Thread: I've got a flathead Ford question.

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I know very little about flathead Ford V8's. I grew up at the end of their popularity, and we were too busy substituting Olds, Caddy, and later on Chevy engines to learn much about them.

About a month ago I bought the flathead and running gear from another member (thanks Paul ) that he removed from his '46 Ford. I'm going to build a little roadster pickup some day from Dan's left over body and these parts. When I tore the heads off to see what things looked like everything was pretty clean, including the bores. But when looking at the block I saw something that I didn't understand, the area surrounding the valves and between the pistons is COUNTERSUNK about 1/8 of an inch. I then looked at Dan's '49 Ford flathead, and his is totally flat in that area.

Is this what is referred to as "relieving" the block? Were '46 engines different in this area than '49's? I sort of remember hearing at one time that some flatheads came relieved, or maybe it was remanufactured engines that were relieved? I have researched this as much as I can on the internet and other old Ford forums, and still can't find anything. Some pictures show all flatheads as having a flat block in this area, some show a partial countersinking around the valves, but mine has a completely open path from the valves to the pistons.

The '46 Paul got these parts from was hot rodded a little, with stuff like a dropped axle, Posies spring, and 15 inch Merc wheels, but the engine appeared stock, except for red paint. I just wonder if someone has been inside here and done this modification or if some factory flatheads were like that.

Thanks for any help guys.

Don

You are right, it is relieving....kinda like porting but after the valves in the flow path. Since you couldnt cut the heads in the area between the valves and the bore (because you would hit water), relieving was a common hop up procedure. I read somewhere where some factory blocks were relieved but dont remember which ones. It was easy to do with a hand grinder.

I'm like you, I remember something about some blocks being factory relieved, but don't know which ones. Everything else in this motor looks bone stock, so I don't think any hop up tricks were performed. I saw a picture of one online and it was partially like mine, it was countersunk right around the valves, but there was a wall between that part and the cylinder. Mine is open all the way through.

Don

The factory relief on truck engines was simple, just a pass with a wide stone. The hotrodders did a more fancy job, matching the relief with the head gasket. The trucks were relieved more for the stress relief of thinner iron in that critical spot, it was thought to reduce cracking of the block. Any power increase was serendipitous.

WOW ........ Don.......I sold you a HOT ROD flattie.......shoot - I should have got more for it!!!

Just pulling your chain Don. All I knew about it was .... it ran. That was it.

Good luck with the parts. I sold the rest of the pull offs this past week - gas tank, steering column, brake/clutch set up, old front seat, skinnie 4.5" steel wheels & nut & bolts.
HaRa

Paul

During my previous search to find a "good" flathead block (not successful) I had occasion to look at a number of flathead blocks. The most sneaky problem is a crack from one of the valve pockets into the cylinder wall. In some cases this may be repaired with a sleeve but if there is a water leak through that crack there seems to be no easy repair if any at all. I have heard of putting a cracked block in an oven and bringing it up to an annealing temperature and welding it or brazing it while hot and then letting it cool slowly. Brazing is usually a standard repair for cracked cast iron but it is not a sure thing. Anyway while looking at a lot of blocks with emphasis on the valve pockets I did see a few of the 59AB (later '46-'48) that had factory reliefs extending from the valves in a tapered way that leads to the rim of the cylinder wall but as far as I know if the lip of the cylinder wall has been ground way that is "hot rod work" that has been done by someone who souped up that engine. If you look at a stock head or even a finned aluminum aftermarket head you can see that on the one hand you can't mill the head more than about 0.080" or the valves may hit the underside of the head and the heads are scalloped out over the valves. Again if you mill too much off a stock head you squeeze/pinch the space between the underside of the head and the top surface of the block and that will actually reduce flow from the valves to the cylinder. Soooo, if you grind away (relieve) the lip of the cylinder wall to provide a path from the valves to the cylinder by about 1/8" you can enhance flow to/from the cylinder to the valve area. The practical limit of the relief depth is that it has to be kept above the top ring in the piston at TDC and not cut into the water jacket. Of course this lowers the compression ratio but if you use aftermarket heads that will compensate. As I recall, more from reading hundreds of Hot Rod Magazine as a teenager than doing the work, you pretty much could not get a car with a flathead featured in HRM unless it was "ported and relieved" where the porting referred to smoothing and straightening the in-block intake passages in the top of the block. So after that long discussion it would seem to me that you have a valuable block that has already been worked on and if it passes the crack test you have a desireable block with a lot of special work already done on it. Probably if the block is relieved you may be able to see that the intake ports have been straightened and polished. Usually an intake gasket was used to make an outline on the intake ports and the iron was ground away to the edge of the gasket lines. In extreme cases the intake ports were filled with molten lead and then the ports were ground out and reshaped to get a "straight shot" path from the intake manifold down to the valve head. I would think that is risky in that overheating might melt lead that would shed chunks into the cylinder. Perhaps the bore is already at 3 5/16" and if so I would resist further boring even though 3 3/8" pistons are available since thin walls can lead to easy overheating.

Don Shillady
Retired SCientist/teen rodder

Paul, I have done some research on this engine and found out that Don Garlits ran it in his very first dragster. Then he sold it to Mickey Thompson, who set a land speed record with it. Hope the check I gave you clears.

Glad you sold off some more of your unneeded parts. Your coupe will live on in several other cars, plus you still have the best parts to build the one you want. Hot rodding at it's best, one rodder helping others. You were very generous in that respect, and I thank you for it.

Don, thank you for that information. It's funny, but I put in a lot of different words on Google and the HAMB, but couldn't turn up much info, especially a picture of other blocks with the contour mine has. I thought at first that Ford made the early blocks (46-48) with the concave configuration, then changed on the '49 up engines. But I found a few pictures of early versions on line, and they were either totally flat in the head mounting surface, or had the partial depression you describe.

The picture below is NOT my engine, but one I found on line. The dished area on my block looks like that, but extends clear into the cylinder bore. I will have to pop the head off and take some pictures of mine and post it for comparison.

Don

It seems to me that the 8CM Merc blocks were relieved from the factory; I am probably all wet, but that little "---toid" sort of sticks in my head. I do know that my 8BA was not, as I did a mild reliving job on it, and it came out looking similar to that picture, only not as deep and more tapered up from the valves to the cylinder wall. Cracks are most common between the valves and almost any adjacent hole, as they get the brunt of the heat during combustion; also between the cylinder wall and the water jacket; less so to the bolt holes. Sometimes they can be hard to detect without a dye job or magnaflux. Last one I checked out, it was an 8CM, they were very obvious; I went to get some tools, and the guy selling it had the heads off by the time I got my toolbox open. I took one look, and told him "no thanks". Then he tried to give the thing to me. We flipped it over and pulled the pan and some bearing caps; the crank was beautiful, and I pulled a couple of pistons, and the rods were in good shape, so I told him he could get a pretty penny for the crank and rods by themselves, but I had no use for a cracked up engine block, nor for a crank without it. Tried to make it worth the guys while; could have taken the stuff and sold it myself, but that didn't seem right to me.

Last night I did some more Googling and read one article that confirms what you are saying, and what we kind of remembered..........some blocks came from the factory relieved already, but for some reason Ford stopped that practice on later engines.

They say it drops the compression ratio about 1/2 point, but that it does breathe easier. I guess I will be learning a lot about flatmotors as time goes on and I get more involved building this one.

Don

Thanks for that info Don......wow.....go figure. Both Garlets & Thompson......I feel good now knowing another Hot Rodding ICON ended up with it!!

Did you check the latest Street Rodder?? Looks like a RPU is fetured with the same flavor as what you guys got going on. Check it out.

I'd have to agree mostly to what Don Shillady said right up to the last info about lead........ the melting point of lead is 327.5C (621.5F) & the boiling point is 1740.0C (3164.0F) so the likelyhood of lead being a problem is not really an issue. I would think your engine would have been long gone prior to the lead effecting it. It would have had other issues......

Paul

You might recall a previous thread on a 217 flathead six a year ago or so. I will get that link for you but also here is a nice picture:

http://www.34hotrod.com/HotRod/page7.htm

Don Shillady

You can check out a previous thread that you participated in as "Plymouth 217 Flathead", but here is that same picture from the Newhouse Speed and Economy Handbook.

Don Shillady
Retired Scientist/teen rodder

Paul, Dan is the magazine buyer in the family. I'll have to ask him if he has that issue, thanks for the heads up.

Don, the drawing you posted is exactly what mine looks like, the first picture that is. I've pretty much resigned myself to the fact it is a factory relief job, at least until someone posts to the contrary. There are no grind marks like someone did it with a die grinder, I think it is factory machined.

These flatheads are interesting little motors. I never looked at one really until Dan bought that 49 shoebox.

Don

One last comment. If the reliefs follow the full outline of the head gasket then it is probably a smooth hot rod job because all of the factory reliefs I have seen only extend from the valves in a tapered way. I wanted such a nostalgia flathead but could not find one not cracked and cannot afford a French or aluminum block. However, in spite of Dave Severenson's comments about how common the SBC is a SBC is really the most bang for the buck with an easy 250 HP on a mild rebuild of a 350 while all the articles I have studied show that even with an Isky cam, max bore, 4" stroked crank and (now expensive) aluminum heads, 250 HP from a flathead is close to the reasonable limit with only three main bearing webs, so for a poor boy like me (all my life!) the SBC looks pretty good. Still if I had a non-cracked 59AB block I would build it and consider it a wonderful time machine! Now if you say you found a set of ARDUN heads in a barn somewhere, that would be exciting, but the prices for real ARDUN heads make my nose bleed!

http://www.oogabooga.ca/oogaboogapag40.htm

Don Shillady
Retires Scientist/teen rodder

The 350 Chevy in my 23 is the first Chevy I have run in over 30 years, and I have to say I have a lot of respect for them. I know they are the most often used engine in hot rodding, but there is a reason for that popularity, they are available, cheap to build, make good HP, look good when dressed out, and are dependable as they can be. Every time I turn the key in my T and it fires off immediately and brings me home at night without a whimper, I like it a little bit more. I still like Fords and Olds engines too, but there is something to be said for the sbc.

Don