Hi guys,
Back to the Flathead rebuild topic. A few questions/ideas I have that I'm hoping someone can help me with:

1951 Ford 8BA original.
Goal more power and usability while maintaining longevity. Possibly increase the usable PM range to +/- 3500

It appears that I'll be rebuilding the flathead and would like to give it a bit more power while preserving it for another 63 years.
1. the block is untouched and am thinking about .060 bore. Should I stick with a .030?
2. I'm considering an Eagle Crank to stroke it. other than HP, is there a difference in longevity between the 4" and 4.25" cranksafts?
2a. Do I need to change the rods from stock? will a 50'ish HP increase be detrimental to the rods and it's potential for longevity.
3. 3 ring pistons or 4?
4. looking at the isky Max-1 cam and offy .400 heads.
5. intake and carb is a bit up in the air. I think I've done so much research it's all imploding under my alcohol soaked brain. my initial thought was to use the super dual offy with a pair of 94's but that is quickly becoming cost and patience prohibitive. My next thought was the single offy running the 2GC or modernize a bit wth an EB/holly/whatever modern carb runing between 300-350 CFM

Any technical, personal experience or general knowledge is welcome.

Thanks,
Yeti

 

Personal opinion:
1. No big benefit to larger than needed O/S; it does raise compression slightly
2. 4.25" cranks IIRC require clearancing the block and special rods; 4" crank uses stock rods with "Merc" pistons (widely available). Personally I'd stick with 4"
2a. If you do all you've listed (cam, carbs, heads, stroker) you might see 50 HP. What is your intended use?
3. Certain 3 ring pistons seem to free up a fair amount of HP due to reduced friction; I'd research it on Ford Barn and HAMB. "Ol Ron" likes them, good enough for me, but not all are equal in quality/durability. Careful honing with a torque plate probably needed for the 3 rings.
4. Popular choices. Going to aluminum heads means studs, potential for leaks... Look nice tho. Read here: Results of milling iron heads. - The Ford Barn
5. Unless you really really care about appearances, the 4-barrel option is far less cantankerous and ultimately cheaper.

"r_reed" on here just got his flatty on the road with the 400, I believe, some head milling, and a 4-barrel. I hope he'll chime in.

Not sure why you want to run it at 3500, that's long past where the stock ports will be efficient, and isn't going to do anything for durability. A professional porting job would be highly recommended if you really intend to do that.

 

Before spending a lot of money on a flathead, do yourself a favor and get a copy of John W. Lawson's book Flathead facts. Information here: Flathead Facts
also available from several sources including new member Mac Van Pelt: L-1006: Flathead Facts by John W Lawson

I have pretty much all the flathead books that you can get and this is the best I have read for real dollars spent in return for drivable power.

 

Thanks for the replies, guys.
My intended use is drivability and daily use. I loved my truck stock but now that I'm rebuilding it, I may as well give it that little extra to get me over the hills. First order is longevity and reliability with the second being a little more smile factor.

I've always been hesitant to mill a head because you can't unscrew something up and valves don't care what you want, they will be valves. While I'm not a fan of studs, I will have to deal with it and the ridiculous cost of ARP stud kits.

I'll stick with a .030 if needed and buy the rebuild kit for the rest. What are your thoughts on balancing? To me it makes sense for my primary use but being an engineer, I over think most everything.

 

My thought. A friend popped in with a very nice 52 the fancy one "Victoria?
for sale his step father passed away. Tell him, ya just got to take me for
a spin, I have'nt rode in one of these for years I'm I truck guy. I was
tottaly blown away, I mean this thing will put you in the back seat plus
its got overdrive. As far as power- quietness- id say its about the same
as my Lincoln town car. Pop the hood I see no nothing, just a EAB
tangarine color narrow belt flathead V8. Although I would never drive
80mph, but he did with no problem. So I'm impressed with just the way
Henry built it. I love how they run so quiet. And yes I would balance it
We are doing a mint std. size EAB as I speak. I personally favor short
stroke rather than the four inch. so it aint double timming.

 

I had mine balanced, but my machinist warned me it would have limited benefit. The flathead rods had little extra meat on them for trimming to balance, but are usually very close to each other to start. Sure enough, I don't notice any difference.

I agree completely with Big Job, as far as the way they run stock when properly built. I'd also note that I am always shocked how much more powerful they feel in a car, compared to a truck. It has to be the wind resistance, the cars just seem to FLY!

It's possible, even likely, that your heads have already been shaved just to flatten them. You can get some indication from looking at the relationship of the back of the thermostat housing to the deck. See below, one is near-stock, the other has been cut around .040 - .050". As you shave them, you start to cut into the back of the thermostat housing, eliminating the step that is there on a stock head. You definitely want to "clay" the clearance before deciding on a cut.