8BA rebuild - do I want a Merc crank

[cederholm]

Hi everyone,

I'm new here at FordBarn but I've been a HAMB member for years. I have a dream of building a traditional 1930 Model A hot rod. Many years ago, in pursuit of this dream, I picked up a 1952 8BA that I got a good deal on.

I've torn the motor down and and plan to get it to the machine shop soon. If the block checks out I'll be replacing the full valve train and all the usual rebuild parts. I'll also be swapping for a hotter cam, aluminum heads and multiple carbs.

My ultimate goal is to build a beautiful car, not a racing demon.

So, my question is, is a Merc crank worth the effort? There are many warning on the HAMB about Scat and old Merc cranks are hard to come by and expensive.

I assume a Merc crank would require new rods. Is that true?


Thanks for any and all feedback.
~ Carl

[Bob C]

Originally Posted by cederholm

Hi everyone,

I'm new here at FordBarn but I've been a HAMB member for years. I have a dream of building a traditional 1930 Model A hot rod. Many years ago, in pursuit of this dream, I picked up a 1952 8BA that I got a good deal on.

I've torn the motor down and and plan to get it to the machine shop soon. If the block checks out I'll be replacing the full valve train and all the usual rebuild parts. I'll also be swapping for a hotter cam, aluminum heads and multiple carbs.

My ultimate goal is to build a beautiful car, not a racing demon.

So, my question is, is a Merc crank worth the effort? There are many warning on the HAMB about Scat and old Merc cranks are hard to come by and expensive.

I assume a Merc crank would require new rods. Is that true?


Thanks for any and all feedback.
~ Carl

No they use different pistons.

Bob

[oldford2]

Your 8ba rods will work just fine with a Mercury 4"crank. I found one for $300 and grind cost $120

[JSeery]

You want a Merc crank if you want a 4 inch stroke and conversely the additional cubic inches. As you have already discovered there are difference opinions on this topic. I'm of the school you can't beat cubic inches and with flatheads one of the easiest routes to increased HP is increased cubic inches. Others see it differently. As for the price, increased performance cost money and with a flathead, increased performance is more expensive than most OHV engines.

You might be interested in JWLs book showing dyno results for various flathead modifications. There are also several of books that are good background information on modifying flatheads.

[rotorwrench]

The EAB series for 52 through 53 have only a few notable changes from the 8BA basic set up. It should have the rotator valve set up that came about in 1951 and Ford discontinued the Stelite valve seats for intakes and even exhausts on some. Everything else is near the same as 8BA. The Mercury 4 inch cranks are out there but would likely need to be turned undersize unless you find a good one. All the 8BA series used the same type rods but some were drilled for quirts and some not. The 52 EAB should have the squirt holes in the con rods. If your replacing valves, you have the option of going back to the earlier types. They are easier to source parts for.

The French SUMB military truck engines used a shorter rod for the 4-inch crankshaft so they could use the same pistons as the 3 3/4" crank but Ford USA never did that. Merc pistons work fine but I don't know if you want to go oversize on them or not. Egge has a 3-ring piston for both Ford & Merc but they start out at a good bit of oversize. It makes for more power going out to 3 5/16" bore and that works good with a 4-inch crank.

[flatford8]

Sponsored Links (Register now to hide all advertisements)

JWL's book "Flathead Facts" and "Nostalgia" by Ron Halleron (both members on here), are great books for what does and doesn't work for flatheads. "GOESFAST" also posts on here and has said he has 4" cranks available........ Mark

[Kurt in NJ]

Go for it, it made all the difference when I was driving a 46 truck with 2 ton load ---it went from I think I can,i think I can to no hill too steep with just changing to a stock 49 Merc----the wipers even kept going all the time ----probably the cheapest modification that you will feel in the seat of the pants

[Lawrie]

4 in scat crank in my 99a engine,loads more torque ,great engine,used the floater rods and .040 over 3-3/16 bore,cast iron heads,single 97 carb,
Lawrie

[drolston]

I have less than 1000 miles on my rebuild using a SCAT rotating assembly kit with 4 1/8 stroke, 3 5/16 bore, H rods with insert bearings, and Ross pistons. 284 cubic inch. It has a ton of torque. I fear for axels and drive shafts if I give in to the temptation to really get down on it. I read all of the SCAT detractors and supporters and took the chance. So far so good. SCAT claims the rotating assembly comes balanced. I had mine balanced anyway. It was pretty good, but worth the price to get it better, and be sure.

If you are not planning to race, do not get carried away on the hot cam. I went with Schneider 248f cam and lifters they provided. It idles well and preserves the low end performance, but really comes to life above 2500 rpm.

[3twinridges]

Just my $0.02 and I am new to the hobby but if you rebuild it all the way, then a merc crank is small in comparison to your total bill so go for it.

JB

[JSeery]

Originally Posted by 3twinridges

Just my $0.02 and I am new to the hobby but if you rebuild it all the way, then a merc crank is small in comparison to your total bill so go for it. JB

Wise advice for a somewhat novice!

[flatjack9]

That 4" crank will help to offset some of the low end loss in torque you will get with a performance cam.

[RalphM]

Go for it!

[quickchange34]

Try it, you will like it .

[GB SISSON]

Best thing I ever did for my old 38 tonner everyday work truck. Bone stock otherwise. It made a huge difference in torque. I also just bought a standard merc crank for 300 bucks and I can't wait to build something around it. You won't regret it.

[Lawrie]

Another plug for the scat 4in crank,we have one in our dragster on my avatar,6 seasons ,best 1/4 mile et 9.3 at 140 mph,
Lawrie

[cederholm]

Whoa, what great responses for my first post - thank you all!

So not one person build a case for staying stock - I guess that tells me something.

~ Carl

[JM 35 Sedan]

If I were building an 8ba or a 59 series engine, I would definitely use a 4" Merc crank, since I bought one about 10 years and it's still sitting on the shelf . Now in your case, if you can find one at a reasonable price with good rod and main jounals, I would so go for it....why not!!

[JSeery]

Traditional Hot Rod and stock flathead do not really go together!

[prpmmp]

Originally Posted by JSeery

Traditional Hot Rod and stock flathead do not really go together!

Yes! But I guess you could say that the Stock flathead gave birth to the Traditional Hot Rod! Pete