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from 2V to 4V heads
Have a '73 Mustang - 351C - 2V heads - FMX - 9 "rear end.
With a new 4V intake manifold Edelbrock Performer (formerly a 4V cast iron intake manifold Ford) and a new Holley Street Avenger 670cfm 4V carb (formerly a 4V carburetor ford)and a Holley electric fuel pump(blue).

Here I would like to mount 4V heads on for more power, is this possible with a FMX tranny?

What is the difference between open and closed chamber heads?

What to replace or must i thinking on:
- Exhaust Hedders
- .... ?

All info is welcome.

I'm curious to do this myself. Will be watching.

2013 Ford Focus SE Flex Fuel 5spd - Daily Driver
Intake manifold makes no difference. But replacing the carb, you may need an adapter for the kick-down attachment.
I purchased this kit :
Holley P/N 20-91

CZ-75;166231 Wrote:Intake manifold makes no difference. But replacing the carb, you may need an adapter for the kick-down attachment.
4V heads and 2V heads do not share interchangability of intake manifolds. That is to say the 4V heads will not seal against a 2V Cleveland manifold even if it is designed for a 4 barrel carb as the port mismatch where the heads and the intake meet is fairly significant.

So you need an intake for 4V heads

Your exhaust will bolt up-but it is wrong. 4V exhaust ports are larger than 2V and if you use the 2V exhaust on 4V heads, you will choke off some of the power gain you are trying to obtain.

To do it right your exhaust needs to be updated to a 4V exhaust.

Closed chamber heads have a smaller chamber chambers-if you don't do anything to the short block, you will see about 3/4 a point compression increase over the stock open chamber heads.

The advantage of closed chamber heads is that they 1) increase compression and 2) when the quench distance between the piston and head is kept below .060 they are very detonation resistant. If you throw them on a stock 2V short block you will see a minor improvement due to the compression increase, but not anything truly significant. You won't get the quench benefits as the piston won't come close enough.

Open Chamber heads are not truly prone to detonation, but are slightly more so than the closed chamber versions. Open chamber head can flow better as a result of the chamber not having as much valve shrouding- but either set really is fine up to pretty significant horsepower levels.

All Cleveland heads with original ford valves used 2 piece intake valves and failure to rep[lace those can result in valves coming apart and destroying engines.

Spring retainers and keepers must match the valves being used I suggest new matching packages for these types of parts.

Some 4V heads are set up for an adjustable drivetrain-if yours are and the 2V's are not, you'll need to replace your rocker arms. I will never use a used rocker arm again, no matter what it looks like! A broken rocker arm destroyed my engine last spring.

Unless you plan a cam change or a future rebuild to increase compression and set that quench height properly, the advantages of 4V heads will never be apparent.

You FMX won't care which heads you use.

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
Hi Eddy. So the engine currently has a '4v' intake on the 2v heads?

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

Pics of modifications included in:
I bought the car dismantled, all the parts were in carton/plastic boxes and i don't know of the engine runs, the seller promised me that the car was a daily driver...
351C engine with a cast iron intake manifold(D3ZE-9425-AA) and a motorcraft carburetor(D6PE AGA).

will e;166277 Wrote:Hi Eddy. So the engine currently has a '4v' intake on the 2v heads?
That intake is a 4V spreadbore, 73 351CJ. Are you sure you have 2V heads, hard to tell from the pictures. Can you see the casting numbers on the heads?

Here is a link to a good decoder site...

1972 H-code Mach1
2010 GT Premium
2015 Hyundai Sonata Sport 2.0T
1995 F150- The "home depot" machine
2012 Harley Davidson Road Glide Ultra
look in the corner you should see a 2 or a 4 . cast in the head

.jpg   2v_or_4v.jpg (Size: 23 KB / Downloads: 121)


1971 Mach 1
408C Stroker
C4 w/3,000 stall
8.8" Rear w/3.73's
Disc brakes all way around.

https://youtu.be/SoW1fhaFPzY  Burn Out Video. 

[Image: 044.jpg]
That's what i see, a metal bubble (NO 2 or 4)
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