59-ab pistons

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fondoffords

Junior Member
Have an odd question. I have a 46-48 59-ab. I'm pretty sure of the years, has the triangular water jackets. Piston number 4 broke. I know, sounds weird, but a large chunk broke out off the top and upper side all the way down to the first ring. Broke not burned. Anyway, in searching for a replacement piston I keep finding domed top pistons galore. The pistons in mine are flat top. Am I missing something? Where the domed top pistons a replacement
Item or am I wrong about the year of my engine? Any ideas? Thanks
 
fondoffords said:
Have an odd question. I have a 46-48 59-ab. I'm pretty sure of the years, has the triangular water jackets. Piston number 4 broke. I know, sounds weird, but a large chunk broke out off the top and upper side all the way down to the first ring. Broke not burned. Anyway, in searching for a replacement piston I keep finding domed top pistons galore. The pistons in mine are flat top. Am I missing something? Where the domed top pistons a replacement
Item or am I wrong about the year of my engine? Any ideas? Thanks
Click to expand...

Do you mean the piston tops are "flat" flat like a pool table, or do they have a slight curved shape? This curved top is what is meant by a 'domed' piston in a flathead and is the stock shape for a 59A engine. Maybe you're thinking of what a domed piston looks like in a modern race engine.
 
The pistons are flat like a pool table. The heads are clearly marked 59-ab. What year did ford go to the 24 stud head? I wonder if the heads were put on an earlier block. How would I identify the approximate year the block was made?
 
Post some photos. 24 stud engines came out in mid 38. If your engine has flat top pistons with the domed heads the compression ratio must be really low.
 
The piston are flat like a pool table. No dome whatever. I believe that the block is a 59-ab like the heads because of the triangular water ports. The car is down at my friends house where we do all of our work so I can't run out and check anything. If the 59-ab heads are domed and the pistons aren't that would result in a lose of horsepower would it not?
 
Sorry I posted that twice, didn't realize that the first posting went through. We checked compression 2 weeks ago before we tore the engine apart. 7 cylinders were pulling 95 lbs and the number 4 was at 45. I would have that my compression would be bad also.
 
I will get a hold of my friend and have him take pictures of the head, the block showing the water ports, and the pistons. We have not removed the pistons yet. Anything else I should get pictures of?
 
Front of the block. Also, if it's a 59 block there should be a 59 cast into the bellhousing.
 

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Get a picture of the head mounting surface on the block, that'll tell us the year. The head pic would just tell us what year the heads are. If they got 59AB on them, then that's 45-48 car, 45-47 pickup.
59AB heads were all for dome top pistons, all 24 stud heads are dome type.
Martin.
 
It'll be a 221 with early flat-top pistons fitted.
Yes...there are replacement 221 59A blocks!
 
As noted by Brian - somebody put in some early 221 pistons in it - should be 3 1/16 or so (plus any oversize). While it will obviously run, the compression will be a lot lower than it should be. If you replaced the pistons with the correct domed top ones, you'll definitely pickup some additional power. Take some pictures of the heads as well - just so we can make sure that somebody didn't mill the crap out of them - thereby making the use of "different pistons" a must . . . or having to have the domes redone in the heads.

There are many examples of miss-matched combinations of parts in these engines - as folks did whatever they could, with whatever they had to get them back on the road!
 
Take a pic of the block. front, rear, and piston side, I think you'll find it a 39-42 block 3-1/16 bore + what ever it's bored, also both sides of the heads, if it was mine I'd bore .125 to 3-3/16 and use 8BA std pistons, there the cheapest you can get, there domed, will work with 59AB heads, check heads so they haven,t been milled over .050. Walt
 
Thanks for the input everyone. There is a stamping of the number 59 on the bellhousing. I will measure everything and take photos of everything. I will post them as soon as I can. Thanks again.
 
There was what was referred to by FoMoCo as the 41A (1944) block. It will most likely have the 59 on the back bell even though it's a 221 replacement block. The 41A has the rear bell characteristics of the 59 series but all the internals are same as the pre-war 221 of 1941/42. The cylinder walls are thinner and the original bore was 3.062" or there abouts.
 
In answer to rotorwrench, that is apparently exactly what is going on. As I said, the engine is at my buddy's house. When he got home from work he put a mic to the bores. 3.0625. It's a 221 post war replacement motor for the pre-war block. This explains the flat top pistons and the 59 molded into the bellhousing. Somebody in the past put the 59-ab heads on an engine they shouldn't be on. I was wrong about my pre tear down compression. I said it was 95 in 7 out of 8 but it was 90. Now the question is do I find the right heads or dome top 3 1/6 pistons. Thanks again everyone.
 
I don't believe you will find any 24 stud heads with a flat combustion chamber. Any 59 block whether it be 3 1/16 or 3 3/16 should have had domed pistons.
 
As Jack said,
All 24 stud heads are for domed pistons.
Someone put the wrong pistons in. Correct this and bolt your heads back on.
Martin.
 
It should be fairly easy to find the correct domed pistons. You can either put some 221 domed ones back in it (freshening up the bore for new rings - if the bores are good), or bore it out to 3 3/16 for the regular 59AB/239 CI pistons. Supposedly these blocks are thinner than the other 59 blocks with 3 3/16 bores, but I've never actually sonic tested one to validate that theory.

When you get the compression where it needs to be, the engine will feel like a whole new engine for sure!

D
 
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