smoke when the rings are completely worn out or if some are broken. Broken rings will do a number on the cylinder wall of the affected cylinder so I hope you don't have that problem on that one cylinder. While your engine does have compression on all 8, some of them aren't as good as a person would like. Overhauls are expensive on these motors but when they need it they will let you know. If all your plugs look like that one in the photo, it doesn't really indicate major problems but it is a bit dark for the modern fuels we have to work with. The 3.54:1 gears aren't all that good in hill country. That's where a Columbia Overdrive with shorter gears works good.

Re: Questions on 1946 flathead engine readings
 

Yes the taller rear tires would result in an effective higher (lower numerically) gear ratio. I would be curious if you put the stock 600X16's on the back if it changed anything. I remember reading Ford changed back to the 3.78's because of complaints of loss of acceleration on the 46's with 3.54's. Sometimes even a slight change in ratio creates a problem. Back around 1995 Ford went to 3.31's in the F150 5.0 trucks I'm sure trying to get better fuel mileage instead of the 3.55's. Sold 5-6 of them right off. Had almost every person that bought one complaining they were shifting in and out of overdrive on the hills. Nothing you could do about it. Every truck I ordered for stock after that had 3.55's.

Re: Questions on 1946 flathead engine readings
 

All plugs do look like that. They are pretty nice, my dark garage does not do them justice. I am fairly certain the engine has never been out of the car, just by judging from the fasteners. I am sure the engine is tried and needs rebuilt...I just cannot find an direct evidence as to why it runs the way it does.

Re: Questions on 1946 flathead engine readings
 

I will check the gears for sure. My 53 convertible has low 3.something gears (I am pretty sure automatic transmission rear end gears) and I am pretty sure a 255 Merc engine. It would run circles around this car. It has a few more cubes...but probably weighs quite a bit more as well.

Re: Questions on 1946 flathead engine readings
 

With compression readings that high, and assuming the dizzy is up to snuff with Bubba going thru it, it seems there are only about two possibilities left. The least-likely of those would be some sort of restriction in the exhaust system. The only other thing left is the cam somehow being out of time. Hope ya find it and report back. I sure do like that car! DD

Re: Questions on 1946 flathead engine readings
 

How about throwing a vacuum gauge on there to see what you see? They can be a very useful tool. Simple and quick test.

Re: Questions on 1946 flathead engine readings
 

Some noise from Ford: before WWII, Ford published performance standards for mileage, acceleration, and top speed in a form that could be used by dealers to evaluate poor performance complaints. The specs gave minimum acceptable performance, and if a car couldn't meet those something was wrong. If the car did meet them the problem was located in the customer.
naturally there's no '46 Ford in the prewar specs, but a car very close in size, power, etc. is in there, assuming that you have 3.54 rear.
See how your ride stacks up...the 1940 Merc I suggest as the reference point needed to reach at least 88 on the speedometer, and top gear only acceleration from 10 to 60 had to happen in no more than 23 seconds. How far off are you?

Re: Questions on 1946 flathead engine readings
 

I'll investigate this weekend haha.

Re: Questions on 1946 flathead engine readings
 

If I can find the actual '46 numbers, you can chug on down to the Ford dealer and order him to fix it! You have rights as a consumer!

Re: Questions on 1946 flathead engine readings
 

Chris, back in the 70's my neighbor worked for the state of Calif investigating auto accidents. He showed me how to rebuild a flathead. One thing that I recall was that he told me that the compression should not vary by more then 10% between cylinders.

Re: Questions on 1946 flathead engine readings
 

Had a similar problem in a '46 Ford pickup but we had one no firing plug.....turned out to be of all things......a bad distributor cap! :)

Re: Questions on 1946 flathead engine readings
 

Lovely looking car.The lack of performance is possibly a combination of issues.The compression pressures are not optimum and if its running 3.54 gears on bigger tyres on what is quite a heavy car then these factors combined would hold it back.Too higher gearing will soon take the edge off the performance of a standard flathead engine and would be interesting on standard tyres on 3.78 ratio.Cheers.