How do you plan on driving to car? This has definate implications for head to utilize. The 2v maintains higher velosity for fuel mixture at lower RPM than the 4v. So for primarily steet use driver they tend to do better. If you intend to run high RPM (race) the 4V will give more total flow and have adequate velosity to keep fuel suspended in air mixture.
OK that’s the opposite of what i expected. I always thought that 4v was better. Ok so what’s the difference between Open chamber and Closed chamber. And what is special about Aussie and Cobra Jet heads.
There are 4 different heads for the Cleveland.
4v quench--big ports closed chamber
4v open--big ports, detonation prone open chamber
2v reallisticly sized ports but cursed with open chamber
Aussie--2v sized ports with closed chamber ---if they only did that here, maybe the motor would have been in production for more then 5 years and the 351m and 400 would be much better too.
The closed chamber is definitely better, but only in combination with a piston with a dish to control compression---unless you want to use race fuel.
The quench of the closed chamber raises the limit of compression with a particular octane in comparison to open chambers. Also the quench increases the efficiancy of the motor.
When I build my cleveland, it'll have the aussie heads and a Keith Black piston with what is called a "reverse dome" piston. Reverse dome just means the dish is designed to make the most of the quench area the cylinder head has to offer.
The last head I'd use would be the 4v open chamber, it lacks low end torque and is prone to detonation.
I haven't used 4v's much, but unless you are going to race the motor between 4000-9000, then stick with the 2v's.
If you decide to rebuild the motor with new pistons, with the aussies, there is a place in California called Power Heads that CNC ports the Aussies and does everything to them like hardened exhaust seats to make them live up to todays standards.
The difference between open and closed chamber heads is the volume of the combustion chamber. On open chamber heads, you have a lot more combustion chamber volume. This results in a lower compression ratio. Generally, the higher the compression ratio, the more power you can get, -- up to a point!
OK now, with that prelude out of the way....
All US-made 351C-2V heads are open chamber, or low compression. All 351C-2V engines used flat top pistons.
The difference with the Australian 2V heads is that they are closed chamber, or high compression. They generally are not seen too much here in the US. If you do see a set, they are generally selling for more than closed chamber US-made 4V heads!
The 351C-4V heads have ports and valves that are almost too big for the street. This results in low velocity in the intake and that results in gas coming out of suspension, bogginess on acceleration, poor volumetric efficiency, (bad gas mileage), etc. At higher rpm ranges, the bigger passages of the 4V heads helps to flow more air/fuel mixture than the 2V port sizing will allow -- more flow=more power! This low-rpm sluggishness is one of the reasons that Ford put a high stall torque converter behind the low-compression 351C-4Vs -- to get the engine up into the higher rpm range faster!
351CJ heads - open chamber 4V heads.
Then in 1973-74 Ford shrunk the valve size of the 4V heads down to the same as the 2V valve size to try to boost intake velocity a bit.
Again I'll have to ask if that is an original 4V intake.
The reason I ask is that aftermarket manufacturers made four barrel intakes that fit 2V heads (2V head port sizing).
If you are trying to run a factory 4V intake on 2V heads you're going to have quite a mis-match of the ports. Factory 4V ports are HUGE!
And again, the factory 4V intakes came in two varieties, both squarebore and spreadbore. The aftermarket four barrel intakes can take either style carb.
OH, very important!!! Be advised that the 73-74 factory 4V intake was made to run with an EGR spacer plate under the carb! If you try to bolt the carb down directly to the intake, the hot gasses from the EGR passages will boil the gas right out of your carb! Can you say 'engine fire' boys and girls?
Cougrrcj is right, the ports on the 4v intake don't match up to the 2v heads. The car will run, but throttle response will be less than desirable. Hopefully you have an aluminum aftermarket 4v intake designed for 2v heads.
If you look at the Edelbrock intake, it will either have a name or part number on the top somwhere that will help us determine if the intake is for the 2V or 4V heads. It might say 'Performer 351C-2V' , 'Performer 351C-4V' , 'F4B' , 'Torker' or some such.
Anyway, that's one of my big beefs when talking to people about Cleveland stuff. I try to distinguish between the factory 4V designation and 4-barrel which could be either with aftermarket parts. I suppose if we went to the big block Chevy nomenclature (oval vs square port) we'd avoid most, if not all, of the confusion. I'm not trying to pick on you, c0ugar69, this is a common problem when people talk about 351Cs
(As an aside, does anyone else remember the old short-lived Edelbrock SP2P tiny port intakes of the gas crisis years?) Wow, I must be getting old!
OK, I‘m just learning here. But I think I’m starting to make so sense of it all. I thought 4-barell (as 4-barrel carb) and 4v (as 4 valves per cylinder) were completely separate. Now that i think about it one flows into another. Now I’m I correct in thinking that my intake (Edelbrock Proformer LB 4V) would be correct in adapting my four-barrel carb to my 2v heads?
Actually, in old car lingo, 4v is the same as 4 barrell. And 2v is the same as 2 barrell. 4v and 2v do not reference the number of valves per cylinder. The majority of engines that we talk about are 2 valves per cylinder, so that is a given.
As for Edelbrock Performer intakes. The following intake can be used *only* for 351C-4v heads:
* Performer 351-4V (non-EGR) #2665*
And, the following intake can *only* be used for 351C-2v heads:
* Performer 351-2V (non-EGR) #2750*
For more information, visit Edelbrock's website at:
No reason to feel dumb. The only dumb thing to do is not to ask!
I have no idea what LB stands for. But, if the manifold says 351-4v on it, then I *think* it is meant for 4v heads. I have the Edelbrock Performer intake for 2v heads installed on my 351C. I'll try to remember to look at the numbers on it when I get home tonight. I'm pretty sure it says 351-2v.
Ford generally used the 'V' to denote the number of Venturis or 'barrels' in the carburetor. 2V = 2barrel, 4V= 4barrel, etc. Then there was the 80s style V-V which stood for Variable Venturi, but we'll forget about that (hopefully) for now. Most Ford engine families offered 2- and 4-barrel engines but they all used the same port sizing for both (for all intents and purposes).
The confusing part is that Ford 351 Clevelands were offered with two different intake and exhaust port or runner sizes. The 2Vs had small ports and the 4Vs had much larger ports. As I noted earlier, the aftermarket manufacturers really started messing things up when they started offering 4-barrel intake manifolds for the smaller 2V port heads.
The 429 was also offered briefly (1970 & 71) with large port heads, but even Ford called them 'CJ' or CobraJet' heads to avoid the confusion with their smaller port brothers.
Cougrrcj is exactly correct.
A related question: are the 302-2v and 302-4v (both offered - or at least listed in the owner's manual - in 1968) engines and heads the same except for the carb and intake, or do they differ like the 351C? I'm trying to remember from my manual (in my glovebox in HI) if the compression was the same on both of those engines...
Funny you should ask that, The 68 302 has defferent heads for the 2V and 4V engines. The combustion chamber is smaller on the 4V heads to raise the compresion. And just for fun, also in 68 the 289 was avalibe and has a third casting. the displacement and carb tipe is cast in the head around the rocker studs. IE 302 and a 4V, 302 and a 2V and 289 2V. In my parts hobby I have had all three. I still have a set of 68, 289 2V heads if any one is interested.
weee doggy... alot of info flying around... one of the ways i check out a Cleveland is to look at the corner of the head and see the number there to determine what at least head the car has on it. a 2 would mean a 2v head and a 4 would mean the 4v head. if you have a 4bbl intake on the car its probably just the 2v engine with an aftermarket 4bbl intake. nothing wrong there. id just check out the corners of the heads to be sure. oh yeah. ... i just feel like posting a pic of the monsterous intake ports of the D0AE 70 closed chamber 4v heads i have lying around awaiting a rebuild and useage. the other head is the "large" port 69 351W head in the pic. yeah, it dwarfs it pretty damn bad. oh yeah.. i also have 2 pairs of 69 351W heads and can get a pair of 70 351W heads this weekend too.. hmm, i just might.. half price day at the junk.........