[marks73ta]

No, I think you have a valid point. Very possible that it could affect the cooling to the rear of the '59 block if used for conventional cooling. I would have to take a look at my '73 block to see how the later blocks were the drilled. I still some the heads on it and will have to remove them for a pic. I wonder if adding a rear water entrance in the block would help even out the coolant's effect on the '59 block?
Mark L

[mechanickeith]

Would be very easy to just drill, tap & plug the front holes on the 59 block so the coolant holes match the newer blocks.

[marks73ta]

Good point Keith. That would allow you to try it both ways. You could always remove the plugs if it makes no difference or an adverse difference. Mark L

[mechanickeith]

Easy,,deck is pretty thick in that area. Use allen head shallow brass pipe plugs & tap the holes to let the plugs set just below deck height. Can remove & reinstall as needed. Or,,,plug all of them & go dry deck. So many possabilities!

[Safari Larry]

Also, you could modify the water ports in the heads rather than the block.

[mechanickeith]

You could,,,but would rather do the block. Whats a block worth vrs. the value of a set of virgin unmolested SD 306 heads??

[tom s]

block is a good boat anchor to most pontiac guys,the heads are another story!Tom

[Safari Larry]

Don't short sell the block, it is desirable to some of us. The 59 block is a bolt-in replacement to 1955-58 blocks making it a desirable/easy 389 cc engine upgrade without changing the appearance of the engine. To some old timers the block would be more desirable than the heads. But I'm sure the 306 heads are worth more.

[U47]

Originally Posted by Safari Larry

Great Mark, that's what I was looking for. Compare the water ports in the '59 block with the '60 block.



On the 59 block, the front/back are mirror images, same water ports in the front half as in the back half. Not so with the 60 block, some water ports are missing on the upper front and some water ports are smaller than the 59 block. In the 59 engine, water enters the heads and is evenly distributed front to back by the water distributing tubes -- then some cooling water flows through the water ports in the deck into the block. In the 60 engine, water enters the block first and the different water passages causes more flow to the rear of block before entering the heads.

That's why I would suspect using the 59 block in a non-reverse-flow (conventional flow) configuration might cause rear cylinders to run hot. The 59 block was designed for reverse flow and 60 block was designed for conventional flow. Each block should be used in the configuration it was designed for -- unless modifications are made.

That's the way I see it but I could be wrong!

Hey Larry, Now I know why when my dad wanted to get rid of the reverse flow he went from our 420 "A" to the 60 425 "A", All I could remember about why was; It would work, but it wouldn't work right. The added benefit was the 53461 heads.

[Doug]

So, just what are a set of unmolested date code matching 540306 heads worth these days?

[Safari Larry]

Originally Posted by U47

Hey Larry, Now I know why when my dad wanted to get rid of the reverse flow he went from our 420 "A" to the 60 425 "A", All I could remember about why was; It would work, but it wouldn't work right. The added benefit was the 53461 heads.

Don, I think you mean 535461 heads -- with the larger intake valves. That surely was one cool, I mean hot, '59!

[mechanickeith]

Originally Posted by Doug

So, just what are a set of unmolested date code matching 540306 heads worth these days?

Start at around $1500 & go up from there!

[Doug]

Originally Posted by mechanickeith

Start at around $1500 & go up from there!

At those prices, I guess it would be worth my making a 100 mile trip to see if that pair of them I saw collecting dust under a bench in a garage shop a few years ago are still there!

Didn't the 540306 "evolve" in that the originals had pressed in studs and latter ones had pinned studs?

[tom s]

as far as I know all 306s had pressed in and pinned studs.Tom

[marks73ta]

I have now placed the heads in the classified section for sale. Mark L

[marks73ta]

Sale is pending payment. They be heading to Texas. Mark L