Flathead Engine Rebuild

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Table of Contents

• Current Status
• Our Plan
• What We Started With
• Tear Down
• Engine Cleaning, Inspection & Machining
• Parts List
• The Rebuild
  • Modify the block for the improved oil filtration system
  • Fuel pump pushrod bushing
  • Paint the block
  • Drill holes for adjustable lifters
  • Relieve the block
  • Port the intake and exhaust
  • Install exhaust baffle
  • Reciprocating Assembly & Camshaft
  • Assemble the valvetrain
  • Heads
  • Ignition
  • Top End
  • Cooling
• Fire In The Hole!
• Engine Tuning
• Compression Test
• Hits & Misses
• Time Line
• Thanks

Current Status

Our Plan

• Better breathing.  Flatheads never did breathe very well, and with the L-head design, breathing and compression are always working against each other.
• More compression.  The stock compression ratio was 6.8:1, which was largely an artifact of the octane rating back in the 1950s (before they learned how to "crack" gasoline).  We were shooting for somewhere between 8.0 and 8.5:1.
  
• Better ignition.  Remember, this thing started with a 6V positive ground electrical system, so it was handicapped to begin with.  The factory distributor wasn't much to brag about when it was new, and after 56 years, it was worn out.
  
• Improved oil filtration.  The stock oiling system did not force all the oil through the oil filter.  The oil pump sent all the oil up the back of the engine block to a tee cast into the block: one side went to the oil filter, the other to the rest of the engine block.  Ford called this "partial-flow oil filtration", but the result was hardly any filtration.  Oddo speculates the oil filter was there for marketing rather than technical reasons.
  
• Modern PCV system.  The original design used a downdraft tube and breather arrangement.  The problem with this arrangement is there is no positive ventilation of the crankcase, and water condensation is common.
  

What is MCF?

What We Started With

Tear down

The Rebuild

Modify the block for the improved oil filtration system

Fuel pump pushrod bushing

Paint the block

Drill holes for adjustable lifters

Relieve the block

Port the intake and exhaust

Install exhaust baffle

Reciprocating Assembly & Camshaft

Assemble the valvetrain

We used Chevy small block valves (or said more correctly, Chevy small blocks use Ford flathead valves [smile]), which required a shim (washer) to get the proper spring height.  When installing the washer, put it on the valve end, not the stem end.  This reduces reciprocating mass.  Unfortunately, I didn't take any pictures while building up the valve/spring/guide assembly, but its pretty straight forward (see exploded view).  You'll need a valve installation tool to install the valve assembly in the block (see pg. 74 in Oddo's book for an illustration of using the tool, pulling the valve guide down so you can insert the retainer).

The Isky Max-1 cam (P/N 811100, see the Isky Flathead Specification sheet 1 and sheet 2) recommended .014" valve lash for both intake and exhaust, which we set.  Adjusting the valves takes a lot of time, and I messed up one of the adjusting nuts in the process, and had to wait for a replacement (more on this below).  Take our advice (it was hard learned):

• Take your time, be thorough!
• See the information below about motor oils!
• Try to minimize the number of revolutions on the camshaft during the adjustment.  Keep in mind that the more times you turn the engine over the more cam lube you're "squishing" off the cam, which it needs during the first start before good lubrication starts, so try to set the valves right the first time, and then check them only once.  This takes a lot a patients.  The following may help you adjust the valves, assuming you are turning the engine in a clockwise direction using the bolt on the front pulley:  4I-3E-1I-2E-1E-3I-4E-2I, 6I-5E-7I-5I-8E-8I-7E-6E.  This is only a guide, and it doesn't mean you don't need to backtrack the crank in a counter-clockwise direction!
• You'll need a thin 7/16" wrench.  There isn't much clearance between the lifter bore and the bottom of the valve spring assembly, especially on the driver's side bank (the engine is asymmetric, see Oddo's intro for the reason).  We just happen to have a cheap Chinese wrench that fit, but you might have to grind down a wrench to make it fit.  You can also buy a wrench from Red's Headers.
• The first time you set the intake manifold, don't use any sealant.  Get a few engine hours in first to make sure you don't have any noisy valves that need more adjustment.  If you use RTV on the intake gasket and need to pull the intake, you'll destroy the gasket, and, more importantly, have to clean the deck surface, which is messy and hard to keep stuff from falling into the lifter galley.  In any case, remember to go back and pull the intake once you're happy everything is fine, and use sealant around the intake runners.  Don't go crazy with RTV here, it only takes a little, and only on the block side (to prevent oil aspiration).  (Believe it or not, we went through a couple of intake gaskets and ended up re-using the factory gasket a couple of times.)
• Don't forget to install the oil baffles.  You can buy new ones from C&G Early Ford Parts, if needed.
  
    
  

Heads

Ignition

We opted for the Mallory dual-point distributor #2527501, which has mechanical advance only. (Refer to the Flathead Tuning page for updates, as I converted this distributor to Pertronix ignition later.) We stabbed the Mallory dual-point distributor and terminated the spark plug ends.  Note that the firing order is slightly different than that of later model Ford V8's... cylinders #2 and #8 are swapped in the firing order.  (The graphic below is from Van Pelt's Flathead website.)

Top End

Both the Offy intake and the Holley carb have provisions for a PCV valve.  We eliminated the downdraft tube, put the PCV valve in its place, and plumbed it to the carb's PCV tap (see Hits & Misses for more info).  See pg. 115 in Oddo's book for the intake torque sequence.

Using an electric fuel pump allowed us to relocate the breather/fill tube to the back of the engine (see photo).  This was just a preference, we could have left it in the stock location, but it does clean up front of the engine, which is busy enough as it is.

Another aesthetic dress up was the use of the spark plug wire looms from Speedway.  These looms have a stainless steel tube for each spark plug wire which terminates at the proper cylinder location.  We mounted the looms on the top of the engine using the intake bolts... you can also put them on the bottom and use the exhaust bolts.  These worked out really nice, but you have to buy a wire set without the distributor ends pre-installed.  We opted to use an electric fan, which allowed us to route the wires to the bank opposite the distributor in front of the generator.  It provides a slightly nostalgiac look (like the old crab-style distributor placement), but if you're keeping the stock fan, you'll need to route the wires on top of the engine. One word of caution, according to Mike Davidson (see References), these can cause interference if using electronic ignition.

Initially, we rebuilt the generator and converted it to 12V to keep the original looks. However, even with a new 12V regulator, we could not get enough out of the generator to run an electric cooling fan at idle, so we decided to "punt" on the generator and instead bought the Powermaster "alternator-that-looks-like-a-generator" from Speedway Motors (see link.) This worked out quite well, the generator is a simple 1-wire hook up, eliminates the voltage regulator, and gives 59 amps at idle and 81 at cruise speed (at least according to the bench test tag). It comes with a new bracket which I had to do a little grinding on, and its a 1/2" bigger in diameter, but we had no clearance issues. (In the pictures, a red strap is a picture of the generator, and the black strap is the Speedway alternator.)

The engine was originally designed with an intake heater (the block has 2 small exhaust passages leading to the intake), and the Offy intake has provisions for this.  An old hot rodder's trick is to block off the exhaust passages to keep the intake cool.  It just so happens that the hole in the block is slightly smaller than the diameter of a penny, and the intake gasket hole is a perfect fit for a penny.  We tried the engine both ways... with and without pennies blocking the exhaust port.  Blocking the intake heater passages gives you really crisp throttle response, but takes a long time to warm up on a cold day.  We tested it during the summer (>90°F) and winter (~25°F), and decided to leave the pennies in, mainly because on a hot day with a hot engine, the engine would stumble on hard acceleration without pennies.  Legend has it that putting the pennies heads up is good luck.

     

Cooling

Fire In The Hole!

Engine Tuning

Compression Test

Hits & Misses

Things that worked great

• Almost everything.  If I went into all the great things, this would turn into a novel, so I'll just mention the real standouts.
• The balancing was great.  The engine is silky smooth, and its sitting on solid mounts in the test stand!
• Parts selection was great.  Everything fits and works together.
• The spark plug wire looms look great and do a great job of keeping the plug wires untangled.
• The compression was quite consistent from cylinder-to-cylinder. The low jug was within 3.5% of the high cylinder.

Important Information about Motor Oils

It is extremely important that you read the Motor Oil Warning sheet that comes with the Isky camshaft.  The warning is NOT specific to Isky cams, but is generally true for all flat tappet cams, even haydraulic ones.  The bottom line is this:  the Federal Government has banned the anti-wear additives that used to be in motor oils, especially ZDDP (which is bad for catalytic convertors). The ban was phased in starting in the 1980's and as of 2004 all Zinc and Phosphates (i.e. ZDDP) were removed from "street legal" motor oils - that is any oil with "API Service Rating SM" or newer.  The OEM manufacturers don't care because all new production vehicles use either roller tappets or are overhead cam followers, which don't need ZDDP. But this is bad news for all us hot rodders who are using flat tappet engines, especially with solid lifters! ZDDP is need for both the break-in and for the long term (Zinc in particular gets in the mircoscopic pours of the cam lobes and reduces wear on contact surfaces). The work around for this problem boils down to a few options:

• Use a Racing or Specialty motor oil.  This is not easy to find, and just because the bottle says "Racing" does not mean it has high levels of ZDDP. See the Motor Oil Warning for recommendations.  Amsoil and Joe Gibbs have formulations with high levels of zinc.  If the oil is meets API Service SM, its probably not what you want.
  • Update: As of early 2011, Valvoline is selling a specialty motor oil with higher ZDDP levels! Referred to as "Racing, Not Street Legal" oil, its availible in 5W-30, 10W-30 and 20W-50. You can get it at your local NAPA store. Try this link if you are interested. According to the datasheets, it has 0.14% Zinc, which is even higher than the Joe Gibbs HR oils (0.127%).
• You can use an oil additive that replaces the ZDDP.  You need to add this at every oil change, even though most are called "break-in" or "assembly" additives.  There are a couple of options:
  • EOS Assembly Lubricant from any GM dealer.  The part number has recently changed (from 1052367 to 88862586), and it says its not recommended as an oil additive, but that appears to be GM's way of saying the EPA doesn't like it.
  • Lucas Engine Break-In Oil Additive TB Plus Zinc, P/N 10063.  You can order it from Summit Racing by the bottle or case
  • Comp Cams Engine Break-In Oil Additive, #159.  You can order it online from Speedway using P/N 282-159 (if the link is broken just search Speedway's website).
• Diesel oils used to be an option, I used Shell Rotella T 15W40 with Triple Protection for a while, but beware even Diesel oils are now under government mandates regarding Zinc levels.  This should not be considered a viable option any more. 
• Or you can replace the cam & lifters every 1000 miles or so.

Things that didn't work so great

• We had a few valvetrain problems.  During the initial engine assembly, I messed up one of the adjusting nuts on the #7E cylinder, and the vendor was nice enough to send us a replacement lifter free of charge.  After running the engine just a few hours, this valve got real noisy.  We subsequently pulled the intake and adjusted the lifter... it took A LOT of adjustment (the lash had opened to .037).  After a few more hours of running it was noisy again, so we pulled the intake again.  This time I could not get enough adjustment (loose again) to get back to .014" lash, so we pulled the head and the #7E valve assembly, but the lifter would not come out.  Dad made a slide hammer and finally got the lifter pulled, and it showed massive wear where the cam rides (about .100", as I remember).  A Rockwell C hardness test showed it was a little soft (48, as I remember), so this was probably the problem.  The guys at Stafford Performance thought the problem might have been that the cam lube dripped off between the initial assembly and first start (3 months had passed) in combination with using motor oils without enough Zinc.  We replaced the bad lifter and reassembled the engine.
• However, after a few more hours of running, the noise seemed to reappear, but on the other side of the engine.  So we checked the valve lift using a magnetic base and dial indicator on May 22, 2008 while trying to troublehsoot the tapping sound:

CYL #	INTAKE (.352 REF)	EXHAUST (.350 REF)
1	.346	.349
2	.345	.345
3	.345	.345
4	.345	.345
5	.346	.346
6	.346	.340
7	.344	.345
8	.346	.344
HI-LO	.002	.009

• The valve lift check didn't show a valve screaming out at us, but it did seem strange that after setting the valve lash, we were already showing .005-.010 of wear, so we decided to pull the cam.  We found cam lobe damage on #7E and lifter damage on #4I.  The #7E cam lobe damage was certainly caused by the soft lifter (described above), but the #4I lifter seems to have been "stuck" in one position and had some wear (however, at the time of disassembly, it rotated freely).  As a result we replaced the cam with another Isky Max-1 and replaced all the lifters with phosphate coated Johnson-style hollow lifters from Red's Headers.  The pictures below show the (1) cam damage, (2) a good lifter from 1E and the bad one from 4I, and (3) the solid lifters we used in the original build, and the hollow Johnson-style lifters we used to replace them.

• Initial PCV placement.  At first, we plumbed the PCV valve to the breather (look closely in this picture and you can see the old location, a nipple on the oil fill tube's base, which is now capped off).  This seemed like a good idea, but at high RPM, there is a fine mist of oil flying around in the lifter galley, which the PCV was sucking up and into the carburetor, causing a little blue smoke.   Relocating the PCV to the downdraft tube fixed this, since it pulls from the crankcase.  Also, we used the smallest PCV valve (orifice size, that is) we could find the second time around.  With 16" vacuum at idle, we were pulling a lot of air through the PCV and diluting the intake charge so much it was hard to tune the carburetor's idle circuit.  Refer to the parts list for the PCV we settled on (it had the smallest opening I could find at the parts store).

• The inital decision to keep the generator caused us to forgo electronic ignition. I wish we would have planned on buying the Powermaster alternator from the beginning, and got the ignition system we really desired, but for now we're sticking with the Mallory dual point distributor.

Unexpected things we learned

• Modern motor oils don't have the same additives they used to (due to EPA restrictions), and this will wipe out a flat tappet cam, especially if its got solid lifters! See the information on Motor Oils, above!
• Don't use the cherry colored cam lube that comes in the little screw-top containers.  This is what came with our cam, and it's very thin and drips off easily, especially if the engine sits too long between cam assembly and first engine fire.  Get the really thick cam lube.  Lunati's cam lube is thick (blue in color), or you can buy Isky cam lube from Speedway.
  

Time Line

• Summer 2005 - removed hood, fenders, engine; disassembled engine
• Fall 2005 - engine cleaning, inspection
• Spring 2006 - engine machining, parts ordered, fabricate engine test stand
• May 2006 - initial assembly (bottom end, valvetrain)
• August 2006 - final assembly & first fire
• December 2006 - fix bad lifter, tuning, engine complete
• December 2007 - swapped generator for alternator, swapped 16" fan for fan & shroud assy
• May 2008 - troubleshooting tapping sound (which originally started with the bad lifter).  Checked valve lift, pulled oil pan.  Found cam damage on 7E and lifter damage on 4I.  Replaced cam and lifters.
• April 2010 - first test drive

Thanks

Last Updated: Monday January 02, 2012

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