from 2V to 4V heads

[eddyw]

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.

Thanks,

Eddy

 

[MechEng]

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

 

[CZ-75]

Intake manifold makes no difference. But replacing the carb, you may need an adapter for the kick-down attachment.

 

[eddyw]

I purchased this kit :

Holley P/N 20-91

Intake manifold makes no difference. But replacing the carb, you may need an adapter for the kick-down attachment.

 

[Jeff73Mach1]

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.

 

[will e]

Hi Eddy. So the engine currently has a '4v' intake on the 2v heads?

 

[eddyw]

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).

Hi Eddy. So the engine currently has a '4v' intake on the 2v heads?

 

[trainey]

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...

http://www.mustangtek.com/FordDateDecoding.html

 

[turtle5353]

look in the corner you should see a 2 or a 4 . cast in the head

 

[eddyw]

That's what i see, a metal bubble (NO 2 or 4)

:huh:

 

[turtle5353]

i'm not sure about that???? I have seev a "4" and a dot, but not a dot by itself. Someone else will have to fill us in.

 

[Jeff73Mach1]

Pull the valve covers and get the casting numbers, I am pretty sure you have 2V quench heads from Australia. If so, you just need a proper intake and you have the compression benefits without the costs associated with upgrading to 4V Closed chamber heads.

If you are just going to change heads and not change the cam or anything else, those heads will perform as well as anything available.

But they don't match that intake and it will cause vacuum leaks.

 

[eddyw]

The 2 or 4 is not grinded/filed/sanded away, you see unevenness in the iron casting.

What i can read is 2318 and white springs and orange paint under the valve covers, that round stamp is coming back on the intake see photo's

**This Mustang is built for Belgium and also in Belgium since 1973**

 

[hyena429]

I'll check with the decode site and see what it says on the numbers...Usually no stamp on front means they a 400 or 351m head..Which do fit on cleveland blocks...Date code 2318" i think it should be something like this...2g18...or something..I think the second number should be month..First is year...So it is a 1972 head..."month unknown at the momment" 18th day...Im thinking it is a 72 400 head..But could be wrong...4v cleveland manifold will work on 2v heads..It just will not flow right....Need the casting pics on the exhaust part of the head to know what car "or truck" it come from.

http://www.mustangtek.com/FordDateDecoding.html

 

[Totalled]

That's under side of the intake port. Use a small mirror and see if it's visible with the head still on the engine.

 

[eddyw]

The intake manifold is already mount on the heads and the engine in the car.

 

[hyena429]

I think those are 400 style heads....Look at the size of the intakes...those are little small to be 4v heads...You will have issues with flow if you run a 4v cleveland manifold...It will still run..But it will not flow right..It will be hitting a wall...Your heads look way closer too 2v heads...And with lack of any stamping on the front...Im just eyeballing from the pic..But they look like the small ones...You can tell they not high enough to the top of the head...here is a pick below showing diff in ports.

Look at the casting diffrence below...Yours are just like the heads on bottom..those are 2v mustang heads...but your heads are a little diff...I think you got 400 heads..Ford started making the 400 in 71..would match the date codes you posted too.

 

[eddyw]

I think 2V heads, little ports.

 

[hyena429]

I think 2V heads, little ports.

2v would be marked 2 on front of the head...which makes me think they are 400 head...From what i know all 71-73 clevelands got a 2 or a 4 on the head.....I have seen a few clevelands get 400 and 351M heads..They fit and look normal and just about the same as a mustang 2v head.....Lacking a 2 or 4 stamped on the front is a tell tale sign you have 400 or 351M heads.