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".
Intake Manifolds

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.
Exhaust headers

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.

Original Post
The 400 is a venerable old engine but since the level of PIBB activity seems to be off a little bit, just to play devil’s advocate here (sorry George, you know I’m contrary), in the context of an economy 500HP swap for the Pantera, let’s consider:

The 400s unique motor mounts pose no problem since motor mount adapters are one of the easiest parts to fabricate in our hobby.

Yes, custom motor mounts and if you have even modest fab skills these are not a problem but it will take some time to mock them up with the engine in position and actually fab them. A good days work with everything apart maybe?

Although the 400 has a different bell housing bolt pattern and different motor mount bosses than the 351C the drawbacks in using the 400 in the context of installation hassle are limited to the exhaust system and the engine screen. The 400 has the 385 series (429/460) bell housing bolt pattern, and a ZF bell housing for that application is available (some Pantera owners have equipped their cars with 385 series crate motors).

So what cost is assigned to acquiring a big block to -2 ZF patterned bell housing? Whatever it is, you’re out of pocket that much against your economy build. They’re not free and will be required if you are to have the non-FMX block to which you refer. Say $500-600 or more?

That leaves fabrication or modification of headers to fit the 4V heads on a wider taller motor.

IMO, this seems to be a bit of an arm wave to me.

Yes, you will definitely need a custom exhaust. I think you will find it more involved than it might first appear. Sort of depends on what headers you start with but in my case, even with high port heads on a 9.5” block, which puts the port in a similar location to the 400 deck, I had to relocate the coolant tank because there was not sufficient clearance of #4 primary. This of course requires that you rework nearly all of your coolant plumbing. I also found it impractical to try to adapt garden variety Pantera headers as the collector on the passenger side was so much higher it created real challenges with the collector position, transition from the collector to tail pipe diameter, and being able to snake the tail pipe through the suspension. The driver’s side header also hit the gas tank heat shield. After returning a set of vendor supplied headers that were supposedly made for my combo, before I was done, it was purpose/scratch built headers and I went ahead and pieced together custom 2.5” tail pipes from mandrel bent tube back to the cans. I couldn’t get 3” through there and accommodate any suspension travel and it would not have done any good with GTS cans at the end of the trail anyway.

So in any event you might shell out >$150 for a header kit and spend a bunch of fab time on this portion of the swap.

Intake manifold selection kind a sucks in my opinion,….


….but there are readily available adapter plates to allow installation of 351C 4V intake manifolds on the 400, which means you have the choice of using the classic 351C 4V intake manifolds including the Shelby/Blue Thunder manifold, the Holley Strip Dominator manifold and the Weiand tunnel ram.

I agree there are no suitable intakes available for this combo and the most practical solution to 4V head fitment to a 400 block are adapters as it gives a reasonable selection of 351C intakes although it has ugly written all over it when you’re done. I have seen people (me for example ;-)….) contour the adapters to match the scallops on the intakes to help with the aesthetics but it’s a bunch of work. You’ll be out $335 for the Price Motorsport #AP30 by the time they are shipped to you and they also will require port matching to the heads and intake so get out the die grinder and cartridge rolls for a few hours.

Since the motor is taller, the engine screen will not fit without modification.

Yes, but this just a matter of taste on this one. Lot’s of Panteras running around without engine screens.

So do the stock Pantera alternator and A/C brackets/mounts work or do these require modification and/or custom fab work as well?

Anyway, I figure that you need to shell at least ~$1000 and a bunch of fab hours to adapt the “economy” 400 build to your 351c equipped Pantera. There are some skilled fabricators on this site that are doing this swap and doing it well. If you enjoy fab and don’t value your time I guess you don’t assign a value to this part of the swap and all-the power-to-you if that’s the case.

IMO you’d be better off taking the dough and applying it toward a 9.2” deck aftermarket block ($1200-1800 new, maybe better used), spend the bucks prepping this engine that you would have spent rebuilding the 400, buy a new bump stick, use your standard motor mounts, bell housing, accessory mounts, headers, avoid all the fab time, and call it a day. Any reasonable valuation of all that fab time buys a stroker kit and gets you comparable performance or more because you have a more solid short block to build power on than the 400 anyway.

And, when you’re all done, if you ever want to sell your car (I know, I know….its personal choice and this will never happen) you still get to explain the virtues of your 400 engine choice to any prospective buyers and those that value it will be few (I would contend devalue it).

I just don’t see the economy or advantage to it.

-Flame away. Roll Eyes

By the way, Quicktime now makes the bellhousing for a 400/460 swap with a ZF in the Pantera position (they just added the right holes to the GT40 kit car bellhousing for the inverted Pantera-style ZF) Just over $400- ask Tim Meyer with Tmeyer Inc.

As Brooke (Pittcrew) told me, the coolant lines to the water pump and thermostat housing have to be slightly modified for the swap, and he said that the mounts were fairly easy to fabricate. His mounts for a 400 in a Pantera look nice (I have seen them) and we talked about using a set of headers intended for high-port heads and then modifying the head flange for a 400 swap.

So what's the difference with using an aftermarket 351 Windsor block? Instead of a bellhousing, mounts, and potentially-modified headers, I understand that one needs to get a "swap kit" from a vendor to get the correct front accessory mounts, pulleys, etc. One would also need to modify or use a specific 9.2 deck height 351w-based manifold if Cleveland-style heads are used. I think that swapping to an aftermarket 351w-based block has it's own issues, and is not a direct comparison with a 400 swap IMHO.

Since I'm looking for a Pantera myself, I would consider a 400 swap an enhancement to the car and not detract from the value. The engine family is the same as the stock. Granted, the engine isn't stock, but if you're swapping motors, you're not going to worry about how "stock" the car is, right? You've probably done other modifications beyond stock if you're considering an engine swap.
Originally posted by Corey Price:
By the way, Quicktime now makes the bellhousing for a 400/460 swap with a ZF in the Pantera position (they just added the right holes to the GT40 kit car bellhousing for the inverted Pantera-style ZF) Just over $400- ask Tim Meyer with Tmeyer Inc.

That's good to know. I took a quick look and notice they had several ZF adapters listed. That price is lower than I been told but have never asked QT directly. Is $400 a retail price?

If i wanted a 400 size motor i think i would use the 400c block. I know there is a lot of stroker kit around now but i really wonder if the rod length/stroke ratio isn't overly compromised by these kits.

I'll tell you of a really good engine that is totally overlooked as it is not available in the US and everyone in AUS just automatically goes for the extra cubes and that is the 302 cleveland.

If you're after a 302 size these are excellent motors. They have 6" rods and 3" stroke, a 2:1 ratio, those pistons dwell for just that bit longer at tdc and bdc, all 351c parts fit them (as they are 351c blocks) including pistons, the're only drawback is for a 302 they are thought to be big and heavy. But i think by the time a lot of alloy parts are used and tube headers you could cut the wieght difference down to 30 or 40lbs.
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