Technical Best Flathead Build for a 150 HP+ Cruiser

Based on the enjoyment I’ve gotten from the flathead in my 53 F600 farm truck so far, I decided to postpone the Crown Vic swap on the 53 Merc M100 pickup that I have owned (without an engine for nearly 30 years) and build a hotrod Flathead for it.

I want to daily drive it. My commute is 45 miles each way, mostly highway. I will likely run an S10 T5 or a T5 from a 4 cylinder Mustang or a 700R4 but I’m worried about the power loss of the auto.

I bought a Canadian 8BA engine yesterday from a 50 Merc to use as my build platform. I’m hoping it has a 4” crank.

I plan to run a 4 bbl carb or injection.

With my plans in mind, how would you build it? What heads? What cam (EAC, 1007, or…)? What pistons? Would you relieve the block (if so how much)? What intake?

I’ve built several Porsche 911 engines and there are numerous well documented build formulas to get various results. I’m amazed that I haven’t been able to find something similar online for the flatheads… there has to be 1000 times more collective experience with hotrodding flatheads than obscure German air cooled flat 6 engines…

 

In my opinion, do not pick a cam until you have what type of intake you plan to use, the final bore size, the stroke, know if you be porting it or not, valve size and type of heads/compression ratio you want to on your motor.

Some cams will really wake things up if you are over 276 c.i., but if used in a smaller motor, you may be disappointed with the final outcome. Some work great for smaller cubic inch motors, but not with bigger ones.

Once you have determined all that, then you can start narrowing down which cam would be a good choice.

 

With a street-driven vehicle (especially a newer pickup truck), you should be thinking maximizing torque, not horsepower. Torque, not horsepower, is what gets you down the road; horse power is just a derived number using a formula where RPM is an important factor. With an engine with good mid-range torque, driveability should be at a maximum. Combining this with the T5 (with it's overdrive fifth gear) will allow you to select a rear end with a low enough ratio to enhance the situation. When I built the Merc for my '51 coupe, I had an Iskenderian MAX-1 ready to install. After discussion here and on "The Ford Barn" and reviewing the specs, I decided to re-use the stock Mercury cam. I'll never know for sure, but I believe I made the right choice.

Here's some interesting reading : https://www.tildentechnologies.com/Cams/FlatheadPerformance.html

 

I love this build and your intended purpose! I think you already have a great plan ahead of you. I also would be concerned with the automatic pulling too much power.

I think the first step is to see if you have the 8CM crank and if so, is it still usable?! I know they make bearings all the way to 0.040" under, but I think that's where they run out. If this is incorrect, please let me know as I have a rough 8CM ground 0.040"... that's headed to the junk pile. Maybe it can be welded and offset ground?

I digress.... with a good Merc crank, punch the block out to 3 5/16" (276CI), light port work, 2 carbs & Stromberg distributor (Mallory will work too, just gotta find a used one), decent heads & studs, L100 cam (seems to be a popular all around cam), 5 spd and go!

You're making me want to build this setup! Keep us posted!

3blap.

 

The Tilden site is a great resource. They even have a cam calculator where you can put in specs and see potential outcomes, etc.

I'll post the name of the company and their grind number later tonight, but there is a company in CA that has a grind identical to the Merc timing events, but with .380" of lift. I have one of these that I plan to use on later "mild street" build.

 

This. This is what my Flatty in my 1500lb T-Bucket was...but the cam was a mystery (I called it the 'Super Awesome' cam). I ran 2 94's on an Offy intake with matching heads. Best tuner I've ever known played with it a bit and it made 136hp at the wheels with a 5spd and a 3:78 Banjo.

 

I agree with the .125 overbore (at least on the later flatheads). I've had 3 of 'em (2 -276" and a 258") and there was still plenty of cylinder wall left. The late '"Ol' Ron" on "The Ford Barn" swore he once built a 3 7/16"+.030".

Thin-wall castings ate for sissies.

 

I'll add, always sonic test the block before boring. Most of the time, your safe to go .125" over. I went 3 3/8ths + .030" on my 59L block and still had enough meat left according to the sonic testing.

Things can get expensive fast if for some reason your block has core shift or rotted out water jackets and you need to sleave it. Not the end of the world, but always good to know what you are dealing with before punching it out.

A 276 c.i. motor is a great all around bore size. Doesn't cost any more to bore it this size, pistons are the same price as smaller ones and the power gains are noticeable.

 

A 258", while mainly ignored, is also a great choice. If you can't find (or afford) the vaunted 4" Merc crank, 1/8" over with the stock 3 3/4" stroke, gives you 3 cubic inches more than a stock Merc with the advantage of lower piston speed for a minimal extra cost (if any).

 

A friend here in Aus has an 8BA not sure on capacity but near 287, built by a local guru, made 180hp it's a nice street car it's in a 34 roadster. The Cam is a secret in house grind not as big as a 400jr but had a nice sounding idle but has good road manners. It was ported according to I think the Bishop/Tardel flatty book

Edit - Hahaha 180hp - Engine Dyno - not the previously claimed 280

 

Unless it's blown, dyno sheets, please.

 

Flatheads are good engines they're just mis-underbuilt. They don't breathe so good, so they need some****istance. I relieved mine, added big valves and ported the beejeevies out of it. I bored it .125 over and used some 8.5:1 Ross pistons, shot peened ford rods, Merc crank. I used the Max-1 cam, Reds headers, bolted a 471 blower on it and some 97's, hot ignition, good heads, good radiator, new pumps, and about a case and a half of Mothers Metal Polish.

10-year-old build, a few thousand miles on it. I get 14 MPG (like it matters) if I keep the end carbs out of the game (progressive linkage) but where's the fun in that? Cruises on the freeway with traffic (T-5 and 4:11 QC). It'll smoke the drag tires and runs on pump gas (albeit 92 Octane, clear if I can find it). Oh, and it has never overheated, and it has been run on 115-degree days. So there's that for them that hate.

Like I said, they don't breathe well. If a human don't breathe so good, you open their airways (sometimes ear to ear) and put them on oxygen. Same, same. Are they big block chevies? Nope, they are way cooler than that. Capeesh?

 

The OP said he believes he has a 4" crank, no?

 

Word. Got to get them to breathe. My secret to having them run cool is to ensure the water passages are surgically clean. It is amazing how much***** gets stuck in there over the years.

This must be done manually. There is no cleaning method that keeps them clean besides getting in there manually and getting it out.

I also run water and use good water pumps. My 292 runs cool enough that it doesn't need a fan unless it is super hot out or very high humidity and high temps.

 

He did! The 258" doesn't sound like a bad plan, if you're building one and don't have the Merc crank.

Bandit Billy... nice sales pitch! I think he was already sold though...

3blap.

 

The Mike Bishop porting guide is essential to anyone who wants to do this themselves. It use to be available with a Google search, but I can't seem to find it. I have a copy. Let me see if I can scan it and upload it here.

I went 1.75" on all exhaust ports and built headers to match. A missed spot for most it take out that damn dog leg out of the end exhaust ports. It's a lot of work to port a block correctly, but it is well worth it.

 

I wonder if I have it, but you're welcome to scan it and send it to me! I have an old copy of someone presenting the process that I found on the interweb 20yrs ago. I just recently copied Dale's (@Bored&Stroked) first one he did and printed it. I want to do the same process with the rowdy one he did for his Cabriolet.

3blap.

 

No, he said he "bought a Canadian 8BA yesterday out of a'50 Merc". Things like that have been the source of more disappointments than my love life. Just posing an option.

 

Ooops... you're right. I clearly buzzed right past that... Doh!

Skip the 4" & go with the***** 4.250" crank.

3blap.

 

My ‘51 Merc is .125 over, Isky 400Jr, Mallory dual point, Meyer 2X2, Stromberg 97’s, and Edelbrock 74 cc heads. Ported by Mile Bishop. Vern says he thinks it will make about 160hp. It sounds very healthy but I haven’t been able to drive it yet. Soon!

 

Ah, right. I think I confused the OP's post with someone who posted on Fordbarn about odd marking on a Canadian Merc crank.

As an educator, I would have corrected a student for missing that key retail. RIF- Reading is fundamental. LOL!

 

Noiyce!

 

Yeah, this aint Facebook. Like the math teacher always said "show your work". There are at least 5 normally aspirated flattys on FB right now advertising 300 HP. Right. I know you can squeeze 200 but I don't know how "streetable" they are.

 

I was hoping to not bore it unless I have to. I pick up the engine on Monday night but leave for another business trip on Tuesday. Calgary has no automotive machine shops anymore so finding a local(ish) shop that can bore it will be a challenge for me.

I was all excited because I found some offy heads for it and some multi carb intakes but they all appear to be 59a parts…

 

Note I detuned his 8ba

 

Can’t believe there are no machine shops left in Calgary anymore. I wonder if there are some in Edmonton? I’ve seen adverts on kijiji and FB from guy in Sask who rebuilds flatheads.

 

I refuse to believe there will ever be anything more disappointing than my love life lol.

And on another note: I know, I know the OP already has the engine but if I were in his position I'd have looked for a 337 which has 152 hp standard... I realize it's big but to me would not be out of place in an M100 plus would enable towing - if ever needed.

Interesting project in any case, will follow it.

 

I think they're a little harder to find, and if you're wanting "go fast" parts, also a little harder to find. I think H&H has heads & Intake, but I bet they cost as much as building the engine he's planning on using. My only real gripe about a 337 is the weight. I think they weigh in at 750lbs, but like you said, it's going in a truck so does that really matter? Probably not as long as your springs are up for the task. I would love to build one myself... I know the Lincolns have steel cranks... they're almost prime for a blower!

The OP also sounds like he might've bought a runner from his last post. I don't blame him, I try and******* them up too when they pop up since it never hurts to have one in the corner waiting!

3blap.