Shoud I relieve my block

[Jack E/NJ]

Pete>>>You give up a LOT of intake port area with those old raised surface blocks.>>>


A LOT? How much? Not much of a ridge. What was it's purpose anyway? Easier to re-surface if needed?

[Tim Ayers]

Now I'm curious. From what I gather, it's not so much higher, but the surface below it is lower. I have a few in the garage and now I feel the need to do some measuring.

[Bored&Stroked]

I think Pete's point is that when doing extremely large full-competition porting (like bigger 'D' ports toward the cylinders), you'll run out of material toward the outside edge of the raised intake area. On later 59x or 8BA blocks the whole surface is flat, so you can be more aggressive and not have a sealing issue.

[Jack E/NJ]

TA>>>it's not so much higher, but the surface below it is lower>>>
B&S>>> On later 59x or 8BA blocks the whole surface is flat, so you can be more aggressive and not have a sealing issue.>>


OK, Makes sense. But why do you suppose the surface was ever milled down that way to make a ridge in the first place? My '38 21-studder doesn't have a ridge either.

[Bored&Stroked]

Originally Posted by Jack E/NJ

TA>>>it's not so much higher, but the surface below it is lower>>>
B&S>>> On later 59x or 8BA blocks the whole surface is flat, so you can be more aggressive and not have a sealing issue.>>


OK, Makes sense. But why do you suppose the surface was ever milled down that way to make a ridge in the first place? My '38 21-studder doesn't have a ridge either.

I've heard various claims - and they are probably all bogus. The most popular one was that "Henry wanted to save a few pennies on the overall cost of cast iron." If that was the case, then why did they go back to the older method in most of the 59x blocks and every 49-53 block that I've had?

My guess is that they made their patterns a few different ways and later decided to go back to a "flat top". Who knows the truth . . .

[Ronnieroadster]

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Hi guys I have had my hands involved in a lot of those so called raised deck blocks. From what I can tell while area for the intake surface appears to be raised the ports are not any higher than a conventual block. This visual appearance on the block between outer edges of the ports to the top edge of the decks are actually just lower than the typical flathead block casting. These blocks are called the 39 Mercury block if the bore is 3 -3/16 however I have seen the same casting with a bore of 3-1/16. Maybe at the time the thought was a little less iron would be used for the casting process thus a cost savings.
The only disadvantage I can see is the difficulty in making the top intake port the D shape other than that they are a cool looking block.
Ronnieroadster

[Bored&Stroked]

Ronnie is correct, they made the raised intake surface blocks in both 221 cubic inch Ford sizes as well as the 239 cubic inch Merc, Truck and WWII production versions.

Another term for them was the 'Keystone" block -- with many tall tales about how they were thicker, had more nickel content, made hair grow on bald heads, that all the "chicks dig them" . . . you get the point . . . lots of urban myths!

I've done quite a bit of analysis; I've managed to corroborate none of the myths - especially the last one mentioned above.

[Jack E/NJ]

I guess if the blocks were actually cast --- instead of milled --- that way, you might save a few milling pennies too?.

[Bored&Stroked]

Originally Posted by Jack E/NJ

I guess if the blocks were actually cast --- instead of milled --- that way, you might save a few milling pennies too?.

They were not milled - this was all due to the casting patterns they used. Why? Who knows . . .

[Pete]

Originally Posted by Jack E/NJ

Pete>>>You give up a LOT of intake port area with those old raised surface blocks.>>>

A LOT? How much? Not much of a ridge. What was it's purpose anyway? Easier to re-surface if needed?

Here is a size comparison of a rough finish port to a stock one.. There is about .030 more to finish size.

[petehoovie]

Originally Posted by Pete

Here is a size comparison of a rough finish port to a stock one.. There is about .030 more to finish size.

[Tim Ayers]

Originally Posted by Ol' Ron

I can understand why relieving the block works do well. most of the cylinder heads have very little transfer area so relieving is there to make up the difference. I was just looking at my Hydro engines, They rak well over 5K and when they came out of the water Pegged the needle, Somebody here suggested Monkey see, monkey do, Yes, I can see how it might work My Grancore heads used apopu piston In my Bvill engine I used 3 3/4 stroke pistons on a 4" crank

Originally Posted by Pete

Here is a size comparison of a rough finish port to a stock one.. There is about .030 more to finish size.

Pete,

I understand what you mean now. Issues with the a large D port not sealing on raised intake block due to the lack of material would be the "lowered" section in the direction towards the deck surface. Never thought of it that way, but I guess you are right.

Regarding D shaped ports, do you guys do this on a mill or freehand? If freehand, any useful tips or tricks?

[Pete]

Originally Posted by Tim Ayers

Pete, Regarding D shaped ports, do you guys do this on a mill or freehand? If freehand, any useful tips or tricks?

We do it by hand with a air die grinder and carbide burrs.
We researched doing it with CNC but what with only doing one every few years, it was not worth the effort.

[Jack E/NJ]

B&S>>They were not milled - this was all due to the casting patterns they used. Why? Who knows>>>


What I meant was only the raised area would need to be milled for a good seal, not the whole top. So less milling costs.

[Jack E/NJ]

Pete >>>We do it by hand with a air die grinder and carbide burrs.>>>


If the cylindrical area defined by an open valve and its seat is probably always gonna considerably smaller than the port area, then how much do you really gain by further enlarging the port area?

[Pete]

Originally Posted by Jack E/NJ

Pete >>>We do it by hand with a air die grinder and carbide burrs.>>>


If the cylindrical area defined by an open valve and its seat is probably always gonna considerably smaller than the port area, then how much do you really gain by further enlarging the port area?

A simple analogy might be a river. You gain more usable pressure by damming it rather than having it free flow.
The valve seat is the dam, the port behind it is the lake.
The more surface area in the lake the higher the pressure at the outflow due to atmospheric effect and dead weight of the water. (fuel charge dead weight plus inertia)
How much gain?? If we get to the finish line 1 inch ahead of the next car, we win.

[Jack E/NJ]

I guess I looked at it more like two funnels or cones having the same minor exit orifice surface areas, same column lengths or heads, but different major entrance orifice surface areas. Flow rates should be about the same due to the same heads at the same minor diameter orifices despite the volume differences

[Bored&Stroked]

I think the way to look at it is the amount of stacked up intake charge (fuel, air and pressure) that the bigger port has on the flow equation.

It is like having your finger over the end of a hose, the more pressure in the hose when you first let your finger off, the bigger the initial "burst" out of the hose end. That is about the best analogy I can come up with . . . after a good bourbon cocktail! LOL

[Jack E/NJ]

Lotsa variables & combinations thereof!

[Ol' Ron]

The biggest problem with FLOW is turbulence. My new port will be Linier very little curvs. Like the wings of an airplane. skin friction causes turbulence.
Everybody has their ideas. What somebody did last year, just improves what somebody does this year,
Graps