So, I am not a flathead guy. I am a 265/283/301 guy. My nephew Colby is looking for a new project and he wants to build a 35/36 pickup (Imagine that). He wants a flathead powered pickup. I am trying to learn as much as I can about them to help him. So, bear with me…. What is the main culprit that causes the flatties to crack? Stress fractures? Corrosion? No antifreeze in the winter? From overheating? Where do they crack and how do I know before dropping the cash?
From what I have gathered the last couple of years,,,the biggest culprit is overheating,,,,and freezing . They are still out there,,,,,I found a great engine in 2019,,,,it is in excellent condition and I am going to try to get it together in the near future . It’s an 8CM,,,,,Mercury version of 8 BA,,,,I’m assuming your kin will be looking for something closer to the year of his truck ? Read up on it all you can,,,,ask around,,,,there are also many threads on here,,,Search and you will find . I even have a thread here,,,,I got sidelined from health reasons,,,,but I hope to get back to it soon . Good luck man . Tommy
Okay,,,,check the oil pan rails,,,,,check the decks . What kind of core is it ? Some of the earlier models had a few more critical areas of concern . Tommy
Excellent,,,,,I hope it is. ,,,,that will be a great core to build ! You don’t know what year do you,,?,,,,,,mine is a 49 . Tommy
Several threads on here about cracks in flatheads and they all mention the cracks between the head bolts or stud holes. The standing joke is that those cracks have a Ford part Number. Cracks in a valve seat are a little more serious. Best advice I can give you is if there aren't any splits in the cylinder walls or the outside of the block, tear it down and have the block magnafluxed. If there are cracks, you're just out the cost of the inspection, if not, it was worth the expense
I just typed " flathead cracks " in the search bar and came up with a lot of threads. You might have to dig into them a little but standard procedure is magnafluxing. Sonic testing for wall thickness is another thing you might want to do. Flatheads tend to build up a lot of rust in the water passages. I washed one out for about 3 hours one day and finally got the water to run clear.
That's a pretty good deal. I've got a 55 gallon barrel of citric acid in my back yard that everything rust
Okay,,,,that’s good to know . So if it’s a 40,,,,it’s not an 8BA,,,8CM . I was gonna ask earlier it was an extended bell block . Tommy
While you are looking for cracks make sure you check the area between the center crankshaft main web upwards to the cam shaft. The three bearing crank puts a lot of strain on the block and they can crack basically right in the middle of the support for the main center bearing.
I have small surface crack on one deck on Flo it's between a head bolt hole and a round water passage . I'm going to run Flo as is . Please show some pictures ? I use a magnifier to see after cleaning block
Do all the checks that have been suggested, then sit him down and help him do a comparison of $$$ between building a flathead vs. a SBC. The 'flatheads forever' crowd will raise hell with me, but the reality is, a young guy may not have a realistic understanding of what costs are involved, and how those costs may derail his project/enthusiasm.
My dad ran a flathead in his 36 until the 265 came out. After that he never owned another one. I was raised that flatheads were scrap iron. Thus the reason, I don’t have a clue about them.
A side valve looks good in a fenderless car...and the light car will run ok with the relatively low power output... Otherwise run a SBC with non bolt hole heads, paint it orange and have a lot more power for a lot less money...
If it's a true 40 Merc block, it could be the "99" block which is considered gold in the flathead world. Some in that era had a higher nickel content in the iron, and thicker cylinder walls. If the intake surface is "raised" that's a good sign. If it's flat no luck. Then check on the upper front right corner of the block for a 99 cast into it. Or stamped. But, some of them actually didn't have any 99 marking at all, just had the better iron and walls. You can also just look in the water jackets and see how damn thick those walls look compared to a scrawny Chevy.
You're right to be concerned about possible cracks, however, you know the application and maybe the intended use of the truck. I think the intended use of the pickup is more important because a younger person may have expectations that the FH can't live up too. Even a mild rebuild on the FH will be double a sbc at least. IMHO, drive-ability of a FH will be improved with a modern full synchro overdrive transmission . Hopefully, I'll be able to prove this out with my own truck project next year.
Interesting. Maybe I shouldn’t have given it to him. Nah, hope it is what you mention. I do know it came out of a 40 Mercury, and was told it was original. But, I also never looked into it much since I didn’t figure I would ever build it. Hoping it can be a decent motor for Colby not needing a fortune spent on it. I’m more like Chris and would rather just throw a bigger V8 in instead of spending a lot on a flathead. I’ll throw away a lot of money on something like a y-block instead.
Flattys are cool, check for cracks around valves, head bolts and in cylinders... Freezing or overheating cause cracks, there are still good blocks out there. There is something about the sound of a Flatty... The look is also cool... But typically a machine shop magnaflux will reveal most things... Side note, the later blocks 8BA etc have better cooling and better iron etc from all I know... We saved this 8ba... Lapped valves, oiled the rings, and she fired up... This is how I bought the car with it in there.
Thanks guys. He is at that stage in life where he has giant dreams and thinks, that since he makes $12 hr he’s rich. Of course he lives at home and has no bills….
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