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Just Idling

Joined: 11 Jun 2021
Posts: 146
Location: QLD

Posted: Fri Aug 20, 2020 8:12 pm    Post subject: Displacements

Does anyone know how many combinations there are of flathead displacements?

For example:
Bore 3+3/8" Stroke 4" gives 286 Cubic Inches.

I read about different combos everywhere, How many are there?
I know if you want triples you need a bit larger displacement, but for salt racing etc, would a smaller CID (or stroke even) be better for revs?

(This ought to sort the brainiacs out)
Go the Chevs!
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Joined: 05 Mar 2021
Posts: 563
Location: at work in Melbourne

Posted: Sat Aug 21, 2020 9:43 am    Post subject:

Try out our frients on the RRT
The older I get the faster I was
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Joined: 02 Apr 2021
Posts: 1212
Location: Melbourne

Posted: Sat Aug 21, 2020 9:20 pm    Post subject:

I think the basic answer is you can get to any cubic inch you want up to just over 300 ( I have heard, but never seen)

If your thinking of building an engine, I would make sure you get your block sonic checked to make sure you have enough meat in the cylinder walls as I have heard of blocks having inconsistancie in the wall thickness, let alone the time they have had to corrode.

A mate of mine in the states builds smaller Cu in motors as with all the tech we have now to make the motors breath and better carburretion we can get more out of them without having to go so big in displacement.

Plus you go to 3 3/8 you havent got much room to go further.

Ross make some great pistons in 3 5/16

check out

always some good info there
Flatheads Forever!

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Site Admin

Joined: 10 Jun 2021
Posts: 504
Location: Melbourne, Australia

Posted: Mon Aug 23, 2020 10:33 am    Post subject:

Ford Flathead Specifications

The Flathead V8 engines produced by Ford Motor Company included basically three versions. The most popular being the 85-125hp that was first produced in 1932, and continued until 1953 (except for Canadian and Australian production which ended in 1954). Ford also designed and produced a smaller 60hp flathead V8 engine from 1937 until 1940. Lastly, the big 337 cubic inch flathead V8 engine, which was produced mainly for truck use and for Lincoln cars from 1948 to 1951. Ford's flathead V8 engines when introduced in 1932 were the first mass-production V8's where the block and cylinder assembly were poured as one single casting.

* 60 hp V8 (136 cubic inch)All Years 17 Stud V8
* 85 - 125 hp V8 (221 to 255 cubic inch) Early Years 21 Stud V8, (1932-38) Middle Years 24 Stud V8 (1938-48), Latter Years 24 Stud V8 (1949-53)
* 125-154 hp V8 (337 cubic inch) Big Lincoln/Truck V8

What Is My Displacement?

The following table shows the common flathead V8 bore and stroke combinations and the overall engine displacement (in cubic inches). The blue numbers in bold print reflect the standard displacements used by Ford on their flathead V8's over the years of the 85 to 125hp engines. If you have had the engine bored out beyond one of the standard bores shown, use the following formula to calculate the displacement.


           Bore (in inches)                                Stroke (in inches)   
(in fractions)   (in decimals)   3.750 (3-3/4)"   4.000 (4)"   4.125 (4-1/8)"   
3-1/16"             3.0625"              221                       235           243   
3-3/16"             3.1875"              239                       255           263   
3-5/16"             3.3125"              258                       274           284   
3-3/8"                3.3750"              268                       286          296   

Formula: Pi (3.1416) times rē (radius is 1/2 the actual bore size) times stroke (see chart above) times 8 cylinders.

Example: Your stock 1947 V8 came with a 3-3/16" bore and 3-3/4" stroke, but you had it bored out thirty thousandths (.030"). Adjust the bore size (3.1875" + 0.030" = 3.2175") for the oversize. The new cylinder diameter is now 3.2175". Radius of the cylinder is one half the bore (3.2175 divided by 2) or 1.60875". Now, square that number (1.60875 x 1.60875) to get 2.58808".

We'll use the formula to calculate the displacement: Pi (3.1416) times rē (2.58808") times stroke (3.75") times 8 cylinders. Using your handy dandy calculator, you should come up with 243.9 cubic inches
Yours in Rodding
Greg Wapling
The years have been kind to me, it's just the weekends that have done the damage.
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Just Idling

Joined: 23 Sep 2020
Posts: 110
Location: Melbourne, Australia

Posted: Sat Aug 28, 2020 2:34 pm    Post subject: Displacement

I thought he was talking about the type of Displacement that happens when your partner throws all you good stuff out of the house!
John Daley sidecar racer
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