The small-block Ford has never been blessed with particularly good cylinder heads in its half-century service life. Even the Boss 302 and 5.0L GT-40 were never impressive in the cylinder head department. The Boss 302 was an excellent racing engine, but it was a real dog on the street because its huge ports didn’t deliver good low-end torque. The 289 High Performance V-8 was a screamer, but never had enough cylinder head to pour on the torque at high RPM. The same can be said for the 5.0L Cobra GT-40 engine – not enough cylinder head to deliver the twist.
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So, what to do about “Lo-Po” cylinder heads in the machine shop? John Da Luz of JMC Motorsports suggests good port and bowl work for improved torque. John has small-block Ford heads down to a science. He knows how to get these heads to flow impressive numbers with some hard and fast grinder work in his Southern California shop. John begins at the exhaust ports, which have a lot of room for improvement. Small-block Ford heads suffer from serious exhaust port restriction issues. John begins by eliminating the thermactor “hump” in the roof of the port. Then he works the rest of the port. The size difference in the port is incredible. Before John begins his port work, the exhaust port has sharp angles that restrict flow. When John is finished, it becomes a straight, unrestricted shot from valve seat to header flange. If you are stepping up to 351W heads, a JMC port and bowl job will wake your heads up.
And one other thing: port and bowl work isn’t suggested for the novice. Good head porting technique – understanding what it takes to achieve good port flow without getting into the water jackets – takes years of experience.
Our stock 289-ci small-block won’t be getting port work. However, it will be getting substantial head work in order to improve reliability and function. Because the original core had been through a rather unconventional rebuild, the cylinder heads suffered damage as a result. This was the first time we had ever witnessed a set of intake valve seats that needed to be replaced because of excessive wear. During a previous rebuild, the valves were reground at such an angle that they wore into the iron valve seats. One of the guys at Grubbs commented that you could shave with these valves because they were so badly worn.
Jim Grubbs Motorsports proved to us that no cylinder head is beyond repair if you know what you’re doing. All exhaust valve seats were replaced with hardened steel seats for reliable use with unleaded fuels. This is suggested anytime you are going to be driving a vehicle daily or expect hard use. Show cars and occasional weekend drivers do not need hardened exhaust valve seats, so you might be able to save some money there.
Our 289 heads also needed new valveguides. Because our heads suffered at the hands of a previous engine builder,some of the guides had to be completely replaced. Others needed only bronze inserts, which saved us money. Most rebuilds need only bronze valveguide inserts for solid reliability. If you want to begin factory fresh, you replace all 16 valveguides completely with oil-impregnated and knurled guides. Expect to spend a lot of money when you do, because valveguide replacement is time consuming.
A valve job should always include new valves. Old valves can be refaced to like-new condition and live 100,000 miles. However, valvestems cannot be reconditioned. New guides tend to take up the slack of worn valvestems. But, you tend to lose something along the way. New valves are cheap. They don’t cost much more than about $10 each from Federal-Mogul’s Speed Pro division. And, you can expect reliability and peace of mind with 16 factory-fresh stopcocks. Spend the money – it’s worth it.
Cylinder head refacing (milling) should be performed only if it is absolutely necessary. Each time we mill a cylinder head deck surface, we change a couple of things that are very important. We make the deck thinner, which adversely affects integrity.We also change the angle of the relationship between the heads and intake manifold, which can sometimes cause vacuum and coolant leak issues. As with the block, shave only the necessary amount off the head decks.
Another issue we were concerned with was rocker-arm studs. Our 289 had the original press-in studs. For stock engines with mild cam grinds, press-in studs work fine. If you are concerned about rocker-arm stud integrity, there are several solutions. One old hot-rodding trick is to “pin” the studs. Pinning the studs involves drilling a hole through the stud pedestal and inserting a tension pin through the pedestal and stud. This keeps the stud “pinned” in the head.
An easier trick is to install screw-in rocker-arm studs. This may be performed several different ways. Jim Grubbs removed our press-in studs and installed screw-in studs. One downside to this idea is one problem we encountered where the studs back out of the head during valve lash adjustment. This mandated the use of poly-lock rocker-arm adjustment nuts, which is an unnecessary expense in our opinion on a stock engine. This is why we prefer the hexshoulder, screw-in rocker-arm studs like we find with the 289 High Performance and Boss 302 engines.
Step by Step: Machining the Heads
Step-01: Remove Rocker- Arm Studs
The stud removal tool and an air impact wrench are used to extract each of the studs.
Step-02: Measure the Stud Hole (Precision Measurement)
The rocker-arm stud hole, which opens right into the water jacket, is measured to determine what sized tap we’re goingto need.
Step-03: Tap the Hole
A tap is gently run into the hole to cut threads for the screw-in stud. In view of some of the problems we had with studs working loose, we suggest the hex-shoulder, adjustable rocker-arm studs like we find with the 289 high performance.
Step-04: Check the Fit
Our rocker-arm stud holes are tapped and ready for a fit check. It screws in nice and smoothly. The stud will have to have Teflon sealer around the threads to keep coolant inside, but that will come later when the studs are permanently installed after the cylinder heads are cleaned.
Step-05: Remove the Valveguides
Our 1965 289 cylinder head castings need a lot of attention due to inadequate engine building procedures in the past. First, we’re going to ream out the bronze valveguides as shown
Step-06: Install the Valveguides
We’re installing new Hastings bronze valveguide liners in these heads. The valvestem rides on this guide, which transfers heat and carries oil down the stem more effectively. Each of the bronze guides is driven into the valveguide as shown.
Step-07: Trim the Excess
Once the guide is driven into place, the excess is trimmed off as shown.
Step-08: Measure the Valvestem (Special Tool)
Now, we have to measure the valvestem and machine the guides to fit. The tool we use to machine the guides is called a spiraling arbor.
Step-09: Resize the Guide
The spiraling arbor is driven through the bronze liner, sizing the guide to the size of the valvestem and securing the liner into the guide.
Step-10: Trim the Guide
The resized guide gets a trim job, machined flush as shown.
Step-11: Countersink the Guide
The end of the guide is countersunk for a smooth valvestem transition.
Step-12: Test-Fit the Valves
Here, Grubbs sets up the dial-bore gauge for proper valvestem and guide sizing. The valvestem must slide smoothly, with a nice glide back and forth, without binding.
Step-13: Hone the Valveguides
Here are two kinds of valveguide hones. On top, a conventional hone. On the bottom, a ball hone. Which one your machine shop uses is a matter of personal preference. The conventional hone is more expensive, but it does a better job. We’re going to use a valveguide hone to put a nice finish on the bronze inserts for good oil control and proper sizing.
Step-14: Observe the Results
Step-15: Prepare for the Valve Seal
We’re getting ready to cut the valveguide outside diameter for the Viton valve seals. Here, we measure the outside diameter to determine what sized cutter we’re going to use. Then the outside diameter of the valveguide is cut to fit the Viton valve seal. The Viton seal is better than the Teflon seal, and remarkably better than the umbrella seals we find inside a lot of these engines.
Step-16: Install the Valve Seal
The machined valveguide on the left is ready for its Viton seal. Note the difference from the unmachined guide on the right. In the second photo, the valve seal has been installed (finger). This is a nice seal because it outlasts virtually everything in the marketplace. It maintains a snug fit around the valvestem, which means good oil control for your new engine
Step-17: Exhaust Valve Seats (Professional Mechanic Tip)
Hardened valve seats should be your next consideration after valveguide replacement. Hardened valve seats became important when tetraethyl lead was removed from automotive fuels in the 1980s. Weekend cruisers and tailored show cars do not need hardened exhaust valve seats; daily drivers and weekend racers do. We’re going to cut out the iron exhaust valve seat and install this hardened seat.
Step-18: Prepare the Valve Seats
The hardened valve seat’s outside diameter is measured and recorded to set up the valve-seat cutter.
Step-19: Prepare the Head
This is the pilot for the cutter. A bubble leveler helps us correctly position the cylinder head for valve seat cutting. The cutter is perfectly matched to the valve seat size.
Step-20: Measure the Valve Seat
Here, we measure the thickness of the valve seat, which helps determine how deep we’re going to cut the cylinder head for valve-seat placement. The old iron valve seat has been cut out, making way for the steel valve-seat insert. The old iron seat was actually part of the iron casting. Iron doesn’t wear as well as hardened steel. Steel valve seats are installed in cast-aluminum heads as well.
Step-21: Install the Valve Seat
The hardened exhaust valve seat is driven into place. Once installed, the exhaust valve seat looks like this. It still has to be ground to mate properly with the valve head.
Step-22: Intake Valve Seats
Close inspection of the intake-valve iron seat shows the result of a poor valve job. The intake valve wore its way deep into the iron seat. When valve seating becomes a problem, we have to install hardened intake valve seats.
Step-23: Look at the Valve
A “valve job” involves shaping the valves and seat so they fit together and seal perfectly. The valve should seat smack in the middle of the machined face as shown.
Step-24: Grind the Intake Seat
Bench racers like to brag about three-angle valve jobs. But, a three-angle valve job is just common sense. A threeangle cut distributes the load more evenly across the valve face and seat. It also offers improved airflow through the port and across the valve seat. Some machine shops make three separate cuts to achieve three angles. Jim Grubbs Motorsports has a cutter that does all three angles at the same time.
Step-25: Grind the Exhaust Seat
Once the guide is driven into place, the excess is trimmed off as shown.
Step-26: Test Fit the Valves
The intake and exhaust valves are checked for proper seating. We’ll get more into proper valve seating in the text ahead. As you can see, the three-angle valve job allows air to flow smoothly across the seat and valve face.
Step-27: Examine the Angles
When we rub the valve face into the freshly ground seat, it scribes a line in the valve face. This shows us where the valve contacts the seat. Later, we’ll grind the valves to match the new seats.
Step-28: Mill the Heads
With valve and seat work finally out of the way, we are ready to mill the head deck surfaces. The head is set up on the mill. Ourapproach here needs to be the same as it was with the block deck. Each head is milled a few thousandths at a time, checking to see where the irregularities are. We shave just enough to get the deck level – and no more.
Step-29: Wash the Heads
With all machining work completed, the cylinder heads are washed with the same diligence as the block.
Step-30: Mark the Valves
A red dye is painted on the valve faces. This dye is there to show us where we have ground the valve faces.
Step-31: Grind the Valves
Valve grinding is the same as it has always been. We grind the face at a specific angle designed to fit the three-angle seat.
Step-32: Lubricate the Valvestems
Valvestems are lubricated with engine assembly lube prior to installation.
Step-33: Find Valvespring Height
The valvespring installed height is determined next.
Step-34: Determine Spring Pressure
Spring pressure is determined next. Then, we dial in the spring pressure at the valve using shims.
Step-35: Install Springs, Retainers, and Keepers
The valvesprings, retainers, and keepers are installed next.Proper seating of the keepers and retainers is ascertained by tapping the keeper with a hammer.
Step-36: Check Valve Seating
We check proper valve seating by applying vacuum at each of the ports. If the vacuum holds, we have excellent valve seating.
Step-37: Install Rocker-Arm Studs
Screw-in, adjustable-rocker-arm studs are installed next. Teflon sealer is used on these studs. Torque these studs to 35 ft-lbs. Use Poly-Loc adjustment nuts.
There are three types of screw-in studs: adjustable, with a hex shoulder; adjustable, without a hex shoulder; and positive-stop, without the hex shoulder. The positive-stop, no adjust rocker-arm stud saw factory use from 1968 to ’77. We suggest using adjustable, hex-shoulder, screw-in rocker-arm studs for best results. Always use Teflon sealer on the threads before screwing them into the cylinder head. This will keep coolant out of your oil.
If you’re working with late-1966 through 1977 cylinder heads with railstyle rocker arms, it’s best you have screwin rocker-arm studs with pushrod guide plates installed. This is a great upgrade for high-performance applications. However, it’s an important revision for just about any small-block Ford you happen to be building because it eliminates the troublesome rail-style rocker arm.
Another important upgrade is using improved valve seals instead of those umbrella seals we’ve been using since the beginning of time. Umbrella seals aren’t happy with engine heat and oil. They become brittle, decay, and crumble, winding up in the oil pan pick-up. To install the improved valve seals, the cylinder head must be machined to fit the seal. This adds to the cost, but it improves longevity.
When it is time to install freeze plugs in the heads and block, always use brass – never steel. Steel freeze plugs corrode with time and use. Brass freeze plugs do not.
Written by George Reid and Republished with Permission of CarTech Inc
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