Projects FlatCab: 1932 Cabriolet, Hot 1941/42 Merc Flathead Build

Thank you for showing this. It looks like a really well done build. My 99 is at the machinist right now getting mag'd so keeping fingers crossed. I'm hoping to do something similar, we'll see...

 

Right On - hoping your block turns out well and you have a solid platform to build from. If I can help you with anything, just let me know - makes me happy to see folks building these engines and paying attention to the details. It is the technical details, parts, machine work and assembly process that determines the outcome - it all matters if you want the best possible result.

I hope to be able to start putting it together in the next few weeks - then I'll have to determine the combustion chamber CNC work that I want to have done (once I can check the final compression/deck height) . . . have some ideas/plans to try!

When they're built right, they're a heck of a fun engine -- especially since one has to consider the design is from 1931 or so!

 

Sweet build. Love that intake.

 

Dale I love your posts, keep em comin brother

 

Thank you for going so in depth for this build. I have been taking notes from here as well as from flatheadv8.org. Both have really helped me during my current engine build

 

Rod Balancing Fixture - Round #2 (Friction is a Fickle Bitch!):
I was not happy with the first version of my rod weighing/balancing fixture. I bought a much more accurate scale - measures .1 of a gram and is very repeatable. So, I naturally figured that if I weighed the same rod twice, I'd get the same weight - wrong! I noticed that I could see a 3 - 4 gram swing, even when I was totally careful about how I gently placed a given rod onto the device.

Friction: Ever So Small Amounts Changed the Weights: I decided that the slightest frictional difference on either end was causing the changes. The aluminum 'roller' on the big end just rotated on an aluminum shaft - highly polished. The pin end was a polished aluminum shaft - with just a bit of play. I tried different lubricants - etc . . . still not repeatable. If it isn't repeatable, then to hell with trying to balance the rods - I'd be chasing a ghost and just ruin them.

So, in figuring it just had to be a minute level of frictional difference, how do you reduce it? Well, put a nice roller bearing in it! I had some flathead pilot bearings, so I grabbed one and modified my fixture to make the big-end roller live.


Also, I made a tool-steel pin for the small end - and precision ground it with my tool-post grinder. I now just gently lay the rod on top of the pin.



Lots of screwing around on this, but now I get repeat-ability to about 1/2 gram, which is a very minute amount. Given what I've learned, I'm very curious how the rod balancing scales are accurate - as they used the same big 'rollers' on the big end - with different sizes that you just slap on for different big end sizes. Heck, they aren't even an exact/close fit - whatever is close enough, use it. I'm going to re-weigh everything at Fowlers when I'm done - just to cross-check things.

Tooling/Fixture to Hold the Rod Caps for Machining: I made a fixture to make it easy to hold the big-end cap and turn it on the lathe - to remove weight around the circumference. As noted in my earlier post, this is the way that Henry did it - they didn't grind the cap reinforcing rib on the bottom like all machine shops I've ever seen do. (And every set of "balanced" flathead rods I've seen over the years).



Well, tomorrow night I can actually begin the balancing job . . . spent a couple more days on this than I'd planned, but I couldn't move forward until I could trust the measurements.

B&S Out . . .

 

Hi Dale
I like your idea using the bearing on the big end I to had similar problems balancing rods using the aluminum dowels. Spent many hours looking for repeatability dam hard for sure.
The best results I came up with was hanging the rod big and small end fixtures from small chain the type used on pull chain light switches that small chain greatly reduced the binding I was experiencing. The rod balance seems to be fine using this method went over 180 MPH with that set of rods so far. But now I'm going to refine the fixtures using the bearing Thanks for keeping us posted good stuff for sure.
Ron

 

Let me know how it works out! I will be posting the work done to the actual rods in the next couple of days, will be fun to see how things turn out. Take care Ron, hope to see you guys soon! (You coming to Ohio this spring?)

 

Dale were heading to Wilmington in June with the new combination hope to sort things out before heading to the salt. In the mean time still finishing the car and have a test block on the milling machine so I can make make fixtures for squaring and valve seat installation.

 

Well, tomorrow night I can actually begin the balancing job . . . spent a couple more days on this than I'd planned, but I couldn't move forward until I could trust the measurements.

And 2 Hours LOL

 

Hey Don . . . just an easy '2 hour' job . . . "good job" Dale, "good job". LOL!

 

Finished the Balancing of the 21A Rods - 4 Hours of Work:

I started with the heaviest of the rods (big end) - needed to shave off about 9 grams. I started with the cap, mounted it on my fixture on the lathe and took off a couple grams (in the machined arc in the picture) on both sides of the cap. The fixture worked out really nice - no slippage and the new carbide cutter worked well. Now, I still needed about 4 more grams, so I took a little bit off the bottom "beams", smoothed the sides, smoothed a couple places on the big-end strengthening webs, etc.. All in all, wasn't too bad and I didn't remove any real strengthening material. As this was the heaviest rod, the rest were done with diminished amount of material -- the last one was 1.5 grams heavy, so it was a piece of cake.



Then I moved onto the pin/small end of the rods. The heaviest one was about 6 grams heavy. So, I started by removing the alignment hole bosses (each was about 1 to 1.5 grams). Then I polished the whole top/radius of the small end, removing the 'parting line' in the middle. Then I polished just a bit of the sides of the beams themselves. The rod shown was the heaviest one - obviously the amount removed down the line was progressively less.

I took the rods to Fowlers today - to validate my work on his high-dollar setup. I compared the heaviest big-ends to the lightest (same with the pin-ends). Per his scale, I was within a .5 gram on the big-end and dead nuts on the pin end. Needless to say, I'm damn happy with those results (gives me confidence for the future).

Here are the finished pictures, along with a 21A rod picture from another site - notice how the balancing was done - see the big 'flat spot' on the bottom of the big-end cap! This was exactly what I was avoiding (weakening the big-end cap) - by doing them like Henry originally did. I'm sure I'll use my whole setup in the future - as I plan to use more 21A rods and 8BA rods. I will only use the H-Beam variety when I have a very high horsepower situation -> blown or Ardun.

My goal is a very light reciprocating assembly - using custom/shorter piston pins as well.

Crank/Rod Clearances: I want .002 to .003 on the big ends - will 'shape' the bearing shells to make sure everything floats as it should.

Side Clearance: I will measure and set this up when I assemble the engine. I'll use my surface grinder to achieve about a .015 to .017 side clearance.

My Philosophy: I like to move a lot of oil through the bearings to cool them, so I tend to run bigger clearances than some. I like things "loose" with plenty of good oil volume and pressure.

Crank Nitriding: I've never nitrided a Merc crank, so I'm going to have this one done to see if it makes a more robust bearing surface (should). Why not give it a try!

Enjoy!

B&S

 

nice Dale

 

What do you think about sanding the parting lines off the sides BEFORE you start balancing? Have you ever seen a flathead rod break in any sort that may have been caused by the parting line?

And, aren't you supposed to sand parallel to the rod, not across?

 

Most folks that I know say to take as little material off as possible - even in the parting line section. These rods are so spindly, polishing the beams only weakens them.

With that said, I wasn't around in the 50's - blowing up motors right and left. I'm sure the weakest area is right at the top - where it is the smallest (but that is just a guess). I ran a set pretty hard on a blown flathead - 35 years ago. Spun it to 6500 at the drags and didn't have problems. I also had loose bearing clearances and plenty of oil.

The material is very nice and if one can find a NOS set in Cosmoline, you'll love the quality of Ford's machine work (the big-end bores are perfect). If I was rebuilding a used set, then I'd have them checked for straightness, sizing, etc. - and probably have them shot-peened to stress relieve them. On sizing the big-ends, most shops are not used to full-floaters and the fact that the big end bores are bearing surfaces - so we want the surface as smooth as possible (polished like). That is the way they came from Ford - just like a new micro-polished crankshaft journal. My guess is that most shops have no real way to accurately polish the bores?

That is a good question - I wonder how one would do it today? Pete1 - you out there???

 

Hey Dale as usual very nice work making your fixtures and balancing the big end without weakening the rod cap. For many years in my first ARDUN block I ran a set of NOS 21A rods that all ended one evening when the wrist pin end on a rod decided it was time to break. Upon inspection of the failed rod I determined the amount of material removed for balancing by Ford on the outer ends of the wrist pin hole made that area of the rod very thin.
Whenever I look for a set of rods I try to find the ones that have no material removed from the rod at least in the area of the wrist pin boss. That dam rod breaking killed a perfect block but I did have a lot of miles on the engine.The rod failure took place at very low RPMS man what a way to learn about rods.
Ron

 

At work we have a jig grinder. With a nice fixture I think it would be just the thing for grinding full floating rod bearing big ends. Google image search for jig grinder: https://www.google.com/search?q=jig grinder&client=ubuntu&hs=QOL&channel=fs&tbm=isch&tbo=u&source=univ&sa=X&ei=32HfVPfnJ9K3ogSo54LYCw&ved=0CB8QsAQ&biw=1920&bih=937


Nice work on the rods. Many thanks for posting the how-to pictures.

 

Thanks Ron and 38Coupe - always good to hear about real world experiences and alternate ways to accomplish things. I'm kind of with Ron on pondering at what level do you STOP using 21A rods . . . I know that many used them back in the day for some high-horsepower situations - but blocks were easy to find and who knows how many failed along the way. I think that if I was pushing much past 200 HP, that I'd at least be thinking about other options - as we have plenty of inexpensive H-beam style rods out there for very affordable prices. Once you get to competition blown/injected engines, I'd probably be looking at Cunningham, Crower, etc

Truth be told, my goal of going 'Pre-WW2' with as many parts as possible is what drove me to use these rods (and I have NOS parts). Also, I just sort of wanted to do this engine 'old school' and document the parts and processes that were common 50+ years ago. It would actually be cheaper in time/money to just buy H-beams off the shelf, balance them and call it a day. But I would learn nothing in that process and also, not be able to show that there are still very viable options out there - going all the way back to 1939?

 

dude...yur becoming as anal as @gwhite

 

RE: dude...yur becoming as anal as @@gwhite

I'm not sure if that is good or bad . . . but what the hell, kind of fun having a plan that is a pain in the ass and sticking with it! I don't tend to take the 'easy road' all that often . . . sometimes to my own dismay!

 

Dale, I'm late to the party on this but, regarding the friction problem when weighing, what if instead of matching sized "hangers" you used smaller pins on each end. Am I making any sense? Wayno

 

Very hard to guarantee 'exact center' locations when hanging them - especially on the 'big end' - this will result in the weights moving all over the place. I think having really smooth and close fitting centers is important and that perfectly smooth roller bearings are a must. Fowler's high-dollar setup has roller bearings for both ends.

 

Fair enough. Carry on. Wayno

 

Thou shalt not use the name of thy Mod in vain. But I shall turn away my fierce anger and shew thee compassion for offering this most righteous build. Hehehehe.

Yes! Love this...us 1930's/early 40's guys are few and far between; great to see another being built - looking forward to following along!!

 

Rock on my traditional Broham, I hope to partake upon those who are following . . . some value . . .

B&S

 

Lovn this thread Dale; awesome work - I LOVE the attention to detail brother (y)

 

Any updates? The detail so far has been great, I'd love to see more.

Thanks!

 

The Beast is Back Home! . . . Has Been a Long Winter in the Machine Shop:
Just picked the engine up from Fowlers, discussed the additional work that I need done, etc..

Here are all the 'bling, bling' pictures of the block, crank, valves etc . . . more on the assembly process in following posts:

1) Block: All the work in complete on the block, very happy with the quality of the machine work, how well the valve work was done (the most complex stuff) and how the new steel billet center main cap and associated align bore/hone operations came off. I love seeing all these freshly machine parts - like fricking Christmas to us motor heads!



2) Crank: The crank work is complete - except I will have it nitrided after I initially measure final compression height with a rod/piston in both banks - so I can calculate the dome height and then setup my quench area CAD model for the head work. (The heads will be CNCd to exactly setup the chambers and valve pockets that I desire - just can't do that work until I have measured a few things).



The bob weight on the crank was 1610, had to add two pieces of Malory metal in the crank to get it to balance correctly. If you look at the large counterweight below, you'll see a 'ghosting' where the Malory was installed, a steel cap put over it and then welded/polished to reduce windage.



Also, I had threaded plugs installed in the rod-journal cleanout traps.



3) Main Caps: I used one of my Ardun Doug King (RIP) center main caps on the block. It probably didn't really require it, but I wanted to build a stout lower end anyway (I'm a big believer in this for all race engines!). This is just in case I decide to put a blower on it some day - which tends to be something I'd do! The bottom of the block was surfaced and then align bored/honed for the new caps. I made sure I had the ARP studs installed before these operations were done.



4) Valve Work: The valve guy put in over two solid days in the block and valve work -- as I wanted to put 1.75" hard seats in the intakes and run 1.72" intake valves. Plus, all the seat work was done in a vertical mill - lots of setup time for each deck. This is the first time I've tried these large valves on a "street" engine - will be interesting to see how well it works out.



5) Forged Pistons: I had custom pistons made by Ross - to my exact compression height specs, ring locations, etc - and with a short and light piston pin. Notice the pin length is a bit shorter than the stock/STD one. I'm trying to run a really light reciprocating assembly - just to see how it helps the engine rev. Just a bit of fun experimentation on this engine. One reason I need to install a rod/piston is to validate that I correctly calculated deck heights for both sides - as I had it square decked with "correcting" depths calculated from measuring with the crank in the block. I want the compression height to be exactly the same on both sides. Guess we'll see if I did my job correctly!



Okay - time to let the fun begin . . . stay tuned folks and check back often!

 

WOW, a work of art. Glad you are showing us now. Too bad it will all be covered up one day.

 

Damn Dale...................a masterpiece