Crank stroke before 49

3

3W Hank

Well-known member
I has a question on cranks how the old guys did this before the 4” stroke came out.
War ended 45 but some guys was still at home and not much ( hotrod ) racing was going on ( streets or El Mirage ) my guess but 46/47 they was back in ( LA )
Ex Pete Henderson I think worked at Boeing in LA under war.
Reson I ask is I build up a 59 engine with a hair more early ideas than late 40’s or in the early 50’s.
So, painted stock heads, Weiand early Hi-Rise, dual 97’s with Wittek style clamps, Kurten modify LZ V12 distributor, Potvin cam, the early 39 alternator and 34 oilfiller cap tube, 32 fan.
Well I could get a new strokerkit, but I like do it the ’hard’ way.
I can find a crank for free and I grind cranks in my shop.
This is not because I’m greedy to save some bucks get a ex 4” ( I had one, just sold it… ) or I must has a big stroker, it’s more the history ( and som stupidety… )
I’m not after the HP.
( my other Merc 41 block will has a baby stroker + 1/8” 4” )

So the cranks ( 3.75 ) on Merc’s at 1940 was std rod 2.139 and Fords at 47 the same.
The older had the 2” rods.

So do this cranks had 2 oil holes per rod throw or just 1 ?
So how did they do it back then ?
Did they use the 21A rods ( 2” ) or did they used the rods to this cranks and welded on and stroke them 1/8”, or even go up to 4” ( or did they go even further upp ? )
If so, what piston companys sold pistons and now we talk before the 4” crank came out.
So go 4” from 3.75” it means C-H was lowered 0.125”.
Did some made them 1948 ?
-Question is also as a historical point,
I guess few or non care now, but I like the history how is was made.
Did they also go over 4” stroke, if some know, please tell the story.
Note, this is before the 4” was out.

I dont kniw whst ex Henderson used but I guess std 3.75 but maybe it was crank shops in LA sold this (?)
 
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When I started in the machine shop business back in the 70's, we had a crank welder. It was a machine you set stroke and it wire feed wire on the crank to build it up. Welding could of been done without a machine, have seen it done. I would guess that in the 40's if strokers were made it was welded up and ground most likely to 2" journals.
 
Anything is possible, including converting a non-flathead V8 Ford crankshaft to fit into the V8 block (done at least a few times to get a flat plane crankshaft). Just because someone did it once does not indicate it was normal practice.

The normal options before 1949 were to use the stock 3 3/4 stroke, or to offset grind a larger rod journal crankshaft and use pre-war Ford rods to get a 3 7/8 stroke crankshaft. According to the article referenced below in this post the first known offset ground 3 7/8 stroker crankshaft was done in 1939 right after the Mercury engine was released.

I suggest reading the series of articles authored by Mark Dees titled A Technical History of the Racing Flathead. These were originally published in 1973 in Rod & Custom magazine. Happily you don't have to go scrounging for 50+ year old magazines, you can get them in pdf format. Just purchase the V8 Times in pdf format from the Early Ford V8 Club (link here: https://shop.efv8.org/collections/media/products/50-years-of-the-v-8-times-flash-drive). Those four articles were reprinted in the V8 Times in 1978 in the January / February, March / April, July / August, and September / October issues.
 
flatrod said:
When I started in the machine shop business back in the 70's, we had a crank welder. It was a machine you set stroke and it wire feed wire on the crank to build it up. Welding could of been done without a machine, have seen it done. I would guess that in the 40's if strokers were made it was welded up and ground most likely to 2" journals.
Click to expand...

Very interesting. Were you able to weld up cast cranks with that machine back then?
My crank grinder today can weld up cranks but not cast cranks.
As a kid I used to go to the machine shop with dad and watched Knobby (I still remember his name) welding up cranks but it was a spray weld process sprays powder onto the red hot crank.
 
1) Easy 1/8" Stroker (Traditional): You take a 3 3/4" stroke crankshaft with 2.138 journals and offset grind the rod journals to fit the 39-42 91A or 21A 2.00" rods. Given that these rods used the full-floating bearings, the crankshaft can be any 3 3/4" stroke crankshaft (39 - 53) with 2.138 rod journals.

Oiling Holes: The 39 - 48 crankshafts only had one oil-hole per journal, so you have to use the full-floater bearings. If you use a 49 - 53 Ford crankshaft, it will have 2 oil holes per journal, so you could use a set of H-Beam rods with insert bearings.

Oil-Slinger vs Rope Real-Main Seal: The 39-42 engines used crankshafts without a rear-main seal - they had an oil slinger setup. If I was going to build an engine like this, I'd use a 45 - 53 crankshaft that supports the later rear-main rope seal. You then use the later 59 AB pot-metal rear-main seal plates and install them in the 39 - 42 block (they fit right in). This gives you a rope rear-main seal (which is a lot better than a slinger setup - especially if you're running larger bearing clearances and a later oil pump).

2) Welded Stroker: There were some high-end racing engines that had their crankshafts welded up (by hand) to add enough material to increase the stroke beyond 3 7/8". They would regrind the rod journals to use the 2.00" 91A or 21A rods and full-floater bearings.

Given the different material types between the cast iron crankshaft and the steel weld material, it was common to initially grind the journals to a bit undersize and then have them hard chromed and finish ground. The hard chrome gave a consistent journal surface for the full-floater bearings to run on.

In later years, one could use a submerged arc machine to weld up the journals for the initial material adding process. I've seen many of these machines in action . . . they work well, but the process is expensive (to do all the journals).

3) Full-Floater Bearings: The standard Ford/Mercury full-floater rod bearings from 39 - 48 used a hard copper alloy. While these will run just fine, they are harder on the journals (wear). In most of my early stroker engines, I'd always look for Ford bearings marked "Heavy Duty Truck and Bus" - these used a much softer cadmium-silver alloy.

Most of the major bearing manufacturers had cad-silver rod journal bearings as an option. In Federal-Mogul full-floater rod bearings, they had a part number suffix of "CS"

Given the longer stroke and higher HP of our race engines, having cad-silver bearings was a blessing as far as crankshaft wear. The cad-silver bearings are a lot harder to find these days, so "squirrels" like me tend to have a bunch stored up for the future.

4) Full-Floater Bearing Fitment: In order for full-floater bearings to work as designed, they must be hand fitted to the rod journals . . . such that they easily float in both the big-end of the rod and on the journal. You can't just buy a set of bearings and throw them in the engine and expect them to float and not score the crank or rods . . . tuning them is key!

Some of the bearing shells will not be perfectly round, so a rubber mallet comes into play. Also, the bearings should be polished with fine Scotch-Brite and lacquer thinner. Also, it isn't a bad idea to increase the diameter of the big end of the 91A or 21A rods about .001 (to help the bearings float). This is all stuff that was/is done for high-performance stroker engines where we always wanted increased bearing clearances and "loose" fitting crankshafts!

Always remember the ole' saying "Loose is fast, tight is death" when considering bearing clearances! LOL
 
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Thank's guys and Dale.
Weld up's is to 'much' real racing, so a babystroke like on my 4" Merc crank is cool.
And then a set A21 rods as I like a crank forged/cast before 48.
So for a later rear olil seal a crank at 1945.
My block to the 4" crank is a 41 Merc block, but this 59 AB block I might use I don't know the year on.
 
Offset grinding the big rod journal Ford 3-3/4 stroke crank is how it was done in the early days. It was actually simple and done often {in secret} by grinding the rod journals to 2 inch diameter and then simply use 21A rods.
Many cheater race engines were built that way a very long time ago before the 1949-53 Merc 4 inch stroke crank became available. I have rebuilt a few of those early engine's with the 3-7/8 stroke over the years that were found in early Hot Rods being restored.
Ronnieroadster
 
Ron, Yes it will be good for this one, block is 1/8 over and that 3.75" crank will be 1/8 over to.
Block is on the edge.
 
Running a 3 7/8" stroke crankshaft:

The only other thing to note is that you need to have pistons with the correct compression height (pin location) to use stroker crankshafts.

With that said, some guys would use the STD stroke 3 3/4" pistons (which would now be 1/16" above the deck) and modify their cylinder heads (re-dome them) to set the final piston to head clearance.

Lots of ways to skin the flathead cat!
 
Dale, that is sound one poor mans race solution.
Reallly like that idea !
One need atleast 0.04” my guess of the old skinny rods, but gaskets is often 0.04” and is there material in a steel Ford 40’s head cut it little ?
On the other hand is compression the key to make HP in a FH or is flow better vs less compression.
If so just more gasket thickness.

Another question.
Did people used Ford pistons bigger OD or did companys made ’race pistons’ ( pre 1949 )
 
Having the correct "squish" clearance above the piston dome is really important. You want .040" to .045" maximum clearance. Also, keep in mind that many Ford cast iron heads have a dome shape for a multi-elliptical piston crown (they are kind of "pointy" in the middle). Back in the day, lots of folks ran Jahn's/J&E pistons on their stroker motors. I'd guess they were available in your build years.

Popping the piston up just a bit and tuning the squish would be a good setup. This is especially true if you have a consistent radius piston crown (like Ross, Jahn's and most others), so you'd re-dome the heads with the correct radius cutter (that matches your piston crown shape). You can also create a 3D model and use a 1/4" ball on a CNC machine and then "polish" it afterwards.

Mockup: You should have the crank ground first, then put together a "mockup" with the crank in the block, with 2 rods (one each side) and 2 wrist pins - one in each rod. Then you can accurately measure and determine what the compression height would be at the deck. This makes it possible to see if you can run a stock stroke piston and understand the pop-up amount, or order exactly the right piston from somebody like Ross. (This is what I do).

Deck Height: By putting two rods in the mockup (one each side), you can also measure the difference between the deck heights for each bank. Usually one is lower than the other. You can then determine how much to clean up the decks on each side - and use those final measurements to determine the final compression height. If you put two rods in the front and two in the back, you can see if the decks are parallel to the crankshaft centerline. When I have blocks decked, I only have it done with a machine that picks up the mains - this ensures the same height and squareness to the crank centerline on both sides.

I always like my head dome shape to match my piston crowns - then tune the squish for exactly .040. If you order pistons from Ross, you can have them put the pin location exactly where you want it (which is what I do).
 
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KiWinUS,
Yes we did cast cranks the same way. Some came out good others had a lot of porosity. I still have a 3 7/8 stroke crank I did way back then. Its not welded just offset ground.
 
I heard on the non equal side of a FH.
If I deck and use a BHJ fixture I can easy set out equal banks.
The Ross don't charge that much to get the C-H as I like.
-But a cool way ( but stupied ) would be to try to find a old set ex JE 1/8 over std C-H for a 3.75 crank ( but who has thoose parts now 2026 ? )

I saw El Mirage start list from 1948, and allot of smaller engines and biggest 268, allot of Edelbrock both heads and intakes, Spalding electrics.
Some Weiand, Evans etc.
 

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On Van Pelts web it shows ex a 268 is a 3.75" stroke but 3.3/8" bore or 3.375".
That is more than the 59 AB block I has, that are 1/8" over std or 3.312".
Thats 0.0625" more than my block ( I thought was 'max' )
So the boys did like big bore, but blocks was also 78 years 'younger'...
 
3W Hank said:
I heard on the non equal side of a FH.
If I deck and use a BHJ fixture I can easy set out equal banks.
The Ross don't charge that much to get the C-H as I like.
-But a cool way ( but stupied ) would be to try to find a old set ex JE 1/8 over std C-H for a 3.75 crank ( but who has thoose parts now 2026 ? )

I saw El Mirage start list from 1948, and allot of smaller engines and biggest 268, allot of Edelbrock both heads and intakes, Spalding electrics.
Some Weiand, Evans etc.
Click to expand...

Just make sure you use the mains as the reference point, not the valve seats! The valve seats on the driver's side are about .040 higher than the passenger side - due to the crankshaft being offset.
 
Bored&Stroked said:
Having the correct "squish" clearance above the piston dome is really important. You want .040" to .045" maximum clearance. Also, keep in mind that many Ford cast iron heads have a dome shape for a multi-elliptical piston crown (they are kind of "pointy" in the middle). Back in the day, lots of folks ran Jahn's/J&E pistons on their stroker motors. I'd guess they were available in your build years.

Popping the piston up just a bit and tuning the squish would be a good setup. This is especially true if you have a consistent radius piston crown (like Ross, Jahn's and most others), so you'd re-dome the heads with the correct radius cutter (that matches your piston crown shape). You can also create a 3D model and use a 1/4" ball on a CNC machine and then "polish" it afterwards.
Click to expand...

Where can one get "the correct radius fly cutter that matches the piston crown"?
 
-I always asked myself that when I worked with the 426 Hemi for decades.
Heard about them, but never saw one in person.

I bought heads from Modesto but when a aluminim head was legal in stock class I had no one do my heads so this tool get the chamber bigger in diameter as if a modern pistons and max bore they could not pop up Ok.
Old way ( big dome ) was modify the dome to chamber ( by hand ) but not legal.
Now pistons need a number.
I had the blueprints from CP ( not easy… ) then I got Hemi blue prints from BHJ and bought their blueprint TQ plate.
Then I machined chambers in CNC.
Bored block with plate on ( as new block it was good ) and machined heads with plate on ( not as good ) as I did like exact centre as its tight for piston to head ( otherwise lose comp ) and as good rods ( incornel bolts ) I had little over 0.04” and near 9K RPM.
A huge work… from a big chamber tool..in a Bridgeport mill.

I has ask on FH blue prints but I has never seen them.
My idea if a drawings I CNC machine head the whole chamfer and 3D out dome and ask Ross the cordinates.
Cordinates is only 1 line in X and Z and a R from a starting point in X/Z, but I guess hard or impossible get them.
 
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Obviously the dome radius changes as the diameter of the piston changes. If I am correct, I believe Ross sets the dome radius based on the height of the dome itself - which is usually .187".

So, one could easily calculate the CNC radius to work with and use a 1/4" ball mill with a fine step-over to mill the chambers in the head to match the pistons. You can then use a hand air tool to polish the chambers to get rid of the toolpath marks.

The critical thing to first understand is where does the pin need to be (compression height) to get the piston dome where you want it.

One could decide to have the piston edge "above deck" the same amount as the gasket thickness (regular gaskets tend to be about .052" thick). If you popped the piston up to the top of the gasket surface (via pin location), then you would know exactly how deep the dome in the head needs to be.

One more thing to note is whether or not your block is relieved and if so, what is the relief depth. This is important in that you may want to move the ring pack down a bit (if you have a heavy relief) so that the top compression ring doesn't get too much heat into it. I do this on custom piston orders and I also specify metric ring packs.
 
You don't has the FH blueprints of boltholes vs where cylinders is located.
On many engines this is out on internet, but I never seen the FH.
I could ask Chris at BHJ but they is out of business.
I asked recently on a TQ plate, nothing to get.
I might mail him and ask.
 
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