Thread: Ford Flat Head

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I am getting set on a new project 1938 ford 5 window coupe . have decided on most but still not sure on motor. leaning toward the flat head however do not know alot about them. parts power ect. This will not be a racer however would like it to preform and cruise down the high way. Any ideas advice would be welcomed . Thanks

I always love it when people want to know if a flathead can be made to "cruise" at highway speeds. What do they think, that they cant go above 35mph stock?

Flatheads are cool and great IF you are building a "period correct" hotrod and have a limited selection of engines to work with.

However, if you're building a modern rod (you know one with A/C and billet bits) the OHV engines are much better in performance and durability than any flathead.

Just my opinion,
Abe

Uh yeah, flatheads arent dependable, cant perform worth a damn and are only good for period correct rods and restos. Might as well relegate them to the back corner of some museum.

Thanks abe, youve changed my opinion. Ill be sure to pull the flat six out of my daily driven 53 plym and put a small block chevy into it with a th350 trans, because ohv engines are dependable and flattys arent.

I said durable, not dependable-as in you will not have to rebuild as often.

And as for perfomance: I'll bet that you can't find any flathead that will produce as many steetable, dependable and smooth HP per cu. in. as a new LS1 smallblock.

Abe

Welcome willy.

There's lots of good info in the prior threads, hope you take the time to read them. Unfortunately you'll have to put up with reading some ignorant crap from wannabes who think old, obsolete stuff is the only "real" thing.

You can do a flathead Ford V8 and have a reliable, reasonably powered car, that you can "cruise down the highway". But there are caveats. While they were a marvel in their day, the technology does date back to the early '30's. The blocks are prone to core shift (where the sand core pieces in the molds moved as the iron was poured) which can lead to thin cylinder walls. Yes, later model engines could experience that too, but technology did progress over time and it's almost a none issue on more recent engines. Also, the flathead Ford V8 had the exhaust passages route past the cylinder walls going from the valves to the exhaust manifold. And then the foundry didn't always get all the core sand out of the cavities. Motor City Flatheads, a noted builder of high quality Ford flatheads, (listed alone with many other sources at this link: http://www.roadsters.com/flathead/#Sites ) goes through a major rodding (meaning steel probes) procedure, along with shocking (dropping repeatedly on a sheet of plywood) to dislodge trapped core sand. The owner of the company claims he's never found a flathead Ford block that didn't have some sand left in it, some more than others. All of these things lead to the tendency for some flathead Ford V8's to run overly hot. But there's more, especially if you plan on highway driving above 50 mph. The rear gears on most stock Fords were in the low 4's. Great for around town driving, neat for stop light games, but not good for freeways. The engine ends up working too hard, and only the best will not overheat on the highway. Higher gears, or overdrive, is advised. Also, the blocks are prone to cracking, particularly in the valve pocket area, especially coming off the exhaust seat.

Before you build a flathead Ford V8 have the machine shop do a magnaflux (check for cracks), and a sonic test (check cylinder wall thickness), and then all the other checks for wear/straightness/flatness that is normal, before spending any money on machine work. It's not uncommon for someone who want to build one of these to go through several block before finding one that will be useable for a quality engine. The best engines to use are the 59AB or 8BA, designations are cast on the blocks/heads.

All of this adds up to a lot of dough, especially if you pay to test 4 or 5 blocks before even getting started. Then the parts are pretty pricey, especially now that these engines are trendy. Some are new after market parts that are still produced, but a lot of the stuff (blocks, cranks, rods, etc.) are either reconditioned or old stock (cha ching!!). However, if that's what you really want then you just have to step up. You will save a little if you keep the original drive train, so it could come close to a wash if you don't get too exotic with the engine.

Those of us who lived in real time back when remember why the small block Chev (and a few others) became the engine of choice, and why hardly anyone even used a flathead Ford V8 much after 1960 except for the hardcore Ford V8'er or the down and outer. If you wanted affordable performance, the flathead couldn't compete. It's only the past 10-12 years that the nostalgia upswing has brought it back into fashion and wider use.

Like Abe said, it depends on the theme you want to build to.

Again, if you do decide to build a flathead the 4" Merc stroker crank will add a lot of torque and I have been trying to unload my crank to someone who would appreciate it. If you want a reclaimable 4" Merc crank with rebuildable rods let me know and I will let you have it for less than a new one is from Speedway. By the way, the Speedway catalog shows a lot of parts for flatheads, but I do not know about the quality; it would seem that if you can find a good block (????) the rest of the parts are available. I can throw in a Merc flywheel that can be chopped to your specs too. The main problem is to find a block that is not cracked. As Bob said a lot of the blocks have been bored at least once and then they tend to crack either from core shift or overheating due to rear ratios that were much higher than are used today, 3.78:1 was standard and a lot of street rods routinely used 4.11:1 and as Bob said that overworked the engine. On the other hand, maybe there are still a few high dollar original blocks left from the "French surplus" site, but you could buy a very good crate 383 SBC for less money than one of the French blocks.

Don Shillady
Retired Scientist/teen rodder

BTW Don, if you really want to shed that Merc crank you should run it on ebay, it'd be gone in a week for top dollar.

Throwing in my biased opinion here...

Do what you want to do, but do it right. Before any parts are purchased or the torch starts cutting, do your research and have a plan. Ask questions... lots of them. I have no idea what your skill level or experience is, so don't take offense at anything I say



Are you trying to achieve the look and feel of a certain era of hot rodding? Are you trying to keep the car all one brand? Are you trying to come up with something unique?

My ideas...

Drop a 312 Y block in it, bonus points if you can get a Paxton for it.
Find a nailhead Buick and a Crower log manifold, see how many carbs can fit on there.
Use a 354 or 392 hemi. Valve covers big enough to serve a turkey in at dinner are cool.

Search until you find the best chrome man possible. See if he will marry your daughter so you can get a discount.

If you want a 50s style rod, why not go with a Olds rocket engine(1st encarnation) bolted up to a Era-matching Caddilac tranny? The Rocket V8 was the first OHV, and it took a lot of the thunder away from the Flathead.

Nothing wrong with using a flathead as I had many in my early cars. But what Bob says is so true. Get the block Magnaflux. I didn't on my first flattie and after putting in alot of time and money I started it up and found the block was cracked. It was carcked so bad that the water would work its way pass the jackets and sit on the piston. If your going to bore it, keep it down to no larger than .040 over. Good luck in finding a good block.