The 400 is a member of the same 335 series engine family as the 351C 2V and 351C 4V. It is popular among Truck & Bronco enthusiasts, but it is generally over-looked in the hot-rod world and ignored in the sports car world. Complete 400 engines sell for peanuts in the wrecking yards due to lack of demand. However, most of the hot-rod parts for the 351C also fit the 400; i.e. water pumps, oil pumps, fuel pumps, distributors, camshafts, timing sets, harmonic dampeners, oil pans and most importantly the 351C heads.
A hot-rodded 400 V8 has five advantages over installing a 4" stroker crankshaft in a 351C :
(1) A better rod length to stroke ratio
(2) The factory iron crank is plenty strong, and negates the need to purchase a stroker kit
(3) There is plenty of room for the ring package above the wrist pin
(4) An inexpensive heavy duty version of the 400 block is available (the 1977 - 1982 truck block)
(5) The 400 build-up is significantly less expensive
Dimensionally the 400 has a foot in two camps, although the bore spacing is identical to the Windsor/Cleveland motors (4.380") its other dimensions are very close to those of the 385 series motors. For instance:
Deck height....................................400 = 10.297"....429/460 = 10.300"
Connecting rod length......................400 = 6.580".....429/460 = 6.605"
Crankshaft main bearing diameter.....400 = 2.998".....429/460 = 3.000"
Nobody would disagree that the 429/460 motors are excellent performance motors, so these dimensions shouldn't be considered a drawback for the 400 either.
Although the 400s connecting rod looks very long to a Cleveland enthusiast, the 400s 1.645:1 rod length to stroke ratio is almost identical to the 351C 1.651:1 rod length to stroke ratio. The 400s wrist pin compression height of 1.65" is identical to the 351C compression height. The one wonky dimension of the 400 is its 0.065" deck clearance; the 400s piston is almost twice as deep in the hole at top dead center as the 351Cs piston. The increase in deck clearance and approximately 16 cc dishes in the piston domes give the 400 a compression ratio of 8.0:1. A new set of pistons with a flat dome and increased compression height is essential when building a 400 for performance.
Replacement of the 400s pistons is necessary to eliminate the dished top of the oem pistons. Since you are replacing the pistons anyway, this creates the opportunity to boost the 400s static compression without resorting to modification of other castings; such as decking the block, installing off-set bushings in the connecting rods or off-set grinding the crankshaft. This simplifies motor assembly.
There are two paths to follow:
(1) Use the Keith Black #2334 forged flat top pistons having a 1.720” pin height.
The Keith Black pistons are designed to be flush with the deck at top dead center (i.e. zero decked). They may in fact stick out of the hole by 0.005” in some blocks. This is overkill in my opinion. Utilizing heads with the largest combustion chamber (78cc) and a standard 0.040” thick head gasket will result in 10.30:1 static compression ratio. The pistons must be used in conjunction with a thicker head gasket to achieve lower compression ratios. To achieve 10.0:1 compression ratio with 78cc heads will require a 0.056” thick head gasket; to achieve the same compression ratio with 75cc heads will require a 0.070” thick head gasket.
(2) order custom pistons with approximately 1.685” pin height.
Using custom pistons alleviates the need to utilize unusually thick head gaskets which are necessary with the Keith Black pistons if your compression ratio goal is less than 10.3:1 or your heads have less than 78cc combustion chamber volume. The motor can use standard 0.040” thick head gaskets and the deck clearance can be a very normal 0.030”; none of the dimensions needs to be extreme or wonky, the engineering of the motor can remain conservative and factory-like. Custom pistons shall remain my preferred method for adjusting the compression ratio of the 400 V8 until a flat-top piston with a 1.685” pin height is available off-the-shelf.
Custom ordered pistons should have these features:
(1) forged aluminum
(2) 351C 4V style flat top (notched for 4V valves)
(3) Full-round (endurance racing) style skirt
(4) 400 size wrist pin
(5) for use with pressed wrist pins
(6) 1.685" wrist pin height
(7) modern "thin" ring package (1/16" or the even slimmer metric style)
The compression height of the custom pistons shall be nominally 1.685", of course you may vary the compression height to adjust for the following factors:
(1) Desired static compression ratio other than 10.0:1
(2) Actual deck height of the block
(3) Head gasket thickness
(4) Cylinder head combustion chamber volume
The 400 engine block has the 385 series (429/460) big block Ford bell housing bolt pattern with one exception; there is a 400 block cast in 1973 that has the small block Ford (Windsor/Cleveland) bell housing bolt pattern. That block, with casting #D3AE-B, is generally referred to as the FMX block. There is little advantage to going through the trouble to locate one of these blocks however as there are many bellhousings available for the big block Ford allowing the 400 to be coupled with almost any manual or automatic transmission, including a Quick Time bellhousing for the ZF transaxle (Pantera), Quick Time model number RM-8012.
In 1977 the 351M and 400 replaced the FE360 and FE390 motors in Fords truck line. A heavy duty truck block was designed for the 351M and 400, casting #D7TE-A2B. This block is not as stout as the rare and expensive NASCAR block designed for the 351C (XE182540, XE192540, M-6015-A3), but it is a step up in durability from the other thin wall Ford castings. Unlike the 351C NASCAR block the 351M/400 truck block is inexpensive and easy to acquire because it was used in all 351M and 400 truck motors from 1977 to 1982, and the F150 Pick-Up is Fords best selling vehicle. The D7TE-A2B block also found its way into many passenger cars and station wagons. This is "THE BLOCK" to use when building a 400, which is another reason why I don't make a big deal about the FMX block.
There is one caveat regarding the D7TE-A2B block. All of the 351M/400 truck blocks were cast in one of two foundries, either the Cleveland Foundry or the Michigan Casting Center. Those cast in the Michigan Casting Center prior to "late" 1977 are known to have a problem with cracking in the water jacket in the lifter valley just above the lifters bores. Tom Monroe, in his book about rebuilding 335/385 series motors, stated only blocks with casting dates earlier than March 1, 1977 (7C01) had a cracking problem, but blocks with later 1977 date codes (at least through June) have been known to crack, so I would avoid any block cast at the Michigan Casting Center with a casting date earlier than January 1, 1978 (8A01). Blocks cast at the Michigan Casting Center have a MCC symbol cast into the top rear of the block near the oil pressure sending unit port, whereas blocks cast in the Cleveland Foundry have a CF symbol cast into the same location. The blocks that crack have "bumps" shaped like truncated pyramids (trapezoids) cast into the water jacket sides of the lifter valley above the lifter bores, the sides of the lifter valley above the lifter bores in the safe blocks are free of bumps.
The 400 has motor mount bosses differing from any other Ford V8. The 400s unique motor mounts should pose no installation problem however since motor mount adapters are one of the easiest parts to fabricate in our hobby. Sometimes all it takes is a strap of flat steel bolted to the block's motor mount bosses.
Any pre-1975 small port (i.e. 2V) open chamber iron head can be used for a performance build, of note the 1970 351C 2V cylinder heads have smaller 76 cc combustion chambers compared to the head found on the 1971 - 1974 351C 2V and 400 which has 78 cc combustion chambers. The 1971 - 1972 351C Cobra Jet heads have combustion chambers of similar volume (75.4 cc) and offer the performance potential of the large 4V ports and valves.
The heads I've just recommended have combustion chamber volumes in the range of 75 cc to 78 cc which are ideal for building a 400 cubic inch performance street motor because the compression ratio we want to obtain can be achieved with custom fllat top pistons, a reasonable 0.030" deck clearance and a standard 0.040" thick head gasket; or Keith Black pistons and a 0.056" to 0.070" head gasket. The heads found on the 1975 and later 351M and 400 are not recommended because the exhaust ports were modified for thermactor air injection and do not flow as well as the earlier heads. The heads with 78cc combustion chambers may need to be milled 0.015" to reduce the chamber volume by 3cc (1cc per 0.005" milled) depending upon your choice of pistons.
Cylinder Head Choices:
(1) 1970 351C 2V .................... Nominal combustion chamber volume is 76.2 cc.
(2) 1971 - 1974 351C 2V........... Nominal combustion chamber volume is 78.4 cc.
(3) 1971 - 1974 400 ................ Nominal combustion chamber volume is 78.4 cc.
(4) 1971 - 1972 Cobra Jet 4V..... Nominal combustion chamber volume is 75.4 cc
Since the topic is a building a 400 based performance motor as opposed to a truck motor, I recommend the 1971/1972 4V Cobra Jet heads (casting number D1ZE) as the least expensive route to high air flow cylinder heads and 10.0:1 compression. When 2V heads are utilized in a performance motor I always recommend having them ported for best performance. 2V cylinder heads may require milling too since most of them have 78cc combustion chambers. Porting and milling are two expenses that are not necessary when utilizing the D1ZE Cobra Jet heads.
A word about open chamber heads:
Some enthusiasts are under the misconception that Cleveland cylinder heads with quench chambers are more resistant to detonation and make more horsepower. Those who believe this have been influenced by books or magazine articles they've read about the small block Chevy authored by Smokey Yunick. This may be true in regards to the small block Chevy but it does not apply to the 335 series Ford cylinder heads.
There is one quote in the OHO book about the differences between open and closed combustion chambers:
"Quench chambers encourage a swirling action of the incoming air-fuel charge. This improves mixture ... especially at low rpm ... when the mixture travels at relatively low velocity. This causes a more complete burning of the fuel and better low rpm torque ... Open chamber designs ... There's no quench area and valves are less shrouded; thereby encouraging excellent breathing. However, you sacrifice some of the good low rpm torque advantage associated with the quench chamber."
This quote is straight from the Ford engineers who designed the 351C. They made no mention of detonation, no mention of a big horsepower difference, the main difference is low rpm torque, which won't be a problem with a 400 cubic inch motor.
Quench combustion chambers having volumes of 58cc to 66cc are too small for a 400 cubic inch street motor, the smaller quench combustion chambers are not needed for detonation prevention or to make additional horsepower. Those who choose to use the closed chamber heads usually minimize the deck clearance too, and then adjust the motor's compression ratio with a set of pistons with deeply dished domes. They believe this increases horsepower, and point to the fact that less ignition advance is needed with this combination as proof of their belief. It is true the turbulence of the quench chamber increases low rpm torque, this is corroberated in Ford literature. It is also true that altering the piston dome changes the amount of ignition advance required by the motor. Domed pistons usually require more ignition advance and dished pistons usually require less ignition advance. However the dynomometer does not corroberate an increase in overall horsepower (thermal efficiency) with this combination.
The fact is Cleveland cylinder heads having about 75 cc combustion chamber volume are ideal for a 400 cubic inch motor, they allow the motor to achieve 10.0:1 compression with fllat top pistons, a reasonable 0.030" deck clearance and a standard 0.040" thick head gasket.
Piston Speed and Limiting Port Velocity
The piston speed of a 400 V8 at 6000 rpm is 4000 FPM! Iron 4V cylinder heads are an excellent choice for this project. They are capable of producing 500 BHP quite readily at 4000 FPM piston speed, assuming the camshaft has enough valve lift. FYI: at 6500 rpm the piston speed is 4333 FPM ... that's quite a bit for a street engine. Equipped with un-ported 4V heads a 400 V8 will tend to make peak horsepower at about 5300 rpm, to bump peak horsepower up to 6000 rpm will require a hydraulic tappet camshaft with about 240° duration at 0.050, or a solid tappet camshaft with about 248° duration at 0.050. With un-ported 4V heads the engine will achieve "limiting port velocity" (i.e. sonic choke) at 6400 RPM.
With un-ported 2V heads "limiting port velocity" will be achieved at about 5400 rpm. If you're going to use 2V heads in a "performance" application, with an engine having a 4.00" stroke crankshaft, you definitely want to have them ported to increase the cross-sectional area of the valve throat to at least 2.40 square inches, and to increase port volume to at least 205cc. Thus ported, the "limiting port velocity" of a 400 V8 with 2V heads shall occur at about 6500 rpm.
There may be aftermarket heads better suited to this project than factory 2V heads, but that is outside the topic Of "using all Ford parts".
An excellent small port head intake manifold for the 400 is available from Weiand and Price Motorsport Engineering (PME) sells adapter plates to allow utilization of 351C 2V or 4V intake manifolds on the 400. The PME #AP-29 2V adapter plate provides the choice of using any 351C 2V intake manifold, such as the new Edelbrock RPM Air Gap intake manifold, in conjunction with 2V heads. The PME #AP-30 4V adapter plate provides the choice of using the classic 351C 4V intake manifolds in conjunction with 4V heads. Classic 4V intake manifolds include the Shelby/Blue Thunder manifold, the Holley Strip Dominator manifold, the Weiand Tunnel Ram manifold and even the Hall Pantera Weber 48 IDA manifold (individual runner).
For a basic performance street motor I recommend choosing a two-plane intake manifold:
(1) Small Port 2V Heads - Weiand #8010 "Action Plus" intake manifold (no manifold spacer is required).
(2) Large Port 4V Heads - Blue Thunder intake manifold (a manifold spacer is required).
The factory distributor will interfere with the intake manifold if the PME manifold spacers are used. In that situation plan to use an aftermarket distributor that has more clearance between the block and distributor housing. MSD #8477 is my personal choice, it utilizes a Ford magnetic pick-up and is therefore compatible with Duraspark ignition modules. Be forewarned the MSD distributor uses a different connector than a Ford distributor, wiring must be spliced, or an adapter must be fabricated.
The availability of exhaust headers for the tall deck 400 are limited, and none exist for the 400 with 4V heads. Some fabrication may be needed, trial fitting headers for other applications may provide a solution, or universal shorty headers like those made by Sanderson may be a viable choice.
Be aware that acquiring headers will most likely pose the biggest challenge to using the 400 as a performance motor, this should be considered before beginning the project. Paying someone else to manufacture custom made exhaust headers will quickly inflate the cost of your engine project.
Those are the specific concerns for building a tall deck 335 series, 400 V8 performance motor. All the usual concerns related to building the 351C for performance apply to this motor as well so I won't rehash that information here.