Go Back   The Ford Barn > General Discussion > Early V8 (1932-53)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 01-01-2019, 09:29 PM   #1
Solo_909
Senior Member
 
Join Date: Oct 2016
Location: NorCal East Bay
Posts: 382
Default 8CM to 8BA

Hey fellas,

So the 51 merc 8CM is shot and needs to be rebuilt good news is I have a 8BA rebuilt motor in the garage and was thinking about just swapping parts and running it Instead. ( yes I know I should rebuild the 8CM, but I donít want to spend the money ) with that said I remember reading that the 8CM and the 8BA are the same blocks so everything such as the intake, heads, water pumps, oil pan, bell housing, and crank pulley all from the 8CM fit the 8BA?

Any wisdom would be greatly appreciated.

Thanks!
Solo_909 is offline   Reply With Quote
Old 01-01-2019, 10:06 PM   #2
GB SISSON
Senior Member
 
GB SISSON's Avatar
 
Join Date: Jan 2014
Location: Orcas Island Washington
Posts: 2,041
Default Re: 8CM to 8BA

If you could use the crank, it makes a huge difference in torque(hill climbing and pulling power). Just my .02
__________________
'47 1/2 ton pickup next project, '47 one ton panel 99% stock nearing completion, '47 2 ton with 8ba and 9' script stakebed, '46 1/2 ton woodie project,'59 F350 9' flareside pickup with cummins 6at. 'Rusty ol' floorboards, hot on their feet' (Alan Jackson)
GB SISSON is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 01-01-2019, 10:24 PM   #3
quickchange34
Senior Member
 
quickchange34's Avatar
 
Join Date: May 2010
Location: charlottesville, Va.
Posts: 549
Default Re: 8CM to 8BA

Water Pumps are different on the 8CM.
quickchange34 is offline   Reply With Quote
Old 01-01-2019, 10:43 PM   #4
Solo_909
Senior Member
 
Join Date: Oct 2016
Location: NorCal East Bay
Posts: 382
Default Re: 8CM to 8BA

Will they fit on the 8BA?
Solo_909 is offline   Reply With Quote
Old 01-01-2019, 10:44 PM   #5
51 MERC-CT
Senior Member
 
51 MERC-CT's Avatar
 
Join Date: May 2010
Location: East Hartford, Ct
Posts: 4,223
Default Re: 8CM to 8BA

If you have a completely assembled, rebuilt 8BA , to me the only thing most necessary to swap would be the water pumps that fit the 8BA and if you find it really necessary the intake to run the original carb.
To swap the heads would be a waste of time and if you don't like looking at the 8BA on the heads just grind them off.
__________________
DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES

Last edited by 51 MERC-CT; 01-01-2019 at 10:49 PM.
51 MERC-CT is offline   Reply With Quote
Old 01-02-2019, 02:29 AM   #6
40 Deluxe
Senior Member
 
Join Date: May 2010
Location: now Kuna, Idaho
Posts: 2,697
Default Re: 8CM to 8BA

Simple answer; Yes, 8CM and 8BA blocks are identical. Swap pumps, intakes, pans, exhaust to your heart's content! Just don't put 8CM heads on an 8BA block! Compression will be way down.
40 Deluxe is offline   Reply With Quote
Old 01-02-2019, 12:16 PM   #7
Solo_909
Senior Member
 
Join Date: Oct 2016
Location: NorCal East Bay
Posts: 382
Default Re: 8CM to 8BA

Thanks guys! Anyone else with any incite?
Solo_909 is offline   Reply With Quote
Old 01-02-2019, 01:39 PM   #8
Flathead
Senior Member
 
Flathead's Avatar
 
Join Date: May 2010
Location: Southern Maine
Posts: 1,016
Default Re: 8CM to 8BA

If you are putting it in a 51 Merc you can swap parts as needed but you will probably miss that extra stroke crank in the 8CM.
Flathead is offline   Reply With Quote
Old 01-02-2019, 02:39 PM   #9
Mike51Merc
Senior Member
 
Mike51Merc's Avatar
 
Join Date: May 2010
Location: Northeast Pennsylvania
Posts: 1,531
Default Re: 8CM to 8BA

The blocks are identical, so everything that bolts on can be swapped over.

I'd put the Merc crankshaft and connecting rods in, together with a new set of pistons and rings, and have a nice 255 again.
Mike51Merc is offline   Reply With Quote
Old 01-02-2019, 03:04 PM   #10
19Fordy
Senior Member
 
19Fordy's Avatar
 
Join Date: May 2010
Location: Coral Springs FL
Posts: 6,536
Default Re: 8CM to 8BA

I think you will need to install the Merc rear sump oil pan in order to clear merc steering linkage.
19Fordy is offline   Reply With Quote
Old 01-02-2019, 03:39 PM   #11
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 9,116
Default Re: 8CM to 8BA

If your not going to use the longer stroke crank then you may want to look for some EAB heads from 52/53 Ford to increase the performance a bit. Mercs are heavier than shoe boxes so any extra power is nice. A 239 will get better performance with those heads.

After you run it a while, you will likely want to rebuild the 255 and put it back in there. A Merc just ain't quite a Merc without the 255 crank & pistons but it's your car man.
rotorwrench is offline   Reply With Quote
Old 01-03-2019, 07:05 PM   #12
scicala
Senior Member
 
scicala's Avatar
 
Join Date: Jun 2010
Location: Detroit suburb, MI
Posts: 2,307
Default Re: 8CM to 8BA

I have heard before on this forum that putting 8CM heads on an 8BA motor will lower the compression ratio. So seems like keeping the 8BA heads on your rebuilt 8BA would make sense.


Sal
scicala is offline   Reply With Quote
Old 01-04-2019, 08:27 AM   #13
Mike51Merc
Senior Member
 
Mike51Merc's Avatar
 
Join Date: May 2010
Location: Northeast Pennsylvania
Posts: 1,531
Default Re: 8CM to 8BA

Quote:
Originally Posted by scicala View Post
I have heard before on this forum that putting 8CM heads on an 8BA motor will lower the compression ratio. So seems like keeping the 8BA heads on your rebuilt 8BA would make sense.


Sal
That's true. I even considered putting a set of 8BA heads on my 8CM, but then I'd lose my 8CM markings that I'm so proud of.....
Mike51Merc is offline   Reply With Quote
Old 01-04-2019, 09:59 AM   #14
tubman
Senior Member
 
tubman's Avatar
 
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 4,200
Default Re: 8CM to 8BA

I went the other way and put a '51 Mercury engine in my '51 Ford. I used the Ford bellhousing, flywheel, clutch, water pumps, and oil pan on the Merc engine. I don't remember changing the oil pump pickup, but it should be obvious with both engines open. There were no problems at all; everything bolted together as it should. Going the other way should be just as simple, but probably not as satisfying.

I would have used the 8BA heads except that I already had a carefully prepared set of Edmunds finned aluminum units.
tubman is offline   Reply With Quote
Old 01-05-2019, 10:57 PM   #15
Solo_909
Senior Member
 
Join Date: Oct 2016
Location: NorCal East Bay
Posts: 382
Default Re: 8CM to 8BA

Quote:
Originally Posted by tubman View Post
I went the other way and put a '51 Mercury engine in my '51 Ford. I used the Ford bellhousing, flywheel, clutch, water pumps, and oil pan on the Merc engine. I don't remember changing the oil pump pickup, but it should be obvious with both engines open. There were no problems at all; everything bolted together as it should. Going the other way should be just as simple, but probably not as satisfying.

I would have used the 8BA heads except that I already had a carefully prepared set of Edmunds finned aluminum units.
Yeah seems pretty straight forward now that I have everything apart. I did have to change the oil pick up though.

The only thing Iím still wonder is if the crank pulley will fit. They are two different size belts so it does need to change.
Solo_909 is offline   Reply With Quote
Old 01-06-2019, 01:25 AM   #16
tubman
Senior Member
 
tubman's Avatar
 
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 4,200
Default Re: 8CM to 8BA

You should have no problem with the crank pulleys as the crankshafts snouts are all the same. One piece of advice I can offer is to be careful removing cast crankshaft pulleys as they are kind of fragile and can be easily broken during removal. Ask me how I know.
tubman is offline   Reply With Quote
Old 01-06-2019, 07:50 AM   #17
FortyNiner
Senior Member
 
FortyNiner's Avatar
 
Join Date: May 2012
Location: u-rah-rah-Wisconsin
Posts: 572
Default Re: 8CM to 8BA

On this same topic, are the fuel pumps different between the Merc and Ford versions?
__________________
19 and 49 F1 jes' like Henry II built
1946 Deluxe - restoration in progress! On the road in '19.
FortyNiner is offline   Reply With Quote
Old 01-06-2019, 08:22 AM   #18
51 MERC-CT
Senior Member
 
51 MERC-CT's Avatar
 
Join Date: May 2010
Location: East Hartford, Ct
Posts: 4,223
Default Re: 8CM to 8BA

Quote:
Originally Posted by FortyNiner View Post
On this same topic, are the fuel pumps different between the Merc and Ford versions?
Both the Ford and Mercury can use the same type 'Double pumper' and 'Single pumper' fuel pumps, just a matter of preference.
__________________
DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES
51 MERC-CT is offline   Reply With Quote
Old 01-06-2019, 08:35 AM   #19
Ol' Ron
Senior Member
 
Ol' Ron's Avatar
 
Join Date: May 2010
Location: Chester Vt
Posts: 6,647
Default Re: 8CM to 8BA

The only difference between these two engines is internal.
Ol' Ron is offline   Reply With Quote
Old 01-06-2019, 08:02 PM   #20
Red98
Junior Member
 
Join Date: Nov 2018
Posts: 29
Default Re: 8CM to 8BA

Quote:
Originally Posted by tubman View Post
I went the other way and put a '51 Mercury engine in my '51 Ford. I used the Ford bellhousing, flywheel, clutch, water pumps, and oil pan on the Merc engine. ...
Quote:
Originally Posted by Ol'Ron;
The only difference between these two engines is internal.
Does this mean the bellhousing, flywheel, clutch, and oil pan are different between 49-50 Merc CM engine and the '51 CM requiring changing those parts between a '51 CM engine but not a 49-50 CM engine to fit the Ford?
Red98 is offline   Reply With Quote
Old 01-07-2019, 09:01 AM   #21
Ol' Ron
Senior Member
 
Ol' Ron's Avatar
 
Join Date: May 2010
Location: Chester Vt
Posts: 6,647
Default Re: 8CM to 8BA

the answer is quite simple. just change the parts that need to be changed. Not sure the flywheel has to be changed, but if it does just change it. I'd keep the 8BA carb and dist tho.
Ol' Ron is offline   Reply With Quote
Old 01-07-2019, 10:35 AM   #22
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 9,116
Default Re: 8CM to 8BA

The Mercury cars of the mid century era did use a different clutch than the Ford cars. They wanted one that was a bit heavier duty than the 9.5-inch Long type so they used the Borg & Beck 10-inch. It has an evenly spaced bolt pattern like the later diaphragm type clutches. The 49 & 50 were the same with the 1 3/8-inch 10-spline type input and sometime in early 1951 around February or so, they changed to a different transmission & bell housing set up. The later 1951 transmission is more like the earlier Ford types with the narrow 4-bolt pattern, diamond cut gears, and a 1-inch 10-spline input pinion. The clutch was still Borg & Beck but was changed for the smaller spline & new style throw out bearing.

Early 1951 Mercs were same as 49 & 50 but the later 51 Mercs were different. The bell housing is a larger cast iron unit but still had the rotating fork equalizer set up for the clutch. In 1952, the Mercs used the same transmission & bell housing as the 52 Ford cars since both made further update changes for commonality.

The Mercury 885 Holley carb would be out of place in a Ford car application but it is a decent carb for a Mercury application. It has a bit larger CFM rating than the Ford 8BA type. The 8BA type is easier to work on and the carb kits are less problem to get a good one. If a person changes away from an OEM Holley type then the ignition has to be changed as well since they are matched as the Holley Load-O-Matic system. Use either the 8BA with all its components or use the 885 but don't try to mix & match. There are slight differences that might cause problems.

Last edited by rotorwrench; 01-21-2019 at 11:25 AM.
rotorwrench is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 01-21-2019, 12:41 AM   #23
Solo_909
Senior Member
 
Join Date: Oct 2016
Location: NorCal East Bay
Posts: 382
Default Re: 8CM to 8BA

Okay for future reference here’s a list of everything that needed to be swapped over. Fairly simple stuff. Thanks fo all the help guys.

Heads, Intake, carb, Oil pan, oil pickup, oil filter, crank pulley, crank extender, water pumps, flywheel, clutch, and bell housing.
Solo_909 is offline   Reply With Quote
Old 01-21-2019, 10:04 AM   #24
tubman
Senior Member
 
tubman's Avatar
 
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 4,200
Default Re: 8CM to 8BA

That list may be OK if you want to make your 8BA LOOK like an 8CM, but again, using the 8CM heads will cut compression from an already low 6.8:1, and combined with the larger (and rarer and harder to work on Merc carb), may cause performance problems. Since the Merc is a larger and heavier car, it will probably be a slug. It'll get you around town OK, but that's about it.
tubman is offline   Reply With Quote
Old 01-23-2019, 12:19 AM   #25
lonewolf
Senior Member
 
Join Date: May 2010
Location: Michigan
Posts: 388
Default Re: 8CM to 8BA

If the Merc is an automatic the crank is machined to work with the air cooled converter. It has kind of a pilot about the size of quarter machined into the end that the converter goes into .If the 8ba was a manual transmission the crank may have to be machined to work with the automatic converter. If the Merc was a manual transmission you will be good
lonewolf is offline   Reply With Quote
Old 01-24-2019, 11:18 PM   #26
Solo_909
Senior Member
 
Join Date: Oct 2016
Location: NorCal East Bay
Posts: 382
Default Re: 8CM to 8BA

Quote:
Originally Posted by lonewolf View Post
If the Merc is an automatic the crank is machined to work with the air cooled converter. It has kind of a pilot about the size of quarter machined into the end that the converter goes into .If the 8ba was a manual transmission the crank may have to be machined to work with the automatic converter. If the Merc was a manual transmission you will be good
Good to know, they both are manual so I guess Iím good.
Solo_909 is offline   Reply With Quote
Old 01-24-2019, 11:19 PM   #27
Solo_909
Senior Member
 
Join Date: Oct 2016
Location: NorCal East Bay
Posts: 382
Default Re: 8CM to 8BA

Quote:
Originally Posted by tubman View Post
That list may be OK if you want to make your 8BA LOOK like an 8CM, but again, using the 8CM heads will cut compression from an already low 6.8:1, and combined with the larger (and rarer and harder to work on Merc carb), may cause performance problems. Since the Merc is a larger and heavier car, it will probably be a slug. It'll get you around town OK, but that's about it.
Hmmm, Iíll be able to tell that much just from swapping the heads? I could use the 8BA head. They just need to be painted. I just wanted things to appear stock.
Solo_909 is offline   Reply With Quote
Old 01-25-2019, 09:10 AM   #28
tubman
Senior Member
 
tubman's Avatar
 
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 4,200
Default Re: 8CM to 8BA

Quote:
Originally Posted by Solo_909 View Post
Hmmm, Iíll be able to tell that much just from swapping the heads? I could use the 8BA head. They just need to be painted. I just wanted things to appear stock.
Or, you could have the 8CM heads milled enough to get you to a .050 "squish" over the piston . You would probably have to do some grinding to bring the head to a uniform combustion chamber. Then you would have the best of both worlds. I believe it is common knowledge that increasing compression is the easiest way to pick up power in an otherwise stock flathead. You might as well take advantage of today's better fuels.
tubman is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 09:00 PM.