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Old 12-26-2010, 12:02 AM   #1
Hitchhiker
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Default Is a 21A flathead desirable?

Is a 21A flathead desirable? It's out of a 1941 ford passenger car I believe. good or bad? what are the draw backs of it? thanks
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Old 12-26-2010, 02:43 AM   #2
mike@earlyfordstore
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Default Re: Is a 21A flathead desirable?

It is like a 59AB except it has a smaller bore, 3 1/16" compared to 3 3/16".
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Old 12-26-2010, 07:53 AM   #3
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Default Re: Is a 21A flathead desirable?

Can easily be bored to 3 3/16 (239 standard) with the sleeves removed. With the smaller heads this gives a good compression ratio. That's what I've got.
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Old 12-26-2010, 07:58 AM   #4
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Default Re: Is a 21A flathead desirable?

I've built alot of those engines. Remove the sleeves and bore the block another .045 and use 8BA std. pistons. Use 59AB heads gaskets and the 41 heads. Makes a nice little engine. If you want to put a cam and dual carbs and a better set of heads it make a good little streete engine. Walt
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Old 12-26-2010, 10:18 AM   #5
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Default Re: Is a 21A flathead desirable?

I've got a couple of those engines and was wondering about the sleeves. Were the sleeves put in at rebuild because of wear, or did Ford put these in from the factory? The way your talking it sounds like they were all sleeved at one time or another.
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Old 12-26-2010, 10:24 AM   #6
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Default Re: Is a 21A flathead desirable?

Hmmmm, Walt. 59 gaskets on 21 stud engine? Little too much Egg Nog and Rum last nite? heh heh
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Old 12-26-2010, 10:33 AM   #7
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Default Re: Is a 21A flathead desirable?

Hmmmm, 21-a engine is 24 stud. I don't think it was Walt that was drinking the rum. LOL John
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Old 12-26-2010, 10:41 AM   #8
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Default Re: Is a 21A flathead desirable?

yes a 21 a is desirable ....I believe in making the most hp out of a stock looking engine....look what simca and the french came up with ....the v8 60 powerhouse!!
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Old 12-26-2010, 11:16 AM   #9
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Default Re: Is a 21A flathead desirable?

Yes the engine came with thin sleeves from the factory. The simple solution here is as WALT says, 86 the sleeves bore .045", late pistons, use 59 head gaskets and 81a heads. Very inexpensive way to gain a fair amount of torque.
Interchangeability, lov that Flathead.
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Old 12-26-2010, 11:56 AM   #10
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Default Re: Is a 21A flathead desirable?

Talk about being a bit hung over, I read it as 21 stud, ha ha
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Old 12-26-2010, 01:28 PM   #11
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Default Re: Is a 21A flathead desirable?

Thanks everyone. Sounds like it will be a good start to a nice street motor for my AV8. I didn't know you could remove the sleeves. concerning the 8ba parts. would it be a good Idea to use the entire 8ba rotating assembly? Mainly for the insert bearing rods? or is that a waste of time. thanks. Matt
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Old 12-26-2010, 03:10 PM   #12
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Default Re: Is a 21A flathead desirable?

Matt, the 8BA crank will fit right in the 39 up block. You'll have to get the aluminum seal retainers for the rear seal. Alot cheaper rod bearings. Use the main bearings that goes with the block. Walt
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Old 12-26-2010, 05:58 PM   #13
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Default Re: Is a 21A flathead desirable?

maybe I should go ahead and source a merc crank. or a scat rotating assembly.
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Old 12-26-2010, 07:01 PM   #14
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Default Re: Is a 21A flathead desirable?

If you can find a crank go for it, my old 41 runs very well with a Merc. crank, Ike cam and adjustable lifters along with Merc pistons. Outside looks very stock. Lots of power for my old panel.

Have fun!

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maybe I should go ahead and source a merc crank. or a scat rotating assembly.
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