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Old 03-14-2026, 09:49 AM   #1
bchrismer
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Default Late flathead heads on 59 block

I recently was gifted this set of heads from the estate of one of my dad's best friends. I had known OF them, but had never seen them, but had asked him to sell them to me for as long as I have known about them.

I know you can run late heads on a 38-48 block with modifying the head to block a water port. Is that what I am seeing in the second photo?

Thanks.
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Old 03-14-2026, 10:51 AM   #2
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Default Re: Late flathead heads on 59 block

Yes, it can be done. What would be the advantage?
https://www.bing.com/search?q=can+yo...ANAB01&PC=HCTS
and
https://www.jalopyjournal.com/forum/...-59ab.1338555/
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Old 03-14-2026, 10:52 AM   #3
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Default Re: Late flathead heads on 59 block

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Originally Posted by bchrismer View Post
I recently was gifted this set of heads from the estate of one of my dad's best friends. I had known OF them, but had never seen them, but had asked him to sell them to me for as long as I have known about them.

I know you can run late heads on a 38-48 block with modifying the head to block a water port. Is that what I am seeing in the second photo?

Thanks.


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Old 03-14-2026, 11:57 AM   #4
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Default Re: Late flathead heads on 59 block

Does the compression ratio of those GRANCOR heads make them usable on an early block?
Check the condition of the spark plug hole threads.
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Old 03-14-2026, 02:42 PM   #5
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Default Re: Late flathead heads on 59 block

You certainly have a great set of heads. A previous owner definitely had them on an early block the plugged bypass hole and the gasket pattern on the deck show that they were at one time bolted onto an early block.
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Old 03-14-2026, 04:06 PM   #6
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Default Re: Late flathead heads on 59 block

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Hmmmm . . . I've never had a set of Grancor 49-53 heads, but I noticed something that makes me believe they were for maybe a marine application?

Here is my logic:

1) Notice the large water holes are toward the thermostat housing side of the head.

2) That is exactly backwards from stock Ford/Merc 49-53 heads and every other set of aftermarket heads that I've owned or seen for the late blocks (49-53).

3) The larger water ports align with the BACK of a 49-53 flathead block - they are NOT in the front.

4) So, unless these heads have large water ports on BOTH ends of the head, I believe they are designed to have the thermostat housings on the BACK of the engine.

5) A wild-ass guess is that possibly these heads were designed for a marine application.

I'd love to see pictures of the water ports on the other end, to see if what I suspect might be true.

Anybody happy to know if Grancor made 49-53 heads to mount them as I noted above?
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Old 03-14-2026, 05:10 PM   #7
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Default Re: Late flathead heads on 59 block

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Hmmmm . . . I've never had a set of Grancor 49-53 heads, but I noticed something that makes me believe they were for maybe a marine application?

Here is my logic:

1) Notice the large water holes are toward the thermostat housing side of the head.

2) That is exactly backwards from stock Ford/Merc 49-53 heads and every other set of aftermarket heads that I've owned or seen for the late blocks (49-53).

3) The larger water ports align with the BACK of a 49-53 flathead block - they are NOT in the front.

4) So, unless these heads have large water ports on BOTH ends of the head, I believe they are designed to have the thermostat housings on the BACK of the engine.

5) A wild-ass guess is that possibly these heads were designed for a marine application.

I'd love to see pictures of the water ports on the other end, to see if what I suspect might be true.

Anybody happy to know if Grancor made 49-53 heads to mount them as I noted above?
Same on both ends.
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Old 03-14-2026, 05:17 PM   #8
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Default Re: Late flathead heads on 59 block

Boy, the back ports look a bit bigger to these old eyes.
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Old 03-14-2026, 06:06 PM   #9
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Default Re: Late flathead heads on 59 block

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Boy, the back ports look a bit bigger to these old eyes.

Bigger or perhaps the angle the photo was taken. In this photo they certainly appear bigger at the rear.
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Old 03-14-2026, 06:31 PM   #10
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Default Re: Late flathead heads on 59 block

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Same on both ends.
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Old 03-14-2026, 06:47 PM   #11
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Default Re: Late flathead heads on 59 block

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Bigger or perhaps the angle the photo was taken. In this photo they certainly appear bigger at the rear.
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Do they really matter? The head gaskets will have the last say.
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Old 03-14-2026, 07:00 PM   #12
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Do they really matter? The head gaskets will have the last say.
Profound!
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Old 03-14-2026, 07:42 PM   #13
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Default Re: Late flathead heads on 59 block

But if you turn the heads around, as Dale suggests, don't you have to turn the gaskets as well?

I have never tried it, so I really don't know.

I have thought about it a time or two; there is something that appeals to me about pushing the cooler water into the front at the bottom and pulling it out the top at the back.
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Old 03-15-2026, 09:48 AM   #14
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Default Re: Late flathead heads on 59 block

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But if you turn the heads around, as Dale suggests, don't you have to turn the gaskets as well?

I have never tried it, so I really don't know.

I have thought about it a time or two; there is something that appeals to me about pushing the cooler water into the front at the bottom and pulling it out the top at the back.
My bet is that having these heads on backwards would help cooling - especially on a race engine. The back of the block always sees the highest temperatures (which is why Ford added the big cooling holes to the rear of the 49-53 blocks), so taking the water back out at the rear makes a lot of sense to me.

If I had a set of those heads on a fully built race engine - I'd be running them backwards!
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Old 03-15-2026, 09:53 AM   #15
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Default Re: Late flathead heads on 59 block

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Originally Posted by Ronnieroadster View Post
You certainly have a great set of heads. A previous owner definitely had them on an early block the plugged bypass hole and the gasket pattern on the deck show that they were at one time bolted onto an early block.
Ronnieroadster
Thanks, @Ronnieroadster. That was my assumption, but wasn't 100% positive.

I'm gonna have to find another decent 46-48 flatty for these.

Dad's deuce sedan has been blown apart since '61, and I was planning on using the '58 283 he had bought for it, but these heads may have changed up that plan.
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Old 03-15-2026, 03:39 PM   #16
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Default Re: Late flathead heads on 59 block

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Originally Posted by bchrismer View Post
Thanks, @Ronnieroadster. That was my assumption, but wasn't 100% positive.

I'm gonna have to find another decent 46-48 flatty for these.

Dad's deuce sedan has been blown apart since '61, and I was planning on using the '58 283 he had bought for it, but these heads may have changed up that plan.



Your Welcome. I have a set of those late model Gran Cor heads in my collection. I need to dig them out and look at them to see if they have the late holes on both end as well.
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First Ford flathead roadster to run 200 MPH at Bonneville Salt Flats setting the record August 7th 2021 at 205.744 MPH reset the record in 2024 to 211.830 running to mile four. Top speed 2024 mile five 220.672 exit speed 221.587
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Old 03-15-2026, 10:43 PM   #17
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Default Re: Late flathead heads on 59 block

Hey Ronnie, keep us posted with some details and pics - am really curious on my end!
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Old 03-17-2026, 10:25 AM   #18
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Default Re: Late flathead heads on 59 block

If you need to find a block to use them on, why not just get a late block?
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