10-07-2016, 05:05 PM | #1 |
Senior Member
Join Date: Jul 2012
Posts: 586
|
21 stud motor
Hey all flathead folks,
Is the 21 stud more or less prone to cracks from valves to water jacket or other areas than later flatheads? I have a lead on a 21 stud that the heads have not been remove and thinking about buying, but concerned about cracks. Thanks. |
10-07-2016, 05:19 PM | #2 |
Senior Member
Join Date: Oct 2011
Location: Shelton, WA
Posts: 3,800
|
Re: 21 stud motor
Not sure one is more prone to those cracks then another, it is an issue to check for on all of them.
|
Sponsored Links (Register now to hide all advertisements) |
|
10-07-2016, 05:23 PM | #3 |
Senior Member
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 16,436
|
Re: 21 stud motor
I don't feel that they are any more susceptible to cracking than the later 24 stud engines are but they are an earlier design. Later designs incorporated changes that improved maintainability and reliability. Excessive heat due to engine overheating and freezing of coolant due to lack of sufficient anti freeze are the most common causes of cracking other than plain old operator mistreatment. Those are all more of an operator error situation than a common design problem. They used the same engine in trucks as they did in cars with only minor adjustments to compression. They could take a lickin & keep on tickin.
|
10-07-2016, 05:37 PM | #4 |
Senior Member
Join Date: May 2010
Location: Masterton, New Zealand
Posts: 3,834
|
Re: 21 stud motor
I'll stick my head out and say that a 21 stud engine is far less prone to cracking than an 8BA series
__________________
Unfortunately, two half wits don't make a whole wit! |
10-07-2016, 06:03 PM | #5 |
Senior Member
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 10,319
|
Re: 21 stud motor
Brian. while most of the folks on here would agree with you, I personally have had very good luck finding good 8BA's. I have purchased 5 so far. One was stuck (which I resold), and two have passed formal crack testing with flying colors and the other two have passed a preliminary visual inspection. I have a '51 Merc that didn't even have "Part Number" cracks! Maybe I should go to the casino.
|
10-07-2016, 07:14 PM | #6 |
Senior Member
Join Date: May 2010
Location: Masterton, New Zealand
Posts: 3,834
|
Re: 21 stud motor
Sponsored Links (Register now to hide all advertisements)
__________________
Unfortunately, two half wits don't make a whole wit! Last edited by Brian; 10-08-2016 at 07:57 PM. |
10-08-2016, 07:51 PM | #7 |
Senior Member
Join Date: May 2010
Location: Lexington, NC
Posts: 861
|
Re: 21 stud motor
Had to tear down seven 8BA's to find one good one.
|
10-08-2016, 10:17 PM | #8 |
Senior Member
Join Date: Dec 2013
Location: Delaware
Posts: 252
|
Re: 21 stud motor
Ugg....how many people are tearing down 21 stud engines to build up? How many looking to build a 8BA? And why do you think you hear more about 8BA's being cracked?
You are dealing with engines that are 70 to 80 years old....Lots of thermal cycles are on them as well as many many mis haps. A 1940 flathead may have over heated in 1943 and cracked the block, but was kept running (unknowingly) until it was replaced with a new car. Now we are looking to rebuild these motors and finding them they way they were left to us. |
10-08-2016, 10:34 PM | #9 |
Senior Member
Join Date: May 2010
Location: Masterton, New Zealand
Posts: 3,834
|
Re: 21 stud motor
1937pickup, Are you able to pull the heads before purchase? Bit of a clean up around valve areas should show any cracks, but I doubt you'll find them. But, I'd exercise due diligence and certainly lift the heads. It'll give you an idea of condition of cylinders and state of water jackets too.
__________________
Unfortunately, two half wits don't make a whole wit! |
10-08-2016, 10:44 PM | #10 |
Senior Member
Join Date: May 2010
Location: Masterton, New Zealand
Posts: 3,834
|
Re: 21 stud motor
aonemarine, why do you think you hear more about 8BA's being cracked?
Because, in my experience, they have more of a tendency to do so than the earlier engines; particularly the pre war blocks. The prewar blocks were certainly a better grade of cast iron [nickel content?], dunno, but I'm of the opinion that after the war there was a shortage of some material[s], consequently, the cast iron is different. It certainly welds differently to the early blocks. And, the blocks cast in that stuff seem to crack easier. Or- maybe it's [the cracking] because the valve angles are changed?? My opinion, based on my experience, in answer to the original poster.
__________________
Unfortunately, two half wits don't make a whole wit! |
10-08-2016, 11:04 PM | #11 | |
Senior Member
Join Date: Dec 2013
Location: Delaware
Posts: 252
|
Re: 21 stud motor
Quote:
I care not to speculate about the composition of the iron as there is so many variables when casting iron that with out a proper assay of the block who is to say? |
|
10-09-2016, 06:20 AM | #12 |
Senior Member
Join Date: May 2010
Location: Near Rising Sun, Maryland
Posts: 10,858
|
Re: 21 stud motor
You can debate this issue 'till the cows come home and both opinions can be right or wrong. In my case, I like the the early 21 stud engines. All of the cars I own came with a 21 stud engine from the factory. They can be built to run with the Big Boys if you know how to build 'em, and Brian knows how to build 'em. You might be surprised how well my Avatar '35 fordor runs with its 0.030" over bored cylinders and higher compression cast iron heads. I don't feel the need for a 59a or an 8ba in my '35 drivers.
__________________
John "Never give up on what you really want to do. The person with big dreams is more powerful than one with all the facts". Albert Einstein Last edited by JM 35 Sedan; 10-09-2016 at 12:13 PM. |
10-09-2016, 11:23 AM | #13 |
Senior Member
Join Date: May 2010
Location: Millersport, central ohio
Posts: 668
|
Re: 21 stud motor
Right on John, My Avatar 35 has it's original Babbit bearing block (repoured and bored in 1970) reringed and valve job in 1996, it will run 80 MPH and run 55-60 all day long. That is pretty good considering it is almost as old as me and thats dammed old. Keith Oh.
|
|
|
Sponsored Links (Register now to hide all advertisements) |
|