Observations about flat head blocks

[Tim Ayers]

We've heard the comment that flat heads run hot a thousand times. After tearing down my fifth motor in search for a good block, I've come up with some observations for most of the blocks were in a similar state when I got them.

1) You should clean/flush your blocks regularly. Overheating and other hot spot cracks are caused by crud getting stuck in the water jackets. The picture of a piece of crud is from a motor that hadn’t run in years.

The crud I was pulling out was still moist. This was even after the motor was sitting in a garage and a barn for a little over a year after being pulled. These pictures really don’t even begin to tell the story. I poked, scraped, vacuumed, prodded, etc. The crud was so caked in there, I can't image how this motor ever cooled itself. I had trouble breaking through it at first with a slender, long straight blade screw driver.

2) I believe those intake valve cracks are caused by poorly maintained vehicles. The dizzy goes out of time and/or the carb runs lean causing the motor to run hot. This then causes the metal to get overheated in the intake pocket and cracks the casting from the valve pounding on the hot metal.

The block is "delicate" at this spot, since it's a pretty thin casting with bore being so close to the valve pocket.

Moral of the story is, if you haven't cleaned or flushed your block, had your dizzy timed or tuned up, and checked for lean conditions with your carb, maybe this spring would be a good time to do so.

Save these blocks!

[1952henry]

Thanks for the post and pics.

[blucar]

My theory on why so many of the old blocks/heads cracked:
There were many factors that contributed to cracked blocks/heads:
Cars were cheap and people did not have much money to spend on maintenance.
In the colder climates it was a semi-annual practice to remove the thermostat's/anti-freeze in the spring and reinstall same in the fall. The theory was two fold, being that these items were only needed in the winter to make the heater work, and the common anti-freeze was alcohol based which will boil at 180 degrees.
Without a thermostat the temp of an engine is constantly cycling, from extremely hot, especially on up hills to very cold on the down grade.
Less than a dollar spent on rust inhibitor in the cooling systems would minimize corrosion and scale in the radiator/block.
Permanent type anti-freeze did not become the norm until the mid 1950's.

[1952henry]

True that. I've seen many old tractor truck car engine with side of the block pushed out due to freezing. Some were stitched with brazing to retain water. My uncle had an old Rugby truck that had quite a pattern of stitching on block side.

[grumppyoldman]

I had a 48 that ran hot when I purchased it, I removed the thermostats thinking it was not getting enough flow through the block. That made it worse, old ford guy told me the water was running through the radiator too fast and didn't have a chance to cool. He told me to take the guts out of the thermostats and put the washer back in, leaving a hole in the center to control flow. That solved the problem, I was 17 and what did I know, surprised me, so there you go. Al

[supereal]

Sponsored Links (Register now to hide all advertisements)

The idea that "the water was moving too fast" is an old fable. The faster you can circulate the coolant, the more efficient the radiator will become. Radiators have a given degree of efficiency. Slowing down circulation causes the coolant entering the radiator to be hotter taxing the ability to transfer the load to the air. Back in my stock car racing days, we did things such as drill holes in the water pump vanes, or remove every other vane. This was not to cool the engine, but prevent the water pumps from blowing the coolant out the overflow as we ran wide open throttle on the track, often in second gear. Old myths die hard, and slowing the coolant to reduce overheating is ready to be killed!

[Talkwrench]

This was just one session on my original block with a .100 overbore, which ran cool. The amount of crud build up in the back of the block was incredible. Lots of scraping and blowing out with the air line .. Must of been filling it up with mud when it was in the U.S. ...

[Tinker]

You would not think that casing sand from the factory would still be there. But it is. The block was made in the 30,40,50. Maybe it didn't get flushed that well.


Nothing a long screwdriver, coathanger, and a hose can't do a decent job on.


Rear of a flathead block is a area that water can be stagnate, just by how the water flows in the block. If you think about it.


.

[JSeery]

Originally Posted by Talkwrench

This was just one session on my original block with a .100 overbore, which ran cool. The amount of crud build up in the back of the block was incredible. Lots of scraping and blowing out with the air line .. Must of been filling it up with mud when it was in the U.S. ...

This is what I have found as well, and most of it seems to be around the rear cylinders on each side. But what I have removed is not mud, it is casting sand for the most part along with a lot of core wires.

[Tinker]

Who knows what additives and crap water has been put in these cars over the yrs. Tim makes a very good point about "checking what condition your condition is in". Spring is a good time. Oil, lube, etc...

[Ziggster]

Good to know my block is at the machinist and will only get a mild acid bath soak. No one in the area has the high temp cleaning capability. He did tell though the block looks pretty clean from he has seen in the past.

[JSeery]

The casting sand is not removed by an acid bath (something I wouldn't do, but whatever). It needs to be removed manually and it is not really visible for the most part. Requires a variety of wires, probes, etc. to get at it. And it takes a lot of time and effort.

[Tim Ayers]

Originally Posted by JSeery

The casting sand is not removed by an acid bath (something I wouldn't do, but whatever). It needs to be removed manually and it is not really visible for the most part. Requires a variety of wires, probes, etc. to get at it. And it takes a lot of time and effort.

Yes, agreed. I’ll post another picture tomorrow of how much wire and crud came out of block that was cleaned by an acid bath. It was surprising. Some pieces were 3”-4” long.

[Ross F-1]

I seriously doubt anyone put distilled water in engines before maybe the '80's. More likely to be filled with ditch water.

[Pete]

Hydrofluoric acid or ammonium bifloride will clean sand out easily. Leaves clean bare metal.

[blucar]

The practice of removing blades from the vanes, drilling holes in same and/or installing large washers in the upper hoses, to slow the water flow down, was a result of an article that Vic Edlebrok wrote in the late '40's that pertained to racing engines he was building.
I agree with 'Super' that the myth that coolant travels through the block of a flat-head to fast should be put to 'killed'.
Just as recent as three years ago a friend of mine, an old time hod rodder, built an engine for a customer's 36 Ford pickup, he cut every other vane from the
impeller and installed large washers in the upper hoses...
Old habits die hard..

[JSeery]

Originally Posted by Pete

Hydrofluoric acid or ammonium bifloride will clean sand out easily. Leaves clean bare metal.

That's good to know! Thanks Pete.

[TomT/Williamsburg]

I have said this before - I collected a gallon bucket of sand from the block in my roadster- and that is just what I collected and not the stuff that got flushed away. I did each bank - scrape,vacuum, flush - 5 times. My engine was a Henry replacement engine and had never had an acid bath or anything. And yes Tim and everyone else - the rear cylinders water jacket areas was where the largest concentrations were and need to be poked, scraped and whatever with a variety of whatever you have in hand. Did I get it all? I have no idea but the proof is in the amount of miles, speeds, and low temps that make my roadster a flattie that is one heck of a little warrior and a blast to drive with overheating a non-issue ....

[grumppyoldman]

I use a lazer heat gun on my block and radiator, it runs 174 deg. through out the entire block. Never owned a flat head that wouldn't boil the water after a while at idle. This engine must have been cleaned very well when overhauled, and I'm talking Texas heat, not up north. Al

[1931 flamingo]

On my newly acquired 40 w/59AB engine, when looking at it and warm it dropped water temp 30* from top of rad to bottom. Had to replace pone water pump (one more to do), refilled with a/freeze and looked thru rad cap opening and amazed to see how much water was running out of the top hoses (no t/stats, yet). Water draining thru radiator, no back up. Part of exposed water passages in the block I could see were squeaky clean as was radiator tubes I could see.
I think I'm lucky.
Paul in CT