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Engine "Build-ups"

May/Jun 2000

I'd like to share with you some of my ideas about engine buildups for the flathead Ford V8.  I will not be addressing V8-60 or the big 337 inch engine. These are my opinions, not rules cut in stone.

Who Is It For?
First, who are you trying to please? Or, what are the rules that govern the acceptance of your results?  If the vehicle is destined to be authentic and for Concourse, then it needs to be correct and also look correct, and run better than new. The engine must be correct for the year vehicle with original equipment.

Maybe you are building it for the Great Race.  Their rules state that the engine must appear correct for the year car it is in. That means that your 34 may have a 36 LB block bored to +.060, with a 4 1/8" crankshaft and the cam of your choice.   You can have Canadian higher compression ratio aluminum heads, with Ford script.  You must have a Ford intake manifold with a stock appearing two barrel carburetor.  And you may run headers and dual exhaust.

What if you want to show your car in Touring Class and also drive it with a lot more horsepower than stock? Start with an engine that has stock 3 3/16" bores, then add the bore and stroke that you want (or have the money to pay for). You can use any cam or other internal parts that suit your purposes.  The exterior accessories must be correct. You will be judged by your peers at the Meet.

Details, Details.

The Concourse engine needs to start with the correct block, heads, pan, and other external parts.

If it is a 32 to mid-36, it will have babbitted mains. If you are going to put many miles on it, you should use a crankshaft that is not ground too far undersize.  As the babbit gets thicker, its life expectancy gets much shorter. IF the crankshaft is under .015" on mains, it should probably be hard chromed back to standard, or another crankshaft should be used. Note that because the babbitted mains are line bored to suit the crankshaft, the crankshaft can be ground to any undersize. If .003 or .007" will clean it up, stop there.

You can install a rope rear seal in place of the labyrinth.  This requires the crankshaft to have the rear slinger ground off to establish a surface for the seal to run on. It also requires a special seal retainer to be fit to the rear main cap and a later year upper seal retainer to be used in the block. The seals then used are the normal later year parts.

You can also install a modern full circle lip seal in the front; it requires no modifications.

Balancing is probably a good idea. Even the oldest of our flatheads were in fair balance from the factory. But many of them have been rebuilt or repaired since then. Some parts may have been exchanged for others whose weights may be quite different. If you are rebuilding the engine, this would be a good time to make all this right again.  Pre-weigh rods for balanceability before the machine work is done.

Boring is usually required. On the 21 stud engines, smaller is better. They blow head gaskets out into the stud below the center of the cylinder bore at larger sizes. I believe that this is why Ford moved those studs to one on either side of the bores for 24 stud engines.

The 24 stud engines that are 221 cubic inches can usually be bored safely to 3 3/16. The engines that came from Ford at 3 3/16 can usually be bored safely to 3 5/16.

If you want to use a longer stroke crankshaft for more displacement and power, the 49-53 Mercury is 4" stroke.  It usually fits into 239 cubic inch blocks with no problems.  Check crankshaft end clearance in at least four crankshaft rotational positions.

On later 38-42, 221 inch blocks, there may be interference between the crankshaft and the block at the front and rear of the #2 main, and at the rear of the #1 main.  There is a "shoulder" on the crankshaft that can be cut back during crankshaft grinding at these points.  Additional clearance may be obtained by grinding the block, and possibly the caps also, as required.

If you use the 4" crankshaft in early 221 inch blocks, you will have to modify the crankshaft or the block, or both.  On 36-38, the main journals need to be turned down to the 2.398-2.399" size for an undersize, depending on bearing availability.  The crankshaft and block will possibly interefere at either or both the front and rear of the #2 main and at the rear of the #1 main.

I have never put a 4" crankshaft into a 32-36 babbit main engine.  If you need or want to do that, create clearance between the crankshaft and the block before pour and bore of the main bearings is done. Hot grinding particles from making clearance could melt into the babbit, then later score and wear the crankshaft.  Plus, the crankshaft main journals will need to be turned to 1.998".  Because the 4" stroke crankshafts crack occasionally in normal service, I don't know how long this combination would be likely to last. Maybe someone has done this and can let me know how it worked out.

On any of the early engines originally built with a labyrinth rear seal, if you use a late crankshaft without the rear slinger, you must convert to a rope seal.

Continued here.

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