Mercury crank

[fordwife]

How do you identify the difference between a 049-53 ford crank and a mercury 'crank? I've forgotten, its been too long.

[RalphM]

Clean out plug on the front will be five eights inch diameter, is the best way

[Tim Ayers]

The counter weight width as well. I forgot the measurement, but if I recall correctly, the Merc crank counter weight is approx. .500" wider than a Ford crank. Something like 6" in total width at the widest part for a Merc crank seems to ring a bell.

[bbrocksr]

A Merc crank is 12" longer than a Ford crank. REALLY?

A merc counterweight is 6" wide, a Ford counterweight is 5 3/4 wide is what I think he meant.

Bill

[Tim Ayers]

Originally Posted by bbrocksr

A Merc crank is 12" longer than a Ford crank. REALLY?

A merc counterweight is 6" wide, a Ford counterweight is 5 3/4 wide is what I think he meant.

Bill

Haha. I meant to say the width of the counter weight is 1/2" wider. I'll correct it. It's been a long day.

[Tim Ayers]

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Originally Posted by bbrocksr

A Merc crank is 12" longer than a Ford crank. REALLY?

A merc counterweight is 6" wide, a Ford counterweight is 5 3/4 wide is what I think he meant.

Bill

Yes, thanks Bill.

[GOSFAST]

I have about 10 Flathead Ford/Merc cranks here at the moment. All are 8BA style, later pieces!

They both measure about 7.000" across the front c/weights, if there is any difference it is immeasurable with a conventional ruler.

The plugs are another story, the Merc is .625" (5/8") like mentioned above. These actually lend themselves very well with this size to drill & tap fpr a 3/8" NPT pipe plug, requires no add'l drilling. We do these all the time!

Thanks, Gary in N.Y.

P.S. Here's a shot of a Merc on one of our balancers now getting balanced. On the left I wrote the dimension (7.000") in "chalk" to show the span of the c'weight, on the right that single line shows the pressed-in oil plug, it measures 5/8". I can supply a shot of the front c'weight on the 239" Ford also if necessary?

[Tim Ayers]

Originally Posted by GOSFAST

I have about 10 Flathead Ford/Merc cranks here at the moment. All are 8BA style, later pieces!

They both measure about 7.000" across the front c/weights, if there is any difference it is immeasurable with a conventional ruler.

The plugs are another story, the Merc is .625" (5/8") like mentioned above. These actually lend themselves very well with this size to drill & tap fpr a 3/8" NPT pipe plug, requires no add'l drilling. We do these all the time!

Thanks, Gary in N.Y.

P.S. Here's a shot of a Merc on one of our balancers now getting balanced. On the left I wrote the dimension (7.000") in "chalk" to show the span of the c'weight, on the right that single line shows the pressed-in oil plug, it measures 5/8". I can supply a shot of the front c'weight on the 239" Ford also if necessary?

Gary: Check the width of the 2nd counter weight in from the one with the chalk line. Is there a difference between the two widths of this weight? That's the one I've always checked.

[r_reed]

i built a simple v shaped rack, rotated the crank and measured the stroke. since the difference is a 1/4" it is not hard to tell.

[Pete]

Besides all of that, I discovered in the mid 50's that some Merc cranks are cast steel and most are cast iron. The steel ones were obviously the better choice for welded strokers.

[Ol' Ron]

I think the Canadian Nerc cranks had a 3/8 oil plug.

[glennpm]

Here's a good article by Bill Boomer I came across a few years ago about the Merc crank identification.


http://myflatheadford.com/identify-4...ry-crankshaft/

[Desoto291Hemi]

Hey Gary,
Do you recommend to tap the front weight for a pipe plug instead of a press in plug?

Tommy

[GOSFAST]

Originally Posted by Desoto291Hemi

Hey Gary,
Do you recommend to tap the front weight for a pipe plug instead of a press in plug?

Tommy

Hi Tom, without a doubt, have all 4 tapped. The nice part about the Merc's starting with the 5/8" plugs is they don't need drilling, they're already the correct size to just tap for the 3/8" NPT thread!

Thanks, Gary in N.Y.

P.S. In all my time doing these builds we've literally done hundreds of those crank holes, more than 90% were Merc's, we did some Ford's way back in time.

[34PKUP]

Originally Posted by GOSFAST

Hi Tom, without a doubt, have all 4 tapped. The nice part about the Merc's starting with the 5/8" plugs is they don't need drilling, they're already the correct size to just tap for the 3/8" NPT thread!

Thanks, Gary in N.Y.

P.S. In all my time doing these builds we've literally done hundreds of those crank holes, more than 90% were Merc's, we did some Ford's way back in time.

Just curious, why is it necessary to take the time and effort to tap holes and insert threaded plugs? When the original Ford type plugs were used on literally millions of cranks (not hundreds) without any problems (known to me).

[Desoto291Hemi]

I would venture to guess that it is just a safety precaution.
One less thing that could go wrong,,,you know.

We tend to run more pressure in our engines now,,,,so a plug could possibly blow out.
Also,,,,you need to remove them to clean the passages . So might be a good time to upgrade. Of course,,,like you said,,a plug worked for millions of engines before.

However,,,I will probably use a fair amount more oil pressure,,,so,,,I know what direction I am leaning towards.
Thanks for the reply Gary.

Tommy

[40 Deluxe]

Originally Posted by Desoto291Hemi

I would venture to guess that it is just a safety precaution.
One less thing that could go wrong,,,you know.

We tend to run more pressure in our engines now,,,,so a plug could possibly blow out.
Also,,,,you need to remove them to clean the passages . So might be a good time to upgrade. Of course,,,like you said,,a plug worked for millions of engines before.

However,,,I will probably use a fair amount more oil pressure,,,so,,,I know what direction I am leaning towards.
Thanks for the reply Gary.

Tommy

Why "use a fair amount more oil pressure"? Is it really needed? It will heat the oil more by churning it through the bypass valve as well as require more horsepower to drive the oil pump. Bearings are lubricated by the hydrodynamic wedge action of a rotating shaft. The oil pump merely supplies the needed oil to the bearing.

[Desoto291Hemi]

Well my reasoning is I have heard many stories of only 10 pounds of pressure before.
I am sure that some engines will live with that,,,,,but,,,the stresses placed on a high performance engine are greater.
Yes,,,the hydrodynamic wedge is there,,,,but,,the added load is detrimental to the oil film provided on the journal.
The load against the journal doesn’t just increase,,,but it could increase by the square,,or even the cube.

Also,,,some oil passages are not as friendly to good flow as others are.
Some cranks are machined where the oil passages actually act as a pump themselves.
The angle of the passage,,,the angle the oil hole comes out on the rod at top stroke.
This can act as a pumping action,,by centrifugal force,,,,it literally helps sling the oil through the crank.

Also,,,,during some high rpm,,,high load forces,,,the oil can stop in its tracks,,,,,for just a millisecond,,,.
There are a lot of forces involved,,,,that is why they went from just dippers and oil slingers.
The power levels got to the point that it couldn’t lubricate anymore and the pressurized oil systems were created
Then later,,,,the full filtration filter systems evolved as well.

I don’t plan on too much pressure,,,I like to have al least about 30 or so at hot idle,,,then around 60 at RPM.
Just my observations.

Tommy

[flatjack9]

I've got over 60,000 miles on my engine and the oil pressure never drops below 30 lbs. 60 at startup. This is with a stock 8BA pump. The 10 lb stories are old history.

[Desoto291Hemi]

Hey Flatjack,

Good to hear that.
Like I said,,,I don’t intend to use too much pressure,,,just a fair amount.
By the way,,,what pump do you use,,,stock type Ford,,,Melling?

Tommy