51 Flathead 8-How Far to Take Rebuild?
 

I,ve posted about my recent 51 F1 purchase, and I have been working on it in the evenings for the past 2 weeks. So far, I've got the Flathead 8 stripped down to the bare block except for the camshaft. I can't get the gear retainer off at the back side, so I am leaving the cam for the engine shop to remove.

I degreased and powerwashed the block several times as I tore it down so that I could see what I was doing and the washing got most of the heavy grease and sludge out of my way. I have poked and prodded the water jacket and power washed it a bunch of times to remove the built up crud and the casting sand and crap.

Monday morning I am dropping the block, heads, rods, pistons, and crankshaft at a local motor shop. They will bake the block then bead blast it clean. After that, they will Magnaflux it. They will also degrease, clean, and Magnaflux the crankshaft, the heads, and the rods.

I found one small crack so far that can be pinned. I'm assuming that they will have to bore the cylinders and grind the valve seats, replacing the hardened seats with new. Once they are done, I plan on doing the rest of the build myself.

So after this is all done, I have to decide how far to go with increasing the performance of the motor. It is going to be a daily driver, both city and highway. I like cars with some balls; I don't need to spin the tires off of every light, but I do like to get to speed pretty quickly.

So where do I start? I need to determine what to change out after I get it back. The PO installed a Edlebrock aluminum intake manifold and Edlebrock 4 barrel carb, and I plan on reusing them. What else to do?

New pistons? I have to replace them anyway, so what do I get for a bit more performance?

Valve assemblies? Replace with what?

Tappets (Lifters)? Replace with what?

If the original cam and crank are good, should I reuse them? Or is that a waste of time if I want better performance?

How do I start? Where do I look for more info?

Thanks!!

John

Good to see your interest in keeping the flatmotor! Whole books (many of them) have been written about many of your questions, I'll try to give you the Cliff's Notes version of what I've learned.

There is no retainer at the rear; if you've got the front cam gear off, lifters are all out, it should pull right out.

Very good!

That's kind of overkill IMO; a regular vatting in caustic is all you should need until you've had it magnaflux'd. Is this shop experienced in flatheads? i.e. will they know where to look for cracks? For high-dollar builds, a pressure test is in order, but not many shops are set up for it (special block-off plates).
Does your engine have hardened valve seats? Most '51's don't. You need them.

Where was the crack? If it was between a water hole and a bolt hole, those are so common they have Ford part numbers. They are usually not worth pinning. If the crack goes to a cylinder bore, or a valve seat, you may want to consider a different block. This is the typical benign crack


https://cimg4.ibsrv.net/gimg/www.for...d698c823f6.jpg

Here's one of the threads on head shaving: Need some head clearance advice - The Ford Barn

Thanks for the quick responses. That is the guidance I was looking for.

The motor shop I am going to has been around since 1972, came recommended by my regular mechanic, and they have experience with flatheads. I found one small crack so far that can be pinned. it is between a valve and the cylinder, and extends down about 1/2". When I described it to the shop, they knew exactly what I talking about and said they commonly pin these, then sleeve the cylinder and install a hardened valve seat.

The bake/blast/shake prior to Magnafluxing is how this shop does it. They told me they need the block extremely clean before Magnafluxing, so that they can detect even the smallest crack.

I figured to have them do the cam, crank, and rods as part of the package. Is Magnafluxing these parts what you meant by overkill? I know that they will have to measure the bearing surfaces and possibly true and polish them. Is Magnafluxing these parts not needed for a street machine? By the way, this was my idea, not theirs; when I deliver the parts on Monday, I plan to ask about it.

I did post this over at Ford Barn. Thanks again.

John

Rebuild
 

Have my 8rt nearing completion. I have done the assembly my self with local help as well as from folks on ford barn. Not my first engine, but my first flathead.
My 2 cents:
Set a goal for your desired use of the engine and then match the components to it. Some folks want a certain nostalgic look or sound and throw out common sense.
Drop me an email and I can call you if interested and I can share what I have learned.
Some of what I've gleaned.
Flatheads can be subject to core shift. Sonic testing may be a reasonable investment before you start. Check with your machinest.
EAB heads are best, milled for .050 squish. I prefer cast iron over aluminum.
Best stock cam is fords EAB cam, few after market cams give full range torque curves, all have performance trade offs. I selected an L-100 with LZ springs (55 # seat pressure) based on my preferences. I wanted good midrange and a bit of a lope, I have an EAB cam to install if I desire later on.
Do your homework on performance "improvements" John Lawson wrote a book which chronicles his findings using a Dyno as he made improvements to various flatheads. Example: headers did not show significant performance gain over stock manifolds....... A good read for $40.

Stock cranks and cams are very stout. Not common to crack. Likewise the rods are also very reliable, if it gives you comfort, go for it. How did your rod and main bearings look when you pulled them? If they were worn and sloppy, rod re-sizing may be needed.

A crack between a valve seat and cylinder is pretty serious. I'd be cautious about investing too much in that block. When you say the shop will "pin" it, what type of pin do you mean? Some are basically screws, others (like in video below) are locks. There's precious little material to work with in that area, as you can see in this cutaway


https://cimg6.ibsrv.net/gimg/www.for...fa3794b08c.jpg

You have to figure that the pinning and sleeving is going to cost about $200 - $300 on top of the other work. That's mighty close to the cost of a good crack-free block.

I'm not sure you could get this type of lock in that area:

PS I saw on your FordBarn post that Ol'Ron said it would cost $5k for a good rebuild. Maybe in his neck of the woods, but I got mine done for <$2500 including balancing (which was a $200 waste IMO).

slick vidio, sure beats drilling and tapping. As far as cam removal, its
usually a little varnish so spray around cam bearings with brake cleaner,
and it will pull right out. Give Clegg Engine a toll free call 888-471-2827
a call for name brand US parts. I believe they have a web site.
New pistons,rings, rod, main cam bearings, M1 oil pump wrist pin
bushings runs around $800 Adj. lifters run around $200. Same lifters
valve guides as a Ford tractor. For some unknown reason, valves for
these are expensive like 12-15$ apiece when sb chev valves are like
6 bucks. (don't worry about sticking chevy valves in there, they
are made by perfect circle anyways)
sam ....We machine 239's and 337's I love 337's

I second Ross's recommendation to get John W. Lawson's book.

I saw on the related thread on the Barn that Mike Bishop and Vern Tardel have just published a book. No disrespect to JWL, but that is one I'd get. Here is Part 1 of Mike's porting how-to:
Flathead Porting
and another bit he wrote under the AV8 handle on the HAMB
Technical - MOTOR, flathead build ... tips tricks??? | The H.A.M.B.

A lot of this stuff isn't a huge benefit for a street truck motor, but it's fascinating stuff IMO.

Update:

I tore the engine down completely and took the block, crank, cam, pistons, rods, valves to Northeast Machine in Tonawanda, NY. They will start by cleaning and magnafluxing the visible crack to determine if it is repairable. If it is, they will work up an estimate to bake and shake the block, Magnaflux, pressure test, repair the crack and bore and sleeve it, bore the cylinders, grind the valve seats and install a seat at the crack. Magnaflux and mill the cast iron head covers. Magnaflux and turn the crank and cam. Install crank, cam, pistons, rods, bearings, valves, etc. Going with Johnson hollow adjustable lifters. I decided at this point to not change out the crank or the cam, as I am not really in need of more HP.

I should hear from them early next week.

John

Does the engine have rotator-style valves? Hardened seats?

The valves are standard flathead-cam with tappets to open and close the valves.

The seats are not hardened. The motor shop suggested only boring and inserting hardened seats where needed-at the repaired crack and at any seats too worn to grind. Their thought was that it is expensive and not needed for the type of motor we are building. Is this generally true, or are the hardened seats a must?

John

Read this: https://www.ford-trucks.com/forums/1...ab-owners.html

With unleaded gas, hardened seats are needed. In late '50/early '51 Ford changed the valves to incorporate a rotator, in combination with eliminating hardened seats. With leaded gas, it was a reasonable move, but with unleaded gasohol you need the seats, rotators or not. Here is the difference between non-rotator and rotator

https://cimg3.ibsrv.net/gimg/www.for...5007cd28fa.jpg




https://cimg4.ibsrv.net/gimg/www.for...cc21d0dbf9.jpg

Definetly not rotator valves.

Good advice about the hardened seats; I had no idea.

I'll add it to the list. Should I do both intake and exhaust?

John