FH V8 design tech

3

3W Hank

Well-known member
I ’m intrested to clear som ol’ FH design upp !

This is from HAMB ( from Dale/B&S show a CAD drawing )


https://www.jalopyjournal.com/forum...-key-dimensions-angles-and-validation.958100/

My first question.
All FH V8 had the crank offsed to driver siide, so why has the pre 41/42 ( maybe ) another valve angle than the later 59 and 8 engines ?
Can’t be - Or ?

On my 41 Merc the valves is equal at deck on driver side and below on passanger.

Its told in thread the crank is moved 0.2651” but it was said centerline is also moved 1.875” ( ? )
Ideas on that.

Then if crank is moved 0.2651” but the cam might also be ’moved’ 0.0242”, so where is the true engine centerline ?
Odd (?)

So when set the valves ( in new seats ) one surface in a diff off 0.044” is that correct ?

Deck height ( in thread ) was discussed to maybe be not equal, but it can’t really be as then iit don’t make sense on stroke/rod/pistons.
It must be equal.

On height io valves I guess on a 3/8 cam etc and normal finned heads it is no big case, but going a ex 425 cam one head will be not equal so more CC.
Maybe a engine don’t see it or if one check with a compression gauge.

My question is most math and I’m intrested.


—-/——

From HAMB thread ;

—-/——

the .0345 number is a 'driven dimension' - it is how far below the deck the edge of the seat would be. On the other side, it is actually .009 above. Keep in mind, the stock Ford only used 1.5" valves - so these numbers were just for me to check the height differences side-to-side . . . adding them together gave me my .044 height difference.

—/——-

The overall length from the center of the cam to the top of the valve seat is the same side to side (about 7.0675), but the valve angle causes the driver's side valve to be higher (at the top side) by about .044.

—-/——

The valve angles are the SAME between 59AB and 8BA (though different from earlier 32-41 engines. The passenger's side valve angle is 48.641 degrees and the driver's side is 51.385 degrees.

—-/——

The bore angles are 45 degrees from vertical, but they are offset to the driver's side by .2651 inches. This results in the crank center-line versus bore center-lines to be offset by .1875" (in the bore center-lines)
 
They changed the valves inclination and angle starting with the 59AB series to help prevent valve seat cracking which had becoming a known problem
 
So what is the change in height etc on a Merc 41 block from a 59 or a 8.
On the drawing, what engine is that ?
It has the 2” rods so it must be before 40’s.
 
I understand one deck equal but what if one set valves at same height both sides ( guess a no-no ) but what hsppends ?
 
3W Hank said:
I understand one deck equal but what if one set valves at same height both sides ( guess a no-no ) but what hsppends ?
Click to expand...

The crank and cam are slightly offset from centerline causing the difference in valve banks. Why do you want to reengineer it?
 
The commentary that you mentioned came from me - based on my parametric CAD models which are based on original Ford blueprints. All the components are the same length (side to side), it is the offset that makes the valve angles different on the passenger vs the driver's side and due to the valve angles, the top of the valve is higher on the driver's side.

I didn't say the deck heights are supposed to be different - they are not. But, in manufacturing they typically differ a slight bit. My method is to put the crankshaft I'm going to run in the block (with a rod, bearings and piston pin on each bank) and measure the compression height difference. Then I square deck the lower side (least amount of material possible) and then square deck the other side to the same height.

Once this is done, then I remeasure the compression height and order my pistons to exactly match the block. I make sure the edge of the piston is exactly flush with the deck, or if I need to tighten up the squish, I might pop-up the piston a small bit (depending on the head gasket thickness and heads I'm going to use). On the last set of custom Ross pistons I ordered I had the piston crown pop-up about .012 or so.

In the end, I like a .040 squish above the piston - that is what I "tune" the setup to be. I usually calculate based on the typical .052 or so thick head gaskets, though sometimes I run MLS gaskets from Cometic (they come in a variety of thichnesses).

In the two drawings I posted (I made them both), the CAD models are setup for a 4.125 stroke crankshaft (late Merc) that has had the rod journals offset ground to 1.999. I then run either 21A rods if I'm going vintage full-floating or with H-Beam aftermarket small-journal rods. The dimensions for the block, valves, crank centerline and cam centerline locations are all correct - regardless of the stroke and journal size.

If I have a custom crankshaft built with a 4.25 stroke, it will also have 1.999 journals as I need the big-ends to clear the bores and cam.
 
Tim.
I will not change, I’ll just ask if valeves is up 0.04” more it would be more comp on that bank so question was ; what happens if one get them equally ( it’s just a question )

Dale !

On the Hamb thread it was not you that said deck must be different, as one in the comments ; said it ’must be’.
Even if Ford made them not ’perfect’ equally we should try get them equally.
I agree.

Then on set both bank equally and C-H is basics machining.

But I has 2 questions ( or 3 )

1.
What diff the pre 41/42 valve angles from the 59/8 engines ?
Your CAD wad that pre 1942 or for 59 or 8 engines ?

2.
In Hamb thread it wad told crank is moved but also cam, so where is ’centerline’ here ?
And it was said crank centre is 0. 2651” but the bore centerline is 0. 1875” (?)

( 3. )
What happends if one set valve height equally ?
( Just information )
 
My thought to the answer to question #3, unless you change the crank/cam centerline and the raise the corresponding lower deck, then the valve would extend from the seat the same distance as the offset centerline if you try to make both banks equal, no?
 
Google AI has some info that might help answer some of your questions.
 

Attachments

  • IMG_8954.jpg
    IMG_8954.jpg
    40.3 KB · Views: 24
  • IMG_8955.jpg
    IMG_8955.jpg
    41.6 KB · Views: 19
  • IMG_8956.jpg
    IMG_8956.jpg
    43.8 KB · Views: 17
  • IMG_8957.jpg
    IMG_8957.jpg
    42.6 KB · Views: 18
1) See my CAD drawing for 32-42 engines - attached. The one you were referring to was for 46 - 53 (as noted, the valve angles are different).

2) Basic Math: The hypotenuse of the isosceles triangle is .2651, so the length of a leg is --- .2651 x squareroot(2) = .2651 x 1.414 = .375. then divide by 2 = .1875.

This represents how much the centerline of the bore (from the crank's perspective) has moved. Again, the cylinder angles are 45 degrees, so the math above represents that.

3) Given the dimensions of the block and the equal deck heights, the only way to set the valve heights equally is to do the following:

a) Modify the height of the valve seats on one side to match the other. This would take a new and taller valve seat on the passenger side.

b) Increase the valve lengths on the passenger side by .044.

Perspective: If the goal is to make sure the chamber CC's are the same, then you can determine the CC's by putting a head on the block, with a gasket and then use oil. Then you can modify the chambers to equalize the CC's. This is normal stuff . . . I can see no reason to try to match the valve heights.

As I noted earlier, at one time Edelbrock had TWO different chamber designs - one for the right and one for the left. The difference was in the angle of the valve chamber area above the valves (to match the different angles).

Hope this helps! Cheers gentleman . . . B&S

View attachment FlatheadFordEngineCrossSection-32-42.PDF
 
Thanks Dale.
I read that Edelbrock had 2 heads, make sense.
But if its tight ( one more clearance = same heads ) what are you see in CC diff.
 
3W Hank said:
Thanks Dale.
I read that Edelbrock had 2 heads, make sense.
But if its tight ( one more clearance = same heads ) what are you see in CC diff.
Click to expand...

I've never attempted to measure just the difference in the block side of the equation. I just make the final CC's the same.
 
Ok got you ( make sense )

I will do it like this ;
I will install the crank and a rod and pin and measure from std deck and down.
Then I will see if deck is equal and I also see side to side.
Then deck it to be equal both sides so all cylinders has the same distance down.
I will also see this in the machine as it has digital scale.
 
Last edited:
Doesn’t the block sit on a fixture in the crank bores when you are going to deck it? Machinist should be aware of the offset. Make both decks equal and parallel. Then if you really want to “blueprint” the engine, order the pistons with the pin to top height measured after decking.
 
alchemy said:
Doesn’t the block sit on a fixture in the crank bores when you are going to deck it? Machinist should be aware of the offset. Make both decks equal and parallel. Then if you really want to “blueprint” the engine, order the pistons with the pin to top height measured after decking.
Click to expand...

Offset doesn't matter - the overall deck height should be the same for both decks (if using the mains to mount the block).
 
The truck blocks were relieved like the one on flea-pay. Car blocks were not. The blocks all changed for the 1941 model year to delete the clean out ports on the pan rails. They also used less material on the intake deck surfaces for the raised flange look. They were mainly trying to save materials for the lend lease items being manufactured for the war effort beginning in early 1941. The improvement change of valve angles happened in 1944 while planning for war time replacement production and post war production.

The Desaxe principle on crankshaft center line offset was to reduce lateral thrust friction on the pistons for better wear and function of the engine design. This was common on most engines with exceptions on radial and opposed engine designs and is still a common part of engine design.
 
Last edited:
rotorwrench said:
The truck blocks were relieved like the one on flea-pay. Car blocks were not. The blocks all changed for the 1941 model year to delete the clean out ports on the pan rails. They also used less material on the intake deck surfaces for the raised flange look. They were mainly trying to save materials for the lend lease items being manufactured for the war effort beginning in early 1941. The improvement change of valve angles happened in 1944 while planning for war time replacement production and post war production.

The Desaxe principle on crankshaft center line offset was to reduce lateral thrust friction on the pistons for better wear and function of the engine design. This was common on most engines with exceptions on radial and opposed engine designs and is still a common part of engine design.
Click to expand...

I have two C59A truck engines. Both were used as industrial engines with the heavy duty truck 4 sp. Both have the truck pans with the large oval cleanout. One is factory relived and had cast iron heads and the other is not relieved and had the aluminum heads. Maybe the second block was swapped out Very weird.
 
You must log in or register to reply here.
Back
Top