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Old 07-25-2012, 03:22 PM   #1
Duffy1
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Default 1938 "B" diamond engine

I have a 1938 "B" diamond engine in my 1931 SW . Can anyone tell me the difference in this engine compared to a model "A" engine ., diamond model "A " engine ,a 1932-1933 "B" engine. As usual all responses are appreciated .

I have an "A" dist and an "A" timing gear cover . If you time this engine using the proceedure for an "A" the timing ends up being advanced way to much. This advanced timing caused the engine to rattle , idle rough ,started acted up ,head gasket seeped and on occasion would vapor lock, no power in over drive . Now that I have retarted the timing it runs very smooth and maintains idle , starter does not stay engaged ,head seep disappeared ,no vapor lock ,no engine rattle, do not have to shift out of OD to get up small inclines . Not as peppy on take off but still keeps up with the rest of the cars in our model a club . Some folks on this forum have a B engine and an A dist and A timing gear cover and time it like an A and have no problems . This was not the case for me . Wonder why ?

Thanks Again .
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Old 07-25-2012, 03:28 PM   #2
Bob C
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Default Re: 1938 "B" diamond engine

Do you use the spark lever correctly or do you use up to start and down to run???

Bob
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Old 07-25-2012, 04:00 PM   #3
Duffy1
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Default Re: 1938 "B" diamond engine

Bob C ; Thanks for the response .

When timed like an "A" ,if the spark lever is all the way to the top there is no rattle . When you start moving the spark lever down the rattle starts and gets substanially louder the further down you go. Also you have all the other things going on as I mentioned when timed like an "A" .
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Old 07-25-2012, 04:12 PM   #4
Duffy1
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Default Re: 1938 "B" diamond engine

Bob ;

To answer your question I now use up to start and down to run. I know this is not in accordance with the owners manual ,etc.etc.. But it works based on the way it is now timed . The gurus in both the clubs I belong to set the timing by run it , reset timing ,run, reset timing until we optimized the timing . They advised that I run with the spark all the way down and the GVA half open . Car runs great .
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Old 07-26-2012, 12:55 AM   #5
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Default Re: 1938 "B" diamond engine

Im running mid 30,s diamond "B" engines with "A" dist & timing covers on both my "A",s & they run great.I run the spark lever about 3/4 down unless over 40 mph.Both my engines have factory installed hard seats on EX valves.
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Old 07-26-2012, 09:45 AM   #6
Duffy1
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Default Re: 1938 "B" diamond engine

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Thanks Columbia ;

Good to know that these engines have hard seats . Anything else different( good/bad) about these engines compared to a model "A" or early model B. I understand the "B " engine casting is thinner around the valves than the "A" and are prone to crack. What type/heat range spark plug do you run? What is the gap on the plugs .
As it relates to the timing , If I time mine like a model "A" it is to far advanced.
If you like ,you can PM with this response .

Thanks again .
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Old 07-26-2012, 12:24 PM   #7
Ron in Quincy
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Default Re: 1938 "B" diamond engine

Duffy 1,

The diamond block A, in addition to the hard seats in the exhaust valves, may also have a B camshaft. If you have the pan off you can look to see if the camshaft has a round lobe at the front; this lobe was for driving the fuel pump on the B and C engines. Often times these blocks are engine number stamped starting with RF**** or LB****; RF= Richmond Ford and LB = Long Beach Ford.

Ron
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Old 07-26-2012, 03:18 PM   #8
juke joint johnny
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Default Re: 1938 "B" diamond engine

It sounds to me like you have a Model B timing cover on the engine , that would explain why the timing is so different!! Have a look at the Service bulletins or Vince Falters Ford Garage site on here . the difference is very subtle and should be measured in this case.
The timing arangement by the so called Guru's may work for them but you must admit its a bit long winded !!! Marco's method works for me and a lot simpler .

Once the timing is right then adjust the GAV to what the car runs best at could be a quarter or half or? ,, It's not a one size fit's all adjustment they all like a different amount so it seems

I hope this helps I'm afraid that some of these Guru's might be false profits!!!

John Cochran
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Old 07-26-2012, 03:29 PM   #9
Randy in Illinois
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Default Re: 1938 "B" diamond engine

Now you guys got me thinking about my diamond block engine in my late 1931 coupe ( July 1931) It's a Model A block, with the diamond casting, no fuel pump, but the camshaft has the FP lobe. The question I have is the block number starts with 18-xxxxx Does it make refence to being made after 1931? as late model parts 1932 & up started with 18-xxxx maybe a ford replacement engine?
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Old 07-26-2012, 03:35 PM   #10
Charlie Stephens
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Default Re: 1938 "B" diamond engine

Quote:
Originally Posted by Randy in Illinois View Post
Now you guys got me thinking about my diamond block engine in my late 1931 coupe ( July 1931) It's a Model A block, with the diamond casting, no fuel pump, but the camshaft has the FP lobe. The question I have is the block number starts with 18-xxxxx Does it make refence to being made after 1931? as late model parts 1932 & up started with 18-
The V8 started in 1932 with *18-xxxxx. The 4 cyl started with *B, or *AB for passenger cars. Does the number look like a restamp?

Charlie Stephens
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Old 07-26-2012, 09:00 PM   #11
Duffy1
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Default Re: 1938 "B" diamond engine

I do not think I have made any contradictory comments . If I have I apologize. The fact is I have a "B " engine with a model A dist and a model A timing gear cover validated by all the sites referenced above and various folks in both the model A clubs I belong to . I think the comment about the right parts and right procedures is the help I am looking for . Example ,Could the timing gear be installed a tooth out of phase with the crankshaft or could it be a repo timing gear not made to spec ,etc,etc.I was hoping some one out in the model A world might have the same problem and would come back with a response.
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Old 07-26-2012, 09:14 PM   #12
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Default Re: 1938 "B" diamond engine

If you have the pan off you will notice that the block has morre gussets in the area of the mains as the a diamond blocks do also you will notice that the Bcrank is bigger than the A and that the mains have pressure going to them and that there are out ward dents in the pan for the rods to clear they are also larger than the A rods if timed right should go good my to cents have a blessed day
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Old 07-27-2012, 01:19 AM   #13
Ron in Quincy
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Default Re: 1938 "B" diamond engine

Duffy 1,

Regarding your last post, it is not likely the cam gear is not one tooth off unless the engine has been apart and some inexperienced person worked on it.

Two years ago the touring engine in my 30 Dlx. Cp always seemed to me it was running advanced. I took the trouble to remove the radiator and front timing cover and found the crank gear and cam gear to be correct. Last year while on a outing in Placerville, CA my friend Les Andrews was there; I told him about my belief that my engine was advanced. We checked the timing, changed the rotor, made sure I had .025 clearance between rotor and body contacts; we double checked our work and after 2 hours I told Les that we had checked everything except the distributor cam, I had rebuilt the distributor and installed a new B cam, I pulled out a spare distributor with a stock cam and installed it; the engine ran wonderrful after we timed it.
The end result was a faulty B cam; the slot that excepts the rotor had been cut in the wrong place advancing the engine when properly timed. This may not be your problem however it will not hurt to check.

Another point I would like to make, when I rebuild my carburetors I size the jets by thousands. With a cold engine I open the GAV 1/4 turn, when the engine is warm I close off the GAV.

Ron
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Old 07-27-2012, 06:06 AM   #14
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Default Re: 1938 "B" diamond engine

Question for Vince that may lead to an answer for Duffey1. Could there be a variation of the B cover that had only a timing hole in a small boss like the A cover but in the B position? I have several early covers that have the lip for the mount all the way across like the cover A-6019-A shown but, these don't have the spot faced bolt holes and the mount boss does not go to the far right bottom hole like the one pictured does. If there could be a variation like this, this could be how Duffey1 is confused. One way to determine this would be the position of the hole in the A cover is close to the second hole from the bottom and the B cover hole would be close to the middle of the second and third hole.
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Old 07-27-2012, 07:29 AM   #15
Duffy1
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Default Re: 1938 "B" diamond engine

Thanks folks . It is an A cover . There is one thing I pointed out in one of my original post about my engine rattling and that is , I have a two piece dist . shaft and I can not pull the lower piece up ,ie it is stuck in the engine.Do you think something could be wrong with this shaft ( bent ? ) causing my problem as it relates to not being able to time the engine following model A procedure. I am about to take a 1,000 mile trip with this car so if I can identify any thing that could give me a problem I would like to fix it now. I was going to run the car as advanced as it was until I read Dream works post on the damage it can do if you run your engine to far advanced. You guys are great for taking the time to help me with this . Thanks again .
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Old 07-27-2012, 11:51 AM   #16
Ron in Quincy
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Default Re: 1938 "B" diamond engine

Fordgarage,

I hate to disagree with you but the index slot in the cam for the rotor if in a wrong position will effect proper timing. Using the timing pin to determine top dead center, adjusting cam to point to number 1 contact in body so points just start to open, with the B cam in question had to move forward (advanced) to point to # 1 contact in body. When I installed the other distributor with stock cam, not changing the timing, the rotor was pointing between #1 and #2 contact in body (advanced); adjusted cam and everything was OK.

I have been timing my A engines since 1962 and this was the first Cam I have ever had a problem with. I have used B cams before without any problems.

Ron
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Old 07-27-2012, 07:50 PM   #17
Ron in Quincy
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Default Re: 1938 "B" diamond engine

If the slot on the cam is not indexd properly it puts the lobes on the cam is in a wrong position. The B cam I had in the distributor was indexd to give a advanced condition. I realize the cam can be moved to any position but if the lobes are in the wrong position that makes a difference. I also realize you have camshaft timing and distributor timing .

Ron
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Old 07-27-2012, 07:50 PM   #18
Duffy1
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Default Re: 1938 "B" diamond engine

So I guess not being able to remove the lower dist .shaft has no affect on engine timing .
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Old 07-27-2012, 09:40 PM   #19
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Default Re: 1938 "B" diamond engine

Unless the lower dist shaft is badly stuck, Ive always been able to remove them by sticking 2 thin screwdrivers side by side in the slot & squeezing the handles together & lifting it out.
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Old 05-20-2019, 08:03 AM   #20
Bob Bidonde
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Default Re: 1938 "B" diamond engine

I have aftermarket Model "B" engines in both of my Model "A's." Both engines are strong runners 5.5:1 heads.



I always iterate the ignition timing starting with #1 at TDC on compression. Typically, this results in timing that is excessively retarded, so I tweak the distributor's cam position until I get full advance without any audible knocking. Both cars will do 70+ MPH.
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