Edelbrock Heads 1125.

[Phil Gillespie]

For Edelbrock Heads for a 1939 Ford 221cu 80 thou over. 3 3/4 " stroke.
Heads are the 1125.



COMPRESSION RATIO: These heads will yield an 8:1 compression ratio with a 3/16" base relief and the stock bore and stroke. There is a 3/10 ratio increase for every 1/8" increase in stroke.


So my questions are: the 3/16 base relief, is this where exactly, is it necessary to be done when using these heads?
The chamber volume is 65cc. The standard heads for these engines are ? chamber volume.
Phii NZ

[Ol' Ron]

The combustion chambers are CNC milled and the volume forget is very accurate, There is a formula here on the barn someplace that can tell you the exact CR. I don't think it's 8:1 on a 239 block tho as it's only 8.5 on a 276

[Phil Gillespie]

Thanks Ron, thats what they state but as you say needs to be checked.
This 3/16 " base relief is it required? Is this carried out around the valves?
Have checked in JWL Flathead facts and his modified Edelbrock heads with a 55cc chamber size at his torque testing results note that for best torque range maximum timing was 16 degrees total advance throughout the tested RPM range. Page 63.
So the 11A distributor with total advance of initail 4 plus Mech Advance of 24 gives 28 degrees. This is where my problem lies with this related detination problem.


Gotta come down on the advance not up!!!
Phil NZ

[Brian]

Here it is;

https://www.fordbarn.com/forum/showt...n+ratio+charts

[Phil Gillespie]

Originally Posted by Brian

Here it is;

https://www.fordbarn.com/forum/showt...n+ratio+charts

Thanks for that link Brian.
Phil NZ

[Ol' Ron]

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I don't think the 16* total is accurate, but I'll check. Max HP requires more adv. AS for the relief, I don't think there is any reason to relieve a flathead under any condition, unless you want to lower the CR.

[Phil Gillespie]

Originally Posted by Ol' Ron

I don't think the 16* total is accurate, but I'll check. Max HP requires more adv. AS for the relief, I don't think there is any reason to relieve a flathead under any condition, unless you want to lower the CR.

Ron, With the distributor , an 11A set up, fitted it gives 28 degrees total. This appears to be a major contributor to the detonation failure along with the heads which have 65cc. It would seem I want to aim for around 20 total. 4 degrees initial and 7 to 8 mechanical and running 96 octane.
Appreciate your input.
Phil NZ

[revkev6]

Originally Posted by Ol' Ron

I don't think the 16* total is accurate, but I'll check. Max HP requires more adv. AS for the relief, I don't think there is any reason to relieve a flathead under any condition, unless you want to lower the CR.

I read the same thing in johns book. He played with lots of ignition scenarios from locked to a 5 degree timing retard that would come in at a predetermined rpm. It was a bit random as to which engine liked which ignition. I think in general he did come to the conclusion that the factory early advance curve was overall extremely good for most applications

[GOSFAST]

Originally Posted by Ol' Ron

The combustion chambers are CNC milled and the volume forget is very accurate, There is a formula here on the barn someplace that can tell you the exact CR. I don't think it's 8:1 on a 239 block tho as it's only 8.5 on a 276

Hi Ron, he should be near 8.7 with that 64cc head on a 239". I would measure the chambers however, at least one on each head!

This is without having ALL his very accurate numbers though! The C.R. with a 64cc head would be much higher on a 276" stroker, closer to 9.8.

Thanks, Gary in N.Y.

P.S. We've been told by Edelbrock the chamber volumes on the 1125 heads could run anywhere from 60cc's to 69cc's and still go out their door?? Not sure how accurate this info from them is though??

[Mart]

The motor is a 221 bored .080 over, not a 239.

The relief isn't a necessity. I looked through the pdf and couldn't see the exact combo as above.

The relief is where the block surface is lowered between the valves and cylinder. It can lower comp ratio but increase flow. I'm no engine builder, so don't rely on me for info.

Mart.

[Ol' Ron]

I don't quite understand the compression figgers your posting. A 65 cc head is actually Aprox, 80 cc's plus the piston to head clearance. Now for the ignition adv, we ran 16/18 degs in the stock car for best acceleration off the corners, To be honest, I've never tuned for max power on a dyno. However I did have a chance to run the stock car on a chassis dyno and picked up 12 hp , by advancing the dist. However at the track the driver complained of poor acceleration of the corners so I went back to the original settings. On Richards Mileage tests he found that 28 degs in his engine gave the best fuel economy.

[glennpm]

A 221 bored .08," over is = 233in*3

The last page of Joe Abbin's pdf says this:

Note 1.
a. Head combustion volume (+)
b. Valves counterbore volume (+)
c. Head gasket volume (+)
d. Block deck relieved volume (+)
e. Piston dome volume (-)

Compression Ratio is a calculation: ((SW + CV)/CV). SW is the volume (in cc's) of one of the cylinders and CV is the total combustion chamber volume. The conversion factor from cubic inches to cc's is to multiply the cubic inches by 16.387064. The cubic inches of one cylinder is easy as it is total motor cubic inches (fourth column from the left)/ 8. The combustion chamber volume is affected by several factors:
Factors a, b, c, d are added together and e. is subtracted from that total. As the piston dome extends into the combustion chamber it takes up space therefore it has to be subtracted from the total combustion chamber volume.

So Compression Ratio = ((SW + CV)/CV)

So for you its =(((233*16.3939387064)/8)+73.18)/73.18

7.52 with "relief"

7.80 with no deck "relief"

I took values from page #5 of the ref. pdf as attached.

[Phil Gillespie]

Originally Posted by revkev6

I read the same thing in johns book. He played with lots of ignition scenarios from locked to a 5 degree timing retard that would come in at a predetermined rpm. It was a bit random as to which engine liked which ignition. I think in general he did come to the conclusion that the factory early advance curve was overall extremely good for most applications

Yes youre right lots of ignition scenarios for sure. And as you say factory setting overall good for most applications.


My case with the 3 1/16 bore plus 80 thou and the Edelbrock heads with the 65 cc combustion chambers is now not quite standard and have set up the best for this. The 11A distributor set up I have with 28 total is too much confirmed with my detonation failure.
So have to diall it back to around 4 initial plus 7 to 8 only mech advance which will bive me a max of 19 to 20.
Phil NZ

[Phil Gillespie]

Originally Posted by Mart

The motor is a 221 bored .080 over, not a 239.

The relief isn't a necessity. I looked through the pdf and couldn't see the exact combo as above.

The relief is where the block surface is lowered between the valves and cylinder. It can lower comp ratio but increase flow. I'm no engine builder, so don't rely on me for info.

Mart.

Mart, Thats what i was thinking also the relief isnt necessary and will again go with the set up i have paying particular attention of course to final squish and distributor set up.
My rods are gettin out there also at + 0.008 on bottom end less bearing, and -0.040 on crank pin.
Presently block is in for checking of all related sizes before parts are ordered.
Phil NZ

[revkev6]

Originally Posted by Phil Gillespie

Yes youre right lots of ignition scenarios for sure. And as you say factory setting overall good for most applications.


My case with the 3 1/16 bore plus 80 thou and the Edelbrock heads with the 65 cc combustion chambers is now not quite standard and have set up the best for this. The 11A distributor set up I have with 28 total is too much confirmed with my detonation failure.
So have to diall it back to around 4 initial plus 7 to 8 only mech advance which will bive me a max of 19 to 20.
Phil NZ

never really heard many people actually have detonation failures with a flathead unless they are running REALLY hi compression. my 8ba 239 +030 ran the old edelbrock heads which actually have smaller as cast chambers than the new ones. I ran this combo with a 24 degree mallory dual point for 25 years before I tore it down and found that the old cracks that had been repaired years ago finally gave up the ghost.

I would verify that you have the correct advance in your distributor and keep an eye on your plugs for lean condition.

I'm just assembling another 239 +040 right now and it will have another set of old edelbrocks on it that are cut about .050 to get the head to piston clearance right. I'm not sure how much that will increase my compression but i'm not too concerned about it. I usually ran 87-91 octane in my other motor, this one I may have to run hi test...